A small multi-threaded C++ library (so, does not include any main) compiled with emscripten and pthread running under the main thread in the browser, a web worker or using node.js.
Note: Emscripten will produce lib.js.
Running this lib in the main thread is fine but, obviously, block the main thread. Running it using a web worker leads no error with modification of the worker script (see below)
Run fine except that it prevents Node app from ever exiting.
| #!/bin/bash | |
| emcc -std=c++17 \ | |
| -O3 --bind \ | |
| -s SINGLE_FILE=1 \ | |
| -s PTHREAD_POOL_SIZE=4 \ | |
| -s USE_PTHREADS=1 \ | |
| -s ASSERTIONS=1 \ | |
| -s EXPORT_NAME=LibModule \ | |
| -s WASM=1 \ | |
| -s MODULARIZE=1 \ | |
| -s ALLOW_MEMORY_GROWTH=1 \ | |
| -o lib.js \ | |
| main.cxx |
| <!DOCTYPE html> | |
| <html> | |
| <title>pthread test</title> | |
| <head> | |
| <style> | |
| .styled:hover { | |
| background-color: rgb(140, 139, 139); | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <button class="favorite styled" type="button" onclick="runMain('thread')">Main thread</button> | |
| <button class="favorite styled" type="button" onclick="runMain('serial')">Main serial</button><br><br> | |
| <button class="favorite styled" type="button" onclick="runWorker('thread')">Worker thread</button> | |
| <button class="favorite styled" type="button" onclick="runWorker('serial')">Worker Serial</button> | |
| <script src="lib.js"></script> | |
| <script> | |
| function runWorker(method) { | |
| const worker = new Worker('./worker.js') | |
| worker.onmessage = e => console.log(e) | |
| worker.postMessage(method) | |
| } | |
| function runMain(method) { | |
| LibModule().then( lib => { | |
| const a = performance.now() | |
| method === 'thread' ? lib.thread() : lib.serial() ; | |
| console.log( `${method} done in ${(performance.now()-a)}ms` ) | |
| }) | |
| } | |
| </script> | |
| </body> | |
| </html> |
| #include <string> | |
| #include <thread> | |
| #include <future> | |
| #include <iostream> | |
| #include <vector> | |
| #include <emscripten/bind.h> | |
| using namespace emscripten ; | |
| std::vector<int> s = {40000, 40000, 40000, 40000} ; | |
| void longCompute(int id, int iterations) { | |
| double val = 0 ; | |
| for (int i=0; i<10000; ++i) { | |
| for (int j=0; j<iterations; ++j) { | |
| val += 3.1415 ; | |
| } | |
| } | |
| std::cout << "thread " << (id) << ": " << val << std::endl ; | |
| } | |
| void testThread() { | |
| std::cout << "Using std::thread" << std::endl ; | |
| std::vector<std::thread> threads ; | |
| for (int i = 0; i < s.size(); i++) { | |
| threads.push_back( std::thread(longCompute, i, s[i]) ) ; | |
| } | |
| std::cerr << "start threads"<< std::endl ; | |
| for (auto &th : threads) { | |
| th.join() ; | |
| } | |
| std::cerr << "end threads"<< std::endl ; | |
| } | |
| void testSerial() { | |
| std::cout << "Using serial" << std::endl ; | |
| for (int i = 0; i < s.size(); i++) { | |
| longCompute(i, s[i]) ; | |
| } | |
| std::cerr << "end serial"<< std::endl ; | |
| } | |
| // ------------------------------ | |
| // Only expose 2 functions in js | |
| // ------------------------------ | |
| EMSCRIPTEN_BINDINGS(test) { | |
| function("thread", &testThread) ; | |
| function("serial", &testSerial) ; | |
| } |
| #!/bin/bash | |
| # Make sure node version is greater than 15.1.0 | |
| ver="$(node --version)" | |
| ver=${ver:1} # remove the prefix 'v' | |
| major="$(cut -d '.' -f 1 <<< "$ver")" | |
| minor="$(cut -d '.' -f 2 <<< "$ver")" | |
| if [ $major -ge 15 ] && [ $minor -ge 1 ]; then | |
| node --experimental-wasm-threads script.js | |
| else | |
| echo "Cannot run node. Require version 15.1.0 or greater" | |
| fi |
| // ---------------------------------------- | |
| // To be used with node.js | |
| // ---------------------------------------- | |
| const LibModule = require('./lib') | |
| function runMain(method) { | |
| LibModule().then( lib => { | |
| const a = performance.now() | |
| method === 'thread' ? lib.thread() : lib.serial() ; | |
| console.log( `${method} done in ${(performance.now()-a)}ms` ) | |
| }) | |
| } | |
| runMain('thread') | |
| runMain('serial') |
| // ---------------------------------------- | |
| // Used with index.html | |
| // ---------------------------------------- | |
| importScripts("lib.js") | |
| onmessage = e => { | |
| const Lib = { | |
| locateFile: (file) => file, | |
| onRuntimeInitialized: () => { | |
| const a = performance.now() | |
| e.data === 'thread' ? Lib.thread() : Lib.serial() ; | |
| console.log( `${e.data} done in ${(performance.now()-a)}ms` ) | |
| }, | |
| mainScriptUrlOrBlob: "lib.js", | |
| }; | |
| // LibModule is the name of the exported library with emscripten | |
| LibModule(Lib) | |
| } | |
| // Was previously (loading of the worker not working) | |
| /* | |
| importScripts("lib.js") | |
| onmessage = e => { | |
| LibModule().then( lib => { | |
| const a = performance.now() | |
| e.data === 'thread' ? lib.thread() : lib.serial() ; | |
| console.log( `${e.data} done in ${(performance.now()-a)}ms` ) | |
| }) | |
| } | |
| */ |
Why have you used "lib.js" both in index.html & worker.js in case of a web worker?
Also can you please explain the use of mainScriptUrlOrBlob ?
Why have you used "lib.js" both in index.html & worker.js in case of a web worker?
It is a browser limitations. Browser can create a thread only from js file and we must provide path to it.
mainScriptUrlOrBlob - main script.
Better explanation
https://web.dev/webassembly-threads/
at 28 line
https://gist.github.com/xaliphostes/6869989fadfb055ea40c2987b1150549#file-worker-js-L28
Did you try to put Lib inside
LibModule(Lib).then( lib => {?