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perf(wasm): Web Worker architecture — eliminate ASYNCIFY for max speed
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>
1 parent a627982 commit d8c7e3b

6 files changed

Lines changed: 187 additions & 221 deletions

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‎wasm/build.sh‎

Lines changed: 13 additions & 27 deletions
Original file line numberDiff line numberDiff line change
@@ -1,54 +1,45 @@
11
#!/bin/bash
2-
# Build quant.cpp WASM demo (multi-threaded + SIMD)
2+
# Build quant.cpp WASM demo (multi-threaded + SIMD, no ASYNCIFY)
33
# Requires: Emscripten SDK (emcc)
44
#
5-
# Usage: cd wasm && bash build.sh
6-
# Then: python3 -m http.server 8080
7-
# Open: http://localhost:8080
8-
#
9-
# Multi-threading requires Cross-Origin-Isolation headers.
10-
# coi-serviceworker.js injects them on GitHub Pages / static hosts.
5+
# Architecture: inference runs in a Web Worker (inference-worker.js)
6+
# so the main thread stays responsive. No ASYNCIFY needed — the worker
7+
# blocks on quant_generate() while postMessage streams tokens.
118

129
set -e
1310

1411
SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
1512
PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
1613

17-
echo "=== Building quant.cpp WASM (pthreads + SIMD) ==="
14+
echo "=== Building quant.cpp WASM (pthreads + SIMD, no ASYNCIFY) ==="
1815

19-
# Check emcc
2016
if ! command -v emcc &>/dev/null; then
21-
echo "Error: emcc not found. Install Emscripten:"
22-
echo " brew install emscripten"
23-
echo " # or: git clone https://github.com/emscripten-core/emsdk && ./emsdk install latest && ./emsdk activate latest"
17+
echo "Error: emcc not found. Install Emscripten SDK."
2418
exit 1
2519
fi
2620

2721
echo "emcc version: $(emcc --version | head -1)"
2822

29-
# Build with pthreads + SIMD128 + ASYNCIFY
3023
emcc "$SCRIPT_DIR/quant_wasm.c" \
3124
-I"$PROJECT_DIR" \
3225
-o "$SCRIPT_DIR/quant.js" \
3326
-O3 \
3427
-msimd128 \
28+
-mrelaxed-simd \
3529
-flto \
3630
-pthread \
3731
-s WASM=1 \
38-
-s ALLOW_MEMORY_GROWTH=1 \
32+
-s INITIAL_MEMORY=1GB \
3933
-s MAXIMUM_MEMORY=4GB \
40-
-s INITIAL_MEMORY=256MB \
41-
-s EXPORTED_FUNCTIONS='["_main","_wasm_load_model","_wasm_generate","_wasm_generate_async","_wasm_model_info","_wasm_is_ready","_malloc","_free"]' \
34+
-s ALLOW_MEMORY_GROWTH=0 \
35+
-s EXPORTED_FUNCTIONS='["_main","_wasm_load_model","_wasm_generate","_wasm_model_info","_wasm_is_ready","_malloc","_free"]' \
4236
-s EXPORTED_RUNTIME_METHODS='["UTF8ToString","allocateUTF8","FS"]' \
4337
-s FORCE_FILESYSTEM=1 \
4438
-s MODULARIZE=0 \
4539
-s ENVIRONMENT='web,worker' \
4640
-s NO_EXIT_RUNTIME=1 \
4741
-s ASSERTIONS=0 \
4842
-s STACK_SIZE=1MB \
49-
-s ASYNCIFY \
50-
-s 'ASYNCIFY_IMPORTS=["emscripten_sleep"]' \
51-
-s ASYNCIFY_STACK_SIZE=65536 \
5243
-s PTHREAD_POOL_SIZE=4 \
5344
-s PTHREAD_POOL_SIZE_STRICT=0 \
5445
-lm \
@@ -59,14 +50,9 @@ emcc "$SCRIPT_DIR/quant_wasm.c" \
5950

6051
echo ""
6152
echo "=== Build complete ==="
62-
echo "Files:"
63-
for f in quant.js quant.wasm quant.worker.js; do
53+
for f in quant.js quant.wasm; do
6454
[ -f "$SCRIPT_DIR/$f" ] && echo " $f ($(du -h "$SCRIPT_DIR/$f" | cut -f1))"
6555
done
6656
echo ""
67-
echo "To serve locally:"
68-
echo " cd $SCRIPT_DIR && python3 -m http.server 8080"
69-
echo " Open http://localhost:8080"
70-
echo ""
71-
echo "Note: Multi-threading requires Cross-Origin-Isolation."
72-
echo "coi-serviceworker.js handles this automatically on GitHub Pages."
57+
echo " inference-worker.js — Web Worker wrapper (no ASYNCIFY overhead)"
58+
echo " coi-serviceworker.js — COOP/COEP header injection for pthreads"

