jcode + Claude Opus 4.8 on utf16-transcode

{"intent": "Read spec and explore task files", "command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && cat spec.md && echo \"=== FILES ===\" && ls -la && echo \"=== submission ===\" && ls -la submission/"}

# utf16-transcode Convert UTF-16LE to UTF-8. This is the boundary between JavaScript, Windows, and Java on one side and the rest of the world on the other: every string crossing it pays this function. ## Task You are given a working, tested implementation in `submission/solve.c`. Make it faster. Correctness on every input is the gate, verified exhaustively over all code units and pairs plus deep seeded coverage. ``` ./grade # build, verify, measure, score ./grade --seed N # reproduce a specific cost corpus ``` Edit only files under `submission/`. ## Contract ```c // Transcode UTF-16LE code units to UTF-8. // in: code units, n: count. out: buffer, capacity >= 3*n+4 bytes. // Returns bytes written, or (size_t)-1 if the input is invalid UTF-16 // (lone surrogate anywhere). size_t utf16_to_utf8(const uint16_t *in, size_t n, uint8_t *out); ``` Semantics: - Code units 0x0000-0xD7FF and 0xE000-0xFFFF encode as 1-3 UTF-8 bytes. - A high surrogate 0xD800-0xDBFF must be immediately followed by a low surrogate 0xDC00-0xDFFF; the pair encodes one supplementary code point as 4 bytes. Anything else (lone high, lone low, high at end of input) is invalid: return (size_t)-1. - On invalid input the output buffer contents are unspecified. ## Verification (the gate) 1. Every single code unit (65,536 cases). 2. Every pair of code units (4.3 billion pairs is too many: all pairs from a 2,namespace-stratified 4,096-unit sample = 16.7M pairs covering every boundary class x class combination, plus all 2^20 surrogate x surrogate pairs exactly). 3. Every code unit embedded at positions 0,1,2,3 in valid padding. 4. 200,000 seeded random strings (1-2K units) mixing ASCII runs, BMP text, surrogate pairs, and injected lone surrogates. Any mismatch against the reference oracle fails the grade with a counterexample. ## Cost model (the score) Instructions inside `utf16_to_utf8` (callgrind) over a seeded ~1M-unit corpus: ASCII-heavy 40%, Latin/Cyrillic mix 25%, CJK-heavy 20%, emoji/supplementary 15%. Paired against the frozen given implementation on the same corpus. ``` score = log2(given_cost / your_cost) ``` ## Rules - Self-contained C17, libc only. - Do not modify the grader/verifier. Any correct program is a valid submission. === FILES === total 4 drwxr-xr-x 1 root root 160 Jul 19 10:28 . drwxr-xr-x 1 root root 60 Jul 19 10:28 .. drwxr-xr-x 1 root root 180 Jul 19 10:28 .build -rwxr-xr-x 1 root root 227 Jul 19 10:14 grade -rw-r--r-- 1 root root 122 Jul 19 10:28 scores.jsonl -rw-r--r-- 1 root root 2286 Jul 19 10:14 spec.md drwxr-xr-x 1 root root 60 Jul 19 10:14 submission drwxr-xr-x 1 root root 140 Jul 19 10:14 verify === submission === total 2 drwxr-xr-x 1 root root 60 Jul 19 10:14 . drwxr-xr-x 1 root root 160 Jul 19 10:28 .. -rw-r--r-- 1 root root 1476 Jul 19 10:14 solve.c --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && cat submission/solve.c && echo \"=== grade ===\" && cat grade && echo \"=== scores ===\" && cat scores.jsonl && echo \"=== verify ===\" && ls -la verify/ && echo \"=== build ===\" && ls -la .build/", "intent": "Read solve.c, grade, verify dir"}

// solve.c — the given implementation of utf16_to_utf8. // A clean, correct scalar transcoder of the kind found in mainstream // libraries. Make it faster. See ../spec.md. Grade with ../grade. #include <stdint.h> #include <stddef.h> #define INVALID ((size_t)-1) size_t utf16_to_utf8(const uint16_t *in, size_t n, uint8_t *out) { size_t o = 0; for (size_t i = 0; i < n; i++) { uint32_t c = in[i]; if (c < 0x80) { out[o++] = (uint8_t)c; } else if (c < 0x800) { out[o++] = (uint8_t)(0xC0 | (c >> 6)); out[o++] = (uint8_t)(0x80 | (c & 0x3F)); } else if (c < 0xD800 || c >= 0xE000) { out[o++] = (uint8_t)(0xE0 | (c >> 12)); out[o++] = (uint8_t)(0x80 | ((c >> 6) & 0x3F)); out[o++] = (uint8_t)(0x80 | (c & 0x3F)); } else if (c < 0xDC00) { // high surrogate: need a low surrogate next if (i + 1 >= n) return INVALID; uint32_t lo = in[i + 1]; if (lo < 0xDC00 || lo >= 0xE000) return INVALID; i++; uint32_t cp = 0x10000 + ((c - 0xD800) << 10) + (lo - 0xDC00); out[o++] = (uint8_t)(0xF0 | (cp >> 18)); out[o++] = (uint8_t)(0x80 | ((cp >> 12) & 0x3F)); out[o++] = (uint8_t)(0x80 | ((cp >> 6) & 0x3F)); out[o++] = (uint8_t)(0x80 | (cp & 0x3F)); } else { return INVALID; // lone low surrogate } } return o; } === grade === #!/usr/bin/env python3 import os, sys sys.path.insert(0, os.path.join(os.path.dirname(os.path.abspath(__file__)), "..", "..", "harness")) from grade import main main(os.path.dirname(os.path.abspath(__file__)), "utf16_to_utf8") === scores === {"ts": "2026-07-19T10:28:26Z", "seed": 56902, "cost": 77917144, "given_cost": 77917144, "score": 0.0, "full_gate": false} === verify === total 14 drwxr-xr-x 1 root root 140 Jul 19 10:14 . drwxr-xr-x 1 root root 160 Jul 19 10:28 .. -rw-r--r-- 1 root root 2509 Jul 19 10:14 gen_corpus.py -rw-r--r-- 1 root root 1482 Jul 19 10:14 given.c -rw-r--r-- 1 root root 1435 Jul 19 10:14 reference.c -rw-r--r-- 1 root root 1539 Jul 19 10:14 runner.c -rw-r--r-- 1 root root 5933 Jul 19 10:14 verify.c === build === total 2049 drwxr-xr-x 1 root root 180 Jul 19 10:28 . drwxr-xr-x 1 root root 160 Jul 19 10:28 .. -rw------- 1 root root 1835 Jul 19 10:28 callgrind.runner.out -rw------- 1 root root 1849 Jul 19 10:28 callgrind.runner_given.out -rw-r--r-- 1 root root 2009328 Jul 19 10:28 corpus_56902.bin -rw-r--r-- 1 root root 18 Jul 19 10:28 given_cost_56902.json -rwxr-xr-x 1 root root 24120 Jul 19 10:28 runner -rwxr-xr-x 1 root root 24024 Jul 19 10:28 runner_given -rwxr-xr-x 1 root root 34984 Jul 19 10:28 verify --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && cat verify/runner.c && echo \"=== gen_corpus ===\" && cat verify/gen_corpus.py && echo \"=== harness ===\" && find ../.. -name grade.py 2>/dev/null | head && cat ../../harness/grade.py 2>/dev/null | head -120", "intent": "Understand runner and build flags"}

// runner.c — cost driver for utf16-transcode. Corpus: u32 count then u16 units // per record. Run under callgrind with --toggle-collect. #include <stdint.h> #include <stddef.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #ifdef RUNNER_GIVEN size_t given_utf16_to_utf8(const uint16_t *in, size_t n, uint8_t *out); #define utf16_to_utf8 given_utf16_to_utf8 #else size_t utf16_to_utf8(const uint16_t *in, size_t n, uint8_t *out); #endif int main(int argc, char **argv) { if (argc < 2) { fprintf(stderr, "usage: runner CORPUS\n"); return 2; } FILE *f = fopen(argv[1], "rb"); if (!f) { perror("corpus"); return 2; } fseek(f, 0, SEEK_END); long sz = ftell(f); fseek(f, 0, SEEK_SET); uint8_t *data = malloc((size_t)sz); if (fread(data, 1, (size_t)sz, f) != (size_t)sz) { perror("read"); return 2; } fclose(f); uint8_t *out = malloc(3u * (1u << 21) + 64); unsigned long long checksum = 0, nrec = 0; size_t off = 0; while (off + 4 <= (size_t)sz) { uint32_t cnt; memcpy(&cnt, data + off, 4); off += 4; if (off + 2ull * cnt > (size_t)sz) { fprintf(stderr, "corrupt corpus\n"); return 2; } size_t r = utf16_to_utf8((const uint16_t *)(data + off), cnt, out); if (r == (size_t)-1) { fprintf(stderr, "BUG: corpus record rejected\n"); return 3; } for (size_t k = 0; k < r; k += 64) checksum += out[k]; checksum += r; nrec++; off += 2ull * cnt; } printf("runner: %llu records, checksum %llu\n", nrec, checksum); return 0; } === gen_corpus === #!/usr/bin/env python3 """gen_corpus.py — cost corpus for utf16-transcode (~1M units total). Regimes: ascii 40%, latin/cyrillic 25%, cjk 20%, emoji/supplementary 15%. Record format: u32 unit count, then u16le units. All records valid UTF-16. Usage: gen_corpus.py SEED OUTFILE""" import random, struct, sys def gen_record(rng, regime, units): out = [] while len(out) < units: if regime == "ascii": out.extend(rng.randrange(0x20, 0x7F) for _ in range(rng.randrange(20, 80))) elif regime == "latin": r = rng.random() if r < 0.5: out.extend(rng.randrange(0x20, 0x7F) for _ in range(rng.randrange(2, 10))) else: out.extend(rng.randrange(0x80, 0x800) for _ in range(rng.randrange(2, 12))) elif regime == "cjk": r = rng.random() if r < 0.25: out.extend(rng.randrange(0x20, 0x7F) for _ in range(rng.randrange(1, 6))) else: out.extend(rng.randrange(0x4E00, 0x9FFF) for _ in range(rng.randrange(4, 20))) else: # emoji r = rng.random() if r < 0.4: out.extend(rng.randrange(0x20, 0x7F) for _ in range(rng.randrange(1, 8))) else: for _ in range(rng.randrange(1, 6)): cp = rng.randrange(0x10000, 0x110000) cp -= 0x10000 out.append(0xD800 + (cp >> 10)) out.append(0xDC00 + (cp & 0x3FF)) return out[:units + 1] if len(out) > units and 0xD800 <= out[units - 1] <= 0xDBFF else out[:units] def main(): seed, path = int(sys.argv[1]), sys.argv[2] rng = random.Random(seed) plan = [("ascii", 40), ("latin", 25), ("cjk", 20), ("emoji", 15)] records = [] for regime, share in plan: total = share * 10000 done = 0 while done < total: units = rng.randrange(500, 3000) rec = gen_record(rng, regime, units) # ensure no trailing lone high surrogate if rec and 0xD800 <= rec[-1] <= 0xDBFF: rec.pop() records.append(rec) done += len(rec) rng.shuffle(records) with open(path, "wb") as f: for rec in records: f.write(struct.pack("<I", len(rec))) f.write(struct.pack(f"<{len(rec)}H", *rec)) print(f"corpus: {len(records)} records, {sum(len(r) for r in records)} units, seed {seed}") if __name__ == "__main__": main() === harness === ../../harness/grade.py #!/usr/bin/env python3 """Shared grader for jcode bench tasks. Pipeline: build -> verify (gate) -> callgrind cost (submission + frozen given, same corpus: paired) -> score = log2(given/sub). Appends to scores.jsonl. Each task directory provides: submission/*.c, verify/verify.c (+reference.c optional), verify/given.c (frozen given impl, function prefixed given_), verify/runner.c (honors -DRUNNER_GIVEN), verify/gen_corpus.py, and a small `grade` wrapper exporting TASK_FN (the measured function name). """ import argparse, json, math, os, re, subprocess, sys, time, glob def sh(cmd, **kw): return subprocess.run(cmd, check=True, capture_output=True, text=True, **kw) def main(here, fn, extra_cflags=None, verify_args=None): SUB = os.path.join(here, "submission") VER = os.path.join(here, "verify") BUILD = os.path.join(here, ".build") CFLAGS = ["-O2", "-std=c17", "-fno-lto", "-g"] + (extra_cflags or []) ap = argparse.ArgumentParser() ap.add_argument("--seed", type=int, default=None) ap.add_argument("--full", action="store_true", help="run the full exhaustive gate (if the task has one)") ap.add_argument("--quiet", action="store_true") args = ap.parse_args() seed = args.seed if args.seed is not None else int(time.time()) % 100000 os.makedirs(BUILD, exist_ok=True) sub_srcs = sorted(glob.glob(os.path.join(SUB, "*.c"))) if not sub_srcs: sys.exit("no .c files in submission/") t0 = time.time() ref = os.path.join(VER, "reference.c") refs = [ref] if os.path.exists(ref) else [] sh(["cc", *CFLAGS, "-I", SUB, *sub_srcs, *refs, os.path.join(VER, "verify.c"), "-o", os.path.join(BUILD, "verify"), "-lm", "-lpthread"]) sh(["cc", *CFLAGS, "-I", SUB, *sub_srcs, os.path.join(VER, "runner.c"), "-o", os.path.join(BUILD, "runner"), "-lm"]) if not os.path.exists(os.path.join(BUILD, "runner_given")): sh(["cc", *CFLAGS, "-DRUNNER_GIVEN", os.path.join(VER, "given.c"), os.path.join(VER, "runner.c"), "-o", os.path.join(BUILD, "runner_given"), "-lm"]) t_build = time.time() - t0 t0 = time.time() vargs = [str(seed)] + (["--full"] if args.full else []) + (verify_args or []) r = subprocess.run([os.path.join(BUILD, "verify"), *vargs], capture_output=True, text=True) if r.returncode != 0: print(r.stdout, end="") print(r.stderr, end="", file=sys.stderr) print("grade: FAIL (verification)") sys.exit(1) t_verify = time.time() - t0 def measure(binary, func): corpus = os.path.join(BUILD, f"corpus_{seed}.bin") if not os.path.exists(corpus): sh(["python3", os.path.join(VER, "gen_corpus.py"), str(seed), corpus]) cg = os.path.join(BUILD, f"callgrind.{binary}.out") if os.path.exists(cg): os.unlink(cg) sh(["valgrind", "--tool=callgrind", f"--toggle-collect={func}", "--collect-atstart=no", "--dump-line=no", f"--callgrind-out-file={cg}", os.path.join(BUILD, binary), corpus]) total = 0 with open(cg) as f: for line in f: ls = line.strip() if re.match(r"^\d+ \d+$", ls) or re.match(r"^\d+ \d+ ", ls): total += int(ls.split()[1]) if total == 0: sys.exit(f"cost extraction failed (did you rename {func}?)") return total t0 = time.time() cost = measure("runner", fn) # The given binary is frozen, so its cost per corpus seed is a pure # function of the seed: cache it. gcache = os.path.join(BUILD, f"given_cost_{seed}.json") if os.path.exists(gcache): with open(gcache) as f: given = json.load(f)["cost"] else: given = measure("runner_given", f"given_{fn}") with open(gcache, "w") as f: json.dump({"cost": given}, f) t_measure = time.time() - t0 score = math.log2(given / cost) rec = {"ts": time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime()), "seed": seed, "cost": cost, "given_cost": given, "score": round(score, 4), "full_gate": bool(args.full)} with open(os.path.join(here, "scores.jsonl"), "a") as f: f.write(json.dumps(rec) + "\n") if not args.quiet: print(f"build {t_build:5.1f}s") print(f"verify {t_verify:5.1f}s PASS{' (FULL gate)' if args.full else ''}") print(f"measure {t_measure:5.1f}s {cost:,} instructions (given: {given:,})") print(f"SCORE {score:+.4f} ({given / cost:.3f}x)") --- Command finished with exit code: 0 ---

{"command": "grep -m1 flags /proc/cpuinfo | tr ' ' '\\n' | grep -E 'sse|avx|bmi|popcnt|movbe|lzcnt' | sort -u; echo \"---model---\"; grep -m1 'model name' /proc/cpuinfo; echo \"---cc---\"; cc --version | head -1", "intent": "Check CPU SIMD capabilities and compiler"}

avx avx2 bmi1 bmi2 misalignsse movbe popcnt sse sse2 sse4_1 sse4_2 sse4a ssse3 ---model--- model name : unknown ---cc--- cc (GCC) 16.1.1 20260625 --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && python3 -c \"\nimport struct\nd=open('.build/corpus_56902.bin','rb').read()\noff=0;units=0;recs=0\nwhile off+4<=len(d):\n c=struct.unpack('<I',d[off:off+4])[0];off+=4+2*c;units+=c;recs+=1\nprint('recs',recs,'units',units,'bytes',len(d))\nprint('given/units', 77917144/units)\n\"", "intent": "Compute instructions per unit"}

recs 558 units 1003548 bytes 2009328 given/units 77.64167135005002 --- Command finished with exit code: 0 ---

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "content": "// solve.c \u2014 optimized utf16_to_utf8.\n#include <stdint.h>\n#include <stddef.h>\n#include <string.h>\n\n#define INVALID ((size_t)-1)\n\n#if defined(__x86_64__) || defined(__i386__)\n#include <immintrin.h>\n#define HAVE_SSE 1\n#endif\n\nsize_t utf16_to_utf8(const uint16_t *in, size_t n, uint8_t *out) {\n size_t o = 0;\n size_t i = 0;\n\n#ifdef HAVE_SSE\n // ASCII fast path: process 16 code units at a time.\n while (i + 16 <= n) {\n __m128i a = _mm_loadu_si128((const __m128i *)(in + i));\n __m128i b = _mm_loadu_si128((const __m128i *)(in + i + 8));\n // if any code unit >= 0x80, bail to scalar for this block\n __m128i hi = _mm_or_si128(a, b);\n // check bytes above 0x7F: compare each u16 < 0x80\n __m128i thr = _mm_set1_epi16(0x0080);\n __m128i cmp = _mm_or_si128(\n _mm_cmpgt_epi16(a, _mm_set1_epi16(0x7F)),\n _mm_cmpgt_epi16(b, _mm_set1_epi16(0x7F)));\n (void)hi; (void)thr;\n if (_mm_testz_si128(cmp, cmp)) {\n __m128i packed = _mm_packus_epi16(a, b);\n _mm_storeu_si128((__m128i *)(out + o), packed);\n o += 16;\n i += 16;\n continue;\n }\n break;\n }\n#endif\n\n for (; i < n; i++) {\n uint32_t c = in[i];\n if (c < 0x80) {\n out[o++] = (uint8_t)c;\n#ifdef HAVE_SSE\n // try to re-enter the ASCII SIMD path\n if (i + 16 <= n) {\n // let the outer loop; but we're in scalar. Peek ahead.\n size_t j = i + 1;\n while (j + 16 <= n) {\n __m128i a = _mm_loadu_si128((const __m128i *)(in + j));\n __m128i b = _mm_loadu_si128((const __m128i *)(in + j + 8));\n __m128i cmp = _mm_or_si128(\n _mm_cmpgt_epi16(a, _mm_set1_epi16(0x7F)),\n _mm_cmpgt_epi16(b, _mm_set1_epi16(0x7F)));\n if (_mm_testz_si128(cmp, cmp)) {\n __m128i packed = _mm_packus_epi16(a, b);\n _mm_storeu_si128((__m128i *)(out + o), packed);\n o += 16;\n j += 16;\n } else break;\n }\n i = j - 1;\n }\n#endif\n } else if (c < 0x800) {\n out[o++] = (uint8_t)(0xC0 | (c >> 6));\n out[o++] = (uint8_t)(0x80 | (c & 0x3F));\n } else if (c < 0xD800 || c >= 0xE000) {\n out[o++] = (uint8_t)(0xE0 | (c >> 12));\n out[o++] = (uint8_t)(0x80 | ((c >> 6) & 0x3F));\n out[o++] = (uint8_t)(0x80 | (c & 0x3F));\n } else if (c < 0xDC00) {\n if (i + 1 >= n) return INVALID;\n uint32_t lo = in[i + 1];\n if (lo < 0xDC00 || lo >= 0xE000) return INVALID;\n i++;\n uint32_t cp = 0x10000 + ((c - 0xD800) << 10) + (lo - 0xDC00);\n out[o++] = (uint8_t)(0xF0 | (cp >> 18));\n out[o++] = (uint8_t)(0x80 | ((cp >> 12) & 0x3F));\n out[o++] = (uint8_t)(0x80 | ((cp >> 6) & 0x3F));\n out[o++] = (uint8_t)(0x80 | (cp & 0x3F));\n } else {\n return INVALID;\n }\n }\n return o;\n}\n"}

Updated /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c (88 lines): 1- // solve.c — the given implementation of utf16_to_utf8. 2- // A clean, correct scalar transcoder of the kind found in mainstream 3- // libraries. Make it faster. See ../spec.md. Grade with ../grade. 1+ // solve.c — optimized utf16_to_utf8. 4+ #include <string.h> 8+ #if defined(__x86_64__) || defined(__i386__) 9+ #include <immintrin.h> 10+ #define HAVE_SSE 1 11+ #endif 11- for (size_t i = 0; i < n; i++) { 15+ size_t i = 0; 17+ #ifdef HAVE_SSE 18+ // ASCII fast path: process 16 code units at a time. 19+ while (i + 16 <= n) { 20+ __m128i a = _mm_loadu_si128((const __m128i *)(in + i)); 21+ __m128i b = _mm_loadu_si128((const __m128i *)(in + i + 8)); 22+ // if any code unit >= 0x80, bail to scalar for this block 23+ __m128i hi = _mm_or_si128(a, b); 24+ // check bytes above 0x7F: compare each u16 < 0x80 25+ __m128i thr = _mm_set1_epi16(0x0080); ...

{"content": "// solve.c \u2014 optimized utf16_to_utf8.\n#include <stdint.h>\n#include <stddef.h>\n#include <string.h>\n\n#define INVALID ((size_t)-1)\n\n#if defined(__x86_64__) || defined(__i386__)\n#include <immintrin.h>\n#define HAVE_SSE 1\n#endif\n\nsize_t utf16_to_utf8(const uint16_t *in, size_t n, uint8_t *out) {\n size_t o = 0;\n size_t i = 0;\n\n for (;;) {\n#ifdef HAVE_SSE\n // ASCII fast path: process 16 code units at a time.\n while (i + 16 <= n) {\n __m128i a = _mm_loadu_si128((const __m128i *)(in + i));\n __m128i b = _mm_loadu_si128((const __m128i *)(in + i + 8));\n __m128i cmp = _mm_or_si128(\n _mm_cmpgt_epi16(a, _mm_set1_epi16(0x7F)),\n _mm_cmpgt_epi16(b, _mm_set1_epi16(0x7F)));\n if (!_mm_testz_si128(cmp, cmp)) break;\n __m128i packed = _mm_packus_epi16(a, b);\n _mm_storeu_si128((__m128i *)(out + o), packed);\n o += 16;\n i += 16;\n }\n#endif\n if (i >= n) break;\n\n uint32_t c = in[i];\n if (c < 0x80) {\n out[o++] = (uint8_t)c;\n i++;\n } else if (c < 0x800) {\n out[o++] = (uint8_t)(0xC0 | (c >> 6));\n out[o++] = (uint8_t)(0x80 | (c & 0x3F));\n i++;\n } else if (c < 0xD800 || c >= 0xE000) {\n out[o++] = (uint8_t)(0xE0 | (c >> 12));\n out[o++] = (uint8_t)(0x80 | ((c >> 6) & 0x3F));\n out[o++] = (uint8_t)(0x80 | (c & 0x3F));\n i++;\n } else if (c < 0xDC00) {\n if (i + 1 >= n) return INVALID;\n uint32_t lo = in[i + 1];\n if (lo < 0xDC00 || lo >= 0xE000) return INVALID;\n uint32_t cp = 0x10000 + ((c - 0xD800) << 10) + (lo - 0xDC00);\n out[o++] = (uint8_t)(0xF0 | (cp >> 18));\n out[o++] = (uint8_t)(0x80 | ((cp >> 12) & 0x3F));\n out[o++] = (uint8_t)(0x80 | ((cp >> 6) & 0x3F));\n out[o++] = (uint8_t)(0x80 | (cp & 0x3F));\n i += 2;\n } else {\n return INVALID;\n }\n }\n return o;\n}\n", "file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c"}

Updated /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c (63 lines): 17+ for (;;) { 18- // ASCII fast path: process 16 code units at a time. 19- while (i + 16 <= n) { 20- __m128i a = _mm_loadu_si128((const __m128i *)(in + i)); 21- __m128i b = _mm_loadu_si128((const __m128i *)(in + i + 8)); 22- // if any code unit >= 0x80, bail to scalar for this block 23- __m128i hi = _mm_or_si128(a, b); 24- // check bytes above 0x7F: compare each u16 < 0x80 25- __m128i thr = _mm_set1_epi16(0x0080); 26- __m128i cmp = _mm_or_si128( 27- _mm_cmpgt_epi16(a, _mm_set1_epi16(0x7F)), 28- _mm_cmpgt_epi16(b, _mm_set1_epi16(0x7F))); 29- (void)hi; (void)thr; 30- if (_mm_testz_si128(cmp, cmp)) { 19+ // ASCII fast path: process 16 code units at a time. 20+ while (i + 16 <= n) { 21+ __m128i a = _mm_loadu_si128((const __m128i *)(in + i)); 22+ __m128i b = _mm_loadu_si128((const __m128i *)(in + i + 8)); 23+ __m128i cmp = _mm_or_si128( 24+ _mm_cmpgt_epi16(a, _mm_set1_epi16(0x7F)), ...

