stockfish.wasm
WebAssembly port of the strong chess engine
Stockfish. See it in action
on https://lichess.org/analysis.
Requirements
Uses the latest WebAssembly threading proposal.
Chrome
- Since 79: Can allocate additional memory. The default allocation suffices
for up to 2 threads and 16 MB hash.
- Enabled by default since 74 (desktop only)
- Origin Trial from 70 to 75
- Flag
chrome://flags/#enable-webassembly-threads
since 70
Firefox
-
Since Firefox 72: Structured cloning can no longer be enabled with flags.
-
Since Firefox 71: Requires javascript.options.shared_memory
and dom.postMessage.sharedArrayBuffer.withCOOP_COEP
to be enabled in about:flags
and these HTTP headers to be set on the top level response:
Cross-Origin-Embedder-Policy: require-corp
Cross-Origin-Opener-Policy: same-origin
-
Firefox 68 to 70: Requires javascript.options.shared_memory
to be enabled in about:flags
Other browsers
No support.
See stockfish.js for a more
portable but single-threaded version.
Feature detection
function wasmThreadsSupported() {
var source = Uint8Array.of(0x0, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00);
if (typeof WebAssembly !== 'object' || !WebAssembly.validate(source)) return false;
if (typeof SharedArrayBuffer !== 'function') return false;
if (typeof Atomics !== 'object') return false;
var mem = new WebAssembly.Memory({shared: true, initial: 8, maximum: 16});
if (!(mem.buffer instanceof SharedArrayBuffer)) return false;
try {
window.postMessage(mem, '*');
} catch (e) {
return false;
}
try {
mem.grow(8);
} catch (e) {
return false;
}
return true;
}
Current limitations
- Hashtable: 1024 MB.
- Threads: 16.
- Can hang when UCI protocol is misused. (Do not send invalid commands or
positions. While the engine is searching, do not change options or start
additional searches).
- No Syzygy tablebase support.
Building
Assuming em++ (>= 1.39.6) is available:
npm run-script prepare
Usage
Requires stockfish.js
, stockfish.wasm
and stockfish.worker.js
(total size ~1.5M, ~200K gzipped) to be served from the same directory.
<script src="stockfish.js"></script>
<script>
var sf = Stockfish();
sf.addMessageListener(function (line) {
console.log(line);
});
sf.postMessage('uci');
</script>
Optional: Callbacks assigned to sf['onRuntimeInitialized']
and
sf['onAbort']
will be called for successful/failed initialization.
License
Thanks to the Stockfish team for sharing the engine under the GPL3.