mapbench_test.go

package mapbench_test

import "testing"

var N = 1000000

func BenchmarkMap(b *testing.B) {
	for i := 0; i < b.N; i++ {
		m := map[int]int{}
		for j := 0; j < N; j++ {
			m[j] = j
		}
	}
}

func BenchmarkMapCap(b *testing.B) {
	for i := 0; i < b.N; i++ {
		m := make(map[int]int, N)
		for j := 0; j < N; j++ {
			m[j] = j
		}
	}
}

func BenchmarkMapLookup(b *testing.B) {
	m := map[int]int{}
	for j := 0; j < N; j++ {
		m[j] = j
	}
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		for j := 0; j < N; j++ {
			_, _ = m[i]
		}
	}
}

func BenchmarkMapCapLookup(b *testing.B) {
	m := make(map[int]int, N)
	for j := 0; j < N; j++ {
		m[j] = j
	}
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		for j := 0; j < N; j++ {
			_, _ = m[i]
		}
	}
}

result

$ go test mapbench_test.go -bench . -benchmem
testing: warning: no tests to run
PASS
BenchmarkMap	       5	 310879905 ns/op	84001936 B/op	   59035 allocs/op
BenchmarkMapCap	      10	 185929105 ns/op	38369164 B/op	    4310 allocs/op
BenchmarkMapLookup	     100	  12966770 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapCapLookup	     100	  13090509 ns/op	       0 B/op	       0 allocs/op