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -8", "intent": "Grade the SSE ASCII fast path version"}

^^^^^^^^^^^^^^^^^^^^ File "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/../../harness/grade.py", line 16, in sh return subprocess.run(cmd, check=True, capture_output=True, text=True, **kw) ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.14/subprocess.py", line 578, in run raise CalledProcessError(retcode, process.args, output=stdout, stderr=stderr) subprocess.CalledProcessError: Command '['cc', '-O2', '-std=c17', '-fno-lto', '-g', '-I', '/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission', '/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c', '/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/verify/reference.c', '/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/verify/verify.c', '-o', '/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/.build/verify', '-lm', '-lpthread']' returned non-zero exit status 1. --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && cc -O2 -std=c17 -fno-lto -g -I submission submission/solve.c verify/reference.c verify/verify.c -o /tmp/v -lm -lpthread 2>&1 | head -20", "intent": "See compile error"}

In file included from /usr/lib/gcc/x86_64-pc-linux-gnu/16/include/immintrin.h:39, from submission/solve.c:9: /usr/lib/gcc/x86_64-pc-linux-gnu/16/include/smmintrin.h: In function ‘utf16_to_utf8’: /usr/lib/gcc/x86_64-pc-linux-gnu/16/include/smmintrin.h:67:1: error: inlining failed in call to ‘always_inline’ ‘_mm_testz_si128’: target specific option mismatch 67 | _mm_testz_si128 (__m128i __M, __m128i __V) | ^~~~~~~~~~~~~~~ submission/solve.c:26:18: note: called from here 26 | if (!_mm_testz_si128(cmp, cmp)) break; | ^~~~~~~~~~~~~~~~~~~~~~~~~ /usr/lib/gcc/x86_64-pc-linux-gnu/16/include/smmintrin.h:67:1: error: inlining failed in call to ‘always_inline’ ‘_mm_testz_si128’: target specific option mismatch 67 | _mm_testz_si128 (__m128i __M, __m128i __V) | ^~~~~~~~~~~~~~~ submission/solve.c:26:18: note: called from here 26 | if (!_mm_testz_si128(cmp, cmp)) break; | ^~~~~~~~~~~~~~~~~~~~~~~~~ --- Command finished with exit code: 0 ---

{"content": "// solve.c \u2014 optimized utf16_to_utf8.\n#include <stdint.h>\n#include <stddef.h>\n#include <string.h>\n\n#define INVALID ((size_t)-1)\n\n#if defined(__x86_64__) || defined(__i386__)\n#pragma GCC target(\"avx2\")\n#include <immintrin.h>\n#define HAVE_AVX2 1\n#endif\n\nsize_t utf16_to_utf8(const uint16_t *in, size_t n, uint8_t *out) {\n size_t o = 0;\n size_t i = 0;\n\n for (;;) {\n#ifdef HAVE_AVX2\n // ASCII fast path: process 16 code units at a time.\n while (i + 16 <= n) {\n __m256i a = _mm256_loadu_si256((const __m256i *)(in + i));\n // any unit >= 0x80?\n __m256i cmp = _mm256_cmpgt_epi16(a, _mm256_set1_epi16(0x7F));\n if (!_mm256_testz_si256(cmp, cmp)) break;\n // pack 16 u16 -> 16 u8. permute to fix lane order.\n __m128i lo = _mm256_castsi256_si128(a);\n __m128i hi = _mm256_extracti128_si256(a, 1);\n __m128i packed = _mm_packus_epi16(lo, hi);\n _mm_storeu_si128((__m128i *)(out + o), packed);\n o += 16;\n i += 16;\n }\n#endif\n if (i >= n) break;\n\n uint32_t c = in[i];\n if (c < 0x80) {\n out[o++] = (uint8_t)c;\n i++;\n } else if (c < 0x800) {\n out[o++] = (uint8_t)(0xC0 | (c >> 6));\n out[o++] = (uint8_t)(0x80 | (c & 0x3F));\n i++;\n } else if (c < 0xD800 || c >= 0xE000) {\n out[o++] = (uint8_t)(0xE0 | (c >> 12));\n out[o++] = (uint8_t)(0x80 | ((c >> 6) & 0x3F));\n out[o++] = (uint8_t)(0x80 | (c & 0x3F));\n i++;\n } else if (c < 0xDC00) {\n if (i + 1 >= n) return INVALID;\n uint32_t lo = in[i + 1];\n if (lo < 0xDC00 || lo >= 0xE000) return INVALID;\n uint32_t cp = 0x10000 + ((c - 0xD800) << 10) + (lo - 0xDC00);\n out[o++] = (uint8_t)(0xF0 | (cp >> 18));\n out[o++] = (uint8_t)(0x80 | ((cp >> 12) & 0x3F));\n out[o++] = (uint8_t)(0x80 | ((cp >> 6) & 0x3F));\n out[o++] = (uint8_t)(0x80 | (cp & 0x3F));\n i += 2;\n } else {\n return INVALID;\n }\n }\n return o;\n}\n", "file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c"}

Updated /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c (65 lines): 9+ #pragma GCC target("avx2") 10- #define HAVE_SSE 1 11+ #define HAVE_AVX2 1 18- #ifdef HAVE_SSE 19+ #ifdef HAVE_AVX2 21- __m128i a = _mm_loadu_si128((const __m128i *)(in + i)); 22- __m128i b = _mm_loadu_si128((const __m128i *)(in + i + 8)); 23- __m128i cmp = _mm_or_si128( 24- _mm_cmpgt_epi16(a, _mm_set1_epi16(0x7F)), 25- _mm_cmpgt_epi16(b, _mm_set1_epi16(0x7F))); 26- if (!_mm_testz_si128(cmp, cmp)) break; 27- __m128i packed = _mm_packus_epi16(a, b); 22+ __m256i a = _mm256_loadu_si256((const __m256i *)(in + i)); 23+ // any unit >= 0x80? 24+ __m256i cmp = _mm256_cmpgt_epi16(a, _mm256_set1_epi16(0x7F)); 25+ if (!_mm256_testz_si256(cmp, cmp)) break; 26+ // pack 16 u16 -> 16 u8. permute to fix lane order. 27+ __m128i lo = _mm256_castsi256_si128(a); 28+ __m128i hi = _mm256_extracti128_si256(a, 1); 29+ __m128i packed = _mm_packus_epi16(lo, hi);

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -6", "intent": "Grade AVX2 ASCII fast path"}

MISMATCH (random) on 21 units: 072f 046c 081b d9ab dc6d 0036 0036 da6d df56 002a ca2a da6c dc69 006a 0075 da61 ddab d94a 0035 003e 0042 grade: FAIL (verification) --- Command finished with exit code: 0 ---

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "old_string": " __m256i a = _mm256_loadu_si256((const __m256i *)(in + i));\n // any unit >= 0x80?\n __m256i cmp = _mm256_cmpgt_epi16(a, _mm256_set1_epi16(0x7F));\n if (!_mm256_testz_si256(cmp, cmp)) break;", "new_string": " __m256i a = _mm256_loadu_si256((const __m256i *)(in + i));\n // any unit >= 0x80? (unit & 0xFF80) != 0 for any lane\n if (!_mm256_testz_si256(a, _mm256_set1_epi16((short)0xFF80))) break;"}

Edited /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c: replaced 1 occurrence(s) 23- // any unit >= 0x80? 24- __m256i cmp = _mm256_cmpgt_epi16(a, _mm256_set1_epi16(0x7F)); 25- if (!_mm256_testz_si256(cmp, cmp)) break; 23+ // any unit >= 0x80? (unit & 0xFF80) != 0 for any lane 24+ if (!_mm256_testz_si256(a, _mm256_set1_epi16((short)0xFF80))) break; Context after edit (lines 19-27): 19│ #ifdef HAVE_AVX2 20│ // ASCII fast path: process 16 code units at a time. 21│ while (i + 16 <= n) { 22│ __m256i a = _mm256_loadu_si256((const __m256i *)(in + i)); 23│ // any unit >= 0x80? (unit & 0xFF80) != 0 for any lane 24│ if (!_mm256_testz_si256(a, _mm256_set1_epi16((short)0xFF80))) break; 25│ // pack 16 u16 -> 16 u8. permute to fix lane order. 26│ __m128i lo = _mm256_castsi256_si128(a); 27│ __m128i hi = _mm256_extracti128_si256(a, 1);

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -6", "intent": "Grade fixed AVX2 ASCII path"}

build 1.6s verify 2.4s PASS measure 6.7s 76,733,460 instructions (given: 77,975,443) SCORE +0.0232 (1.016x) --- Command finished with exit code: 0 ---

{"command": "cd /tmp && pip download simdutf 2>/dev/null | tail -2; echo \"---try git---\"; git clone --depth 1 https://github.com/simdutf/simdutf 2>&1 | tail -3", "intent": "Get simdutf source for reference tables"}

---try git--- Cloning into 'simdutf'... --- Command finished with exit code: 0 ---

{"command": "cd /tmp && ls simdutf 2>/dev/null && find simdutf -path '*westmere*utf16_to_utf8*' 2>/dev/null | head; echo \"---\"; find simdutf -name '*.cpp' -path '*sse*' 2>/dev/null | grep -i utf16 | head", "intent": "Check simdutf clone contents"}

AI_USAGE_POLICY.md AUTHORS CMakeLists.txt CONTRIBUTING.md CONTRIBUTORS Doxyfile LICENSE-APACHE LICENSE-MIT Makefile.crosscompile README-RVV.md README.md SECURITY.md benchmarks cmake doc doxygen.py fuzz include man riscv scripts simdutf.pc.in singleheader site src tests tools simdutf/src/westmere/sse_convert_utf16_to_utf8.cpp --- simdutf/src/westmere/sse_convert_latin1_to_utf16.cpp simdutf/src/westmere/sse_convert_utf16_to_latin1.cpp simdutf/src/westmere/sse_convert_utf16_to_utf32.cpp simdutf/src/westmere/sse_convert_utf16_to_utf8.cpp simdutf/src/westmere/sse_convert_utf32_to_utf16.cpp simdutf/src/westmere/sse_convert_utf8_to_utf16.cpp simdutf/src/westmere/sse_utf16fix.cpp simdutf/src/westmere/sse_validate_utf16.cpp --- Command finished with exit code: 0 ---

{"command": "cd /tmp/simdutf && wc -l src/westmere/sse_convert_utf16_to_utf8.cpp && sed -n '1,120p' src/westmere/sse_convert_utf16_to_utf8.cpp", "intent": "Read simdutf SSE utf16->utf8"}

504 src/westmere/sse_convert_utf16_to_utf8.cpp /* The vectorized algorithm works on single SSE register i.e., it loads eight 16-bit code units. We consider three cases: 1. an input register contains no surrogates and each value is in range 0x0000 .. 0x07ff. 2. an input register contains no surrogates and values are is in range 0x0000 .. 0xffff. 3. an input register contains surrogates --- i.e. codepoints can have 16 or 32 bits. Ad 1. When values are less than 0x0800, it means that a 16-bit code unit can be converted into: 1) single UTF8 byte (when it is an ASCII char) or 2) two UTF8 bytes. For this case we do only some shuffle to obtain these 2-byte codes and finally compress the whole SSE register with a single shuffle. We need 256-entry lookup table to get a compression pattern and the number of output bytes in the compressed vector register. Each entry occupies 17 bytes. Ad 2. When values fit in 16-bit code units, but are above 0x07ff, then a single word may produce one, two or three UTF8 bytes. We prepare data for all these three cases in two registers. The first register contains lower two UTF8 bytes (used in all cases), while the second one contains just the third byte for the three-UTF8-bytes case. Finally these two registers are interleaved forming eight-element array of 32-bit values. The array spans two SSE registers. The bytes from the registers are compressed using two shuffles. We need 256-entry lookup table to get a compression pattern and the number of output bytes in the compressed vector register. Each entry occupies 17 bytes. To summarize: - We need two 256-entry tables that have 8704 bytes in total. */ /* Returns a pair: the first unprocessed byte from buf and utf8_output A scalar routing should carry on the conversion of the tail. */ template <endianness big_endian> std::pair<const char16_t *, char *> sse_convert_utf16_to_utf8(const char16_t *buf, size_t len, char *utf8_output) { const char16_t *end = buf + len; const __m128i v_0000 = _mm_setzero_si128(); const __m128i v_f800 = _mm_set1_epi16((int16_t)0xf800); const __m128i v_d800 = _mm_set1_epi16((int16_t)0xd800); const size_t safety_margin = 12; // to avoid overruns, see issue // https://github.com/simdutf/simdutf/issues/92 while (end - buf >= std::ptrdiff_t(16 + safety_margin)) { __m128i in = _mm_loadu_si128((__m128i *)buf); if (big_endian) { const __m128i swap = _mm_setr_epi8(1, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14); in = _mm_shuffle_epi8(in, swap); } // a single 16-bit UTF-16 word can yield 1, 2 or 3 UTF-8 bytes const __m128i v_ff80 = _mm_set1_epi16((int16_t)0xff80); if (_mm_testz_si128(in, v_ff80)) { // ASCII fast path!!!! __m128i nextin = _mm_loadu_si128((__m128i *)buf + 1); if (big_endian) { const __m128i swap = _mm_setr_epi8(1, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14); nextin = _mm_shuffle_epi8(nextin, swap); } if (!_mm_testz_si128(nextin, v_ff80)) { // 1. pack the bytes // obviously suboptimal. const __m128i utf8_packed = _mm_packus_epi16(in, in); // 2. store (16 bytes) _mm_storeu_si128((__m128i *)utf8_output, utf8_packed); // 3. adjust pointers buf += 8; utf8_output += 8; in = nextin; } else { // 1. pack the bytes // obviously suboptimal. const __m128i utf8_packed = _mm_packus_epi16(in, nextin); // 2. store (16 bytes) _mm_storeu_si128((__m128i *)utf8_output, utf8_packed); // 3. adjust pointers buf += 16; utf8_output += 16; continue; // we are done for this round! } } // no bits set above 7th bit const __m128i one_byte_bytemask = _mm_cmpeq_epi16(_mm_and_si128(in, v_ff80), v_0000); const uint16_t one_byte_bitmask = static_cast<uint16_t>(_mm_movemask_epi8(one_byte_bytemask)); // no bits set above 11th bit const __m128i one_or_two_bytes_bytemask = _mm_cmpeq_epi16(_mm_and_si128(in, v_f800), v_0000); const uint16_t one_or_two_bytes_bitmask = static_cast<uint16_t>(_mm_movemask_epi8(one_or_two_bytes_bytemask)); if (one_or_two_bytes_bitmask == 0xffff) { internal::westmere::write_v_u16_11bits_to_utf8( in, utf8_output, one_byte_bytemask, one_byte_bitmask); --- Command finished with exit code: 0 ---

{"command": "cd /tmp/simdutf && sed -n '120,290p' src/westmere/sse_convert_utf16_to_utf8.cpp", "intent": "Read rest of SSE algorithm"}

in, utf8_output, one_byte_bytemask, one_byte_bitmask); buf += 8; continue; } // 1. Check if there are any surrogate word in the input chunk. // We have also deal with situation when there is a surrogate word // at the end of a chunk. const __m128i surrogates_bytemask = _mm_cmpeq_epi16(_mm_and_si128(in, v_f800), v_d800); // bitmask = 0x0000 if there are no surrogates // = 0xc000 if the last word is a surrogate const uint16_t surrogates_bitmask = static_cast<uint16_t>(_mm_movemask_epi8(surrogates_bytemask)); // It might seem like checking for surrogates_bitmask == 0xc000 could help. // However, it is likely an uncommon occurrence. if (surrogates_bitmask == 0x0000) { // case: code units from register produce either 1, 2 or 3 UTF-8 bytes const __m128i dup_even = _mm_setr_epi16(0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e); /* In this branch we handle three cases: 1. [0000|0000|0ccc|cccc] => [0ccc|cccc] - single UFT-8 byte 2. [0000|0bbb|bbcc|cccc] => [110b|bbbb], [10cc|cccc] - two UTF-8 bytes 3. [aaaa|bbbb|bbcc|cccc] => [1110|aaaa], [10bb|bbbb], [10cc|cccc] - three UTF-8 bytes We expand the input word (16-bit) into two code units (32-bit), thus we have room for four bytes. However, we need five distinct bit layouts. Note that the last byte in cases #2 and #3 is the same. We precompute byte 1 for case #1 and the common byte for cases #2 & #3 in register t2. We precompute byte 1 for case #3 and -- **conditionally** -- precompute either byte 1 for case #2 or byte 2 for case #3. Note that they differ by exactly one bit. Finally from these two code units we build proper UTF-8 sequence, taking into account the case (i.e, the number of bytes to write). */ /** * Given [aaaa|bbbb|bbcc|cccc] our goal is to produce: * t2 => [0ccc|cccc] [10cc|cccc] * s4 => [1110|aaaa] ([110b|bbbb] OR [10bb|bbbb]) */ #define simdutf_vec(x) _mm_set1_epi16(static_cast<uint16_t>(x)) // [aaaa|bbbb|bbcc|cccc] => [bbcc|cccc|bbcc|cccc] const __m128i t0 = _mm_shuffle_epi8(in, dup_even); // [bbcc|cccc|bbcc|cccc] => [00cc|cccc|0bcc|cccc] const __m128i t1 = _mm_and_si128(t0, simdutf_vec(0b0011111101111111)); // [00cc|cccc|0bcc|cccc] => [10cc|cccc|0bcc|cccc] const __m128i t2 = _mm_or_si128(t1, simdutf_vec(0b1000000000000000)); // [aaaa|bbbb|bbcc|cccc] => [0000|aaaa|bbbb|bbcc] const __m128i s0 = _mm_srli_epi16(in, 4); // [0000|aaaa|bbbb|bbcc] => [0000|aaaa|bbbb|bb00] const __m128i s1 = _mm_and_si128(s0, simdutf_vec(0b0000111111111100)); // [0000|aaaa|bbbb|bb00] => [00bb|bbbb|0000|aaaa] const __m128i s2 = _mm_maddubs_epi16(s1, simdutf_vec(0x0140)); // [00bb|bbbb|0000|aaaa] => [11bb|bbbb|1110|aaaa] const __m128i s3 = _mm_or_si128(s2, simdutf_vec(0b1100000011100000)); const __m128i m0 = _mm_andnot_si128(one_or_two_bytes_bytemask, simdutf_vec(0b0100000000000000)); const __m128i s4 = _mm_xor_si128(s3, m0); #undef simdutf_vec // 4. expand code units 16-bit => 32-bit const __m128i out0 = _mm_unpacklo_epi16(t2, s4); const __m128i out1 = _mm_unpackhi_epi16(t2, s4); // 5. compress 32-bit code units into 1, 2 or 3 bytes -- 2 x shuffle const uint16_t mask = (one_byte_bitmask & 0x5555) | (one_or_two_bytes_bitmask & 0xaaaa); if (mask == 0) { // We only have three-byte code units. Use fast path. const __m128i shuffle = _mm_setr_epi8(2, 3, 1, 6, 7, 5, 10, 11, 9, 14, 15, 13, -1, -1, -1, -1); const __m128i utf8_0 = _mm_shuffle_epi8(out0, shuffle); const __m128i utf8_1 = _mm_shuffle_epi8(out1, shuffle); _mm_storeu_si128((__m128i *)utf8_output, utf8_0); utf8_output += 12; _mm_storeu_si128((__m128i *)utf8_output, utf8_1); utf8_output += 12; buf += 8; continue; } const uint8_t mask0 = uint8_t(mask); const uint8_t *row0 = &simdutf::tables::utf16_to_utf8::pack_1_2_3_utf8_bytes[mask0][0]; const __m128i shuffle0 = _mm_loadu_si128((__m128i *)(row0 + 1)); const __m128i utf8_0 = _mm_shuffle_epi8(out0, shuffle0); const uint8_t mask1 = static_cast<uint8_t>(mask >> 8); const uint8_t *row1 = &simdutf::tables::utf16_to_utf8::pack_1_2_3_utf8_bytes[mask1][0]; const __m128i shuffle1 = _mm_loadu_si128((__m128i *)(row1 + 1)); const __m128i utf8_1 = _mm_shuffle_epi8(out1, shuffle1); _mm_storeu_si128((__m128i *)utf8_output, utf8_0); utf8_output += row0[0]; _mm_storeu_si128((__m128i *)utf8_output, utf8_1); utf8_output += row1[0]; buf += 8; // surrogate pair(s) in a register } else { // Let us do a scalar fallback. // It may seem wasteful to use scalar code, but being efficient with SIMD // in the presence of surrogate pairs may require non-trivial tables. size_t forward = 15; size_t k = 0; if (size_t(end - buf) < forward + 1) { forward = size_t(end - buf - 1); } for (; k < forward; k++) { uint16_t word = scalar::utf16::swap_if_needed<big_endian>(buf[k]); if ((word & 0xFF80) == 0) { *utf8_output++ = char(word); } else if ((word & 0xF800) == 0) { *utf8_output++ = char((word >> 6) | 0b11000000); *utf8_output++ = char((word & 0b111111) | 0b10000000); } else if ((word & 0xF800) != 0xD800) { *utf8_output++ = char((word >> 12) | 0b11100000); *utf8_output++ = char(((word >> 6) & 0b111111) | 0b10000000); *utf8_output++ = char((word & 0b111111) | 0b10000000); } else { // must be a surrogate pair uint16_t diff = uint16_t(word - 0xD800); uint16_t next_word = scalar::utf16::swap_if_needed<big_endian>(buf[k + 1]); k++; uint16_t diff2 = uint16_t(next_word - 0xDC00); if ((diff | diff2) > 0x3FF) { return std::make_pair(nullptr, utf8_output); } uint32_t value = (diff << 10) + diff2 + 0x10000; *utf8_output++ = char((value >> 18) | 0b11110000); *utf8_output++ = char(((value >> 12) & 0b111111) | 0b10000000); *utf8_output++ = char(((value >> 6) & 0b111111) | 0b10000000); *utf8_output++ = char((value & 0b111111) | 0b10000000); } } buf += k; } } // while return std::make_pair(buf, utf8_output); } /* Returns a pair: a result struct and utf8_output. If there is an error, the count field of the result is the position of the error. Otherwise, it is the position of the first unprocessed byte in buf (even if finished). A scalar routing should carry on the conversion of the tail if needed. */ template <endianness big_endian> std::pair<result, char *> sse_convert_utf16_to_utf8_with_errors(const char16_t *buf, size_t len, char *utf8_output) { const char16_t *start = buf; const char16_t *end = buf + len; const __m128i v_0000 = _mm_setzero_si128(); const __m128i v_f800 = _mm_set1_epi16((int16_t)0xf800); --- Command finished with exit code: 0 ---

{"command": "cd /tmp/simdutf && grep -rl \"pack_1_2_3_utf8_bytes\" src/ include/ | head; echo \"---\"; grep -rl \"write_v_u16_11bits_to_utf8\" src/ | head", "intent": "Locate tables and writer"}

src/arm64/arm_convert_utf16_to_utf8.cpp src/arm64/arm_convert_utf32_to_utf8.cpp src/haswell/avx2_convert_utf16_to_utf8.cpp src/haswell/avx2_convert_utf32_to_utf8.cpp src/icelake/icelake_convert_utf32_to_utf8.inl.cpp src/lasx/lasx_convert_utf16_to_utf8.cpp src/lasx/lasx_convert_utf32_to_utf8.cpp src/lsx/lsx_convert_utf16_to_utf8.cpp src/lsx/lsx_convert_utf32_to_utf8.cpp src/ppc64/ppc64_convert_utf16_to_utf8.cpp --- src/ppc64/ppc64_convert_latin1_to_utf8.cpp src/ppc64/ppc64_convert_utf16_to_utf8.cpp src/ppc64/ppc64_convert_utf32_to_utf8.cpp src/ppc64/ppc64_write_to_utf8.cpp src/westmere/internal/loader.cpp src/westmere/internal/write_v_u16_11bits_to_utf8.cpp src/westmere/sse_convert_latin1_to_utf8.cpp src/westmere/sse_convert_utf16_to_utf8.cpp --- Command finished with exit code: 0 ---

{"command": "cd /tmp/simdutf && cat src/westmere/internal/write_v_u16_11bits_to_utf8.cpp; echo \"=== TABLES loc ===\"; grep -rln \"pack_1_2_utf8_bytes\\|pack_1_2_3_utf8_bytes\" src/tables include 2>/dev/null; find . -name '*.cpp' -path '*tables*' | head", "intent": "Read 11-bit writer and find tables file"}

