# Threading in WASM
*last updated: 2021-04-04*

Experimental (but stable) support for `pthreads` using `SharedArrayBuffer`, `postMessage` and web workers
* works in Firefox & Chrome but needs special headers
* `Cross-Origin-Opener-Policy: same-origin`<br>`Cross-Origin-Embedder-Policy: require-corp`
* `postMessage` latency ~0.5-1ms for structured clone (size dependent)
* can be architected to setup worker pool at startup via compiler options
* however the job distribution might still happen through structured clone
* **emscripten** compiler toolchain implements `POSIX` threads with few caveats but mostly addressable.
* can be useful if a multistage function/complex operation needs to be parallelized
* no obvious higher order components/syntactic sugar to simplify job distribution and reduction/joining,
* could still be faster because of LLVM compiled instructions.

However for job distribution on batch level (and concurrency safe single threaded WASM function/operation), webworkers or nodejs workers (or `threads` package) can themselves be further optimized to reduce job distribution latency without going into WASM multithreading.

---------------------------------------
PS: *this work has not been funded or granted by anyone. if you think this adds value to the ecosystem you could tip the author at: [0xb44ddd63d0e27bb3cd8046478b20c0465058ff04](https://etherscan.io/address/0xb44ddd63d0e27bb3cd8046478b20c0465058ff04)*