GopherJS vs Wasm

main.go

package main

func array() []float32 {
        return make([]float32, 16)
}

func heavyTask() float32 {
        arr := array()

        result := float32(0.0)

        for i := 0; i < 10000000; i++ {
                u0, v0, u1, v1 := float32(0.0), float32(0.0), float32(1.0), float32(1.0)
                arr[0] = u0
                arr[1] = v0
                arr[2] = u1
                arr[3] = u1

                arr[4] = u1
                arr[5] = v0
                arr[6] = u0
                arr[7] = u1

                arr[8] = u0
                arr[9] = v1
                arr[10] = u1
                arr[11] = u0

                arr[12] = u1
                arr[13] = v1
                arr[14] = u0
                arr[15] = u0

                result += arr[i % 16]
        }
        return result
}

func main() {
        println(heavyTask())
}

main.js

function array() {
  return new Float32Array(16);
}

function heavyTask() {
  const arr = array();
  result = 0.0;
  for (let i = 0; i < 10000000; i++) {
    const u0 = 0.0;
    const v0 = 0.0;
    const u1 = 1.0;
    const v1 = 1.0;

    arr[0] = u0
    arr[1] = v0
    arr[2] = u1
    arr[3] = u1

    arr[4] = u1
    arr[5] = v0
    arr[6] = u0
    arr[7] = u1

    arr[8] = u0
    arr[9] = v1
    arr[10] = u1
    arr[11] = u0

    arr[12] = u1
    arr[13] = v1
    arr[14] = u0
    arr[15] = u0

    result += arr[i % 16]
  }
  return result;
}

function main() {
  console.log(heavyTask());
}

main();

result.txt

$ # Go -> Wasm
$ GOOS=js GOARCH=wasm ~/go-code/bin/go build -o test.wasm .
$ time ./go_js_wasm_exec test.wasm
+5.000000e+006

real    0m0.740s
user    0m1.480s
sys     0m0.066s

$ # GopherJS
$ gopherjs build -o test.js main.go
$ time node test.js

5000000

real    0m0.268s
user    0m0.236s
sys     0m0.024s

$ # Plain JS
$ time node main.js
5000000

real    0m0.309s
user    0m0.142s
sys     0m0.043s

that's a big difference

Right, significantly different...

How much of that is the heavy task itself?

Good point. I'll add time.Now before and after heavyTask() call.

https://gist.github.com/hajimehoshi/f9299abc0890283dfe803ed80767f5b5 Here you are: this takes wall-time clock before and after the heavy task.

Which browser are you using to test wasm?