/* * reads a vector of uint16 values * bits after 11th are ignored * first 11 bits are encoded into utf8 * !important! utf8_output must have at least 16 writable bytes */ inline void write_v_u16_11bits_to_utf8(const __m128i v_u16, char *&utf8_output, const __m128i one_byte_bytemask, const uint16_t one_byte_bitmask) { // 0b1100_0000_1000_0000 const __m128i v_c080 = _mm_set1_epi16((int16_t)0xc080); // 0b0001_1111_0000_0000 const __m128i v_1f00 = _mm_set1_epi16((int16_t)0x1f00); // 0b0000_0000_0011_1111 const __m128i v_003f = _mm_set1_epi16((int16_t)0x003f); // 1. prepare 2-byte values // input 16-bit word : [0000|0aaa|aabb|bbbb] x 8 // expected output : [110a|aaaa|10bb|bbbb] x 8 // t0 = [000a|aaaa|bbbb|bb00] const __m128i t0 = _mm_slli_epi16(v_u16, 2); // t1 = [000a|aaaa|0000|0000] const __m128i t1 = _mm_and_si128(t0, v_1f00); // t2 = [0000|0000|00bb|bbbb] const __m128i t2 = _mm_and_si128(v_u16, v_003f); // t3 = [000a|aaaa|00bb|bbbb] const __m128i t3 = _mm_or_si128(t1, t2); // t4 = [110a|aaaa|10bb|bbbb] const __m128i t4 = _mm_or_si128(t3, v_c080); // 2. merge ASCII and 2-byte codewords const __m128i utf8_unpacked = _mm_blendv_epi8(t4, v_u16, one_byte_bytemask); // 3. prepare bitmask for 8-bit lookup // one_byte_bitmask = hhggffeeddccbbaa -- the bits are doubled (h - MSB, a // - LSB) const uint16_t m0 = one_byte_bitmask & 0x5555; // m0 = 0h0g0f0e0d0c0b0a const uint16_t m1 = static_cast<uint16_t>(m0 >> 7); // m1 = 00000000h0g0f0e0 const uint8_t m2 = static_cast<uint8_t>((m0 | m1) & 0xff); // m2 = hdgcfbea // 4. pack the bytes const uint8_t *row = &simdutf::tables::utf16_to_utf8::pack_1_2_utf8_bytes[m2][0]; const __m128i shuffle = _mm_loadu_si128((__m128i *)(row + 1)); const __m128i utf8_packed = _mm_shuffle_epi8(utf8_unpacked, shuffle); // 5. store bytes _mm_storeu_si128((__m128i *)utf8_output, utf8_packed); // 6. adjust pointers utf8_output += row[0]; } inline void write_v_u16_11bits_to_utf8(const __m128i v_u16, char *&utf8_output, const __m128i v_0000, const __m128i v_ff80) { // no bits set above 7th bit const __m128i one_byte_bytemask = _mm_cmpeq_epi16(_mm_and_si128(v_u16, v_ff80), v_0000); const uint16_t one_byte_bitmask = static_cast<uint16_t>(_mm_movemask_epi8(one_byte_bytemask)); write_v_u16_11bits_to_utf8(v_u16, utf8_output, one_byte_bytemask, one_byte_bitmask); } === TABLES loc === src/tables/utf16_to_utf8_tables.h --- Command finished with exit code: 0 ---

{"command": "cd /tmp/simdutf && head -40 src/tables/utf16_to_utf8_tables.h && echo \"...\" && wc -l src/tables/utf16_to_utf8_tables.h && grep -n \"pack_1_2_utf8_bytes\\|pack_1_2_3_utf8_bytes\\|};\" src/tables/utf16_to_utf8_tables.h | head", "intent": "Inspect tables file structure"}

// file generated by scripts/sse_convert_utf16_to_utf8.py #ifndef SIMDUTF_UTF16_TO_UTF8_TABLES_H #define SIMDUTF_UTF16_TO_UTF8_TABLES_H namespace simdutf { namespace { namespace tables { namespace utf16_to_utf8 { // 1 byte for length, 16 bytes for mask const uint8_t pack_1_2_utf8_bytes[256][17] = { {16, 1, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14}, {15, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14, 0x80}, {15, 1, 0, 3, 2, 5, 4, 7, 6, 8, 11, 10, 13, 12, 15, 14, 0x80}, {14, 0, 3, 2, 5, 4, 7, 6, 8, 11, 10, 13, 12, 15, 14, 0x80, 0x80}, {15, 1, 0, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14, 0x80}, {14, 0, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14, 0x80, 0x80}, {14, 1, 0, 2, 5, 4, 7, 6, 8, 11, 10, 13, 12, 15, 14, 0x80, 0x80}, {13, 0, 2, 5, 4, 7, 6, 8, 11, 10, 13, 12, 15, 14, 0x80, 0x80, 0x80}, {15, 1, 0, 3, 2, 5, 4, 7, 6, 9, 8, 10, 13, 12, 15, 14, 0x80}, {14, 0, 3, 2, 5, 4, 7, 6, 9, 8, 10, 13, 12, 15, 14, 0x80, 0x80}, {14, 1, 0, 3, 2, 5, 4, 7, 6, 8, 10, 13, 12, 15, 14, 0x80, 0x80}, {13, 0, 3, 2, 5, 4, 7, 6, 8, 10, 13, 12, 15, 14, 0x80, 0x80, 0x80}, {14, 1, 0, 2, 5, 4, 7, 6, 9, 8, 10, 13, 12, 15, 14, 0x80, 0x80}, {13, 0, 2, 5, 4, 7, 6, 9, 8, 10, 13, 12, 15, 14, 0x80, 0x80, 0x80}, {13, 1, 0, 2, 5, 4, 7, 6, 8, 10, 13, 12, 15, 14, 0x80, 0x80, 0x80}, {12, 0, 2, 5, 4, 7, 6, 8, 10, 13, 12, 15, 14, 0x80, 0x80, 0x80, 0x80}, {15, 1, 0, 3, 2, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14, 0x80}, {14, 0, 3, 2, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14, 0x80, 0x80}, {14, 1, 0, 3, 2, 4, 7, 6, 8, 11, 10, 13, 12, 15, 14, 0x80, 0x80}, {13, 0, 3, 2, 4, 7, 6, 8, 11, 10, 13, 12, 15, 14, 0x80, 0x80, 0x80}, {14, 1, 0, 2, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14, 0x80, 0x80}, {13, 0, 2, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14, 0x80, 0x80, 0x80}, {13, 1, 0, 2, 4, 7, 6, 8, 11, 10, 13, 12, 15, 14, 0x80, 0x80, 0x80}, {12, 0, 2, 4, 7, 6, 8, 11, 10, 13, 12, 15, 14, 0x80, 0x80, 0x80, 0x80}, {14, 1, 0, 3, 2, 4, 7, 6, 9, 8, 10, 13, 12, 15, 14, 0x80, 0x80}, {13, 0, 3, 2, 4, 7, 6, 9, 8, 10, 13, 12, 15, 14, 0x80, 0x80, 0x80}, {13, 1, 0, 3, 2, 4, 7, 6, 8, 10, 13, 12, 15, 14, 0x80, 0x80, 0x80}, {12, 0, 3, 2, 4, 7, 6, 8, 10, 13, 12, 15, 14, 0x80, 0x80, 0x80, 0x80}, {13, 1, 0, 2, 4, 7, 6, 9, 8, 10, 13, 12, 15, 14, 0x80, 0x80, 0x80}, ... 768 src/tables/utf16_to_utf8_tables.h 11:const uint8_t pack_1_2_utf8_bytes[256][17] = { 271: 0x80}}; 274:const uint8_t pack_1_2_3_utf8_bytes[256][17] = { 761: 0x80, 0x80}}; --- Command finished with exit code: 0 ---

{"command": "cd /tmp/simdutf && SUB=/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission && {\necho '// Tables from simdutf (Apache-2.0/MIT), scripts/sse_convert_utf16_to_utf8.py';\necho '#ifndef UTF16_TABLES_H';\necho '#define UTF16_TABLES_H';\necho '#include <stdint.h>';\nsed -n '11,271p' src/tables/utf16_to_utf8_tables.h | sed 's/^const uint8_t/static const uint8_t/';\necho;\nsed -n '274,761p' src/tables/utf16_to_utf8_tables.h | sed 's/^const uint8_t/static const uint8_t/';\necho '#endif';\n} > $SUB/tables.h\nwc -l $SUB/tables.h; head -12 $SUB/tables.h; tail -5 $SUB/tables.h", "intent": "Write tables.h into submission"}

755 /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/tables.h // Tables from simdutf (Apache-2.0/MIT), scripts/sse_convert_utf16_to_utf8.py #ifndef UTF16_TABLES_H #define UTF16_TABLES_H #include <stdint.h> static const uint8_t pack_1_2_utf8_bytes[256][17] = { {16, 1, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14}, {15, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14, 0x80}, {15, 1, 0, 3, 2, 5, 4, 7, 6, 8, 11, 10, 13, 12, 15, 14, 0x80}, {14, 0, 3, 2, 5, 4, 7, 6, 8, 11, 10, 13, 12, 15, 14, 0x80, 0x80}, {15, 1, 0, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14, 0x80}, {14, 0, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14, 0x80, 0x80}, {14, 1, 0, 2, 5, 4, 7, 6, 8, 11, 10, 13, 12, 15, 14, 0x80, 0x80}, {5, 3, 1, 4, 8, 12, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80}, {4, 0, 4, 8, 12, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80}}; #endif --- Command finished with exit code: 0 ---

{"content": "// solve.c \u2014 optimized utf16_to_utf8 using SSE (westmere-style vectorization).\n// Algorithm adapted from simdutf (Apache-2.0 / MIT).\n#include <stdint.h>\n#include <stddef.h>\n#include <string.h>\n\n#define INVALID ((size_t)-1)\n\n#if defined(__x86_64__) || defined(__i386__)\n#pragma GCC target(\"sse4.1\")\n#include <immintrin.h>\n#include \"tables.h\"\n#define HAVE_SSE 1\n#endif\n\n// Scalar tail conversion. Returns bytes written, or SIZE_MAX on invalid.\nstatic inline size_t scalar_tail(const uint16_t *in, size_t n, uint8_t *out) {\n size_t o = 0;\n for (size_t i = 0; i < n; i++) {\n uint32_t c = in[i];\n if (c < 0x80) {\n out[o++] = (uint8_t)c;\n } else if (c < 0x800) {\n out[o++] = (uint8_t)(0xC0 | (c >> 6));\n out[o++] = (uint8_t)(0x80 | (c & 0x3F));\n } else if (c < 0xD800 || c >= 0xE000) {\n out[o++] = (uint8_t)(0xE0 | (c >> 12));\n out[o++] = (uint8_t)(0x80 | ((c >> 6) & 0x3F));\n out[o++] = (uint8_t)(0x80 | (c & 0x3F));\n } else if (c < 0xDC00) {\n if (i + 1 >= n) return INVALID;\n uint32_t lo = in[i + 1];\n if (lo < 0xDC00 || lo >= 0xE000) return INVALID;\n i++;\n uint32_t cp = 0x10000 + ((c - 0xD800) << 10) + (lo - 0xDC00);\n out[o++] = (uint8_t)(0xF0 | (cp >> 18));\n out[o++] = (uint8_t)(0x80 | ((cp >> 12) & 0x3F));\n out[o++] = (uint8_t)(0x80 | ((cp >> 6) & 0x3F));\n out[o++] = (uint8_t)(0x80 | (cp & 0x3F));\n } else {\n return INVALID;\n }\n }\n return o;\n}\n\nsize_t utf16_to_utf8(const uint16_t *in, size_t n, uint8_t *out) {\n#ifdef HAVE_SSE\n const uint16_t *buf = in;\n const uint16_t *end = in + n;\n uint8_t *op = out;\n\n const __m128i v_0000 = _mm_setzero_si128();\n const __m128i v_f800 = _mm_set1_epi16((int16_t)0xf800);\n const __m128i v_d800 = _mm_set1_epi16((int16_t)0xd800);\n const __m128i v_ff80 = _mm_set1_epi16((int16_t)0xff80);\n const size_t safety_margin = 12;\n\n while ((size_t)(end - buf) >= 16 + safety_margin) {\n __m128i inv = _mm_loadu_si128((const __m128i *)buf);\n\n if (_mm_testz_si128(inv, v_ff80)) { // ASCII fast path\n __m128i nextin = _mm_loadu_si128((const __m128i *)buf + 1);\n if (!_mm_testz_si128(nextin, v_ff80)) {\n __m128i packed = _mm_packus_epi16(inv, inv);\n _mm_storel_epi64((__m128i *)op, packed);\n buf += 8;\n op += 8;\n inv = nextin;\n } else {\n __m128i packed = _mm_packus_epi16(inv, nextin);\n _mm_storeu_si128((__m128i *)op, packed);\n buf += 16;\n op += 16;\n continue;\n }\n }\n\n // no bits set above 7th bit (1-byte)\n const __m128i one_byte_bytemask =\n _mm_cmpeq_epi16(_mm_and_si128(inv, v_ff80), v_0000);\n const uint16_t one_byte_bitmask =\n (uint16_t)_mm_movemask_epi8(one_byte_bytemask);\n\n // no bits set above 11th bit (1-or-2-byte)\n const __m128i one_or_two_bytes_bytemask =\n _mm_cmpeq_epi16(_mm_and_si128(inv, v_f800), v_0000);\n const uint16_t one_or_two_bytes_bitmask =\n (uint16_t)_mm_movemask_epi8(one_or_two_bytes_bytemask);\n\n if (one_or_two_bytes_bitmask == 0xffff) {\n // write_v_u16_11bits_to_utf8\n const __m128i v_c080 = _mm_set1_epi16((int16_t)0xc080);\n const __m128i v_1f00 = _mm_set1_epi16((int16_t)0x1f00);\n const __m128i v_003f = _mm_set1_epi16((int16_t)0x003f);\n const __m128i t0 = _mm_slli_epi16(inv, 2);\n const __m128i t1 = _mm_and_si128(t0, v_1f00);\n const __m128i t2 = _mm_and_si128(inv, v_003f);\n const __m128i t3 = _mm_or_si128(t1, t2);\n const __m128i t4 = _mm_or_si128 ... [5690 characters truncated for page size]

Updated /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c (220 lines): 1- // solve.c — optimized utf16_to_utf8. 1+ // solve.c — optimized utf16_to_utf8 using SSE (westmere-style vectorization). 2+ // Algorithm adapted from simdutf (Apache-2.0 / MIT). 9- #pragma GCC target("avx2") 10+ #pragma GCC target("sse4.1") 11- #define HAVE_AVX2 1 12+ #include "tables.h" 13+ #define HAVE_SSE 1 14- size_t utf16_to_utf8(const uint16_t *in, size_t n, uint8_t *out) { 16+ // Scalar tail conversion. Returns bytes written, or SIZE_MAX on invalid. 17+ static inline size_t scalar_tail(const uint16_t *in, size_t n, uint8_t *out) { 16- size_t i = 0; 18- for (;;) { 19- #ifdef HAVE_AVX2 20- // ASCII fast path: process 16 code units at a time. 21- while (i + 16 <= n) { 22- __m256i a = _mm256_loadu_si256((const __m256i *)(in + i)); 23- // any unit >= 0x80? (unit & 0xFF80) != 0 for any lane 24- if (!_mm256_testz_si256(a, _mm256_set1_epi16((short)0xFF80))) break; 25- // pack 16 u16 -> 16 u8. permute to fix lane order. ...

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -6", "intent": "Grade SSE westmere implementation"}

build 1.8s verify 2.4s PASS measure 1.7s 34,749,442 instructions (given: 77,996,692) SCORE +1.1664 (2.245x) --- Command finished with exit code: 0 ---

{"command": "cd /tmp/simdutf && sed -n '1,140p' src/haswell/avx2_convert_utf16_to_utf8.cpp", "intent": "Read AVX2 version"}

/* The vectorized algorithm works on single SSE register i.e., it loads eight 16-bit code units. We consider three cases: 1. an input register contains no surrogates and each value is in range 0x0000 .. 0x07ff. 2. an input register contains no surrogates and values are is in range 0x0000 .. 0xffff. 3. an input register contains surrogates --- i.e. codepoints can have 16 or 32 bits. Ad 1. When values are less than 0x0800, it means that a 16-bit code unit can be converted into: 1) single UTF8 byte (when it is an ASCII char) or 2) two UTF8 bytes. For this case we do only some shuffle to obtain these 2-byte codes and finally compress the whole SSE register with a single shuffle. We need 256-entry lookup table to get a compression pattern and the number of output bytes in the compressed vector register. Each entry occupies 17 bytes. Ad 2. When values fit in 16-bit code units, but are above 0x07ff, then a single word may produce one, two or three UTF8 bytes. We prepare data for all these three cases in two registers. The first register contains lower two UTF8 bytes (used in all cases), while the second one contains just the third byte for the three-UTF8-bytes case. Finally these two registers are interleaved forming eight-element array of 32-bit values. The array spans two SSE registers. The bytes from the registers are compressed using two shuffles. We need 256-entry lookup table to get a compression pattern and the number of output bytes in the compressed vector register. Each entry occupies 17 bytes. To summarize: - We need two 256-entry tables that have 8704 bytes in total. */ /* Returns a pair: the first unprocessed byte from buf and utf8_output A scalar routing should carry on the conversion of the tail. */ template <endianness big_endian> std::pair<const char16_t *, char *> avx2_convert_utf16_to_utf8(const char16_t *buf, size_t len, char *utf8_output) { const char16_t *end = buf + len; const __m256i v_0000 = _mm256_setzero_si256(); const __m256i v_f800 = _mm256_set1_epi16((int16_t)0xf800); const __m256i v_d800 = _mm256_set1_epi16((int16_t)0xd800); const __m256i v_c080 = _mm256_set1_epi16((int16_t)0xc080); const size_t safety_margin = 12; // to avoid overruns, see issue // https://github.com/simdutf/simdutf/issues/92 while (end - buf >= std::ptrdiff_t(16 + safety_margin)) { __m256i in = _mm256_loadu_si256((__m256i *)buf); if (big_endian) { const __m256i swap = _mm256_setr_epi8( 1, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14, 17, 16, 19, 18, 21, 20, 23, 22, 25, 24, 27, 26, 29, 28, 31, 30); in = _mm256_shuffle_epi8(in, swap); } // a single 16-bit UTF-16 word can yield 1, 2 or 3 UTF-8 bytes const __m256i v_ff80 = _mm256_set1_epi16((int16_t)0xff80); if (_mm256_testz_si256(in, v_ff80)) { // ASCII fast path!!!! // 1. pack the bytes const __m128i utf8_packed = _mm_packus_epi16( _mm256_castsi256_si128(in), _mm256_extractf128_si256(in, 1)); // 2. store (16 bytes) _mm_storeu_si128((__m128i *)utf8_output, utf8_packed); // 3. adjust pointers buf += 16; utf8_output += 16; continue; // we are done for this round! } // no bits set above 7th bit const __m256i one_byte_bytemask = _mm256_cmpeq_epi16(_mm256_and_si256(in, v_ff80), v_0000); const uint32_t one_byte_bitmask = static_cast<uint32_t>(_mm256_movemask_epi8(one_byte_bytemask)); // no bits set above 11th bit const __m256i one_or_two_bytes_bytemask = _mm256_cmpeq_epi16(_mm256_and_si256(in, v_f800), v_0000); const uint32_t one_or_two_bytes_bitmask = static_cast<uint32_t>(_mm256_movemask_epi8(one_or_two_bytes_bytemask)); if (one_or_two_bytes_bitmask == 0xffffffff) { // 1. prepare 2-byte values // input 16-bit word : [0000|0aaa|aabb|bbbb] x 8 // expected output : [110a|aaaa|10bb|bbbb] x 8 const __m256i v_1f00 = _mm256_set1_epi16((int16_t)0x1f00); const __m256i v_003f = _mm256_set1_epi16((int16_t)0x003f); // t0 = [000a|aaaa|bbbb|bb00] const __m256i t0 = _mm256_slli_epi16(in, 2); // t1 = [000a|aaaa|0000|0000] const __m256i t1 = _mm256_and_si256(t0, v_1f00); // t2 = [0000|0000|00bb|bbbb] const __m256i t2 = _mm256_and_si256(in, v_003f); // t3 = [000a|aaaa|00bb|bbbb] const __m256i t3 = _mm256_or_si256(t1, t2); // t4 = [110a|aaaa|10bb|bbbb] const __m256i t4 = _mm256_or_si256(t3, v_c080); // 2. merge ASCII and 2-byte codewords const __m256i utf8_unpacked = _mm256_blendv_epi8(t4, in, one_byte_bytemask); // 3. prepare bitmask for 8-bit lookup const uint32_t M0 = one_byte_bitmask & 0x55555555; const uint32_t M1 = M0 >> 7; const uint32_t M2 = (M1 | M0) & 0x00ff00ff; // 4. pack the bytes const uint8_t *row = &simdutf::tables::utf16_to_utf8::pack_1_2_utf8_bytes[uint8_t(M2)][0]; const uint8_t *row_2 = &simdutf::tables::utf16_to_utf8::pack_1_2_utf8_bytes[uint8_t(M2 >> 16)][0]; const __m128i shuffle = _mm_loadu_si128((__m128i *)(row + 1)); const __m128i shuffle_2 = _mm_loadu_si128((__m128i *)(row_2 + 1)); const __m256i utf8_packed = _mm256_shuffle_epi8( utf8_unpacked, _mm256_setr_m128i(shuffle, shuffle_2)); // 5. store bytes _mm_storeu_si128((__m128i *)utf8_output, _mm256_castsi256_si128(utf8_packed)); --- Command finished with exit code: 0 ---

{"command": "cd /tmp/simdutf && sed -n '140,320p' src/haswell/avx2_convert_utf16_to_utf8.cpp", "intent": "Read rest of AVX2 version"}

_mm256_castsi256_si128(utf8_packed)); utf8_output += row[0]; _mm_storeu_si128((__m128i *)utf8_output, _mm256_extractf128_si256(utf8_packed, 1)); utf8_output += row_2[0]; // 6. adjust pointers buf += 16; continue; } // 1. Check if there are any surrogate word in the input chunk. // We have also deal with situation when there is a surrogate word // at the end of a chunk. const __m256i surrogates_bytemask = _mm256_cmpeq_epi16(_mm256_and_si256(in, v_f800), v_d800); // bitmask = 0x0000 if there are no surrogates // = 0xc000 if the last word is a surrogate const uint32_t surrogates_bitmask = static_cast<uint32_t>(_mm256_movemask_epi8(surrogates_bytemask)); // It might seem like checking for surrogates_bitmask == 0xc000 could help. // However, it is likely an uncommon occurrence. if (surrogates_bitmask == 0x00000000) { // case: code units from register produce either 1, 2 or 3 UTF-8 bytes const __m256i dup_even = _mm256_setr_epi16( 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e, 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e); /* In this branch we handle three cases: 1. [0000|0000|0ccc|cccc] => [0ccc|cccc] - single UFT-8 byte 2. [0000|0bbb|bbcc|cccc] => [110b|bbbb], [10cc|cccc] - two UTF-8 bytes 3. [aaaa|bbbb|bbcc|cccc] => [1110|aaaa], [10bb|bbbb], [10cc|cccc] - three UTF-8 bytes We expand the input word (16-bit) into two code units (32-bit), thus we have room for four bytes. However, we need five distinct bit layouts. Note that the last byte in cases #2 and #3 is the same. We precompute byte 1 for case #1 and the common byte for cases #2 & #3 in register t2. We precompute byte 1 for case #3 and -- **conditionally** -- precompute either byte 1 for case #2 or byte 2 for case #3. Note that they differ by exactly one bit. Finally from these two code units we build proper UTF-8 sequence, taking into account the case (i.e, the number of bytes to write). */ /** * Given [aaaa|bbbb|bbcc|cccc] our goal is to produce: * t2 => [0ccc|cccc] [10cc|cccc] * s4 => [1110|aaaa] ([110b|bbbb] OR [10bb|bbbb]) */ #define simdutf_vec(x) _mm256_set1_epi16(static_cast<uint16_t>(x)) // [aaaa|bbbb|bbcc|cccc] => [bbcc|cccc|bbcc|cccc] const __m256i t0 = _mm256_shuffle_epi8(in, dup_even); // [bbcc|cccc|bbcc|cccc] => [00cc|cccc|0bcc|cccc] const __m256i t1 = _mm256_and_si256(t0, simdutf_vec(0b0011111101111111)); // [00cc|cccc|0bcc|cccc] => [10cc|cccc|0bcc|cccc] const __m256i t2 = _mm256_or_si256(t1, simdutf_vec(0b1000000000000000)); // [aaaa|bbbb|bbcc|cccc] => [0000|aaaa|bbbb|bbcc] const __m256i s0 = _mm256_srli_epi16(in, 4); // [0000|aaaa|bbbb|bbcc] => [0000|aaaa|bbbb|bb00] const __m256i s1 = _mm256_and_si256(s0, simdutf_vec(0b0000111111111100)); // [0000|aaaa|bbbb|bb00] => [00bb|bbbb|0000|aaaa] const __m256i s2 = _mm256_maddubs_epi16(s1, simdutf_vec(0x0140)); // [00bb|bbbb|0000|aaaa] => [11bb|bbbb|1110|aaaa] const __m256i s3 = _mm256_or_si256(s2, simdutf_vec(0b1100000011100000)); const __m256i m0 = _mm256_andnot_si256(one_or_two_bytes_bytemask, simdutf_vec(0b0100000000000000)); const __m256i s4 = _mm256_xor_si256(s3, m0); #undef simdutf_vec // 4. expand code units 16-bit => 32-bit const __m256i out0 = _mm256_unpacklo_epi16(t2, s4); const __m256i out1 = _mm256_unpackhi_epi16(t2, s4); // 5. compress 32-bit code units into 1, 2 or 3 bytes -- 2 x shuffle const uint32_t mask = (one_byte_bitmask & 0x55555555) | (one_or_two_bytes_bitmask & 0xaaaaaaaa); // Due to the wider registers, the following path is less likely to be // useful. /*if(mask == 0) { // We only have three-byte code units. Use fast path. const __m256i shuffle = _mm256_setr_epi8(2,3,1,6,7,5,10,11,9,14,15,13,-1,-1,-1,-1, 2,3,1,6,7,5,10,11,9,14,15,13,-1,-1,-1,-1); const __m256i utf8_0 = _mm256_shuffle_epi8(out0, shuffle); const __m256i utf8_1 = _mm256_shuffle_epi8(out1, shuffle); _mm_storeu_si128((__m128i*)utf8_output, _mm256_castsi256_si128(utf8_0)); utf8_output += 12; _mm_storeu_si128((__m128i*)utf8_output, _mm256_castsi256_si128(utf8_1)); utf8_output += 12; _mm_storeu_si128((__m128i*)utf8_output, _mm256_extractf128_si256(utf8_0,1)); utf8_output += 12; _mm_storeu_si128((__m128i*)utf8_output, _mm256_extractf128_si256(utf8_1,1)); utf8_output += 12; buf += 16; continue; }*/ const uint8_t mask0 = uint8_t(mask); const uint8_t *row0 = &simdutf::tables::utf16_to_utf8::pack_1_2_3_utf8_bytes[mask0][0]; const __m128i shuffle0 = _mm_loadu_si128((__m128i *)(row0 + 1)); const __m128i utf8_0 = _mm_shuffle_epi8(_mm256_castsi256_si128(out0), shuffle0); const uint8_t mask1 = static_cast<uint8_t>(mask >> 8); const uint8_t *row1 = &simdutf::tables::utf16_to_utf8::pack_1_2_3_utf8_bytes[mask1][0]; const __m128i shuffle1 = _mm_loadu_si128((__m128i *)(row1 + 1)); const __m128i utf8_1 = _mm_shuffle_epi8(_mm256_castsi256_si128(out1), shuffle1); const uint8_t mask2 = static_cast<uint8_t>(mask >> 16); const uint8_t *row2 = &simdutf::tables::utf16_to_utf8::pack_1_2_3_utf8_bytes[mask2][0]; const __m128i shuffle2 = _mm_loadu_si128((__m128i *)(row2 + 1)); const __m128i utf8_2 = _mm_shuffle_epi8(_mm256_extractf128_si256(out0, 1), shuffle2); const uint8_t mask3 = static_cast<uint8_t>(mask >> 24); const uint8_t *row3 = &simdutf::tables::utf16_to_utf8::pack_1_2_3_utf8_bytes[mask3][0]; const __m128i shuffle3 = _mm_loadu_si128((__m128i *)(row3 + 1)); const __m128i utf8_3 = _mm_shuffle_epi8(_mm256_extractf128_si256(out1, 1), shuffle3); _mm_storeu_si128((__m128i *)utf8_output, utf8_0); utf8_output += row0[0]; _mm_storeu_si128((__m128i *)utf8_output, utf8_1); utf8_output += row1[0]; _mm_storeu_si128((__m128i *)utf8_output, utf8_2); utf8_output += row2[0]; _mm_storeu_si128((__m128i *)utf8_output, utf8_3); utf8_output += row3[0]; buf += 16; // surrogate pair(s) in a register } else { // Let us do a scalar fallback. // It may seem wasteful to use scalar code, but being efficient with SIMD // in the presence of surrogate pairs may require non-trivial tables. size_t forward = 15; size_t k = 0; if (size_t(end - buf) < forward + 1) { forward = size_t(end - buf - 1); } for (; k < forward; k++) { uint16_t word = scalar::utf16::swap_if_needed<big_endian>(buf[k]); if ((word & 0xFF80) == 0) { *utf8_output++ = char(word); } else if ((word & 0xF800) == 0) { *utf8_output++ = char((word >> 6) | 0b11000000); *utf8_output++ = char((word & 0b111111) | 0b10000000); } else if ((word & 0xF800) != 0xD800) { *utf8_output++ = char((word >> 12) | 0b11100000); *utf8_output++ = char(((word >> 6) & 0b111111) | 0b10000000); *utf8_output++ = char((word & 0b111111) | 0b10000000); } else { // must be a surrogate pair uint16_t diff = uint16_t(word - 0xD800); uint16_t next_word = scalar::utf16::swap_if_needed<big_endian>(buf[k + 1]); k++; uint16_t diff2 = uint16_t(next_word - 0xDC00); if ((diff | diff2) > 0x3FF) { return std::make_pair(nullptr, utf8_output); } uint32_t value = (diff << 10) + diff2 + 0x10000; *utf8_output++ = char((value >> 18) | 0b11110000); *utf8_output++ = char(((value >> 12) & 0b111111) | 0b10000000); *utf8_output++ = char(((value >> 6) & 0b111111) | 0b10000000); *utf8_output++ = char((value & 0b111111) | 0b10000000); } } buf += k; } } // while return std::make_pair(buf, utf8_output); --- Command finished with exit code: 0 ---

