Enable emscripten build with parallelization

.github/workflows/manifold.yml

@@ -286,7 +286,7 @@ jobs:
     timeout-minutes: 30
     strategy:
       matrix:
-        variant: [manifold-none, manifold-tbb, manifold-js, manifold3d]
+        variant: [manifold-none, manifold-tbb, manifold-js, manifold-js-tbb, manifold3d]
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4

CMakeLists.txt

@@ -121,10 +121,6 @@ if(EMSCRIPTEN)
   if(MANIFOLD_PAR)
     set(CMAKE_THREAD_LIBS_INIT "-pthread")
     add_compile_options(-pthread)
-    # PTHREAD_POOL_SIZE is set to 4 for OK-ish performance, in general we are
-    # not getting too much speedup for very large number of cores, and a lot of
-    # CPUs now have 4 cores...
-    add_link_options(-sPTHREAD_POOL_SIZE=4)
     # mimalloc is needed for good performance
     add_link_options(-sMALLOC=mimalloc)
     # The default stack size apparently causes problem when parallelization is

bindings/wasm/CMakeLists.txt

@@ -49,6 +49,10 @@ add_custom_target(
 add_custom_command(
   TARGET js_deps
   POST_BUILD
+  # fix js file
+  COMMAND
+    ${Python_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/fixup.py
+    ${CMAKE_CURRENT_BINARY_DIR}/manifold.js
   # copy WASM build back here for publishing to npm
   COMMAND
     ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/manifold.*

bindings/wasm/bindings.cpp

@@ -22,6 +22,30 @@
 #include "manifold/manifold.h"
 #include "manifold/polygon.h"
 
+#if (MANIFOLD_PAR == 1)
+#include <tbb/parallel_for.h>
+
+#include <atomic>
+#endif
+
+// https://github.com/oneapi-src/oneTBB/blob/master/WASM_Support.md#limitations
+void initTBB() {
+#if (MANIFOLD_PAR == 1)
+  int num_threads = tbb::this_task_arena::max_concurrency();
+  std::atomic<int> barrier{num_threads};
+  tbb::parallel_for(
+      0, num_threads,
+      [&barrier](int) {
+        barrier--;
+        while (barrier > 0) {
+          // Send browser thread to event loop
+          std::this_thread::yield();
+        }
+      },
+      tbb::static_partitioner{});
+#endif
+}
+
 using namespace emscripten;
 using namespace manifold;
 
@@ -195,4 +219,6 @@ EMSCRIPTEN_BINDINGS(whatever) {
   function("setCircularSegments", &Quality::SetCircularSegments);
   function("getCircularSegments", &Quality::GetCircularSegments);
   function("resetToCircularDefaults", &Quality::ResetToDefaults);
+
+  function("initTBB", &initTBB);
 }

bindings/wasm/bindings.js

@@ -17,6 +17,9 @@ Module.setup = function() {
   if (_ManifoldInitialized) return;
   _ManifoldInitialized = true;
 
+  // warmup tbb for emscripten, according to
+  // https://github.com/oneapi-src/oneTBB/blob/master/WASM_Support.md#limitations
+  Module.initTBB();
   // conversion utilities
 
   function toVec(vec, list, f = x => x) {

bindings/wasm/examples/vite.config.js

@@ -7,6 +7,12 @@ export default defineConfig({
   worker: {
     format: 'es',
   },
+  server: {
+    headers: {
+      'Cross-Origin-Embedder-Policy': 'require-corp',
+      'Cross-Origin-Opener-Policy': 'same-origin',
+    },
+  },
   build: {
     target: 'esnext',
     sourcemap: true,

bindings/wasm/fixup.py

@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+import sys
+
+if len(sys.argv) != 2:
+    print("Usage: python fixup.py <SOURCE_DIR>")
+
+filename = sys.argv[1]
+with open(filename, "r") as file:
+    data = file.read()
+
+data = data.replace(
+    'var workerOptions={type:"module",workerData:"em-pthread",name:"em-pthread"};', ""
+)
+data = data.replace(
+    "workerOptions", '{type:"module",workerData:"em-pthread",name:"em-pthread"}'
+)
+
+with open(filename, "w") as file:
+    file.write(data)