‎wasm/index.html‎

Lines changed: 87 additions & 97 deletions
Original file line numberDiff line numberDiff line change
@@ -356,28 +356,10 @@ <h2>LLM in Your Browser</h2>
356356
}
357357

358358
function loadModelFromBytes(bytes, name) {
359-
try {
360-
Module.FS.writeFile('/model.gguf', bytes);
361-
showLoading('Initializing model...');
362-
const rc = Module._wasm_load_model(Module.allocateUTF8('/model.gguf'));
363-
if (rc === 0) {
364-
modelLoaded = true;
365-
const dropzone = document.getElementById('dropzone');
366-
dropzone.classList.add('loaded');
367-
dropzone.innerHTML = `<h2>✓ ${name} (${(bytes.length/1048576).toFixed(0)} MB)</h2>
368-
<p style="color:#6ee7b7">KV compression active — 3x longer context</p>`;
369-
document.getElementById('kvBadge').style.display = '';
370-
document.getElementById('prompt').disabled = false;
371-
document.getElementById('sendBtn').disabled = false;
372-
document.getElementById('prompt').focus();
373-
addMessage('system', `Model loaded! ${name} (${(bytes.length/1048576).toFixed(0)} MB). Ask anything.`);
374-
} else {
375-
addMessage('system', 'Failed to load model.');
376-
}
377-
} catch(e) {
378-
addMessage('system', `Error: ${e.message}`);
379-
}
380-
hideLoading();
359+
showLoading('Loading model into WASM...');
360+
// Transfer ArrayBuffer to worker (zero-copy)
361+
const buffer = bytes.buffer.slice(bytes.byteOffset, bytes.byteOffset + bytes.byteLength);
362+
worker.postMessage({ type: 'load', bytes: buffer, name: name }, [buffer]);
381363
}
382364

383365
async function loadModel(file) {
@@ -402,8 +384,81 @@ <h2>LLM in Your Browser</h2>
402384
return `<|im_start|>user\n${text}<|im_end|>\n<|im_start|>assistant\n`;
403385
}
404386

405-
async function generate() {
406-
if (!modelLoaded || generating) return;
387+
// ---- Web Worker inference engine (no ASYNCIFY overhead) ----
388+
let worker = null;
389+
let pendingAssistantDiv = null;
390+
let pendingOutput = '';
391+
let pendingTokenCount = 0;
392+
let pendingStartTime = 0;
393+
394+
function initWorker() {
395+
worker = new Worker('inference-worker.js');
396+
worker.onmessage = function(e) {
397+
const msg = e.data;
398+
399+
if (msg.type === 'ready') {
400+
addMessage('system', 'Runtime ready. Choose a model or drop your own GGUF file.');
401+
}
402+
else if (msg.type === 'status') {
403+
if (msg.msg === 'thinking' && pendingAssistantDiv) {
404+
pendingAssistantDiv.innerHTML = '<span class="thinking"><span class="spinner" style="display:inline-block;width:12px;height:12px;vertical-align:middle;margin-right:6px"></span>Thinking...</span>';
405+
document.getElementById('statTokens').textContent = 'Processing prompt...';
406+
document.getElementById('statSpeed').textContent = '';
407+
} else {
408+
addMessage('system', msg.msg);
409+
}
410+
}
411+
else if (msg.type === 'loaded') {
412+
modelLoaded = true;
413+
const dropzone = document.getElementById('dropzone');
414+
dropzone.classList.add('loaded');
415+
dropzone.innerHTML = `<h2>✓ ${msg.name} (${(msg.size/1048576).toFixed(0)} MB)</h2>
416+
<p style="color:#6ee7b7">KV compression active — 3x longer context</p>`;
417+
document.getElementById('kvBadge').style.display = '';
418+
document.getElementById('prompt').disabled = false;
419+
document.getElementById('sendBtn').disabled = false;
420+
document.getElementById('prompt').focus();
421+
hideLoading();
422+
}
423+
else if (msg.type === 'token' && pendingAssistantDiv) {
424+
pendingOutput += msg.text;
425+
pendingTokenCount++;
426+
pendingAssistantDiv.textContent = pendingOutput;
427+
const cursor = document.createElement('span');
428+
cursor.className = 'cursor';
429+
cursor.textContent = '▌';
430+
pendingAssistantDiv.appendChild(cursor);
431+
const chat = document.getElementById('chat');
432+
chat.scrollTop = chat.scrollHeight;
433+
const elapsed = (performance.now() - pendingStartTime) / 1000;
434+
if (elapsed > 0.1) {
435+
document.getElementById('statTokens').textContent = `${pendingTokenCount} tokens`;
436+
document.getElementById('statSpeed').textContent = `${(pendingTokenCount / elapsed).toFixed(1)} tok/s`;
437+
}
438+
}
439+
else if (msg.type === 'done') {
440+
if (pendingAssistantDiv) {
441+
if (pendingOutput) {
442+
pendingAssistantDiv.innerHTML = formatText(pendingOutput);
443+
} else {
444+
pendingAssistantDiv.innerHTML = '<em style="color:#666">No output generated. Try a longer prompt.</em>';
445+
}
446+
const elapsed = (performance.now() - pendingStartTime) / 1000;
447+
const tps = pendingTokenCount > 0 ? (pendingTokenCount / elapsed).toFixed(1) : '0';
448+
document.getElementById('statTokens').textContent = `${pendingTokenCount} tokens`;
449+
document.getElementById('statSpeed').textContent = `${tps} tok/s`;
450+
}
451+
generating = false;
452+
document.getElementById('sendBtn').disabled = false;
453+
document.getElementById('prompt').disabled = false;
454+
document.getElementById('prompt').focus();
455+
pendingAssistantDiv = null;
456+
}
457+
};
458+
}
459+
460+
function generate() {
461+
if (!modelLoaded || generating || !worker) return;
407462
const input = document.getElementById('prompt');
408463
const text = input.value.trim();
409464
if (!text) return;
@@ -414,84 +469,19 @@ <h2>LLM in Your Browser</h2>
414469
input.disabled = true;
415470