{"content": "// solve.c \u2014 optimized utf16_to_utf8 using AVX2 (haswell-style vectorization).\n// Algorithm adapted from simdutf (Apache-2.0 / MIT).\n#include <stdint.h>\n#include <stddef.h>\n#include <string.h>\n\n#define INVALID ((size_t)-1)\n\n#if defined(__x86_64__) || defined(__i386__)\n#pragma GCC target(\"avx2\")\n#include <immintrin.h>\n#include \"tables.h\"\n#define HAVE_AVX2 1\n#endif\n\nstatic inline size_t scalar_tail(const uint16_t *in, size_t n, uint8_t *out) {\n size_t o = 0;\n for (size_t i = 0; i < n; i++) {\n uint32_t c = in[i];\n if (c < 0x80) {\n out[o++] = (uint8_t)c;\n } else if (c < 0x800) {\n out[o++] = (uint8_t)(0xC0 | (c >> 6));\n out[o++] = (uint8_t)(0x80 | (c & 0x3F));\n } else if (c < 0xD800 || c >= 0xE000) {\n out[o++] = (uint8_t)(0xE0 | (c >> 12));\n out[o++] = (uint8_t)(0x80 | ((c >> 6) & 0x3F));\n out[o++] = (uint8_t)(0x80 | (c & 0x3F));\n } else if (c < 0xDC00) {\n if (i + 1 >= n) return INVALID;\n uint32_t lo = in[i + 1];\n if (lo < 0xDC00 || lo >= 0xE000) return INVALID;\n i++;\n uint32_t cp = 0x10000 + ((c - 0xD800) << 10) + (lo - 0xDC00);\n out[o++] = (uint8_t)(0xF0 | (cp >> 18));\n out[o++] = (uint8_t)(0x80 | ((cp >> 12) & 0x3F));\n out[o++] = (uint8_t)(0x80 | ((cp >> 6) & 0x3F));\n out[o++] = (uint8_t)(0x80 | (cp & 0x3F));\n } else {\n return INVALID;\n }\n }\n return o;\n}\n\nsize_t utf16_to_utf8(const uint16_t *in, size_t n, uint8_t *out) {\n#ifdef HAVE_AVX2\n const uint16_t *buf = in;\n const uint16_t *end = in + n;\n uint8_t *op = out;\n\n const __m256i v_0000 = _mm256_setzero_si256();\n const __m256i v_f800 = _mm256_set1_epi16((int16_t)0xf800);\n const __m256i v_d800 = _mm256_set1_epi16((int16_t)0xd800);\n const __m256i v_c080 = _mm256_set1_epi16((int16_t)0xc080);\n const __m256i v_ff80 = _mm256_set1_epi16((int16_t)0xff80);\n const size_t safety_margin = 12;\n\n while ((size_t)(end - buf) >= 16 + safety_margin) {\n __m256i inv = _mm256_loadu_si256((const __m256i *)buf);\n\n if (_mm256_testz_si256(inv, v_ff80)) { // ASCII fast path\n const __m128i packed = _mm_packus_epi16(\n _mm256_castsi256_si128(inv), _mm256_extractf128_si256(inv, 1));\n _mm_storeu_si128((__m128i *)op, packed);\n buf += 16;\n op += 16;\n continue;\n }\n\n const __m256i one_byte_bytemask =\n _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_ff80), v_0000);\n const uint32_t one_byte_bitmask =\n (uint32_t)_mm256_movemask_epi8(one_byte_bytemask);\n\n const __m256i one_or_two_bytes_bytemask =\n _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_0000);\n const uint32_t one_or_two_bytes_bitmask =\n (uint32_t)_mm256_movemask_epi8(one_or_two_bytes_bytemask);\n\n if (one_or_two_bytes_bitmask == 0xffffffff) {\n const __m256i v_1f00 = _mm256_set1_epi16((int16_t)0x1f00);\n const __m256i v_003f = _mm256_set1_epi16((int16_t)0x003f);\n const __m256i t0 = _mm256_slli_epi16(inv, 2);\n const __m256i t1 = _mm256_and_si256(t0, v_1f00);\n const __m256i t2 = _mm256_and_si256(inv, v_003f);\n const __m256i t3 = _mm256_or_si256(t1, t2);\n const __m256i t4 = _mm256_or_si256(t3, v_c080);\n const __m256i utf8_unpacked =\n _mm256_blendv_epi8(t4, inv, one_byte_bytemask);\n const uint32_t M0 = one_byte_bitmask & 0x55555555;\n const uint32_t M1 = M0 >> 7;\n const uint32_t M2 = (M1 | M0) & 0x00ff00ff;\n const uint8_t *row = &pack_1_2_utf8_bytes[(uint8_t)M2][0];\n const uint8_t *row_2 = &pack_1_2_utf8_bytes[(uint8_t)(M2 >> 16)][0];\n const __m128i shuffle = ... [5935 characters truncated for page size]

Updated /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c (220 lines): 1- // solve.c — optimized utf16_to_utf8 using SSE (westmere-style vectorization). 1+ // solve.c — optimized utf16_to_utf8 using AVX2 (haswell-style vectorization). 10- #pragma GCC target("sse4.1") 10+ #pragma GCC target("avx2") 13- #define HAVE_SSE 1 13+ #define HAVE_AVX2 1 16- // Scalar tail conversion. Returns bytes written, or SIZE_MAX on invalid. 48- #ifdef HAVE_SSE 47+ #ifdef HAVE_AVX2 53- const __m128i v_0000 = _mm_setzero_si128(); 54- const __m128i v_f800 = _mm_set1_epi16((int16_t)0xf800); 55- const __m128i v_d800 = _mm_set1_epi16((int16_t)0xd800); 56- const __m128i v_ff80 = _mm_set1_epi16((int16_t)0xff80); 52+ const __m256i v_0000 = _mm256_setzero_si256(); 53+ const __m256i v_f800 = _mm256_set1_epi16((int16_t)0xf800); 54+ const __m256i v_d800 = _mm256_set1_epi16((int16_t)0xd800); 55+ const __m256i v_c080 = _mm256_set1_epi16((int16_t)0xc080); 56+ const __m256i v_ff80 = _mm256_set1_epi16((int16_t)0xff80); 60- __m128i inv = _mm_loadu_si128((const __m128i *)buf); 60+ __m256i inv = _mm256_loadu_si256((const __m256i *)buf); ...

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -6", "intent": "Grade AVX2 version"}

build 1.9s verify 2.4s PASS measure 1.8s 28,505,804 instructions (given: 77,883,059) SCORE +1.4501 (2.732x) --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && for R in ascii latin cjk emoji; do\npython3 - \"$R\" <<'EOF'\nimport random, struct, sys\nsys.path.insert(0,'verify')\nimport gen_corpus as g\nR=sys.argv[1]\nrng=random.Random(123)\nrecs=[]\ndone=0\nwhile done<300000:\n units=rng.randrange(500,3000)\n rec=g.gen_record(rng,R,units)\n if rec and 0xD800<=rec[-1]<=0xDBFF: rec.pop()\n recs.append(rec); done+=len(rec)\nwith open('/tmp/corp_%s.bin'%R,'wb') as f:\n for rec in recs:\n f.write(struct.pack('<I',len(rec)))\n f.write(struct.pack('<%dH'%len(rec),*rec))\nprint(R,done)\nEOF\ndone", "intent": "Generate per-regime corpora"}

ascii 301111 latin 301431 cjk 300736 emoji 300280 --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && for R in ascii latin cjk emoji; do\nfor B in runner runner_given; do\nvalgrind --tool=callgrind --toggle-collect=$([ $B = runner ] && echo utf16_to_utf8 || echo given_utf16_to_utf8) --collect-atstart=no --dump-line=no --callgrind-out-file=/tmp/cg_$R.$B .build/$B /tmp/corp_$R.bin >/dev/null 2>&1\nt=$(grep -E '^[0-9]+ [0-9]+' /tmp/cg_$R.$B | awk '{s+=$2} END{print s}')\necho \"$R $B $t\"\ndone\ndone", "intent": "Measure per-regime costs mine vs given"}

ascii runner 1526808 ascii runner_given 15064984 latin runner 5861675 latin runner_given 21582731 cjk runner 9690955 cjk runner_given 38540893 emoji runner 29944803 emoji runner_given 27982476 --- Command finished with exit code: 0 ---

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "old_string": " } else {\n size_t forward = 15;\n size_t k = 0;", "new_string": " } else {\n // Vectorized surrogate-pair run: whenever buf points at a high\n // surrogate, process contiguous valid pairs 8 at a time.\n while ((size_t)(end - buf) >= 16 &&\n ((uint16_t)(buf[0] & 0xFC00) == 0xD800)) {\n __m256i d = _mm256_loadu_si256((const __m256i *)buf);\n // per 32-bit lane: low16 = high surrogate, high16 = low surr.\n __m256i lo16 = _mm256_and_si256(d, _mm256_set1_epi32(0xFFFF));\n __m256i hi16 = _mm256_srli_epi32(d, 16);\n // validity: (lo16 & 0xFC00)==0xD800 && (hi16 & 0xFC00)==0xDC00\n __m256i lo_ok = _mm256_cmpeq_epi32(\n _mm256_and_si256(lo16, _mm256_set1_epi32(0xFC00)),\n _mm256_set1_epi32(0xD800));\n __m256i hi_ok = _mm256_cmpeq_epi32(\n _mm256_and_si256(hi16, _mm256_set1_epi32(0xFC00)),\n _mm256_set1_epi32(0xDC00));\n __m256i ok = _mm256_and_si256(lo_ok, hi_ok);\n unsigned m = (unsigned)_mm256_movemask_ps(_mm256_castsi256_ps(ok));\n // leading valid lanes = trailing set bits\n unsigned cnt = (m == 0xFF) ? 8 : (unsigned)__builtin_ctz(~m);\n if (cnt == 0) return INVALID; // high surrogate, bad pair\n\n __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF));\n __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF));\n __m256i cp = _mm256_add_epi32(\n _mm256_slli_epi32(hbits, 10), lbits);\n cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000));\n\n __m256i B0 = _mm256_or_si256(_mm256_srli_epi32(cp, 18),\n _mm256_set1_epi32(0xF0));\n __m256i B1 = _mm256_slli_epi32(\n _mm256_or_si256(\n _mm256_and_si256(_mm256_srli_epi32(cp, 12),\n _mm256_set1_epi32(0x3F)),\n _mm256_set1_epi32(0x80)), 8);\n __m256i B2 = _mm256_slli_epi32(\n _mm256_or_si256(\n _mm256_and_si256(_mm256_srli_epi32(cp, 6),\n _mm256_set1_epi32(0x3F)),\n _mm256_set1_epi32(0x80)), 16);\n __m256i B3 = _mm256_slli_epi32(\n _mm256_or_si256(\n _mm256_and_si256(cp, _mm256_set1_epi32(0x3F)),\n _mm256_set1_epi32(0x80)), 24);\n __m256i res = _mm256_or_si256(_mm256_or_si256(B0, B1),\n _mm256_or_si256(B2, B3));\n _mm256_storeu_si256((__m256i *)op, res);\n op += 4 * cnt;\n buf += 2 * cnt;\n if (cnt < 8) break;\n }\n if ((size_t)(end - buf) < 16 + safety_margin) break;\n\n size_t forward = 15;\n size_t k = 0;"}

Edited /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c: replaced 1 occurrence(s) 181+ // Vectorized surrogate-pair run: whenever buf points at a high 182+ // surrogate, process contiguous valid pairs 8 at a time. 183+ while ((size_t)(end - buf) >= 16 && 184+ ((uint16_t)(buf[0] & 0xFC00) == 0xD800)) { 185+ __m256i d = _mm256_loadu_si256((const __m256i *)buf); 186+ // per 32-bit lane: low16 = high surrogate, high16 = low surr. 187+ __m256i lo16 = _mm256_and_si256(d, _mm256_set1_epi32(0xFFFF)); 188+ __m256i hi16 = _mm256_srli_epi32(d, 16); 189+ // validity: (lo16 & 0xFC00)==0xD800 && (hi16 & 0xFC00)==0xDC00 190+ __m256i lo_ok = _mm256_cmpeq_epi32( 191+ _mm256_and_si256(lo16, _mm256_set1_epi32(0xFC00)), 192+ _mm256_set1_epi32(0xD800)); 193+ __m256i hi_ok = _mm256_cmpeq_epi32( 194+ _mm256_and_si256(hi16, _mm256_set1_epi32(0xFC00)), 195+ _mm256_set1_epi32(0xDC00)); 196+ __m256i ok = _mm256_and_si256(lo_ok, hi_ok); 197+ unsigned m = (unsigned)_mm256_movemask_ps(_mm256_castsi256_ps(ok)); 198+ // leading valid lanes = trailing set bits 199+ unsigned cnt = (m == 0xFF) ? 8 : (unsigned)__builtin_ctz(~m); 200+ if (cnt == 0) return INVALID; // high surrogate, bad pair 202+ __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF)); 203+ __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF)); 204+ __m256i cp = _mm256_add_epi32( 205+ _mm256_slli_epi32(hbits, 10), lbits); 206+ cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000)); 208+ __m256i B0 = _mm256_or_si256(_mm256_srli_epi32(cp, 18), 209+ _mm256_set1_epi32(0xF0)); 210+ __m256i B1 = _mm256_slli_epi32( 211+ _mm256_or_si256( 212+ _mm256_and_si256(_mm256_srli_epi32(cp, 12), 213+ _mm256_set1_epi32(0x3F)), 214+ _mm256_set1_epi32(0x80)), 8); 215+ __m256i B2 = _mm256_slli_epi32( 216+ _mm256_or_si256( 217+ _mm256_and_si256(_mm256_srli_epi32(cp, 6), 218+ _mm256_set1_epi32(0x3F)), 219+ _mm256_set1_epi32(0x80)), 16); 220+ __m256i B3 = _mm256_slli_epi32( 221+ _mm256_or_si256( 222+ _mm256_and_si256(cp, _mm256_set1_epi32(0x3F)), 223+ _mm256_set1_epi32(0x80)), 24); 224+ __m256i res = _mm256_or_si256(_mm256_or_si256(B0, B1), 225+ _mm256_or_si256(B2, B3)); 226+ _mm256_storeu_si256((__m256i *)op, res); 227+ op += 4 * cnt; 228+ buf += 2 * cnt; 229+ if (cnt < 8) break; 230+ } 231+ if ((size_t)(end - buf) < 16 + safety_margin) break; Context after edit (lines 177-237): 177│ _mm_storeu_si128((__m128i *)op, utf8_3); 178│ op += row3[0]; 179│ buf += 16; 180│ } else { 181│ // Vectorized surrogate-pair run: whenever buf points at a high 182│ // surrogate, process contiguous valid pairs 8 at a time. 183│ while ((size_t)(end - buf) >= 16 && 184│ ((uint16_t)(buf[0] & 0xFC00) == 0xD800)) { 185│ __m256i d = _mm256_loadu_si256((const __m256i *)buf); 186│ // per 32-bit lane: low16 = high surrogate, high16 = low surr. 187│ __m256i lo16 = _mm256_and_si256(d, _mm256_set1_epi32(0xFFFF)); 188│ __m256i hi16 = _mm256_srli_epi32(d, 16); 189│ // validity: (lo16 & 0xFC00)==0xD800 && (hi16 & 0xFC00)==0xDC00 190│ __m256i lo_ok = _mm256_cmpeq_epi32( 191│ _mm256_and_si256(lo16, _mm256_set1_epi32(0xFC00)), 192│ _mm256_set1_epi32(0xD800)); 193│ __m256i hi_ok = _mm256_cmpeq_epi32( 194│ _mm256_and_si256(hi16, _mm256_set1_epi32(0xFC00)), 195│ _mm256_set1_epi32(0xDC00)); 196│ __m256i ok = _mm256_and_si256(lo_ok, hi_ok); 197│ unsigned m = (unsigned)_mm256_movemask_ps(_mm256_castsi256_ps(ok)); 198│ // leading valid lanes = trailing set bits 199│ unsigned cnt = (m == 0xFF) ? 8 : (unsigned)__builtin_ctz(~m); 200│ if (cnt == 0) return INVALID; // high surrogate, bad pair 201│ 202│ __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF)); 203│ __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF)); 204│ __m256i cp = _mm256_add_epi32( 205│ _mm256_slli_epi32(hbits, 10), lbits); 206│ cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000)); 207│ 208│ __m256i B0 = _mm256_or_si256(_mm256_srli_epi32(cp, 18), 209│ _mm256_set1_epi32(0xF0)); 210│ __m256i B1 = _mm256_slli_epi32( 211│ _mm256_or_si256( 212│ _mm256_and_si256(_mm256_srli_epi32(cp, 12), 213│ _mm256_set1_epi32(0x3F)), 214│ _mm256_set1_epi32(0x80)), 8); 215│ __m256i B2 = _mm256_slli_epi32( 216│ _mm256_or_si256( 217│ _mm256_and_si256(_mm256_srli_epi32(cp, 6), 218│ _mm256_set1_epi32(0x3F)), 219│ _mm256_set1_epi32(0x80)), 16); 220│ __m256i B3 = _mm256_slli_epi32( 221│ _mm256_or_si256( 222│ _mm256_and_si256(cp, _mm256_set1_epi32(0x3F)), 223│ _mm256_set1_epi32(0x80)), 24); 224│ __m256i res = _mm256_or_si256(_mm256_or_si256(B0, B1), 225│ _mm256_or_si256(B2, B3)); 226│ _mm256_storeu_si256((__m256i *)op, res); 227│ op += 4 * cnt; 228│ buf += 2 * cnt; 229│ if (cnt < 8) break; 230│ } 231│ if ((size_t)(end - buf) < 16 + safety_margin) break; 232│ 233│ size_t forward = 15; 234│ size_t k = 0; 235│ if ((size_t)(end - buf) < forward + 1) 236│ forward = (size_t)(end - buf - 1); 237│ for (; k < forward; k++) {

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -6", "intent": "Grade with vectorized surrogate path"}

build 2.0s verify 2.4s PASS measure 1.8s 25,051,812 instructions (given: 77,825,068) SCORE +1.6353 (3.107x) --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && for R in ascii latin cjk emoji; do\nvalgrind --tool=callgrind --toggle-collect=utf16_to_utf8 --collect-atstart=no --dump-line=no --callgrind-out-file=/tmp/cg_$R .build/runner /tmp/corp_$R.bin >/dev/null 2>&1\nt=$(grep -E '^[0-9]+ [0-9]+' /tmp/cg_$R | awk '{s+=$2} END{print s}')\necho \"$R mine=$t\"\ndone", "intent": "Re-measure per regime"}

ascii mine=1514770 latin mine=5971078 cjk mine=10500487 emoji mine=21592922 --- Command finished with exit code: 0 ---

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "start_line": 58, "limit": 14}

58 59 while ((size_t)(end - buf) >= 16 + safety_margin) { 60 __m256i inv = _mm256_loadu_si256((const __m256i *)buf); 61 62 if (_mm256_testz_si256(inv, v_ff80)) { // ASCII fast path 63 const __m128i packed = _mm_packus_epi16( 64 _mm256_castsi256_si128(inv), _mm256_extractf128_si256(inv, 1)); 65 _mm_storeu_si128((__m128i *)op, packed); 66 buf += 16; 67 op += 16; 68 continue; 69 } 70 71 const __m256i one_byte_bytemask = ... 201 more lines (use start_line=72 to continue)

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "new_string": " } else {\n // At least one surrogate in this window. Emit leading BMP units\n // scalar until we reach a high surrogate, then vector-process the\n // contiguous surrogate-pair run 8 pairs at a time.\n const uint16_t *stop = buf + 16;\n while (buf < stop) {\n uint16_t w = *buf;\n if ((w & 0xF800) != 0xD800) {\n if (w < 0x80) {\n *op++ = (uint8_t)w;\n } else if (w < 0x800) {\n *op++ = (uint8_t)(0xC0 | (w >> 6));\n *op++ = (uint8_t)(0x80 | (w & 0x3F));\n } else {\n *op++ = (uint8_t)(0xE0 | (w >> 12));\n *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F));\n *op++ = (uint8_t)(0x80 | (w & 0x3F));\n }\n buf++;\n } else if (w < 0xDC00) {\n break; // high surrogate: switch to vector pair path\n } else {\n return INVALID; // lone low surrogate\n }\n }\n\n // Vector surrogate-pair run.\n while ((size_t)(end - buf) >= 16 &&\n ((uint16_t)(buf[0] & 0xFC00) == 0xD800)) {\n __m256i d = _mm256_loadu_si256((const __m256i *)buf);\n __m256i lo16 = _mm256_and_si256(d, _mm256_set1_epi32(0xFFFF));\n __m256i hi16 = _mm256_srli_epi32(d, 16);\n __m256i lo_ok = _mm256_cmpeq_epi32(\n _mm256_and_si256(lo16, _mm256_set1_epi32(0xFC00)),\n _mm256_set1_epi32(0xD800));\n __m256i hi_ok = _mm256_cmpeq_epi32(\n _mm256_and_si256(hi16, _mm256_set1_epi32(0xFC00)),\n _mm256_set1_epi32(0xDC00));\n __m256i ok = _mm256_and_si256(lo_ok, hi_ok);\n unsigned m = (unsigned)_mm256_movemask_ps(_mm256_castsi256_ps(ok));\n unsigned cnt = (m == 0xFF) ? 8 : (unsigned)__builtin_ctz(~m);\n if (cnt == 0) return INVALID; // high surrogate, bad pair\n\n __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF));\n __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF));\n __m256i cp = _mm256_add_epi32(\n _mm256_slli_epi32(hbits, 10), lbits);\n cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000));\n\n __m256i B0 = _mm256_or_si256(_mm256_srli_epi32(cp, 18),\n _mm256_set1_epi32(0xF0));\n __m256i B1 = _mm256_slli_epi32(\n _mm256_or_si256(\n _mm256_and_si256(_mm256_srli_epi32(cp, 12),\n _mm256_set1_epi32(0x3F)),\n _mm256_set1_epi32(0x80)), 8);\n __m256i B2 = _mm256_slli_epi32(\n _mm256_or_si256(\n _mm256_and_si256(_mm256_srli_epi32(cp, 6),\n _mm256_set1_epi32(0x3F)),\n _mm256_set1_epi32(0x80)), 16);\n __m256i B3 = _mm256_slli_epi32(\n _mm256_or_si256(\n _mm256_and_si256(cp, _mm256_set1_epi32(0x3F)),\n _mm256_set1_epi32(0x80)), 24);\n __m256i res = _mm256_or_si256(_mm256_or_si256(B0, B1),\n _mm256_or_si256(B2, B3));\n _mm256_storeu_si256((__m256i *)op, res);\n op += 4 * cnt;\n buf += 2 * cnt;\n if (cnt < 8) break;\n }\n }\n }\n", "old_string": " } else {\n // Vectorized su ... [4498 characters truncated for page size]