bindings/wasm/helpers.cpp

@@ -208,7 +208,7 @@ Manifold SetProperties(Manifold& manifold, int numProp, uintptr_t funcPtr) {
 Manifold LevelSet(uintptr_t funcPtr, Box bounds, double edgeLength,
                   double level, double tolerance) {
   double (*f)(const vec3&) = reinterpret_cast<double (*)(const vec3&)>(funcPtr);
-  return Manifold::LevelSet(f, bounds, edgeLength, level, tolerance);
+  return Manifold::LevelSet(f, bounds, edgeLength, level, tolerance, false);
 }
 
 std::vector<Manifold> Split(Manifold& a, Manifold& b) {

cmake/manifoldDeps.cmake

@@ -218,6 +218,10 @@ if(MANIFOLD_TEST)
   endif()
 endif()
 
+if(EMSCRIPTEN)
+  find_package(Python REQUIRED)
+endif()
+
 if(MANIFOLD_FUZZ)
   logmissingdep("fuzztest" , "MANIFOLD_FUZZ")
   FetchContent_Declare(

flake.nix

@@ -112,7 +112,7 @@
               cd ../
             '';
           };
-        manifold-emscripten = { doCheck ? true }: pkgs.buildEmscriptenPackage {
+        manifold-emscripten = { doCheck ? true, parallel ? false }: pkgs.buildEmscriptenPackage {
           name = "manifold-js";
           version = manifold-version;
           src = self;
@@ -126,7 +126,9 @@
             mkdir build
             cd build
             emcmake cmake -DCMAKE_BUILD_TYPE=Release \
+            -DMANIFOLD_PAR=${if parallel then "ON" else "OFF"} \
             -DFETCHCONTENT_SOURCE_DIR_GOOGLETEST=${gtest-src} \
+            -DFETCHCONTENT_SOURCE_DIR_TBB=${onetbb-src} \
             -DFETCHCONTENT_SOURCE_DIR_CLIPPER2=../clipper2 ..
           '';
           buildPhase = ''
@@ -148,6 +150,7 @@
           manifold-tbb = manifold { };
           manifold-none = manifold { parallel = false; };
           manifold-js = manifold-emscripten { };
+          manifold-js-tbb = manifold-emscripten { parallel = true; };
           # but how should we make it work with other python versions?
           manifold3d = with pkgs.python3Packages; buildPythonPackage {
             pname = "manifold3d";
@@ -197,6 +200,7 @@
             # useful tools
             clang-tools_18
             clang_18
+            llvmPackages_18.bintools
             tracy
           ];
         };

test/test_main.cpp

@@ -17,6 +17,10 @@
 #include "manifold/polygon.h"
 #include "test.h"
 
+#if (MANIFOLD_PAR == 1)
+#include <tbb/parallel_for.h>
+#endif
+
 // we need to call some tracy API to establish the connection
 #if __has_include(<tracy/Tracy.hpp>)
 #include <tracy/Tracy.hpp>
@@ -45,6 +49,23 @@ int main(int argc, char** argv) {
   const char* name = "test setup";
   FrameMarkStart(name);
 
+  // warmup tbb for emscripten, according to
+  // https://github.com/oneapi-src/oneTBB/blob/master/WASM_Support.md#limitations
+#if defined(__EMSCRIPTEN__) && (MANIFOLD_PAR == 1)
+  int num_threads = tbb::this_task_arena::max_concurrency();
+  std::atomic<int> barrier{num_threads};
+  tbb::parallel_for(
+      0, num_threads,
+      [&barrier](int) {
+        barrier--;
+        while (barrier > 0) {
+          // Send browser thread to event loop
+          std::this_thread::yield();
+        }
+      },
+      tbb::static_partitioner{});
+#endif
+
   for (int i = 1; i < argc; i++) {
     if (argv[i][0] != '-') {
       fprintf(stderr, "Unknown option: %s\n", argv[i]);