A benchmark of slice versus map iteration. Go 1.1.

itereate_test.go

package iterate

import "testing"

func BenchmarkSlice100(b *testing.B)    { benchmarkSlice(b, 100) }
func BenchmarkSlice1000(b *testing.B)   { benchmarkSlice(b, 1000) }
func BenchmarkSlice10000(b *testing.B)  { benchmarkSlice(b, 10000) }
func BenchmarkSlice100000(b *testing.B) { benchmarkSlice(b, 100000) }

func benchmarkSlice(b *testing.B, n int) {
	s := make([]int, n)
	for i := 0; i < n; i++ {
		s[i] = i
	}
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		for _, _ = range s {
		}
	}
}

func BenchmarkMap100(b *testing.B)    { benchmarkMap(b, 100) }
func BenchmarkMap1000(b *testing.B)   { benchmarkMap(b, 1000) }
func BenchmarkMap10000(b *testing.B)  { benchmarkMap(b, 10000) }
func BenchmarkMap100000(b *testing.B) { benchmarkMap(b, 100000) }

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

Output

BenchmarkSlice100	20000000	       121 ns/op
BenchmarkSlice1000	 1000000	      1170 ns/op
BenchmarkSlice10000	  200000	     11658 ns/op
BenchmarkSlice100000	   10000	    116510 ns/op
BenchmarkMap100	 5000000	       670 ns/op
BenchmarkMap1000	  200000	      9249 ns/op
BenchmarkMap10000	   20000	     76125 ns/op
BenchmarkMap100000	    2000	    798339 ns/op