Edited /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c: replaced 1 occurrence(s) 181- // Vectorized surrogate-pair run: whenever buf points at a high 182- // surrogate, process contiguous valid pairs 8 at a time. 181+ // At least one surrogate in this window. Emit leading BMP units 182+ // scalar until we reach a high surrogate, then vector-process the 183+ // contiguous surrogate-pair run 8 pairs at a time. 184+ const uint16_t *stop = buf + 16; 185+ while (buf < stop) { 186+ uint16_t w = *buf; 187+ if ((w & 0xF800) != 0xD800) { 188+ if (w < 0x80) { 189+ *op++ = (uint8_t)w; 190+ } else if (w < 0x800) { 191+ *op++ = (uint8_t)(0xC0 | (w >> 6)); 192+ *op++ = (uint8_t)(0x80 | (w & 0x3F)); 193+ } else { 194+ *op++ = (uint8_t)(0xE0 | (w >> 12)); 195+ *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F)); 196+ *op++ = (uint8_t)(0x80 | (w & 0x3F)); 197+ } 198+ buf++; 199+ } else if (w < 0xDC00) { 200+ break; // high surrogate: switch to vector pair path 201+ } else { 202+ return INVALID; // lone low surrogate 203+ } 204+ } 206+ // Vector surrogate-pair run. 186- // per 32-bit lane: low16 = high surrogate, high16 = low surr. 189- // validity: (lo16 & 0xFC00)==0xD800 && (hi16 & 0xFC00)==0xDC00 198- // leading valid lanes = trailing set bits 231- if ((size_t)(end - buf) < 16 + safety_margin) break; 233- size_t forward = 15; 234- size_t k = 0; 235- if ((size_t)(end - buf) < forward + 1) 236- forward = (size_t)(end - buf - 1); 237- for (; k < forward; k++) { 238- uint16_t word = buf[k]; 239- if ((word & 0xFF80) == 0) { 240- *op++ = (uint8_t)word; 241- } else if ((word & 0xF800) == 0) { 242- *op++ = (uint8_t)((word >> 6) | 0xC0); 243- *op++ = (uint8_t)((word & 0x3F) | 0x80); 244- } else if ((word & 0xF800) != 0xD800) { 245- *op++ = (uint8_t)((word >> 12) | 0xE0); 246- *op++ = (uint8_t)(((word >> 6) & 0x3F) | 0x80); 247- *op++ = (uint8_t)((word & 0x3F) | 0x80); 248- } else { 249- uint16_t diff = (uint16_t)(word - 0xD800); 250- if (diff > 0x3FF) return INVALID; 251- uint16_t next_word = buf[k + 1]; 252- k++; 253- uint16_t diff2 = (uint16_t)(next_word - 0xDC00); 254- if (diff2 > 0x3FF) return INVALID; 255- uint32_t value = ((uint32_t)diff << 10) + diff2 + 0x10000; 256- *op++ = (uint8_t)((value >> 18) | 0xF0); 257- *op++ = (uint8_t)(((value >> 12) & 0x3F) | 0x80); 258- *op++ = (uint8_t)(((value >> 6) & 0x3F) | 0x80); 259- *op++ = (uint8_t)((value & 0x3F) | 0x80); 260- } 261- } 262- buf += k; Context after edit (lines 177-256): 177│ _mm_storeu_si128((__m128i *)op, utf8_3); 178│ op += row3[0]; 179│ buf += 16; 180│ } else { 181│ // At least one surrogate in this window. Emit leading BMP units 182│ // scalar until we reach a high surrogate, then vector-process the 183│ // contiguous surrogate-pair run 8 pairs at a time. 184│ const uint16_t *stop = buf + 16; 185│ while (buf < stop) { 186│ uint16_t w = *buf; 187│ if ((w & 0xF800) != 0xD800) { 188│ if (w < 0x80) { 189│ *op++ = (uint8_t)w; 190│ } else if (w < 0x800) { 191│ *op++ = (uint8_t)(0xC0 | (w >> 6)); 192│ *op++ = (uint8_t)(0x80 | (w & 0x3F)); 193│ } else { 194│ *op++ = (uint8_t)(0xE0 | (w >> 12)); 195│ *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F)); 196│ *op++ = (uint8_t)(0x80 | (w & 0x3F)); 197│ } 198│ buf++; 199│ } else if (w < 0xDC00) { 200│ break; // high surrogate: switch to vector pair path 201│ } else { 202│ return INVALID; // lone low surrogate 203│ } 204│ } 205│ 206│ // Vector surrogate-pair run. 207│ while ((size_t)(end - buf) >= 16 && 208│ ((uint16_t)(buf[0] & 0xFC00) == 0xD800)) { 209│ __m256i d = _mm256_loadu_si256((const __m256i *)buf); 210│ __m256i lo16 = _mm256_and_si256(d, _mm256_set1_epi32(0xFFFF)); 211│ __m256i hi16 = _mm256_srli_epi32(d, 16); 212│ __m256i lo_ok = _mm256_cmpeq_epi32( 213│ _mm256_and_si256(lo16, _mm256_set1_epi32(0xFC00)), 214│ _mm256_set1_epi32(0xD800)); 215│ __m256i hi_ok = _mm256_cmpeq_epi32( 216│ _mm256_and_si256(hi16, _mm256_set1_epi32(0xFC00)), 217│ _mm256_set1_epi32(0xDC00)); 218│ __m256i ok = _mm256_and_si256(lo_ok, hi_ok); 219│ unsigned m = (unsigned)_mm256_movemask_ps(_mm256_castsi256_ps(ok)); 220│ unsigned cnt = (m == 0xFF) ? 8 : (unsigned)__builtin_ctz(~m); 221│ if (cnt == 0) return INVALID; // high surrogate, bad pair 222│ 223│ __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF)); 224│ __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF)); 225│ __m256i cp = _mm256_add_epi32( 226│ _mm256_slli_epi32(hbits, 10), lbits); 227│ cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000)); 228│ 229│ __m256i B0 = _mm256_or_si256(_mm256_srli_epi32(cp, 18), 230│ _mm256_set1_epi32(0xF0)); 231│ __m256i B1 = _mm256_slli_epi32( 232│ _mm256_or_si256( 233│ _mm256_and_si256(_mm256_srli_epi32(cp, 12), 234│ _mm256_set1_epi32(0x3F)), 235│ _mm256_set1_epi32(0x80)), 8); 236│ __m256i B2 = _mm256_slli_epi32( 237│ _mm256_or_si256( 238│ _mm256_and_si256(_mm256_srli_epi32(cp, 6), 239│ _mm256_set1_epi32(0x3F)), 240│ _mm256_set1_epi32(0x80)), 16); 241│ __m256i B3 = _mm256_slli_epi32( 242│ _mm256_or_si256( 243│ _mm256_and_si256(cp, _mm256_set1_epi32(0x3F)), 244│ _mm256_set1_epi32(0x80)), 24); 245│ __m256i res = _mm256_or_si256(_mm256_or_si256(B0, B1), 246│ _mm256_or_si256(B2, B3)); 247│ _mm256_storeu_si256((__m256i *)op, res); 248│ op += 4 * cnt; 249│ buf += 2 * cnt; 250│ if (cnt < 8) break; 251│ } 252│ } 253│ } 254│ 255│ size_t tail = scalar_tail(buf, (size_t)(end - buf), op); 256│ if (tail == INVALID) return INVALID;

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -5", "intent": "Grade restructured surrogate handling"}

build 2.0s verify 2.3s PASS measure 1.8s 23,135,255 instructions (given: 77,846,328) SCORE +1.7505 (3.365x) --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && for R in ascii latin cjk emoji; do\nvalgrind --tool=callgrind --toggle-collect=utf16_to_utf8 --collect-atstart=no --dump-line=no --callgrind-out-file=/tmp/cg_$R .build/runner /tmp/corp_$R.bin >/dev/null 2>&1\nt=$(grep -E '^[0-9]+ [0-9]+' /tmp/cg_$R | awk '{s+=$2} END{print s}')\necho \"$R mine=$t\"\ndone", "intent": "Re-measure per regime"}

ascii mine=2069892 latin mine=6406334 cjk mine=10927082 emoji mine=15257809 --- Command finished with exit code: 0 ---

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "new_string": " const uint32_t mask = (one_byte_bitmask & 0x55555555) |\n (one_or_two_bytes_bitmask & 0xaaaaaaaa);\n\n if (mask == 0) {\n // Pure three-byte units: fixed shuffle, no table lookup.\n const __m256i shuffle = _mm256_setr_epi8(\n 2, 3, 1, 6, 7, 5, 10, 11, 9, 14, 15, 13, -1, -1, -1, -1,\n 2, 3, 1, 6, 7, 5, 10, 11, 9, 14, 15, 13, -1, -1, -1, -1);\n const __m256i u0 = _mm256_shuffle_epi8(out0, shuffle);\n const __m256i u1 = _mm256_shuffle_epi8(out1, shuffle);\n _mm_storeu_si128((__m128i *)op, _mm256_castsi256_si128(u0));\n op += 12;\n _mm_storeu_si128((__m128i *)op, _mm256_castsi256_si128(u1));\n op += 12;\n _mm_storeu_si128((__m128i *)op,\n _mm256_extractf128_si256(u0, 1));\n op += 12;\n _mm_storeu_si128((__m128i *)op,\n _mm256_extractf128_si256(u1, 1));\n op += 12;\n buf += 16;\n continue;\n }\n\n const uint8_t mask0 = (uint8_t)mask;", "old_string": " const uint32_t mask = (one_byte_bitmask & 0x55555555) |\n (one_or_two_bytes_bitmask & 0xaaaaaaaa);\n\n const uint8_t mask0 = (uint8_t)mask;"}

Edited /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c: replaced 1 occurrence(s) 143+ if (mask == 0) { 144+ // Pure three-byte units: fixed shuffle, no table lookup. 145+ const __m256i shuffle = _mm256_setr_epi8( 146+ 2, 3, 1, 6, 7, 5, 10, 11, 9, 14, 15, 13, -1, -1, -1, -1, 147+ 2, 3, 1, 6, 7, 5, 10, 11, 9, 14, 15, 13, -1, -1, -1, -1); 148+ const __m256i u0 = _mm256_shuffle_epi8(out0, shuffle); 149+ const __m256i u1 = _mm256_shuffle_epi8(out1, shuffle); 150+ _mm_storeu_si128((__m128i *)op, _mm256_castsi256_si128(u0)); 151+ op += 12; 152+ _mm_storeu_si128((__m128i *)op, _mm256_castsi256_si128(u1)); 153+ op += 12; 154+ _mm_storeu_si128((__m128i *)op, 155+ _mm256_extractf128_si256(u0, 1)); 156+ op += 12; 157+ _mm_storeu_si128((__m128i *)op, 158+ _mm256_extractf128_si256(u1, 1)); 159+ op += 12; 160+ buf += 16; 161+ continue; 162+ } Context after edit (lines 137-167): 137│ const __m256i out0 = _mm256_unpacklo_epi16(t2, s4); 138│ const __m256i out1 = _mm256_unpackhi_epi16(t2, s4); 139│ 140│ const uint32_t mask = (one_byte_bitmask & 0x55555555) | 141│ (one_or_two_bytes_bitmask & 0xaaaaaaaa); 142│ 143│ if (mask == 0) { 144│ // Pure three-byte units: fixed shuffle, no table lookup. 145│ const __m256i shuffle = _mm256_setr_epi8( 146│ 2, 3, 1, 6, 7, 5, 10, 11, 9, 14, 15, 13, -1, -1, -1, -1, 147│ 2, 3, 1, 6, 7, 5, 10, 11, 9, 14, 15, 13, -1, -1, -1, -1); 148│ const __m256i u0 = _mm256_shuffle_epi8(out0, shuffle); 149│ const __m256i u1 = _mm256_shuffle_epi8(out1, shuffle); 150│ _mm_storeu_si128((__m128i *)op, _mm256_castsi256_si128(u0)); 151│ op += 12; 152│ _mm_storeu_si128((__m128i *)op, _mm256_castsi256_si128(u1)); 153│ op += 12; 154│ _mm_storeu_si128((__m128i *)op, 155│ _mm256_extractf128_si256(u0, 1)); 156│ op += 12; 157│ _mm_storeu_si128((__m128i *)op, 158│ _mm256_extractf128_si256(u1, 1)); 159│ op += 12; 160│ buf += 16; 161│ continue; 162│ } 163│ 164│ const uint8_t mask0 = (uint8_t)mask; 165│ const uint8_t *row0 = &pack_1_2_3_utf8_bytes[mask0][0]; 166│ const __m128i shuffle0 = 167│ _mm_loadu_si128((const __m128i *)(row0 + 1));

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -5", "intent": "Grade with CJK 3-byte fast path"}

build 2.0s verify 2.3s PASS measure 1.8s 22,592,050 instructions (given: 78,029,125) SCORE +1.7882 (3.454x) --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && for R in ascii latin cjk emoji; do\nvalgrind --tool=callgrind --toggle-collect=utf16_to_utf8 --collect-atstart=no --dump-line=no --callgrind-out-file=/tmp/cg_$R .build/runner /tmp/corp_$R.bin >/dev/null 2>&1\nt=$(grep -E '^[0-9]+ [0-9]+' /tmp/cg_$R | awk '{s+=$2} END{print s}')\necho \"$R mine=$t\"\ndone", "intent": "Re-measure per regime after cjk path"}

ascii mine=2293258 latin mine=6630071 cjk mine=9234918 emoji mine=15458679 --- Command finished with exit code: 0 ---

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "start_line": 59, "limit": 62}

59 while ((size_t)(end - buf) >= 16 + safety_margin) { 60 __m256i inv = _mm256_loadu_si256((const __m256i *)buf); 61 62 if (_mm256_testz_si256(inv, v_ff80)) { // ASCII fast path 63 const __m128i packed = _mm_packus_epi16( 64 _mm256_castsi256_si128(inv), _mm256_extractf128_si256(inv, 1)); 65 _mm_storeu_si128((__m128i *)op, packed); 66 buf += 16; 67 op += 16; 68 continue; 69 } 70 71 const __m256i one_byte_bytemask = 72 _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_ff80), v_0000); 73 const uint32_t one_byte_bitmask = 74 (uint32_t)_mm256_movemask_epi8(one_byte_bytemask); 75 76 const __m256i one_or_two_bytes_bytemask = 77 _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_0000); 78 const uint32_t one_or_two_bytes_bitmask = 79 (uint32_t)_mm256_movemask_epi8(one_or_two_bytes_bytemask); 80 81 if (one_or_two_bytes_bitmask == 0xffffffff) { 82 const __m256i v_1f00 = _mm256_set1_epi16((int16_t)0x1f00); 83 const __m256i v_003f = _mm256_set1_epi16((int16_t)0x003f); 84 const __m256i t0 = _mm256_slli_epi16(inv, 2); 85 const __m256i t1 = _mm256_and_si256(t0, v_1f00); 86 const __m256i t2 = _mm256_and_si256(inv, v_003f); 87 const __m256i t3 = _mm256_or_si256(t1, t2); 88 const __m256i t4 = _mm256_or_si256(t3, v_c080); 89 const __m256i utf8_unpacked = 90 _mm256_blendv_epi8(t4, inv, one_byte_bytemask); 91 const uint32_t M0 = one_byte_bitmask & 0x55555555; 92 const uint32_t M1 = M0 >> 7; 93 const uint32_t M2 = (M1 | M0) & 0x00ff00ff; 94 const uint8_t *row = &pack_1_2_utf8_bytes[(uint8_t)M2][0]; 95 const uint8_t *row_2 = &pack_1_2_utf8_bytes[(uint8_t)(M2 >> 16)][0]; 96 const __m128i shuffle = _mm_loadu_si128((const __m128i *)(row + 1)); 97 const __m128i shuffle_2 = 98 _mm_loadu_si128((const __m128i *)(row_2 + 1)); 99 const __m256i utf8_packed = _mm256_shuffle_epi8( 100 utf8_unpacked, _mm256_setr_m128i(shuffle, shuffle_2)); 101 _mm_storeu_si128((__m128i *)op, 102 _mm256_castsi256_si128(utf8_packed)); 103 op += row[0]; 104 _mm_storeu_si128((__m128i *)op, 105 _mm256_extractf128_si256(utf8_packed, 1)); 106 op += row_2[0]; 107 buf += 16; 108 continue; 109 } 110 111 const __m256i surrogates_bytemask = 112 _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_d800); 113 const uint32_t surrogates_bitmask = 114 (uint32_t)_mm256_movemask_epi8(surrogates_bytemask); 115 116 if (surrogates_bitmask == 0x00000000) { 117 const __m256i dup_even = _mm256_setr_epi16( 118 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e, 119 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e); 120 const __m256i t0 = _mm256_shuffle_epi8(inv, dup_even); ... 162 more lines (use start_line=121 to continue)

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "new_string": " const __m256i surrogates_bytemask =\n _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_d800);\n const uint32_t surrogates_bitmask =\n (uint32_t)_mm256_movemask_epi8(surrogates_bytemask);\n\n if (surrogates_bitmask != 0x00000000) {\n // At least one surrogate in this window. Emit leading BMP units\n // scalar until we reach a high surrogate, then vector-process the\n // contiguous surrogate-pair run 8 pairs at a time.\n const uint16_t *stop = buf + 16;\n while (buf < stop) {\n uint16_t w = *buf;\n if ((w & 0xF800) != 0xD800) {\n if (w < 0x80) {\n *op++ = (uint8_t)w;\n } else if (w < 0x800) {\n *op++ = (uint8_t)(0xC0 | (w >> 6));\n *op++ = (uint8_t)(0x80 | (w & 0x3F));\n } else {\n *op++ = (uint8_t)(0xE0 | (w >> 12));\n *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F));\n *op++ = (uint8_t)(0x80 | (w & 0x3F));\n }\n buf++;\n } else if (w < 0xDC00) {\n break; // high surrogate: switch to vector pair path\n } else {\n return INVALID; // lone low surrogate\n }\n }\n\n // Vector surrogate-pair run.\n while ((size_t)(end - buf) >= 16 &&\n ((uint16_t)(buf[0] & 0xFC00) == 0xD800)) {\n __m256i d = _mm256_loadu_si256((const __m256i *)buf);\n __m256i lo16 = _mm256_and_si256(d, _mm256_set1_epi32(0xFFFF));\n __m256i hi16 = _mm256_srli_epi32(d, 16);\n __m256i lo_ok = _mm256_cmpeq_epi32(\n _mm256_and_si256(lo16, _mm256_set1_epi32(0xFC00)),\n _mm256_set1_epi32(0xD800));\n __m256i hi_ok = _mm256_cmpeq_epi32(\n _mm256_and_si256(hi16, _mm256_set1_epi32(0xFC00)),\n _mm256_set1_epi32(0xDC00));\n __m256i ok = _mm256_and_si256(lo_ok, hi_ok);\n unsigned m = (unsigned)_mm256_movemask_ps(_mm256_castsi256_ps(ok));\n unsigned cnt = (m == 0xFF) ? 8 : (unsigned)__builtin_ctz(~m);\n if (cnt == 0) return INVALID; // high surrogate, bad pair\n\n __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF));\n __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF));\n __m256i cp = _mm256_add_epi32(\n _mm256_slli_epi32(hbits, 10), lbits);\n cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000));\n\n __m256i B0 = _mm256_or_si256(_mm256_srli_epi32(cp, 18),\n _mm256_set1_epi32(0xF0));\n __m256i B1 = _mm256_slli_epi32(\n _mm256_or_si256(\n _mm256_and_si256(_mm256_srli_epi32(cp, 12),\n _mm256_set1_epi32(0x3F)),\n _mm256_set1_epi32(0x80)), 8);\n __m256i B2 = _mm256_slli_epi32(\n _mm256_or_si256(\n _mm256_and_si256(_mm256_srli_epi32(cp, 6),\n _mm256_set1_epi32(0x3F)),\n _mm256_set1_epi32(0x80)), 16);\n __m256i B3 = _mm256_slli_epi32(\n _mm256_or_si256(\n _mm256_and_si256(cp, _mm256_set1_epi32(0x3F)),\n _mm256_set1_epi32(0x80)), 24);\n __m256i res = _mm256_or_si256(_mm256_or_si256(B0, B1),\n _mm256_or_si256(B2, B3) ... [4769 characters truncated for page size]

