GO compiler

main.cpp

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <float.h>

#include <sys/time.h>
#include <stdint.h>

typedef int64_t TimeVal;

TimeVal getPerfTime()
{
    timeval now;
    gettimeofday(&now, 0);
    return (TimeVal)now.tv_sec*1000000L + (TimeVal)now.tv_usec;
}

int getPerfDeltaTimeUsec(const TimeVal start, const TimeVal end)
{
    return (int)(end - start);
}

float InvSqrt(float x)
{
    float xhalf = 0.5f*x;
    int i = *(int *)&x;
    i = 0x5f3759df - (i >> 1);
    x = *(float *)&i;
    x = x*(1.5f - xhalf*x*x);
    return x;
}

int main(int argc, char *argv[])
{
    TimeVal timeStart = getPerfTime();

    double res = 0.0;

    for (int z = 0; z < 10000000; ++z)
    {
        res += InvSqrt(double(4121214.151244124125));
    }

    TimeVal timeEnd = getPerfTime();

    printf("%f # %.3fms\n", res, getPerfDeltaTimeUsec(timeStart, timeEnd) / 1000.0);

    return 0;
}

main1_main.go

package main

import (
    "fmt"
    "time"
    "math"
)

func InvSqrt(x float32) float32 {
    xhalf := 0.5 * x
    i     := math.Float32bits(x)
    i      = 0x5f3759df - (i >> 1)
    x      = math.Float32frombits(i)
    x      = x * (1.5 - xhalf * x * x)

    return x
}


func main() {
    time_start := time.Now()

    var res float64

    for z := 0; z < 10000000; z++ {
        res += float64(InvSqrt(4121214.151244124125))
    }

    fmt.Print(res)
    fmt.Print(" # ")
    fmt.Println(time.Now().Sub(time_start));
}

main2.cpp

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <float.h>

#include <sys/time.h>
#include <stdint.h>

typedef int64_t TimeVal;

TimeVal getPerfTime()
{
    timeval now;
    gettimeofday(&now, 0);
    return (TimeVal)now.tv_sec*1000000L + (TimeVal)now.tv_usec;
}

int getPerfDeltaTimeUsec(const TimeVal start, const TimeVal end)
{
    return (int)(end - start);
}

float InvSqrt(float x)
{
    return 1.0 / sqrtf(x);
}

int main(int argc, char *argv[])
{
    TimeVal timeStart = getPerfTime();

    double res = 0.0;

    for (int z = 0; z < 10000000; ++z)
    {
        res += InvSqrt(4121214.151244124125);
    }

    TimeVal timeEnd = getPerfTime();

    printf("%f # %.3fms\n", res, getPerfDeltaTimeUsec(timeStart, timeEnd) / 1000.0);

    return 0;
}

main2_main2.go

package main

import (
    "fmt"
    "time"
)

//go:noescape

func Sqrt(x float32) float32 // ./main2_$GOARCH.s

func InvSqrt(x float32) float32 {
    return float32(1.0 / Sqrt(x))
}

func main() {
    time_start := time.Now()

    var res float64

    for z := 0; z < 10000000; z++ {
        res += float64(InvSqrt(4121214.151244124125))
    }

    fmt.Print(res)
    fmt.Print(" # ")
    fmt.Println(time.Now().Sub(time_start));
}

main2_main2_amd64.s

// func Sqrt(x float32) float32
TEXT ·Sqrt+0(SB),$0-16
    SQRTSS   x+0(FP), X0
    MOVSS   X0,r+8(FP)
    RET

result.txt

v1
4917.670739814639 # 24.788318ms

v2
4925.920511595905 # 50.62856ms

v3
4917.670740 # 8.815ms

v4
4925.920512 # 12.797ms

run_bench

#!/bin/sh

cd main1; go build -o "v1"; cd ..
cd main2; go build -o "v2"; cd ..
g++ -O3 -o v3 main.cpp
g++ -O3 -o v4 main2.cpp

echo
echo "v1"
./main1/v1

echo
echo "v2"
./main2/v2


echo
echo "v3"
./v3

echo
echo "v4"
./v4