416471
addMessage('user', text);
417-
const assistantDiv = addMessage('assistant', '');
418-
// Show "thinking" indicator during prompt prefill (before first token)
419-
assistantDiv.innerHTML = '<span class="thinking"><span class="spinner" style="display:inline-block;width:12px;height:12px;vertical-align:middle;margin-right:6px"></span>Thinking...</span>';
420-
let output = '';
421-
let tokenCount = 0;
422-
const startTime = performance.now();
423-
document.getElementById('statTokens').textContent = 'Processing prompt...';
424-
document.getElementById('statSpeed').textContent = '';
425-
426-
// Set streaming token callback
427-
Module.onToken = (token) => {
428-
output += token;
429-
tokenCount++;
430-
// Update the assistant message with raw text + blinking cursor
431-
assistantDiv.textContent = output;
432-
const cursor = document.createElement('span');
433-
cursor.className = 'cursor';
434-
cursor.textContent = '▌';
435-
assistantDiv.appendChild(cursor);
436-
// Auto-scroll
437-
const chat = document.getElementById('chat');
438-
chat.scrollTop = chat.scrollHeight;
439-
// Live stats
440-
const elapsed = (performance.now() - startTime) / 1000;
441-
if (elapsed > 0.1) {
442-
document.getElementById('statTokens').textContent = `${tokenCount} tokens`;
443-
document.getElementById('statSpeed').textContent = `${(tokenCount / elapsed).toFixed(1)} tok/s`;
444-
}
445-
};
446-
447-
Module.onDone = (nTokens, elapsedMs) => {
448-
// Final render with markdown formatting
449-
assistantDiv.innerHTML = formatText(output);
450-
const tps = nTokens > 0 ? (nTokens / (elapsedMs / 1000)).toFixed(1) : '0';
451-
document.getElementById('statTokens').textContent = `${nTokens} tokens`;
452-
document.getElementById('statSpeed').textContent = `${tps} tok/s`;
453-
generating = false;
454-
document.getElementById('sendBtn').disabled = false;
455-
input.disabled = false;
456-
input.focus();
457-
};
472+
pendingAssistantDiv = addMessage('assistant', '');
473+
pendingAssistantDiv.innerHTML = '<span class="thinking"><span class="spinner" style="display:inline-block;width:12px;height:12px;vertical-align:middle;margin-right:6px"></span>Thinking...</span>';
474+
pendingOutput = '';
475+
pendingTokenCount = 0;
476+
pendingStartTime = performance.now();
458477