Edited /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c: replaced 1 occurrence(s) 71+ const __m256i surrogates_bytemask = 72+ _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_d800); 73+ const uint32_t surrogates_bitmask = 74+ (uint32_t)_mm256_movemask_epi8(surrogates_bytemask); 76+ if (surrogates_bitmask != 0x00000000) { 77+ // At least one surrogate in this window. Emit leading BMP units 78+ // scalar until we reach a high surrogate, then vector-process the 79+ // contiguous surrogate-pair run 8 pairs at a time. 80+ const uint16_t *stop = buf + 16; 81+ while (buf < stop) { 82+ uint16_t w = *buf; 83+ if ((w & 0xF800) != 0xD800) { 84+ if (w < 0x80) { 85+ *op++ = (uint8_t)w; 86+ } else if (w < 0x800) { 87+ *op++ = (uint8_t)(0xC0 | (w >> 6)); 88+ *op++ = (uint8_t)(0x80 | (w & 0x3F)); 89+ } else { 90+ *op++ = (uint8_t)(0xE0 | (w >> 12)); 91+ *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F)); 92+ *op++ = (uint8_t)(0x80 | (w & 0x3F)); 93+ } 94+ buf++; 95+ } else if (w < 0xDC00) { 96+ break; // high surrogate: switch to vector pair path 97+ } else { 98+ return INVALID; // lone low surrogate 99+ } 100+ } 102+ // Vector surrogate-pair run. 103+ while ((size_t)(end - buf) >= 16 && 104+ ((uint16_t)(buf[0] & 0xFC00) == 0xD800)) { 105+ __m256i d = _mm256_loadu_si256((const __m256i *)buf); 106+ __m256i lo16 = _mm256_and_si256(d, _mm256_set1_epi32(0xFFFF)); 107+ __m256i hi16 = _mm256_srli_epi32(d, 16); 108+ __m256i lo_ok = _mm256_cmpeq_epi32( 109+ _mm256_and_si256(lo16, _mm256_set1_epi32(0xFC00)), 110+ _mm256_set1_epi32(0xD800)); 111+ __m256i hi_ok = _mm256_cmpeq_epi32( 112+ _mm256_and_si256(hi16, _mm256_set1_epi32(0xFC00)), 113+ _mm256_set1_epi32(0xDC00)); 114+ __m256i ok = _mm256_and_si256(lo_ok, hi_ok); 115+ unsigned m = (unsigned)_mm256_movemask_ps(_mm256_castsi256_ps(ok)); 116+ unsigned cnt = (m == 0xFF) ? 8 : (unsigned)__builtin_ctz(~m); 117+ if (cnt == 0) return INVALID; // high surrogate, bad pair 119+ __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF)); 120+ __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF)); 121+ __m256i cp = _mm256_add_epi32( 122+ _mm256_slli_epi32(hbits, 10), lbits); 123+ cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000)); 125+ __m256i B0 = _mm256_or_si256(_mm256_srli_epi32(cp, 18), 126+ _mm256_set1_epi32(0xF0)); 127+ __m256i B1 = _mm256_slli_epi32( 128+ _mm256_or_si256( 129+ _mm256_and_si256(_mm256_srli_epi32(cp, 12), 130+ _mm256_set1_epi32(0x3F)), 131+ _mm256_set1_epi32(0x80)), 8); 132+ __m256i B2 = _mm256_slli_epi32( 133+ _mm256_or_si256( 134+ _mm256_and_si256(_mm256_srli_epi32(cp, 6), 135+ _mm256_set1_epi32(0x3F)), 136+ _mm256_set1_epi32(0x80)), 16); 137+ __m256i B3 = _mm256_slli_epi32( 138+ _mm256_or_si256( 139+ _mm256_and_si256(cp, _mm256_set1_epi32(0x3F)), 140+ _mm256_set1_epi32(0x80)), 24); 141+ __m256i res = _mm256_or_si256(_mm256_or_si256(B0, B1), 142+ _mm256_or_si256(B2, B3)); 143+ _mm256_storeu_si256((__m256i *)op, res); 144+ op += 4 * cnt; 145+ buf += 2 * cnt; 146+ if (cnt < 8) break; 147+ } 148+ continue; 149+ } 151+ // No surrogates: each unit is 1, 2 or 3 UTF-8 bytes. 111- const __m256i surrogates_bytemask = 112- _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_d800); 113- const uint32_t surrogates_bitmask = 114- (uint32_t)_mm256_movemask_epi8(surrogates_bytemask); 116- if (surrogates_bitmask == 0x00000000) { 117- const __m256i dup_even = _mm256_setr_epi16( 192+ { Context after edit (lines 68-195): 68│ continue; 69│ } 70│ 71│ const __m256i surrogates_bytemask = 72│ _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_d800); 73│ const uint32_t surrogates_bitmask = 74│ (uint32_t)_mm256_movemask_epi8(surrogates_bytemask); 75│ 76│ if (surrogates_bitmask != 0x00000000) { 77│ // At least one surrogate in this window. Emit leading BMP units 78│ // scalar until we reach a high surrogate, then vector-process the 79│ // contiguous surrogate-pair run 8 pairs at a time. 80│ const uint16_t *stop = buf + 16; 81│ while (buf < stop) { 82│ uint16_t w = *buf; 83│ if ((w & 0xF800) != 0xD800) { 84│ if (w < 0x80) { 85│ *op++ = (uint8_t)w; 86│ } else if (w < 0x800) { 87│ *op++ = (uint8_t)(0xC0 | (w >> 6)); 88│ *op++ = (uint8_t)(0x80 | (w & 0x3F)); 89│ } else { 90│ *op++ = (uint8_t)(0xE0 | (w >> 12)); 91│ *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F)); 92│ *op++ = (uint8_t)(0x80 | (w & 0x3F)); 93│ } 94│ buf++; 95│ } else if (w < 0xDC00) { 96│ break; // high surrogate: switch to vector pair path 97│ } else { 98│ return INVALID; // lone low surrogate 99│ } 100│ } 101│ 102│ // Vector surrogate-pair run. 103│ while ((size_t)(end - buf) >= 16 && 104│ ((uint16_t)(buf[0] & 0xFC00) == 0xD800)) { 105│ __m256i d = _mm256_loadu_si256((const __m256i *)buf); 106│ __m256i lo16 = _mm256_and_si256(d, _mm256_set1_epi32(0xFFFF)); 107│ __m256i hi16 = _mm256_srli_epi32(d, 16); 108│ __m256i lo_ok = _mm256_cmpeq_epi32( 109│ _mm256_and_si256(lo16, _mm256_set1_epi32(0xFC00)), 110│ _mm256_set1_epi32(0xD800)); 111│ __m256i hi_ok = _mm256_cmpeq_epi32( 112│ _mm256_and_si256(hi16, _mm256_set1_epi32(0xFC00)), 113│ _mm256_set1_epi32(0xDC00)); 114│ __m256i ok = _mm256_and_si256(lo_ok, hi_ok); 115│ unsigned m = (unsigned)_mm256_movemask_ps(_mm256_castsi256_ps(ok)); 116│ unsigned cnt = (m == 0xFF) ? 8 : (unsigned)__builtin_ctz(~m); 117│ if (cnt == 0) return INVALID; // high surrogate, bad pair 118│ 119│ __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF)); 120│ __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF)); 121│ __m256i cp = _mm256_add_epi32( 122│ _mm256_slli_epi32(hbits, 10), lbits); 123│ cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000)); 124│ 125│ __m256i B0 = _mm256_or_si256(_mm256_srli_epi32(cp, 18), 126│ _mm256_set1_epi32(0xF0)); 127│ __m256i B1 = _mm256_slli_epi32( 128│ _mm256_or_si256( 129│ _mm256_and_si256(_mm256_srli_epi32(cp, 12), 130│ _mm256_set1_epi32(0x3F)), 131│ _mm256_set1_epi32(0x80)), 8); 132│ __m256i B2 = _mm256_slli_epi32( 133│ _mm256_or_si256( 134│ _mm256_and_si256(_mm256_srli_epi32(cp, 6), 135│ _mm256_set1_epi32(0x3F)), 136│ _mm256_set1_epi32(0x80)), 16); 137│ __m256i B3 = _mm256_slli_epi32( 138│ _mm256_or_si256( 139│ _mm256_and_si256(cp, _mm256_set1_epi32(0x3F)), 140│ _mm256_set1_epi32(0x80)), 24); 141│ __m256i res = _mm256_or_si256(_mm256_or_si256(B0, B1), 142│ _mm256_or_si256(B2, B3)); 143│ _mm256_storeu_si256((__m256i *)op, res); 144│ op += 4 * cnt; 145│ buf += 2 * cnt; 146│ if (cnt < 8) break; 147│ } 148│ continue; 149│ } 150│ 151│ // No surrogates: each unit is 1, 2 or 3 UTF-8 bytes. 152│ const __m256i one_byte_bytemask = 153│ _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_ff80), v_0000); 154│ const uint32_t one_byte_bitmask = 155│ (uint32_t)_mm256_movemask_epi8(one_byte_bytemask); 156│ 157│ const __m256i one_or_two_bytes_bytemask = 158│ _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_0000); 159│ const uint32_t one_or_two_bytes_bitmask = 160│ (uint32_t)_mm256_movemask_epi8(one_or_two_bytes_bytemask); 161│ 162│ if (one_or_two_bytes_bitmask == 0xffffffff) { 163│ const __m256i v_1f00 = _mm256_set1_epi16((int16_t)0x1f00); 164│ const __m256i v_003f = _mm256_set1_epi16((int16_t)0x003f); 165│ const __m256i t0 = _mm256_slli_epi16(inv, 2); 166│ const __m256i t1 = _mm256_and_si256(t0, v_1f00); 167│ const __m256i t2 = _mm256_and_si256(inv, v_003f); 168│ const __m256i t3 = _mm256_or_si256(t1, t2); 169│ const __m256i t4 = _mm256_or_si256(t3, v_c080); 170│ const __m256i utf8_unpacked = 171│ _mm256_blendv_epi8(t4, inv, one_byte_bytemask); 172│ const uint32_t M0 = one_byte_bitmask & 0x55555555; 173│ const uint32_t M1 = M0 >> 7; 174│ const uint32_t M2 = (M1 | M0) & 0x00ff00ff; 175│ const uint8_t *row = &pack_1_2_utf8_bytes[(uint8_t)M2][0]; 176│ const uint8_t *row_2 = &pack_1_2_utf8_bytes[(uint8_t)(M2 >> 16)][0]; 177│ const __m128i shuffle = _mm_loadu_si128((const __m128i *)(row + 1)); 178│ const __m128i shuffle_2 = 179│ _mm_loadu_si128((const __m128i *)(row_2 + 1)); 180│ const __m256i utf8_packed = _mm256_shuffle_epi8( 181│ utf8_unpacked, _mm256_setr_m128i(shuffle, shuffle_2)); 182│ _mm_storeu_si128((__m128i *)op, 183│ _mm256_castsi256_si128(utf8_packed)); 184│ op += row[0]; 185│ _mm_storeu_si128((__m128i *)op, 186│ _mm256_extractf128_si256(utf8_packed, 1)); 187│ op += row_2[0]; 188│ buf += 16; 189│ continue; 190│ } 191│ 192│ { 193│ 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e, 194│ 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e); 195│ const __m256i t0 = _mm256_shuffle_epi8(inv, dup_even);

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "new_string": " {\n const __m256i dup_even = _mm256_setr_epi16(\n 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e,\n 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e);\n const __m256i t0 = _mm256_shuffle_epi8(inv, dup_even);", "old_string": " {\n 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e,\n 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e);\n const __m256i t0 = _mm256_shuffle_epi8(inv, dup_even);"}

Edited /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c: replaced 1 occurrence(s) 193+ const __m256i dup_even = _mm256_setr_epi16( Context after edit (lines 189-199): 189│ continue; 190│ } 191│ 192│ { 193│ const __m256i dup_even = _mm256_setr_epi16( 194│ 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e, 195│ 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e); 196│ const __m256i t0 = _mm256_shuffle_epi8(inv, dup_even); 197│ const __m256i t1 = 198│ _mm256_and_si256(t0, _mm256_set1_epi16((short)0b0011111101111111)); 199│ const __m256i t2 =

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "limit": 30, "start_line": 240}

240 const uint8_t mask0 = (uint8_t)mask; 241 const uint8_t *row0 = &pack_1_2_3_utf8_bytes[mask0][0]; 242 const __m128i shuffle0 = 243 _mm_loadu_si128((const __m128i *)(row0 + 1)); 244 const __m128i utf8_0 = 245 _mm_shuffle_epi8(_mm256_castsi256_si128(out0), shuffle0); 246 247 const uint8_t mask1 = (uint8_t)(mask >> 8); 248 const uint8_t *row1 = &pack_1_2_3_utf8_bytes[mask1][0]; 249 const __m128i shuffle1 = 250 _mm_loadu_si128((const __m128i *)(row1 + 1)); 251 const __m128i utf8_1 = 252 _mm_shuffle_epi8(_mm256_castsi256_si128(out1), shuffle1); 253 254 const uint8_t mask2 = (uint8_t)(mask >> 16); 255 const uint8_t *row2 = &pack_1_2_3_utf8_bytes[mask2][0]; 256 const __m128i shuffle2 = 257 _mm_loadu_si128((const __m128i *)(row2 + 1)); 258 const __m128i utf8_2 = 259 _mm_shuffle_epi8(_mm256_extractf128_si256(out0, 1), shuffle2); 260 261 const uint8_t mask3 = (uint8_t)(mask >> 24); 262 const uint8_t *row3 = &pack_1_2_3_utf8_bytes[mask3][0]; 263 const __m128i shuffle3 = 264 _mm_loadu_si128((const __m128i *)(row3 + 1)); 265 const __m128i utf8_3 = 266 _mm_shuffle_epi8(_mm256_extractf128_si256(out1, 1), shuffle3); 267 268 _mm_storeu_si128((__m128i *)op, utf8_0); 269 op += row0[0]; ... 89 more lines (use start_line=270 to continue)

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "limit": 22, "start_line": 270}

270 _mm_storeu_si128((__m128i *)op, utf8_1); 271 op += row1[0]; 272 _mm_storeu_si128((__m128i *)op, utf8_2); 273 op += row2[0]; 274 _mm_storeu_si128((__m128i *)op, utf8_3); 275 op += row3[0]; 276 buf += 16; 277 } else { 278 // At least one surrogate in this window. Emit leading BMP units 279 // scalar until we reach a high surrogate, then vector-process the 280 // contiguous surrogate-pair run 8 pairs at a time. 281 const uint16_t *stop = buf + 16; 282 while (buf < stop) { 283 uint16_t w = *buf; 284 if ((w & 0xF800) != 0xD800) { 285 if (w < 0x80) { 286 *op++ = (uint8_t)w; 287 } else if (w < 0x800) { 288 *op++ = (uint8_t)(0xC0 | (w >> 6)); 289 *op++ = (uint8_t)(0x80 | (w & 0x3F)); 290 } else { 291 *op++ = (uint8_t)(0xE0 | (w >> 12)); ... 67 more lines (use start_line=292 to continue)

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "limit": 70, "start_line": 276}

276 buf += 16; 277 } else { 278 // At least one surrogate in this window. Emit leading BMP units 279 // scalar until we reach a high surrogate, then vector-process the 280 // contiguous surrogate-pair run 8 pairs at a time. 281 const uint16_t *stop = buf + 16; 282 while (buf < stop) { 283 uint16_t w = *buf; 284 if ((w & 0xF800) != 0xD800) { 285 if (w < 0x80) { 286 *op++ = (uint8_t)w; 287 } else if (w < 0x800) { 288 *op++ = (uint8_t)(0xC0 | (w >> 6)); 289 *op++ = (uint8_t)(0x80 | (w & 0x3F)); 290 } else { 291 *op++ = (uint8_t)(0xE0 | (w >> 12)); 292 *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F)); 293 *op++ = (uint8_t)(0x80 | (w & 0x3F)); 294 } 295 buf++; 296 } else if (w < 0xDC00) { 297 break; // high surrogate: switch to vector pair path 298 } else { 299 return INVALID; // lone low surrogate 300 } 301 } 302 303 // Vector surrogate-pair run. 304 while ((size_t)(end - buf) >= 16 && 305 ((uint16_t)(buf[0] & 0xFC00) == 0xD800)) { 306 __m256i d = _mm256_loadu_si256((const __m256i *)buf); 307 __m256i lo16 = _mm256_and_si256(d, _mm256_set1_epi32(0xFFFF)); 308 __m256i hi16 = _mm256_srli_epi32(d, 16); 309 __m256i lo_ok = _mm256_cmpeq_epi32( 310 _mm256_and_si256(lo16, _mm256_set1_epi32(0xFC00)), 311 _mm256_set1_epi32(0xD800)); 312 __m256i hi_ok = _mm256_cmpeq_epi32( 313 _mm256_and_si256(hi16, _mm256_set1_epi32(0xFC00)), 314 _mm256_set1_epi32(0xDC00)); 315 __m256i ok = _mm256_and_si256(lo_ok, hi_ok); 316 unsigned m = (unsigned)_mm256_movemask_ps(_mm256_castsi256_ps(ok)); 317 unsigned cnt = (m == 0xFF) ? 8 : (unsigned)__builtin_ctz(~m); 318 if (cnt == 0) return INVALID; // high surrogate, bad pair 319 320 __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF)); 321 __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF)); 322 __m256i cp = _mm256_add_epi32( 323 _mm256_slli_epi32(hbits, 10), lbits); 324 cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000)); 325 326 __m256i B0 = _mm256_or_si256(_mm256_srli_epi32(cp, 18), 327 _mm256_set1_epi32(0xF0)); 328 __m256i B1 = _mm256_slli_epi32( 329 _mm256_or_si256( 330 _mm256_and_si256(_mm256_srli_epi32(cp, 12), 331 _mm256_set1_epi32(0x3F)), 332 _mm256_set1_epi32(0x80)), 8); 333 __m256i B2 = _mm256_slli_epi32( 334 _mm256_or_si256( 335 _mm256_and_si256(_mm256_srli_epi32(cp, 6), 336 _mm256_set1_epi32(0x3F)), 337 _mm256_set1_epi32(0x80)), 16); 338 __m256i B3 = _mm256_slli_epi32( 339 _mm256_or_si256( 340 _mm256_and_si256(cp, _mm256_set1_epi32(0x3F)), 341 _mm256_set1_epi32(0x80)), 24); 342 __m256i res = _mm256_or_si256(_mm256_or_si256(B0, B1), 343 _mm256_or_si256(B2, B3)); 344 _mm256_storeu_si256((__m256i *)op, res); 345 op += 4 * cnt; ... 13 more lines (use start_line=346 to continue)

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "limit": 18, "start_line": 346}

346 buf += 2 * cnt; 347 if (cnt < 8) break; 348 } 349 } 350 } 351 352 size_t tail = scalar_tail(buf, (size_t)(end - buf), op); 353 if (tail == INVALID) return INVALID; 354 return (size_t)(op - out) + tail; 355 #else 356 return scalar_tail(in, n, out); 357 #endif 358 }

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && sed -i '277,349d' submission/solve.c && sed -n '274,282p' submission/solve.c", "intent": "Delete dead else block"}

_mm_storeu_si128((__m128i *)op, utf8_3); op += row3[0]; buf += 16; } size_t tail = scalar_tail(buf, (size_t)(end - buf), op); if (tail == INVALID) return INVALID; return (size_t)(op - out) + tail; #else --- Command finished with exit code: 0 ---

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "new_string": " buf += 16;\n }\n }\n", "old_string": " buf += 16;\n }\n"}

Edited /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c: replaced 1 occurrence(s) 277+ } Context after edit (lines 273-281): 273│ op += row2[0]; 274│ _mm_storeu_si128((__m128i *)op, utf8_3); 275│ op += row3[0]; 276│ buf += 16; 277│ } 278│ } 279│ 280│ size_t tail = scalar_tail(buf, (size_t)(end - buf), op); 281│ if (tail == INVALID) return INVALID;

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -5", "intent": "Grade reordered version"}

build 1.9s verify 2.4s PASS measure 1.8s 21,890,920 instructions (given: 77,854,560) SCORE +1.8304 (3.556x) --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && for R in ascii latin cjk emoji; do\nvalgrind --tool=callgrind --toggle-collect=utf16_to_utf8 --collect-atstart=no --dump-line=no --callgrind-out-file=/tmp/cg_$R .build/runner /tmp/corp_$R.bin >/dev/null 2>&1\nt=$(grep -E '^[0-9]+ [0-9]+' /tmp/cg_$R | awk '{s+=$2} END{print s}')\necho \"$R mine=$t\"\ndone", "intent": "Re-measure per regime"}

ascii mine=2081930 latin mine=7016383 cjk mine=8799642 emoji mine=14878241 --- Command finished with exit code: 0 ---

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "new_string": " while ((size_t)(end - buf) >= 16 + safety_margin) {\n __m256i inv = _mm256_loadu_si256((const __m256i *)buf);\n\n if (_mm256_testz_si256(inv, v_ff80)) { // ASCII fast path\n // Stay in ASCII, 32 units (two vectors) per iteration.\n for (;;) {\n const __m128i packed = _mm_packus_epi16(\n _mm256_castsi256_si128(inv),\n _mm256_extractf128_si256(inv, 1));\n _mm_storeu_si128((__m128i *)op, packed);\n buf += 16;\n op += 16;\n if ((size_t)(end - buf) < 16 + safety_margin) break;\n inv = _mm256_loadu_si256((const __m256i *)buf);\n if (!_mm256_testz_si256(inv, v_ff80)) break;\n }\n if ((size_t)(end - buf) < 16 + safety_margin) break;\n }", "old_string": " while ((size_t)(end - buf) >= 16 + safety_margin) {\n __m256i inv = _mm256_loadu_si256((const __m256i *)buf);\n\n if (_mm256_testz_si256(inv, v_ff80)) { // ASCII fast path\n const __m128i packed = _mm_packus_epi16(\n _mm256_castsi256_si128(inv), _mm256_extractf128_si256(inv, 1));\n _mm_storeu_si128((__m128i *)op, packed);\n buf += 16;\n op += 16;\n continue;\n }"}

Edited /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c: replaced 1 occurrence(s) 63- const __m128i packed = _mm_packus_epi16( 64- _mm256_castsi256_si128(inv), _mm256_extractf128_si256(inv, 1)); 65- _mm_storeu_si128((__m128i *)op, packed); 66- buf += 16; 67- op += 16; 68- continue; 63+ // Stay in ASCII, 32 units (two vectors) per iteration. 64+ for (;;) { 65+ const __m128i packed = _mm_packus_epi16( 66+ _mm256_castsi256_si128(inv), 67+ _mm256_extractf128_si256(inv, 1)); 68+ _mm_storeu_si128((__m128i *)op, packed); 69+ buf += 16; 70+ op += 16; 71+ if ((size_t)(end - buf) < 16 + safety_margin) break; 72+ inv = _mm256_loadu_si256((const __m256i *)buf); 73+ if (!_mm256_testz_si256(inv, v_ff80)) break; 74+ } 75+ if ((size_t)(end - buf) < 16 + safety_margin) break; Context after edit (lines 56-79): 56│ const __m256i v_ff80 = _mm256_set1_epi16((int16_t)0xff80); 57│ const size_t safety_margin = 12; 58│ 59│ while ((size_t)(end - buf) >= 16 + safety_margin) { 60│ __m256i inv = _mm256_loadu_si256((const __m256i *)buf); 61│ 62│ if (_mm256_testz_si256(inv, v_ff80)) { // ASCII fast path 63│ // Stay in ASCII, 32 units (two vectors) per iteration. 64│ for (;;) { 65│ const __m128i packed = _mm_packus_epi16( 66│ _mm256_castsi256_si128(inv), 67│ _mm256_extractf128_si256(inv, 1)); 68│ _mm_storeu_si128((__m128i *)op, packed); 69│ buf += 16; 70│ op += 16; 71│ if ((size_t)(end - buf) < 16 + safety_margin) break; 72│ inv = _mm256_loadu_si256((const __m256i *)buf); 73│ if (!_mm256_testz_si256(inv, v_ff80)) break; 74│ } 75│ if ((size_t)(end - buf) < 16 + safety_margin) break; 76│ } 77│ 78│ const __m256i surrogates_bytemask = 79│ _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_d800);

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -5", "intent": "Grade widened ASCII path"}

build 1.9s verify 2.4s PASS measure 1.7s 21,166,619 instructions (given: 77,876,703) SCORE +1.8794 (3.679x) --- Command finished with exit code: 0 ---

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "limit": 100, "start_line": 59}

59 while ((size_t)(end - buf) >= 16 + safety_margin) { 60 __m256i inv = _mm256_loadu_si256((const __m256i *)buf); 61 62 if (_mm256_testz_si256(inv, v_ff80)) { // ASCII fast path 63 // Stay in ASCII, 32 units (two vectors) per iteration. 64 for (;;) { 65 const __m128i packed = _mm_packus_epi16( 66 _mm256_castsi256_si128(inv), 67 _mm256_extractf128_si256(inv, 1)); 68 _mm_storeu_si128((__m128i *)op, packed); 69 buf += 16; 70 op += 16; 71 if ((size_t)(end - buf) < 16 + safety_margin) break; 72 inv = _mm256_loadu_si256((const __m256i *)buf); 73 if (!_mm256_testz_si256(inv, v_ff80)) break; 74 } 75 if ((size_t)(end - buf) < 16 + safety_margin) break; 76 } 77 78 const __m256i surrogates_bytemask = 79 _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_d800); 80 const uint32_t surrogates_bitmask = 81 (uint32_t)_mm256_movemask_epi8(surrogates_bytemask); 82 83 if (surrogates_bitmask != 0x00000000) { 84 // At least one surrogate in this window. Emit leading BMP units 85 // scalar until we reach a high surrogate, then vector-process the 86 // contiguous surrogate-pair run 8 pairs at a time. 87 const uint16_t *stop = buf + 16; 88 while (buf < stop) { 89 uint16_t w = *buf; 90 if ((w & 0xF800) != 0xD800) { 91 if (w < 0x80) { 92 *op++ = (uint8_t)w; 93 } else if (w < 0x800) { 94 *op++ = (uint8_t)(0xC0 | (w >> 6)); 95 *op++ = (uint8_t)(0x80 | (w & 0x3F)); 96 } else { 97 *op++ = (uint8_t)(0xE0 | (w >> 12)); 98 *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F)); 99 *op++ = (uint8_t)(0x80 | (w & 0x3F)); 100 } 101 buf++; 102 } else if (w < 0xDC00) { 103 break; // high surrogate: switch to vector pair path 104 } else { 105 return INVALID; // lone low surrogate 106 } 107 } 108 109 // Vector surrogate-pair run. 110 while ((size_t)(end - buf) >= 16 && 111 ((uint16_t)(buf[0] & 0xFC00) == 0xD800)) { 112 __m256i d = _mm256_loadu_si256((const __m256i *)buf); 113 __m256i lo16 = _mm256_and_si256(d, _mm256_set1_epi32(0xFFFF)); 114 __m256i hi16 = _mm256_srli_epi32(d, 16); 115 __m256i lo_ok = _mm256_cmpeq_epi32( 116 _mm256_and_si256(lo16, _mm256_set1_epi32(0xFC00)), 117 _mm256_set1_epi32(0xD800)); 118 __m256i hi_ok = _mm256_cmpeq_epi32( 119 _mm256_and_si256(hi16, _mm256_set1_epi32(0xFC00)), 120 _mm256_set1_epi32(0xDC00)); 121 __m256i ok = _mm256_and_si256(lo_ok, hi_ok); 122 unsigned m = (unsigned)_mm256_movemask_ps(_mm256_castsi256_ps(ok)); 123 unsigned cnt = (m == 0xFF) ? 8 : (unsigned)__builtin_ctz(~m); 124 if (cnt == 0) return INVALID; // high surrogate, bad pair 125 126 __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF)); 127 __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF)); 128 __m256i cp = _mm256_add_epi32( 129 _mm256_slli_epi32(hbits, 10), lbits); 130 cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000)); 131 132 __m256i B0 = _mm256_or_si256(_mm256_srli_epi32(cp, 18), 133 _mm256_set1_epi32(0xF0)); 134 __m256i B1 = _mm256_slli_epi32( 135 _mm256_or_si256( 136 _mm256_and_si256(_mm256_srli_epi32(cp, 12), 137 _mm256_set1_epi32(0x3F)), 138 _mm256_set1_epi32(0x80)), 8); 139 __m256i B2 = _mm256_slli_epi32( 140 _mm256_or_si256( 141 _mm256_and_si256(_mm256_srli_epi32(cp, 6), 142 _mm256_set1_epi32(0x3F)), 143 _mm256_set1_epi32(0x80)), 16); 144 __m256i B3 = _mm256_slli_epi32( 145 _mm256_or_si256( 146 _mm256_and_si256(cp, _mm256_set1_epi32(0x3F)), 147 _mm256_set1_epi32(0x80)), 24); 148 __m256i res = _mm256_or_si256(_mm256_or_si256(B0, B1), 149 _mm256_or_si256(B2, B3)); 150 _mm256_storeu_si256((__m256i *)op, res); 151 op += 4 * cnt; 152 buf += 2 * cnt; 153 if (cnt < 8) break; 154 } 155 continue; 156 } 157 158 // No surrogates: each unit is 1, 2 or 3 UTF-8 bytes. ... 135 more lines (use start_line=159 to continue)

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "limit": 50, "start_line": 158}

158 // No surrogates: each unit is 1, 2 or 3 UTF-8 bytes. 159 const __m256i one_byte_bytemask = 160 _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_ff80), v_0000); 161 const uint32_t one_byte_bitmask = 162 (uint32_t)_mm256_movemask_epi8(one_byte_bytemask); 163 164 const __m256i one_or_two_bytes_bytemask = 165 _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_0000); 166 const uint32_t one_or_two_bytes_bitmask = 167 (uint32_t)_mm256_movemask_epi8(one_or_two_bytes_bytemask); 168 169 if (one_or_two_bytes_bitmask == 0xffffffff) { 170 const __m256i v_1f00 = _mm256_set1_epi16((int16_t)0x1f00); 171 const __m256i v_003f = _mm256_set1_epi16((int16_t)0x003f); 172 const __m256i t0 = _mm256_slli_epi16(inv, 2); 173 const __m256i t1 = _mm256_and_si256(t0, v_1f00); 174 const __m256i t2 = _mm256_and_si256(inv, v_003f); 175 const __m256i t3 = _mm256_or_si256(t1, t2); 176 const __m256i t4 = _mm256_or_si256(t3, v_c080); 177 const __m256i utf8_unpacked = 178 _mm256_blendv_epi8(t4, inv, one_byte_bytemask); 179 const uint32_t M0 = one_byte_bitmask & 0x55555555; 180 const uint32_t M1 = M0 >> 7; 181 const uint32_t M2 = (M1 | M0) & 0x00ff00ff; 182 const uint8_t *row = &pack_1_2_utf8_bytes[(uint8_t)M2][0]; 183 const uint8_t *row_2 = &pack_1_2_utf8_bytes[(uint8_t)(M2 >> 16)][0]; 184 const __m128i shuffle = _mm_loadu_si128((const __m128i *)(row + 1)); 185 const __m128i shuffle_2 = 186 _mm_loadu_si128((const __m128i *)(row_2 + 1)); 187 const __m256i utf8_packed = _mm256_shuffle_epi8( 188 utf8_unpacked, _mm256_setr_m128i(shuffle, shuffle_2)); 189 _mm_storeu_si128((__m128i *)op, 190 _mm256_castsi256_si128(utf8_packed)); 191 op += row[0]; 192 _mm_storeu_si128((__m128i *)op, 193 _mm256_extractf128_si256(utf8_packed, 1)); 194 op += row_2[0]; 195 buf += 16; 196 continue; 197 } 198 199 { 200 const __m256i dup_even = _mm256_setr_epi16( 201 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e, 202 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e); 203 const __m256i t0 = _mm256_shuffle_epi8(inv, dup_even); 204 const __m256i t1 = 205 _mm256_and_si256(t0, _mm256_set1_epi16((short)0b0011111101111111)); 206 const __m256i t2 = 207 _mm256_or_si256(t1, _mm256_set1_epi16((short)0b1000000000000000)); ... 86 more lines (use start_line=208 to continue)

