go_range_vs_index_test.go

package main

import (
	"crypto/rand"
	"testing"
)

var sample = makeSample()

const sampleSize = 4096

func makeSample() []byte {
	s := make([]byte, sampleSize)

	rand.Read(s)

	return s
}

func BenchmarkRangeIndex(b *testing.B) {
	var result uint64

	b.ReportAllocs()
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		for ss := range sample {
			result += uint64(sample[ss])
		}
	}
}

func BenchmarkRangeValue(b *testing.B) {
	var result uint64

	b.ReportAllocs()
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		for _, ss := range sample {
			result += uint64(ss)
		}
	}
}

func BenchmarkIndex(b *testing.B) {
	var result uint64

	sLen := len(sample)

	b.ReportAllocs()
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		for s := 0; s < sLen; s++ {
			result += uint64(sample[s])
		}
	}
}

Benchmark	Exec/Sec	Cost/Exec	Allocated/Op	Allocations/Op
BenchmarkRangeIndex-2	1000000	1887 ns/op	0 B/op	0 allocs/op
BenchmarkRangeValue-2	1000000	1851 ns/op	0 B/op	0 allocs/op
BenchmarkIndex-2	500000	3673 ns/op	0 B/op	0 allocs/op