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January 27, 2015 18:12
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Michael Tiller created this gist
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This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode charactersOriginal file line number Diff line number Diff line change @@ -0,0 +1,103 @@ package copy_vs_append import ( "testing" ) func buildArray(n int64) []int64 { ret := make([]int64, n, n) var i int64 for i = 0; i < n; i++ { ret[i] = i } return ret } func checkArray(y []int64, t *testing.T) { if len(y) != 1000 { t.Fatalf("Expected len(y) to be 1000 but was %d", len(y)) } for i := int64(0); i < int64(1000); i++ { if y[i] != i { t.Fatalf("Expected y[%d] = %d but was %d", i, i, y[i]) } } } func TestCopy(t *testing.T) { existing := buildArray(1000) y := doCopy(existing, true, false) checkArray(y, t) } func TestAppend(t *testing.T) { existing := buildArray(1000) y := doCopy(existing, false, false) checkArray(y, t) } func TestAppendAlloc(t *testing.T) { existing := buildArray(1000) y := doCopy(existing, false, true) checkArray(y, t) } func doCopy(src []int64, useCopy bool, preAlloc bool) []int64 { var y []int64 if useCopy { y = make([]int64, 1000, 1000) copy(y, src) } else { var init []int64 if preAlloc { init = make([]int64, 0, 1000) } else { init = []int64{} } y = append(init, src...) } return y } func BenchmarkAppend(b *testing.B) { existing := buildArray(1000) for i := 0; i < b.N; i++ { doCopy(existing, false, false) } } func BenchmarkAppendAlloc(b *testing.B) { existing := buildArray(1000) for i := 0; i < b.N; i++ { doCopy(existing, false, true) } } func BenchmarkAppendAllocInline(b *testing.B) { existing := buildArray(1000) for i := 0; i < b.N; i++ { var init []int64 init = make([]int64, 0, 1000) _ = append(init, existing...) } } func BenchmarkAppendAllocInlineNoFunc(b *testing.B) { existing := make([]int64, 1000, 1000) for i := 0; i < b.N; i++ { var init []int64 init = make([]int64, 0, 1000) _ = append(init, existing...) } } func BenchmarkCopy(b *testing.B) { existing := buildArray(1000) for i := 0; i < b.N; i++ { doCopy(existing, true, true) } }