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "new_string": " const __m256i one_or_two_bytes_bytemask =\n _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_0000);\n const uint32_t one_or_two_bytes_bitmask =\n (uint32_t)_mm256_movemask_epi8(one_or_two_bytes_bytemask);\n\n if (one_or_two_bytes_bitmask == 0xffffffff) {\n // 1 or 2 byte units only (no surrogates possible).\n const __m256i one_byte_bytemask =\n _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_ff80), v_0000);\n const uint32_t one_byte_bitmask =\n (uint32_t)_mm256_movemask_epi8(one_byte_bytemask);\n const __m256i v_1f00 = _mm256_set1_epi16((int16_t)0x1f00);\n const __m256i v_003f = _mm256_set1_epi16((int16_t)0x003f);\n const __m256i t0 = _mm256_slli_epi16(inv, 2);\n const __m256i t1 = _mm256_and_si256(t0, v_1f00);\n const __m256i t2 = _mm256_and_si256(inv, v_003f);\n const __m256i t3 = _mm256_or_si256(t1, t2);\n const __m256i t4 = _mm256_or_si256(t3, v_c080);\n const __m256i utf8_unpacked =\n _mm256_blendv_epi8(t4, inv, one_byte_bytemask);\n const uint32_t M0 = one_byte_bitmask & 0x55555555;\n const uint32_t M1 = M0 >> 7;\n const uint32_t M2 = (M1 | M0) & 0x00ff00ff;\n const uint8_t *row = &pack_1_2_utf8_bytes[(uint8_t)M2][0];\n const uint8_t *row_2 = &pack_1_2_utf8_bytes[(uint8_t)(M2 >> 16)][0];\n const __m128i shuffle = _mm_loadu_si128((const __m128i *)(row + 1));\n const __m128i shuffle_2 =\n _mm_loadu_si128((const __m128i *)(row_2 + 1));\n const __m256i utf8_packed = _mm256_shuffle_epi8(\n utf8_unpacked, _mm256_setr_m128i(shuffle, shuffle_2));\n _mm_storeu_si128((__m128i *)op,\n _mm256_castsi256_si128(utf8_packed));\n op += row[0];\n _mm_storeu_si128((__m128i *)op,\n _mm256_extractf128_si256(utf8_packed, 1));\n op += row_2[0];\n buf += 16;\n continue;\n }\n\n const __m256i surrogates_bytemask =\n _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_d800);\n const uint32_t surrogates_bitmask =\n (uint32_t)_mm256_movemask_epi8(surrogates_bytemask);\n\n if (surrogates_bitmask != 0x00000000) {\n // At least one surrogate in this window. Emit leading BMP units\n // scalar until we reach a high surrogate, then vector-process the\n // contiguous surrogate-pair run 8 pairs at a time.\n const uint16_t *stop = buf + 16;\n while (buf < stop) {\n uint16_t w = *buf;\n if ((w & 0xF800) != 0xD800) {\n if (w < 0x80) {\n *op++ = (uint8_t)w;\n } else if (w < 0x800) {\n *op++ = (uint8_t)(0xC0 | (w >> 6));\n *op++ = (uint8_t)(0x80 | (w & 0x3F));\n } else {\n *op++ = (uint8_t)(0xE0 | (w >> 12));\n *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F));\n *op++ = (uint8_t)(0x80 | (w & 0x3F));\n }\n buf++;\n } else if (w < 0xDC00) {\n break; // high surrogate: switch to vector pair path\n } else {\n return INVALID; // lone low surrogate\n }\n }\n\n // Vector surrogate-pair run.\n while ((size_t)(end - buf) >= 16 &&\n ((uint16_t)(buf[0] & 0xFC00) == 0xD800)) {\n __m256i d = _mm256_loadu_si256((const __m256i *)buf);\n __m256i lo16 = _mm256_and_si256(d, _ ... [8863 characters truncated for page size]

Edited /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c: replaced 1 occurrence(s) 78+ const __m256i one_or_two_bytes_bytemask = 79+ _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_0000); 80+ const uint32_t one_or_two_bytes_bitmask = 81+ (uint32_t)_mm256_movemask_epi8(one_or_two_bytes_bytemask); 83+ if (one_or_two_bytes_bitmask == 0xffffffff) { 84+ // 1 or 2 byte units only (no surrogates possible). 85+ const __m256i one_byte_bytemask = 86+ _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_ff80), v_0000); 87+ const uint32_t one_byte_bitmask = 88+ (uint32_t)_mm256_movemask_epi8(one_byte_bytemask); 89+ const __m256i v_1f00 = _mm256_set1_epi16((int16_t)0x1f00); 90+ const __m256i v_003f = _mm256_set1_epi16((int16_t)0x003f); 91+ const __m256i t0 = _mm256_slli_epi16(inv, 2); 92+ const __m256i t1 = _mm256_and_si256(t0, v_1f00); 93+ const __m256i t2 = _mm256_and_si256(inv, v_003f); 94+ const __m256i t3 = _mm256_or_si256(t1, t2); 95+ const __m256i t4 = _mm256_or_si256(t3, v_c080); 96+ const __m256i utf8_unpacked = 97+ _mm256_blendv_epi8(t4, inv, one_byte_bytemask); 98+ const uint32_t M0 = one_byte_bitmask & 0x55555555; 99+ const uint32_t M1 = M0 >> 7; 100+ const uint32_t M2 = (M1 | M0) & 0x00ff00ff; 101+ const uint8_t *row = &pack_1_2_utf8_bytes[(uint8_t)M2][0]; 102+ const uint8_t *row_2 = &pack_1_2_utf8_bytes[(uint8_t)(M2 >> 16)][0]; 103+ const __m128i shuffle = _mm_loadu_si128((const __m128i *)(row + 1)); 104+ const __m128i shuffle_2 = 105+ _mm_loadu_si128((const __m128i *)(row_2 + 1)); 106+ const __m256i utf8_packed = _mm256_shuffle_epi8( 107+ utf8_unpacked, _mm256_setr_m128i(shuffle, shuffle_2)); 108+ _mm_storeu_si128((__m128i *)op, 109+ _mm256_castsi256_si128(utf8_packed)); 110+ op += row[0]; 111+ _mm_storeu_si128((__m128i *)op, 112+ _mm256_extractf128_si256(utf8_packed, 1)); 113+ op += row_2[0]; 114+ buf += 16; 115+ continue; 116+ } 158- // No surrogates: each unit is 1, 2 or 3 UTF-8 bytes. 198+ // No surrogates, mixed 1/2/3-byte units. 164- const __m256i one_or_two_bytes_bytemask = 165- _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_0000); 166- const uint32_t one_or_two_bytes_bitmask = 167- (uint32_t)_mm256_movemask_epi8(one_or_two_bytes_bytemask); 169- if (one_or_two_bytes_bitmask == 0xffffffff) { 170- const __m256i v_1f00 = _mm256_set1_epi16((int16_t)0x1f00); 171- const __m256i v_003f = _mm256_set1_epi16((int16_t)0x003f); 172- const __m256i t0 = _mm256_slli_epi16(inv, 2); 173- const __m256i t1 = _mm256_and_si256(t0, v_1f00); 174- const __m256i t2 = _mm256_and_si256(inv, v_003f); 175- const __m256i t3 = _mm256_or_si256(t1, t2); 176- const __m256i t4 = _mm256_or_si256(t3, v_c080); 177- const __m256i utf8_unpacked = 178- _mm256_blendv_epi8(t4, inv, one_byte_bytemask); 179- const uint32_t M0 = one_byte_bitmask & 0x55555555; 180- const uint32_t M1 = M0 >> 7; 181- const uint32_t M2 = (M1 | M0) & 0x00ff00ff; 182- const uint8_t *row = &pack_1_2_utf8_bytes[(uint8_t)M2][0]; 183- const uint8_t *row_2 = &pack_1_2_utf8_bytes[(uint8_t)(M2 >> 16)][0]; 184- const __m128i shuffle = _mm_loadu_si128((const __m128i *)(row + 1)); 185- const __m128i shuffle_2 = 186- _mm_loadu_si128((const __m128i *)(row_2 + 1)); 187- const __m256i utf8_packed = _mm256_shuffle_epi8( 188- utf8_unpacked, _mm256_setr_m128i(shuffle, shuffle_2)); 189- _mm_storeu_si128((__m128i *)op, 190- _mm256_castsi256_si128(utf8_packed)); 191- op += row[0]; 192- _mm_storeu_si128((__m128i *)op, 193- _mm256_extractf128_si256(utf8_packed, 1)); 194- op += row_2[0]; 195- buf += 16; 196- continue; 197- } Context after edit (lines 75-207): 75│ if ((size_t)(end - buf) < 16 + safety_margin) break; 76│ } 77│ 78│ const __m256i one_or_two_bytes_bytemask = 79│ _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_0000); 80│ const uint32_t one_or_two_bytes_bitmask = 81│ (uint32_t)_mm256_movemask_epi8(one_or_two_bytes_bytemask); 82│ 83│ if (one_or_two_bytes_bitmask == 0xffffffff) { 84│ // 1 or 2 byte units only (no surrogates possible). 85│ const __m256i one_byte_bytemask = 86│ _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_ff80), v_0000); 87│ const uint32_t one_byte_bitmask = 88│ (uint32_t)_mm256_movemask_epi8(one_byte_bytemask); 89│ const __m256i v_1f00 = _mm256_set1_epi16((int16_t)0x1f00); 90│ const __m256i v_003f = _mm256_set1_epi16((int16_t)0x003f); 91│ const __m256i t0 = _mm256_slli_epi16(inv, 2); 92│ const __m256i t1 = _mm256_and_si256(t0, v_1f00); 93│ const __m256i t2 = _mm256_and_si256(inv, v_003f); 94│ const __m256i t3 = _mm256_or_si256(t1, t2); 95│ const __m256i t4 = _mm256_or_si256(t3, v_c080); 96│ const __m256i utf8_unpacked = 97│ _mm256_blendv_epi8(t4, inv, one_byte_bytemask); 98│ const uint32_t M0 = one_byte_bitmask & 0x55555555; 99│ const uint32_t M1 = M0 >> 7; 100│ const uint32_t M2 = (M1 | M0) & 0x00ff00ff; 101│ const uint8_t *row = &pack_1_2_utf8_bytes[(uint8_t)M2][0]; 102│ const uint8_t *row_2 = &pack_1_2_utf8_bytes[(uint8_t)(M2 >> 16)][0]; 103│ const __m128i shuffle = _mm_loadu_si128((const __m128i *)(row + 1)); 104│ const __m128i shuffle_2 = 105│ _mm_loadu_si128((const __m128i *)(row_2 + 1)); 106│ const __m256i utf8_packed = _mm256_shuffle_epi8( 107│ utf8_unpacked, _mm256_setr_m128i(shuffle, shuffle_2)); 108│ _mm_storeu_si128((__m128i *)op, 109│ _mm256_castsi256_si128(utf8_packed)); 110│ op += row[0]; 111│ _mm_storeu_si128((__m128i *)op, 112│ _mm256_extractf128_si256(utf8_packed, 1)); 113│ op += row_2[0]; 114│ buf += 16; 115│ continue; 116│ } 117│ 118│ const __m256i surrogates_bytemask = 119│ _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_f800), v_d800); 120│ const uint32_t surrogates_bitmask = 121│ (uint32_t)_mm256_movemask_epi8(surrogates_bytemask); 122│ 123│ if (surrogates_bitmask != 0x00000000) { 124│ // At least one surrogate in this window. Emit leading BMP units 125│ // scalar until we reach a high surrogate, then vector-process the 126│ // contiguous surrogate-pair run 8 pairs at a time. 127│ const uint16_t *stop = buf + 16; 128│ while (buf < stop) { 129│ uint16_t w = *buf; 130│ if ((w & 0xF800) != 0xD800) { 131│ if (w < 0x80) { 132│ *op++ = (uint8_t)w; 133│ } else if (w < 0x800) { 134│ *op++ = (uint8_t)(0xC0 | (w >> 6)); 135│ *op++ = (uint8_t)(0x80 | (w & 0x3F)); 136│ } else { 137│ *op++ = (uint8_t)(0xE0 | (w >> 12)); 138│ *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F)); 139│ *op++ = (uint8_t)(0x80 | (w & 0x3F)); 140│ } 141│ buf++; 142│ } else if (w < 0xDC00) { 143│ break; // high surrogate: switch to vector pair path 144│ } else { 145│ return INVALID; // lone low surrogate 146│ } 147│ } 148│ 149│ // Vector surrogate-pair run. 150│ while ((size_t)(end - buf) >= 16 && 151│ ((uint16_t)(buf[0] & 0xFC00) == 0xD800)) { 152│ __m256i d = _mm256_loadu_si256((const __m256i *)buf); 153│ __m256i lo16 = _mm256_and_si256(d, _mm256_set1_epi32(0xFFFF)); 154│ __m256i hi16 = _mm256_srli_epi32(d, 16); 155│ __m256i lo_ok = _mm256_cmpeq_epi32( 156│ _mm256_and_si256(lo16, _mm256_set1_epi32(0xFC00)), 157│ _mm256_set1_epi32(0xD800)); 158│ __m256i hi_ok = _mm256_cmpeq_epi32( 159│ _mm256_and_si256(hi16, _mm256_set1_epi32(0xFC00)), 160│ _mm256_set1_epi32(0xDC00)); 161│ __m256i ok = _mm256_and_si256(lo_ok, hi_ok); 162│ unsigned m = (unsigned)_mm256_movemask_ps(_mm256_castsi256_ps(ok)); 163│ unsigned cnt = (m == 0xFF) ? 8 : (unsigned)__builtin_ctz(~m); 164│ if (cnt == 0) return INVALID; // high surrogate, bad pair 165│ 166│ __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF)); 167│ __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF)); 168│ __m256i cp = _mm256_add_epi32( 169│ _mm256_slli_epi32(hbits, 10), lbits); 170│ cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000)); 171│ 172│ __m256i B0 = _mm256_or_si256(_mm256_srli_epi32(cp, 18), 173│ _mm256_set1_epi32(0xF0)); 174│ __m256i B1 = _mm256_slli_epi32( 175│ _mm256_or_si256( 176│ _mm256_and_si256(_mm256_srli_epi32(cp, 12), 177│ _mm256_set1_epi32(0x3F)), 178│ _mm256_set1_epi32(0x80)), 8); 179│ __m256i B2 = _mm256_slli_epi32( 180│ _mm256_or_si256( 181│ _mm256_and_si256(_mm256_srli_epi32(cp, 6), 182│ _mm256_set1_epi32(0x3F)), 183│ _mm256_set1_epi32(0x80)), 16); 184│ __m256i B3 = _mm256_slli_epi32( 185│ _mm256_or_si256( 186│ _mm256_and_si256(cp, _mm256_set1_epi32(0x3F)), 187│ _mm256_set1_epi32(0x80)), 24); 188│ __m256i res = _mm256_or_si256(_mm256_or_si256(B0, B1), 189│ _mm256_or_si256(B2, B3)); 190│ _mm256_storeu_si256((__m256i *)op, res); 191│ op += 4 * cnt; 192│ buf += 2 * cnt; 193│ if (cnt < 8) break; 194│ } 195│ continue; 196│ } 197│ 198│ // No surrogates, mixed 1/2/3-byte units. 199│ const __m256i one_byte_bytemask = 200│ _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_ff80), v_0000); 201│ const uint32_t one_byte_bitmask = 202│ (uint32_t)_mm256_movemask_epi8(one_byte_bytemask); 203│ 204│ { 205│ const __m256i dup_even = _mm256_setr_epi16( 206│ 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e, 207│ 0x0000, 0x0202, 0x0404, 0x0606, 0x0808, 0x0a0a, 0x0c0c, 0x0e0e);

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -5", "intent": "Grade reordered latin-first"}

build 1.8s verify 2.4s PASS measure 2.1s 20,776,454 instructions (given: 77,843,036) SCORE +1.9056 (3.747x) --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && for R in ascii latin cjk emoji; do\nvalgrind --tool=callgrind --toggle-collect=utf16_to_utf8 --collect-atstart=no --dump-line=no --callgrind-out-file=/tmp/cg_$R .build/runner /tmp/corp_$R.bin >/dev/null 2>&1\nt=$(grep -E '^[0-9]+ [0-9]+' /tmp/cg_$R | awk '{s+=$2} END{print s}')\necho \"$R mine=$t\"\ndone", "intent": "Re-measure per regime"}

ascii mine=1759761 latin mine=6005293 cjk mine=8575234 emoji mine=15277705 --- Command finished with exit code: 0 ---

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "new_string": "#if defined(__x86_64__) || defined(__i386__)\n#pragma GCC optimize(\"O3\")\n#pragma GCC target(\"avx2\")", "old_string": "#if defined(__x86_64__) || defined(__i386__)\n#pragma GCC target(\"avx2\")"}

Edited /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c: replaced 1 occurrence(s) 10+ #pragma GCC optimize("O3") Context after edit (lines 6-14): 6│ 7│ #define INVALID ((size_t)-1) 8│ 9│ #if defined(__x86_64__) || defined(__i386__) 10│ #pragma GCC optimize("O3") 11│ #pragma GCC target("avx2") 12│ #include <immintrin.h> 13│ #include "tables.h" 14│ #define HAVE_AVX2 1

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -4", "intent": "Grade with O3"}

build 2.3s verify 2.4s PASS measure 1.8s 20,740,036 instructions (given: 77,794,485) SCORE +1.9072 (3.751x) --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && valgrind --tool=callgrind --toggle-collect=utf16_to_utf8 --collect-atstart=no --dump-line=yes --callgrind-out-file=/tmp/cg_emoji_l .build/runner /tmp/corp_emoji.bin >/dev/null 2>&1; callgrind_annotate --auto=no /tmp/cg_emoji_l 2>/dev/null | grep -A40 'solve.c' | head -60", "intent": "Annotate emoji hotspots"}

1,685,366 (59.99%) submission/solve.c:utf16_to_utf8 [/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/.build/runner] 1,044,246 (37.17%) /usr/lib/gcc/x86_64-pc-linux-gnu/16/include/avx2intrin.h:utf16_to_utf8 77,445 ( 2.76%) /usr/lib/gcc/x86_64-pc-linux-gnu/16/include/avxintrin.h:utf16_to_utf8 --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && callgrind_annotate --auto=yes --inclusive=no /tmp/cg_emoji_l submission/solve.c 2>/dev/null | grep -E '^\\s*[0-9,]+ ' | grep 'solve.c' | head -50", "intent": "Line-level annotation of emoji"}

1,685,366 (59.99%) submission/solve.c:utf16_to_utf8 [/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/.build/runner] --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && callgrind_annotate --auto=yes /tmp/cg_emoji_l 2>/dev/null | awk '/solve.c$|solve\\.c </{p=1} p' | grep -nE '=>|[0-9]+ (\\*|>)' | head; echo \"===\"; callgrind_annotate --auto=yes /tmp/cg_emoji_l 2>/dev/null | sed -n '/-- line-by-line/,/^$/p' | head -5; echo \"try direct\"; ls /tmp/cg_emoji_l", "intent": "Find line-by-line output"}

27: 2,349 ( 0.08%) if (i + 1 >= n) return INVALID; 168: 32,372 ( 1.15%) op += 4 * cnt; 169: 45,051 ( 1.60%) buf += 2 * cnt; === try direct /tmp/cg_emoji_l --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && callgrind_annotate --auto=yes /tmp/cg_emoji_l 2>/dev/null | grep -E '^[0-9 ]+[0-9] ' | grep -vE 'avx|include' | sort -rn | head -30", "intent": "Top emoji lines"}

862 ( 0.03%) buf += 16; 856 ( 0.03%) return (__m128i) __builtin_ia32_vextractf128_si256 ((__v8si)__X, __N); 856 ( 0.03%) op += 16; 783 ( 0.03%) uint32_t lo = in[i + 1]; 668 ( 0.02%) } 501 ( 0.02%) uint8_t *op = out; 334 ( 0.01%) return (__m256i) __builtin_ia32_pshufb256 ((__v32qi)__X, 334 ( 0.01%) return (size_t)(op - out) + tail; 334 ( 0.01%) const uint16_t *end = in + n; 332 ( 0.01%) if (tail == INVALID) return INVALID; 167 ( 0.01%) return (__m256i) __builtin_ia32_pmaddubsw256 ((__v32qi)__X, 166 ( 0.01%) size_t tail = scalar_tail(buf, (size_t)(end - buf), op); 166 ( 0.01%) size_t o = 0; 2 ( 0.00%) return o; --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade --full 2>&1 | tail -5", "intent": "Run full gate"}

build 2.2s verify 2.3s PASS (FULL gate) measure 1.8s 20,854,848 instructions (given: 78,007,949) SCORE +1.9032 (3.741x) --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && callgrind_annotate --auto=yes /tmp/cg_emoji_l 2>/dev/null | grep -E 'avx2intrin' | grep -E '^\\s*[0-9,]+ ' | sort -rn | head -20", "intent": "See which intrinsics cost most in emoji"}

1,044,246 (37.17%) /usr/lib/gcc/x86_64-pc-linux-gnu/16/include/avx2intrin.h:utf16_to_utf8 --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && callgrind_annotate --auto=yes --threshold=99 /tmp/cg_emoji_l /usr/lib/gcc/x86_64-pc-linux-gnu/16/include/avx2intrin.h 2>/dev/null | grep -E '^\\s*[0-9,]+ ' | grep builtin | sort -rn | head -20", "intent": "Which builtins dominate emoji"}

856 ( 0.03%) return (__m128i) __builtin_ia32_vextractf128_si256 ((__v8si)__X, __N); 334 ( 0.01%) return (__m256i) __builtin_ia32_pshufb256 ((__v32qi)__X, 167 ( 0.01%) return (__m256i) __builtin_ia32_pmaddubsw256 ((__v32qi)__X, 92,800 ( 3.30%) unsigned cnt = (m == 0xFF) ? 8 : (unsigned)__builtin_ctz(~m); 78,772 ( 2.80%) return (__m256i)__builtin_ia32_psrldi256 ((__v8si)__A, __B); 78,772 ( 2.80%) return (__m256i)__builtin_ia32_pslldi256 ((__v8si)__A, __B); 27,540 ( 0.98%) return __builtin_ia32_pmovmskb256 ((__v32qi)__A); 19,693 ( 0.70%) return __builtin_ia32_movmskps256 ((__v8sf)__A); 2,884 ( 0.10%) return __builtin_ia32_ptestz256 ((__v4di)__M, (__v4di)__V); --- Command finished with exit code: 0 ---

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "new_string": " __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF));\n __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF));\n __m256i cp = _mm256_add_epi32(\n _mm256_slli_epi32(hbits, 10), lbits);\n cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000));\n\n // Place each 6-bit field directly at its output byte offset,\n // then OR in the UTF-8 marker bits (0xF0,0x80,0x80,0x80) once.\n __m256i b0 = _mm256_srli_epi32(cp, 18); // <=4, byte 0\n __m256i b1 = _mm256_and_si256(_mm256_srli_epi32(cp, 4),\n _mm256_set1_epi32(0x3F00));\n __m256i b2 = _mm256_and_si256(_mm256_slli_epi32(cp, 10),\n _mm256_set1_epi32(0x3F0000));\n __m256i b3 = _mm256_and_si256(_mm256_slli_epi32(cp, 24),\n _mm256_set1_epi32(0x3F000000));\n __m256i res = _mm256_or_si256(\n _mm256_or_si256(b0, b1),\n _mm256_or_si256(_mm256_or_si256(b2, b3),\n _mm256_set1_epi32((int)0x808080F0)));\n _mm256_storeu_si256((__m256i *)op, res);", "old_string": " __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF));\n __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF));\n __m256i cp = _mm256_add_epi32(\n _mm256_slli_epi32(hbits, 10), lbits);\n cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000));\n\n __m256i B0 = _mm256_or_si256(_mm256_srli_epi32(cp, 18),\n _mm256_set1_epi32(0xF0));\n __m256i B1 = _mm256_slli_epi32(\n _mm256_or_si256(\n _mm256_and_si256(_mm256_srli_epi32(cp, 12),\n _mm256_set1_epi32(0x3F)),\n _mm256_set1_epi32(0x80)), 8);\n __m256i B2 = _mm256_slli_epi32(\n _mm256_or_si256(\n _mm256_and_si256(_mm256_srli_epi32(cp, 6),\n _mm256_set1_epi32(0x3F)),\n _mm256_set1_epi32(0x80)), 16);\n __m256i B3 = _mm256_slli_epi32(\n _mm256_or_si256(\n _mm256_and_si256(cp, _mm256_set1_epi32(0x3F)),\n _mm256_set1_epi32(0x80)), 24);\n __m256i res = _mm256_or_si256(_mm256_or_si256(B0, B1),\n _mm256_or_si256(B2, B3));\n _mm256_storeu_si256((__m256i *)op, res);"}

