GC and GCCGO unrolled loop benchmarks.

loop-unrolling.go

// AMD A4-5000 Quad-Core 1.5GHz APU

// GC benchmark

// Normal For Loop     : 669.966032ms
// Double Unrolled Loop: 422.242497ms
// Triple Unrolled Loop: 363.525022ms
// Quad Unrolled Loop  : 281.522688ms
// Octo Unrolled loop  : 312.757938ms

// GCCGO -O1 benchmark

// Normal For Loop     : 200.698ms
// Double Unrolled Loop: 67.139ms
// Triple Unrolled Loop: 44.696ms
// Quad Unrolled Loop  : 33.559ms
// Octo Unrolled loop  : 16.783ms


package main

import "fmt"
import "time"

// loopOne is a regular idiomatic Go for loop.
func loopOne(start time.Time) time.Duration {
	x := 0
	for index := 0; index < 100000000; index++ {
		if index % 5 == 0 { x += index }
	}
	return time.Since(start)
}

// loopTwo is a double-unrolled for loop
func loopTwo(start time.Time) time.Duration {
	x := 0
	for index := 0; index < 100000000; index += 2 {
		if index % 5 == 0 { x += index }
		if index+1 % 5 == 0 { x += index+1 }
	}
	return time.Since(start)
}

// loopThree is a triple-unrolled for loop
func loopThree(start time.Time) time.Duration {
	x := 0
	for index := 0; index < 100000000; index += 3 {
		if index % 5 == 0 { x += index }
		if index+1 % 5 == 0 { x += index+1 }
		if index+2 % 5 == 0 { x += index+2 }
	}
	return time.Since(start)
}
// loopFour is a quad-unrolled for loop
func loopFour(start time.Time) time.Duration {
	x := 0
	for index := 0; index < 100000000; index += 4 {
		if index % 5 == 0 { x += index }
		if index+1 % 5 == 0 { x += index+1 }
		if index+2 % 5 == 0 { x += index+2 }
		if index+3 % 5 == 0 { x += index+3 }
	}
	return time.Since(start)
}

// loopEight is an octo-unrolled for loop
func loopEight(start time.Time) time.Duration {
	x := 0
	for index := 0; index < 100000000; index += 8 {
		if index % 5 == 0 { x += index }
		if index+1 % 5 == 0 { x += index+1 }
		if index+2 % 5 == 0 { x += index+2 }
		if index+3 % 5 == 0 { x += index+3 }
		if index+4 % 5 == 0 { x += index+4 }
		if index+5 % 5 == 0 { x += index+5 }
		if index+6 % 5 == 0 { x += index+6 }
		if index+7 % 5 == 0 { x += index+7 }
	}
	return time.Since(start)
}


func main() {
	fmt.Println("Normal For Loop     :", loopOne(time.Now()))
	fmt.Println("Double Unrolled Loop:", loopTwo(time.Now()))
	fmt.Println("Triple Unrolled Loop:", loopThree(time.Now()))
	fmt.Println("Quad Unrolled Loop  :", loopFour(time.Now()))
	fmt.Println("Octo Unrolled loop  :", loopEight(time.Now()))
}