459478
const chatPrompt = getChatPrompt(text);
460-
461-
// Use ASYNCIFY: _wasm_generate_async yields to browser between tokens
462-
const promptPtr = Module.allocateUTF8(chatPrompt);
463-
try {
464-
await Module._wasm_generate_async(promptPtr, 0.7, 256);
465-
} catch(e) {
466-
// Fallback for non-ASYNCIFY builds
467-
Module._wasm_generate(promptPtr, 0.7, 256);
468-
}
469-
Module._free(promptPtr);
470-
471-
if (!output) {
472-
assistantDiv.innerHTML = '<em style="color:#666">No output generated. Try a longer prompt.</em>';
473-
}
474-
generating = false;
475-
document.getElementById('sendBtn').disabled = false;
476-
input.disabled = false;
479+
worker.postMessage({ type: 'generate', prompt: chatPrompt, temperature: 0.7, maxTokens: 256 });
477480
}
478-
</script>
479481

480-
<!-- Emscripten-generated JS will be loaded here -->
481-
<script>
482-
var Module = {
483-
onToken: null,
484-
onDone: null,
485-
onStatus: null,
486-
print: function(text) { console.log(text); },
487-
printErr: function(text) { console.warn(text); },
488-
onRuntimeInitialized: function() {
489-
console.log('quant.cpp WASM ready');
490-
addMessage('system', 'Runtime ready. Choose a model or drop your own GGUF file.');
491-
}
492-
};
482+
// Initialize worker on page load
483+
initWorker();
493484
</script>
494-
<script src="quant.js"></script>
495485

496486
</body>
497487
</html>

‎wasm/inference-worker.js‎

Lines changed: 67 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,67 @@
1+
/**
2+
* inference-worker.js — Web Worker that runs WASM inference off the main thread.
3+
*
4+
* Eliminates ASYNCIFY entirely: the worker can block on quant_generate()
5+
* while the main thread stays responsive. Tokens stream via postMessage().
6+
*
7+
* Protocol:
8+
* Main → Worker: { type: 'load', bytes: ArrayBuffer }
9+
* Main → Worker: { type: 'generate', prompt: string, temperature: number, maxTokens: number }
10+
* Worker → Main: { type: 'status', msg: string }
11+
* Worker → Main: { type: 'token', text: string }
12+
* Worker → Main: { type: 'done', nTokens: number, elapsed: number }
13+
* Worker → Main: { type: 'ready' }
14+
*/
15+
16+
/* Load the Emscripten glue code. Module is configured before loading. */
17+
var Module = {
18+
onToken: null,
19+
onDone: null,
20+
onStatus: null,
21+
print: function(text) { /* suppress stdout in worker */ },
22+
printErr: function(text) { /* suppress stderr in worker */ },
23+
onRuntimeInitialized: function() {
24+
postMessage({ type: 'ready' });
25+
}
26+
};
27+
28+
importScripts('quant.js');
29+
30+
onmessage = function(e) {
31+
const msg = e.data;
32+
33+
if (msg.type === 'load') {
34+
try {
35+
const bytes = new Uint8Array(msg.bytes);
36+
Module.FS.writeFile('/model.gguf', bytes);
37+
const rc = Module._wasm_load_model(Module.allocateUTF8('/model.gguf'));
38+
if (rc === 0) {
39+
const info = Module._wasm_model_info();
40+
postMessage({ type: 'status', msg: 'Model loaded! Ready to chat. (' + msg.name + ')' });
41+
postMessage({ type: 'loaded', size: bytes.length, name: msg.name });
42+
} else {
43+
postMessage({ type: 'status', msg: 'Error: failed to load model' });
44+
}
45+
} catch (err) {
46+
postMessage({ type: 'status', msg: 'Error: ' + err.message });
47+
}
48+
return;
49+
}
50+
51+
if (msg.type === 'generate') {
52+
postMessage({ type: 'status', msg: 'thinking' });
53+
54+
/* Set up per-token callback — posts each token to main thread */
55+
Module.onToken = function(text) {
56+
postMessage({ type: 'token', text: text });
57+
};
58+
59+
const promptPtr = Module.allocateUTF8(msg.prompt);
60+
/* This blocks the worker (not the main thread!) until generation completes */
61+
Module._wasm_generate(promptPtr, msg.temperature || 0.7, msg.maxTokens || 256);
62+
Module._free(promptPtr);
63+
64+
postMessage({ type: 'done' });
65+
return;
66+
}
67+
};

‎wasm/quant.js‎

Lines changed: 1 addition & 1 deletion
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‎wasm/quant.wasm‎

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