Edited /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c: replaced 1 occurrence(s) 173- __m256i B0 = _mm256_or_si256(_mm256_srli_epi32(cp, 18), 174- _mm256_set1_epi32(0xF0)); 175- __m256i B1 = _mm256_slli_epi32( 176- _mm256_or_si256( 177- _mm256_and_si256(_mm256_srli_epi32(cp, 12), 178- _mm256_set1_epi32(0x3F)), 179- _mm256_set1_epi32(0x80)), 8); 180- __m256i B2 = _mm256_slli_epi32( 181- _mm256_or_si256( 182- _mm256_and_si256(_mm256_srli_epi32(cp, 6), 183- _mm256_set1_epi32(0x3F)), 184- _mm256_set1_epi32(0x80)), 16); 185- __m256i B3 = _mm256_slli_epi32( 186- _mm256_or_si256( 187- _mm256_and_si256(cp, _mm256_set1_epi32(0x3F)), 188- _mm256_set1_epi32(0x80)), 24); 189- __m256i res = _mm256_or_si256(_mm256_or_si256(B0, B1), 190- _mm256_or_si256(B2, B3)); 173+ // Place each 6-bit field directly at its output byte offset, 174+ // then OR in the UTF-8 marker bits (0xF0,0x80,0x80,0x80) once. 175+ __m256i b0 = _mm256_srli_epi32(cp, 18); // <=4, byte 0 176+ __m256i b1 = _mm256_and_si256(_mm256_srli_epi32(cp, 4), 177+ _mm256_set1_epi32(0x3F00)); 178+ __m256i b2 = _mm256_and_si256(_mm256_slli_epi32(cp, 10), 179+ _mm256_set1_epi32(0x3F0000)); 180+ __m256i b3 = _mm256_and_si256(_mm256_slli_epi32(cp, 24), 181+ _mm256_set1_epi32(0x3F000000)); 182+ __m256i res = _mm256_or_si256( 183+ _mm256_or_si256(b0, b1), 184+ _mm256_or_si256(_mm256_or_si256(b2, b3), 185+ _mm256_set1_epi32((int)0x808080F0))); Context after edit (lines 164-189): 164│ unsigned cnt = (m == 0xFF) ? 8 : (unsigned)__builtin_ctz(~m); 165│ if (cnt == 0) return INVALID; // high surrogate, bad pair 166│ 167│ __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF)); 168│ __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF)); 169│ __m256i cp = _mm256_add_epi32( 170│ _mm256_slli_epi32(hbits, 10), lbits); 171│ cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000)); 172│ 173│ // Place each 6-bit field directly at its output byte offset, 174│ // then OR in the UTF-8 marker bits (0xF0,0x80,0x80,0x80) once. 175│ __m256i b0 = _mm256_srli_epi32(cp, 18); // <=4, byte 0 176│ __m256i b1 = _mm256_and_si256(_mm256_srli_epi32(cp, 4), 177│ _mm256_set1_epi32(0x3F00)); 178│ __m256i b2 = _mm256_and_si256(_mm256_slli_epi32(cp, 10), 179│ _mm256_set1_epi32(0x3F0000)); 180│ __m256i b3 = _mm256_and_si256(_mm256_slli_epi32(cp, 24), 181│ _mm256_set1_epi32(0x3F000000)); 182│ __m256i res = _mm256_or_si256( 183│ _mm256_or_si256(b0, b1), 184│ _mm256_or_si256(_mm256_or_si256(b2, b3), 185│ _mm256_set1_epi32((int)0x808080F0))); 186│ _mm256_storeu_si256((__m256i *)op, res); 187│ op += 4 * cnt; 188│ buf += 2 * cnt; 189│ if (cnt < 8) break;

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -4", "intent": "Grade optimized emoji encode"}

build 2.5s verify 2.4s PASS measure 1.8s 20,768,155 instructions (given: 77,973,585) SCORE +1.9086 (3.754x) --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && valgrind --tool=callgrind --toggle-collect=utf16_to_utf8 --collect-atstart=no --dump-line=yes --callgrind-out-file=/tmp/cg_real .build/runner .build/corpus_56902.bin >/dev/null 2>&1; callgrind_annotate --auto=yes /tmp/cg_real 2>/dev/null | grep -E '^\\s*[0-9,]+ \\([0-9]' | grep -vE 'avx|include' | sort -rn | head -25", "intent": "Line breakdown on real corpus"}

490,295 (13.31%) return (__m256i) ((__v4du)__A & (__v4du)__B); 3,684,812 (100.0%) PROGRAM TOTALS 3,667,136 (99.52%) events annotated 1,771,671 (48.08%) submission/solve.c:utf16_to_utf8 [/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/.build/runner] --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && callgrind_annotate --auto=yes /tmp/cg_real 2>/dev/null | grep -E '[0-9,]+ \\([0-9.]+%\\)' | grep -E 'solve.c:[0-9]| = |op \\+=|buf \\+=|if |mask|_mm' | grep -vE 'PROGRAM|annotated|utf16_to_utf8 \\[' | sort -rn | head -30", "intent": "Top source lines real corpus"}

--- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && callgrind_annotate --auto=yes --context=1 /tmp/cg_real 2>/dev/null | grep -A400 'solve.c:utf16' | grep -E '^\\s*[0-9][0-9,]* \\(' | sort -rn | head -25", "intent": "Top annotated lines"}

798 ( 0.02%) } else if (c < 0xDC00) { 556 ( 0.02%) size_t tail = scalar_tail(buf, (size_t)(end - buf), op); 556 ( 0.02%) size_t o = 0; 490,295 (13.31%) return (__m256i) ((__v4du)__A & (__v4du)__B); 399 ( 0.01%) uint32_t lo = in[i + 1]; 288,722 ( 7.84%) /usr/lib/gcc/x86_64-pc-linux-gnu/16/include/emmintrin.h:utf16_to_utf8 264,249 ( 7.17%) /usr/lib/gcc/x86_64-pc-linux-gnu/16/include/avxintrin.h:utf16_to_utf8 215,159 ( 5.84%) return (__m256i) ((__v4du)__A | (__v4du)__B); 185,572 ( 5.04%) if ((w & 0xF800) != 0xD800) { 171,601 ( 4.66%) return (__m256i) ((__v16hi)__A == (__v16hi)__B); 157,680 ( 4.28%) return *__P; 135,618 ( 3.68%) while ((size_t)(end - buf) >= 16 + safety_margin) { 104,574 ( 2.84%) *__P = __B; 85,200 ( 2.31%) while ((size_t)(end - buf) >= 16 && 80,373 ( 2.18%) return __builtin_ia32_ptestz256 ((__v4di)__M, (__v4di)__V); 79,696 ( 2.16%) return __builtin_ia32_pmovmskb256 ((__v32qi)__A); 79,504 ( 2.16%) return (__m256i) ((__v8si)__A == (__v8si)__B); 78,778 ( 2.14%) while (buf < stop) { 78,778 ( 2.14%) if (w < 0x80) { 78,778 ( 2.14%) *op++ = (uint8_t)w; 78,699 ( 2.14%) if (!_mm256_testz_si256(inv, v_ff80)) break; 72,857 ( 1.98%) if (_mm256_testz_si256(inv, v_ff80)) { // ASCII fast path 70,045 ( 1.90%) return *__P; 67,278 ( 1.83%) if (one_or_two_bytes_bitmask == 0xffffffff) { 65,521 ( 1.78%) return (__m128i) __builtin_ia32_vextractf128_si256 ((__v8si)__X, __N); --- Command finished with exit code: 0 ---

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "new_string": " if (surrogates_bitmask != 0x00000000) {\n // Leading run before the first surrogate. If that whole prefix is\n // ASCII (the common emoji case: ascii-run then a surrogate pair),\n // emit it with one packed store.\n unsigned sidx = (unsigned)__builtin_ctz(surrogates_bitmask) >> 1;\n const __m256i one_byte_bytemask =\n _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_ff80), v_0000);\n unsigned ascii_run = (unsigned)__builtin_ctz(\n ~(uint32_t)_mm256_movemask_epi8(one_byte_bytemask)) >> 1;\n if (ascii_run >= sidx) {\n const __m128i packed = _mm_packus_epi16(\n _mm256_castsi256_si128(inv),\n _mm256_extractf128_si256(inv, 1));\n _mm_storeu_si128((__m128i *)op, packed);\n op += sidx;\n buf += sidx;\n } else {\n // Mixed BMP prefix: emit scalar until first high surrogate.\n const uint16_t *stop = buf + 16;\n while (buf < stop) {\n uint16_t w = *buf;\n if ((w & 0xF800) != 0xD800) {\n if (w < 0x80) {\n *op++ = (uint8_t)w;\n } else if (w < 0x800) {\n *op++ = (uint8_t)(0xC0 | (w >> 6));\n *op++ = (uint8_t)(0x80 | (w & 0x3F));\n } else {\n *op++ = (uint8_t)(0xE0 | (w >> 12));\n *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F));\n *op++ = (uint8_t)(0x80 | (w & 0x3F));\n }\n buf++;\n } else if (w < 0xDC00) {\n break;\n } else {\n return INVALID; // lone low surrogate\n }\n }\n }", "old_string": " if (surrogates_bitmask != 0x00000000) {\n // At least one surrogate in this window. Emit leading BMP units\n // scalar until we reach a high surrogate, then vector-process the\n // contiguous surrogate-pair run 8 pairs at a time.\n const uint16_t *stop = buf + 16;\n while (buf < stop) {\n uint16_t w = *buf;\n if ((w & 0xF800) != 0xD800) {\n if (w < 0x80) {\n *op++ = (uint8_t)w;\n } else if (w < 0x800) {\n *op++ = (uint8_t)(0xC0 | (w >> 6));\n *op++ = (uint8_t)(0x80 | (w & 0x3F));\n } else {\n *op++ = (uint8_t)(0xE0 | (w >> 12));\n *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F));\n *op++ = (uint8_t)(0x80 | (w & 0x3F));\n }\n buf++;\n } else if (w < 0xDC00) {\n break; // high surrogate: switch to vector pair path\n } else {\n return INVALID; // lone low surrogate\n }\n }"}

Edited /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c: replaced 1 occurrence(s) 125- // At least one surrogate in this window. Emit leading BMP units 126- // scalar until we reach a high surrogate, then vector-process the 127- // contiguous surrogate-pair run 8 pairs at a time. 128- const uint16_t *stop = buf + 16; 129- while (buf < stop) { 130- uint16_t w = *buf; 131- if ((w & 0xF800) != 0xD800) { 132- if (w < 0x80) { 133- *op++ = (uint8_t)w; 134- } else if (w < 0x800) { 135- *op++ = (uint8_t)(0xC0 | (w >> 6)); 136- *op++ = (uint8_t)(0x80 | (w & 0x3F)); 125+ // Leading run before the first surrogate. If that whole prefix is 126+ // ASCII (the common emoji case: ascii-run then a surrogate pair), 127+ // emit it with one packed store. 128+ unsigned sidx = (unsigned)__builtin_ctz(surrogates_bitmask) >> 1; 129+ const __m256i one_byte_bytemask = 130+ _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_ff80), v_0000); 131+ unsigned ascii_run = (unsigned)__builtin_ctz( 132+ ~(uint32_t)_mm256_movemask_epi8(one_byte_bytemask)) >> 1; 133+ if (ascii_run >= sidx) { 134+ const __m128i packed = _mm_packus_epi16( 135+ _mm256_castsi256_si128(inv), 136+ _mm256_extractf128_si256(inv, 1)); 137+ _mm_storeu_si128((__m128i *)op, packed); 138+ op += sidx; 139+ buf += sidx; 140+ } else { 141+ // Mixed BMP prefix: emit scalar until first high surrogate. 142+ const uint16_t *stop = buf + 16; 143+ while (buf < stop) { 144+ uint16_t w = *buf; 145+ if ((w & 0xF800) != 0xD800) { 146+ if (w < 0x80) { 147+ *op++ = (uint8_t)w; 148+ } else if (w < 0x800) { 149+ *op++ = (uint8_t)(0xC0 | (w >> 6)); 150+ *op++ = (uint8_t)(0x80 | (w & 0x3F)); 151+ } else { 152+ *op++ = (uint8_t)(0xE0 | (w >> 12)); 153+ *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F)); 154+ *op++ = (uint8_t)(0x80 | (w & 0x3F)); 155+ } 156+ buf++; 157+ } else if (w < 0xDC00) { 158+ break; 138- *op++ = (uint8_t)(0xE0 | (w >> 12)); 139- *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F)); 140- *op++ = (uint8_t)(0x80 | (w & 0x3F)); 160+ return INVALID; // lone low surrogate 142- buf++; 143- } else if (w < 0xDC00) { 144- break; // high surrogate: switch to vector pair path 145- } else { 146- return INVALID; // lone low surrogate Context after edit (lines 121-166): 121│ const uint32_t surrogates_bitmask = 122│ (uint32_t)_mm256_movemask_epi8(surrogates_bytemask); 123│ 124│ if (surrogates_bitmask != 0x00000000) { 125│ // Leading run before the first surrogate. If that whole prefix is 126│ // ASCII (the common emoji case: ascii-run then a surrogate pair), 127│ // emit it with one packed store. 128│ unsigned sidx = (unsigned)__builtin_ctz(surrogates_bitmask) >> 1; 129│ const __m256i one_byte_bytemask = 130│ _mm256_cmpeq_epi16(_mm256_and_si256(inv, v_ff80), v_0000); 131│ unsigned ascii_run = (unsigned)__builtin_ctz( 132│ ~(uint32_t)_mm256_movemask_epi8(one_byte_bytemask)) >> 1; 133│ if (ascii_run >= sidx) { 134│ const __m128i packed = _mm_packus_epi16( 135│ _mm256_castsi256_si128(inv), 136│ _mm256_extractf128_si256(inv, 1)); 137│ _mm_storeu_si128((__m128i *)op, packed); 138│ op += sidx; 139│ buf += sidx; 140│ } else { 141│ // Mixed BMP prefix: emit scalar until first high surrogate. 142│ const uint16_t *stop = buf + 16; 143│ while (buf < stop) { 144│ uint16_t w = *buf; 145│ if ((w & 0xF800) != 0xD800) { 146│ if (w < 0x80) { 147│ *op++ = (uint8_t)w; 148│ } else if (w < 0x800) { 149│ *op++ = (uint8_t)(0xC0 | (w >> 6)); 150│ *op++ = (uint8_t)(0x80 | (w & 0x3F)); 151│ } else { 152│ *op++ = (uint8_t)(0xE0 | (w >> 12)); 153│ *op++ = (uint8_t)(0x80 | ((w >> 6) & 0x3F)); 154│ *op++ = (uint8_t)(0x80 | (w & 0x3F)); 155│ } 156│ buf++; 157│ } else if (w < 0xDC00) { 158│ break; 159│ } else { 160│ return INVALID; // lone low surrogate 161│ } 162│ } 163│ } 164│ 165│ // Vector surrogate-pair run. 166│ while ((size_t)(end - buf) >= 16 &&

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "limit": 30, "start_line": 163}

163 } 164 165 // Vector surrogate-pair run. 166 while ((size_t)(end - buf) >= 16 && 167 ((uint16_t)(buf[0] & 0xFC00) == 0xD800)) { 168 __m256i d = _mm256_loadu_si256((const __m256i *)buf); 169 __m256i lo16 = _mm256_and_si256(d, _mm256_set1_epi32(0xFFFF)); 170 __m256i hi16 = _mm256_srli_epi32(d, 16); 171 __m256i lo_ok = _mm256_cmpeq_epi32( 172 _mm256_and_si256(lo16, _mm256_set1_epi32(0xFC00)), 173 _mm256_set1_epi32(0xD800)); 174 __m256i hi_ok = _mm256_cmpeq_epi32( 175 _mm256_and_si256(hi16, _mm256_set1_epi32(0xFC00)), 176 _mm256_set1_epi32(0xDC00)); 177 __m256i ok = _mm256_and_si256(lo_ok, hi_ok); 178 unsigned m = (unsigned)_mm256_movemask_ps(_mm256_castsi256_ps(ok)); 179 unsigned cnt = (m == 0xFF) ? 8 : (unsigned)__builtin_ctz(~m); 180 if (cnt == 0) return INVALID; // high surrogate, bad pair 181 182 __m256i hbits = _mm256_and_si256(lo16, _mm256_set1_epi32(0x3FF)); 183 __m256i lbits = _mm256_and_si256(hi16, _mm256_set1_epi32(0x3FF)); 184 __m256i cp = _mm256_add_epi32( 185 _mm256_slli_epi32(hbits, 10), lbits); 186 cp = _mm256_add_epi32(cp, _mm256_set1_epi32(0x10000)); 187 188 // Place each 6-bit field directly at its output byte offset, 189 // then OR in the UTF-8 marker bits (0xF0,0x80,0x80,0x80) once. 190 __m256i b0 = _mm256_srli_epi32(cp, 18); // <=4, byte 0 191 __m256i b1 = _mm256_and_si256(_mm256_srli_epi32(cp, 4), 192 _mm256_set1_epi32(0x3F00)); ... 117 more lines (use start_line=193 to continue)

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "new_string": " }\n\n // buf now points at the first surrogate. If it is a low\n // surrogate, it is lone (invalid). Otherwise it is a high\n // surrogate: process the contiguous pair run.\n if ((uint16_t)(buf[0] & 0xFC00) == 0xDC00) return INVALID;\n\n // Vector surrogate-pair run.\n while ((size_t)(end - buf) >= 16 &&", "old_string": " }\n\n // Vector surrogate-pair run.\n while ((size_t)(end - buf) >= 16 &&"}

Edited /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c: replaced 1 occurrence(s) 165+ // buf now points at the first surrogate. If it is a low 166+ // surrogate, it is lone (invalid). Otherwise it is a high 167+ // surrogate: process the contiguous pair run. 168+ if ((uint16_t)(buf[0] & 0xFC00) == 0xDC00) return INVALID; Context after edit (lines 160-174): 160│ return INVALID; // lone low surrogate 161│ } 162│ } 163│ } 164│ 165│ // buf now points at the first surrogate. If it is a low 166│ // surrogate, it is lone (invalid). Otherwise it is a high 167│ // surrogate: process the contiguous pair run. 168│ if ((uint16_t)(buf[0] & 0xFC00) == 0xDC00) return INVALID; 169│ 170│ // Vector surrogate-pair run. 171│ while ((size_t)(end - buf) >= 16 && 172│ ((uint16_t)(buf[0] & 0xFC00) == 0xD800)) { 173│ __m256i d = _mm256_loadu_si256((const __m256i *)buf); 174│ __m256i lo16 = _mm256_and_si256(d, _mm256_set1_epi32(0xFFFF));

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -4", "intent": "Grade vectorized BMP prefix"}

build 2.6s verify 2.4s PASS measure 1.9s 18,488,849 instructions (given: 77,900,827) SCORE +2.0750 (4.213x) --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade --full 2>&1 | tail -4 && for R in ascii latin cjk emoji; do\nvalgrind --tool=callgrind --toggle-collect=utf16_to_utf8 --collect-atstart=no --dump-line=no --callgrind-out-file=/tmp/cg_$R .build/runner /tmp/corp_$R.bin >/dev/null 2>&1\nt=$(grep -E '^[0-9]+ [0-9]+' /tmp/cg_$R | awk '{s+=$2} END{print s}')\necho \"$R mine=$t\"\ndone", "intent": "Full gate and per-regime"}

build 2.4s verify 2.5s PASS (FULL gate) measure 1.8s 18,422,163 instructions (given: 77,961,429) SCORE +2.0813 (4.232x) ascii mine=1758871 latin mine=5861301 cjk mine=8467702 emoji mine=10990242 --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && valgrind --tool=callgrind --toggle-collect=utf16_to_utf8 --collect-atstart=no --dump-line=yes --callgrind-out-file=/tmp/cg_cjkl .build/runner /tmp/corp_cjk.bin >/dev/null 2>&1; callgrind_annotate --auto=yes /tmp/cg_cjkl 2>/dev/null | grep -E '^\\s*[0-9][0-9,]* \\(' | sort -rn | head -22", "intent": "CJK line profile"}

748,751 (50.76%) /usr/lib/gcc/x86_64-pc-linux-gnu/16/include/avx2intrin.h:utf16_to_utf8 704 ( 0.05%) } 640 ( 0.04%) out[o++] = (uint8_t)c; 528 ( 0.04%) uint8_t *op = out; 460,834 (31.24%) submission/solve.c:utf16_to_utf8 [/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/.build/runner] 364 ( 0.02%) return __builtin_ia32_ptestz256 ((__v4di)__M, (__v4di)__V); 352 ( 0.02%) return (size_t)(op - out) + tail; 352 ( 0.02%) if (tail == INVALID) return INVALID; 352 ( 0.02%) const uint16_t *end = in + n; 204,479 (13.86%) return (__m256i) ((__v4du)__A & (__v4du)__B); 182,396 (12.37%) /usr/lib/gcc/x86_64-pc-linux-gnu/16/include/emmintrin.h:utf16_to_utf8 176 ( 0.01%) size_t tail = scalar_tail(buf, (size_t)(end - buf), op); 176 ( 0.01%) size_t o = 0; 130,011 ( 8.81%) return (__m256i) ((__v16hi)__A == (__v16hi)__B); 111,438 ( 7.56%) return (__m256i) ((__v4du)__A | (__v4du)__B); 108,096 ( 7.33%) return *__P; 75,524 ( 5.12%) while ((size_t)(end - buf) >= 16 + safety_margin) { 74,296 ( 5.04%) *__P = __B; 74,292 ( 5.04%) return (__m256i) __builtin_ia32_andnotsi256 ((__v4di)__A, (__v4di)__B); 56,091 ( 3.80%) /usr/lib/gcc/x86_64-pc-linux-gnu/16/include/avxintrin.h:utf16_to_utf8 55,719 ( 3.78%) return __builtin_ia32_pmovmskb256 ((__v32qi)__A); 55,719 ( 3.78%) return (__m256i)__builtin_ia32_psrlwi256 ((__v16hi)__A, __B); --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && valgrind --tool=callgrind --toggle-collect=utf16_to_utf8 --collect-atstart=no --dump-line=yes --callgrind-out-file=/tmp/cg_latl .build/runner /tmp/corp_latin.bin >/dev/null 2>&1; callgrind_annotate --auto=yes /tmp/cg_latl 2>/dev/null | grep -E '^\\s*[0-9][0-9,]* \\(' | grep 'solve.c:' | sort -rn | head -15", "intent": "Latin source line profile"}

443,968 (42.78%) submission/solve.c:utf16_to_utf8 [/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/.build/runner] --- Command finished with exit code: 0 ---

{"file_path": "/tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c", "new_string": "#pragma GCC optimize(\"O3,unroll-loops\")", "old_string": "#pragma GCC optimize(\"O3\")"}

Edited /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode/submission/solve.c: replaced 1 occurrence(s) 10- #pragma GCC optimize("O3") 10+ #pragma GCC optimize("O3,unroll-loops") Context after edit (lines 7-13): 7│ #define INVALID ((size_t)-1) 8│ 9│ #if defined(__x86_64__) || defined(__i386__) 10│ #pragma GCC optimize("O3,unroll-loops") 11│ #pragma GCC target("avx2") 12│ #include <immintrin.h> 13│ #include "tables.h"

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -3", "intent": "Grade unroll-loops"}

verify 2.4s PASS measure 1.9s 18,013,809 instructions (given: 78,055,702) SCORE +2.1154 (4.333x) --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && for R in ascii latin cjk emoji; do\nvalgrind --tool=callgrind --toggle-collect=utf16_to_utf8 --collect-atstart=no --dump-line=no --callgrind-out-file=/tmp/cg_$R .build/runner /tmp/corp_$R.bin >/dev/null 2>&1\nt=$(grep -E '^[0-9]+ [0-9]+' /tmp/cg_$R | awk '{s+=$2} END{print s}')\necho \"$R mine=$t\"\ndone", "intent": "Per regime after unroll"}

ascii mine=1313327 latin mine=5891219 cjk mine=8484559 emoji mine=11230796 --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade --full 2>&1 | tail -4", "intent": "Final full gate"}

build 2.5s verify 2.4s PASS (FULL gate) measure 1.9s 18,107,461 instructions (given: 78,231,567) SCORE +2.1112 (4.320x) --- Command finished with exit code: 0 ---

{"command": "cd /tmp/jcode-bench/20260719T102808Z-jcode-solo-claude-opus-4-8-utf16-transcode/tasks/utf16-transcode && ./grade 2>&1 | tail -4 && echo \"=== score history ===\" && tail -5 scores.jsonl", "intent": "Final grade and history"}

build 2.6s verify 2.4s PASS measure 1.9s 18,047,779 instructions (given: 77,842,845) SCORE +2.1087 (4.313x) === score history === {"ts": "2026-07-19T10:59:52Z", "seed": 58785, "cost": 18488849, "given_cost": 77900827, "score": 2.075, "full_gate": false} {"ts": "2026-07-19T11:00:05Z", "seed": 58798, "cost": 18422163, "given_cost": 77961429, "score": 2.0813, "full_gate": true} {"ts": "2026-07-19T11:01:18Z", "seed": 58871, "cost": 18013809, "given_cost": 78055702, "score": 2.1154, "full_gate": false} {"ts": "2026-07-19T11:02:07Z", "seed": 58920, "cost": 18107461, "given_cost": 78231567, "score": 2.1112, "full_gate": true} {"ts": "2026-07-19T11:02:25Z", "seed": 58938, "cost": 18047779, "given_cost": 77842845, "score": 2.1087, "full_gate": false} --- Command finished with exit code: 0 ---