rayon

Cargo.toml

@@ -6,3 +6,4 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+rayon = "1.8"

index.js

@@ -9,10 +9,10 @@ const { WASI } = require("wasi");
 const { argv, env } = require("node:process");
 const { join } = require("node:path");
 
-const wasi = new WASI({ version: "preview1", args: argv, env });
-
 const file = readFile(join(__dirname, "wasi-threads.wasm"));
 
+const wasi = new WASI({ version: "preview1", args: argv, env });
+
 if (isMainThread) {
   (async () => {
     const wasm = await WebAssembly.compile(await file);
@@ -31,23 +31,33 @@ if (isMainThread) {
     wasi.start(instance);
   })();
 } else {
-  parentPort.on("message", async (start_arg) => {
-    const wasm = await WebAssembly.compile(await file);
-    const { memory } = workerData;
-    const instance = await WebAssembly.instantiate(wasm, {
-      ...wasi.getImportObject(),
-      wasi: {
-        "thread-spawn": (arg) => {
-          const worker = new Worker(__filename, { workerData: { memory } });
-          worker.postMessage(arg);
+  const handler = async (start_arg) => {
+    try {
+      const wasm = await WebAssembly.compile(await file);
+      const { memory } = workerData;
+      const instance = await WebAssembly.instantiate(wasm, {
+        ...wasi.getImportObject(),
+        wasi: {
+          "thread-spawn": (arg) => {
+            const worker = new Worker(__filename, { workerData: { memory } });
+            worker.postMessage(arg);
+          },
         },
-      },
-      env: { memory },
-    });
-    // thread id and start_arg
-    instance.exports.wasi_thread_start(1, start_arg);
-    process.exit(0);
-  });
+        env: { memory },
+      });
+      // thread id and start_arg
+      instance.exports.wasi_thread_start(1, start_arg);
+      parentPort.removeListener("message", handler);
+    } catch (e) {
+      if (e.code.includes("ERR_WASI_NOT_STARTED")) {
+        // NOP
+        return;
+      }
+      throw e;
+    } finally {
+      process.exit(0);
+    }
+  };
+  parentPort.addListener("message", handler);
 }
 
-//

src/main.rs

@@ -1,11 +1,13 @@
-use std::thread;
+use rayon::prelude::*;
+
+fn sum_of_squares(input: &[i32]) -> i32 {
+    input
+        .par_iter() // <-- just change that!
+        .map(|&i| i * i)
+        .sum()
+}
 
 fn main() {
-    let mut x = 10;
-    thread::scope(|s| {
-        s.spawn(|| {
-            x += 20;
-        });
-    });
+    let x = sum_of_squares(&[10, 20, 30, 40]);
     println!("{x}");
 }