Branch prediction Go

benchmark.txt

$ go test -test.bench .
BenchmarkLoop-4         	   10000	    146857 ns/op
BenchmarkLoopSorted-4   	  100000	     19901 ns/op
PASS
ok  	test/branch	3.706s

branch_test.go

package branch

import (
	"math/rand"
	"sort"
	"testing"
	"time"
)

const N = 32768

func prepareArray(toSort bool) []int {
	data := make([]int, N, N)

	rand.Seed(time.Now().UnixNano())

	for i := 0; i < N; i++ {
		data[i] = rand.Intn(256)
	}

	if toSort {
		sort.Ints(data)
	}

	return data
}

func runLoop(data []int) int64 {
	var sum int64

	for i := 0; i < N; i++ {
		if data[i] >= 128 {
			sum += int64(data[i])
		}
	}

	return sum
}

func BenchmarkLoop(b *testing.B) {
	slice := prepareArray(false)

	for i := 0; i < b.N; i++ {
		_ = runLoop(slice)
	}
}

func BenchmarkLoopSorted(b *testing.B) {
	slice := prepareArray(true)

	for i := 0; i < b.N; i++ {
		_ = runLoop(slice)
	}
}