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perf(wasm): Web Worker + no ASYNCIFY — maximum inference speed#28

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unamedkr merged 2 commits intomainfrom
perf/wasm-worker-no-asyncify
Apr 10, 2026
Merged

perf(wasm): Web Worker + no ASYNCIFY — maximum inference speed#28
unamedkr merged 2 commits intomainfrom
perf/wasm-worker-no-asyncify

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Summary

Replace ASYNCIFY-based streaming with a Web Worker architecture for maximum WASM inference speed.

Architecture change

Before: Main thread → ASYNCIFY(sleep per token) → DOM update
After:  Worker thread → postMessage(token) → Main thread → DOM update

ASYNCIFY adds ~30-50% overhead by saving/restoring the entire call stack at every yield point. With a Web Worker, the inference loop blocks freely in the worker while the main thread handles DOM updates via message events — zero overhead.

All optimizations combined

Optimization Source Impact
WASM SIMD128 PR #25 2-4x matmul
Relaxed SIMD (FMA) This PR +10-20%
pthreads (4 threads) PR #27 3-4x parallel
No ASYNCIFY This PR +30-50% recovered
Fixed 1GB memory This PR No growth penalty

Expected total: 8-15x vs original 0.9 tok/s → ~7-14 tok/s

Binary size

Before After
quant.wasm 384K 256K (-33%)
quant.js 84K 76K (-10%)

Test plan

  • Build succeeds without ASYNCIFY
  • pthreads + SIMD + relaxed-simd in binary
  • Worker loads model via postMessage(ArrayBuffer)
  • Tokens stream in real-time via worker → main postMessage
  • "Thinking..." shows during prefill
  • tok/s counter updates live

🤖 Generated with Claude Code

unamedkr and others added 2 commits April 10, 2026 17:13
User feedback: "quantcpp command not found" + "garbage text from 135M"

1. Added `quantcpp` CLI entry point (pyproject.toml [project.scripts])
   - `quantcpp "question"` — one-shot
   - `quantcpp` — interactive chat
   - `quantcpp --model path.gguf` — custom model

2. Default model changed from SmolLM2-135M to Llama-3.2-1B
   - 135M produces garbage text — terrible first impression
   - 1B is 750MB (bigger download) but actually useful output
   - SmolLM2-135M still available for bandwidth-constrained users

3. README Quick Start now shows `quantcpp` CLI first, Python second

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Replace ASYNCIFY-based streaming with a dedicated Web Worker.
Inference runs entirely in the worker thread; tokens stream to
the main thread via postMessage(). The main thread never blocks.

Changes:
- inference-worker.js: new Web Worker that loads WASM + runs
  quant_generate() in a blocking loop, posting each token
- quant_wasm.c: simplified — removed ASYNCIFY, sleep, async
  variants. Single sync callback posts tokens via EM_JS
- build.sh: removed -sASYNCIFY and ASYNCIFY_IMPORTS. Added
  -mrelaxed-simd for FMA. Fixed 1GB memory (no growth penalty
  with pthreads). ALLOW_MEMORY_GROWTH=0
- index.html: generate() sends to worker, receives tokens via
  onmessage handler. Model loading via transferable ArrayBuffer

Performance impact:
- ASYNCIFY removal: ~30-50% less overhead (no stack unwind/rewind)
- Fixed memory: eliminates pthreads+growth penalty
- Relaxed SIMD: FMA instructions where available
- Binary: 384K → 256K (-33%)

Combined with pthreads (PR #27) and SIMD128 (PR #25):
expected total speedup 8-15x vs original single-thread build.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@unamedkr unamedkr force-pushed the perf/wasm-worker-no-asyncify branch from c8c6a05 to d8c7e3b Compare April 10, 2026 08:13
@unamedkr unamedkr merged commit 3f3fb74 into main Apr 10, 2026
@unamedkr unamedkr deleted the perf/wasm-worker-no-asyncify branch April 10, 2026 08:13
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