The profiling results constantly show that more time are spent on
memclrNoHeapPointers if N is a big even integer (1615118) than a big odd
integer (1615119).
On Thursday, May 13, 2021 at 5:07:49 AM UTC-4 tapi...@gmail.com wrote:
> Sorry, there is a temp tweak, the N/5 should be N/2.
> The second conclusion should be:
>
> // And if N is odd number, the InsertOneline
> // implementations are about 10% faster than the others.
>
> On Thursday, May 13, 2021 at 4:52:32 AM UTC-4 tapi...@gmail.com wrote:
>
>>
>> package main
>>
>> import "testing"
>>
>> const N = 1615119
>> // It is strange that if N is large enough,
>> // the one line implementations are fast as the others.
>> // And if N is odd number, the InsertOneline_Disassemble
>> // implementation is about 10% faster than the others.
>>
>> func init() {
>> println("==================== N =", N)
>> }
>>
>> func InsertOneline(s []int, k int, vs ...int) []int {
>> return append(s[:k], append(vs, s[k:]...)...)
>> }
>>
>> func InsertOneline_Disassemble(s []int, k int, vs ...int) []int {
>> z := append(vs, s[k:]...)
>> return append(s[:k], z...)
>> }
>>
>> func InsertVerbose(s []int, k int, vs ...int) []int {
>> if n := len(s) + len(vs); n <= cap(s) {
>> s2 := s[:n]
>> copy(s2[k+len(vs):], s[k:])
>> copy(s2[k:], vs)
>> return s2
>> }
>> s2 := make([]int, len(s) + len(vs))
>> copy(s2, s[:k])
>> copy(s2[k:], vs)
>> copy(s2[k+len(vs):], s[k:])
>> return s2
>> }
>>
>>
>> func InsertVerbose_b(s []int, k int, vs ...int) []int {
>> if n := len(s) + len(vs); n <= cap(s) {
>> s2 := s[:n]
>> copy(s2[k+len(vs):], s[k:])
>> copy(s2[k:], vs)
>> return s2
>> }
>> s2 := make([]int, 0, len(s) + len(vs))
>> s2 = append(s2, s[:k]...)
>> s2 = append(s2, vs...)
>> s2 = append(s2, s[k:]...)
>> return s2
>> }
>>
>> func InsertVerbose_c(s []int, k int, vs ...int) []int {
>> if n := len(s) + len(vs); n <= cap(s) {
>> s2 := s[:n]
>> copy(s2[k+len(vs):], s[k:])
>> copy(s2[k:], vs)
>> return s2
>> }
>> s2 := append([]int(nil), make([]int, len(s) + len(vs))...)[:0]
>> s2 = append(s2, s[:k]...)
>> s2 = append(s2, vs...)
>> s2 = append(s2, s[k:]...)
>> return s2
>> }
>>
>> var s1 []int
>> func Benchmark_InsertOneline(b *testing.B) {
>> var x = make([]int, N)
>> var y = make([]int, N/2)
>> var k = N/5
>> b.ResetTimer()
>> for i := 0; i < b.N; i++ {
>> s1 = InsertOneline(x, k, y...)
>> }
>> }
>>
>> var s1b []int
>> func Benchmark_InsertOneline_Disassemble(b *testing.B) {
>> var x = make([]int, N)
>> var y = make([]int, N/2)
>> var k = N/2
>> b.ResetTimer()
>> for i := 0; i < b.N; i++ {
>> s1b = InsertOneline_Disassemble(x, k, y...)
>> }
>> }
>>
>> var s2 []int
>> func Benchmark_InsertVerbose(b *testing.B) {
>> var x = make([]int, N)
>> var y = make([]int, N/2)
>> var k = N/2
>> b.ResetTimer()
>> for i := 0; i < b.N; i++ {
>> s2 = InsertVerbose(x, k, y...)
>> }
>> }
>>
>> var s3 []int
>> func Benchmark_InsertVerbose_b(b *testing.B) {
>> var x = make([]int, N)
>> var y = make([]int, N/2)
>> var k = N/2
>> b.ResetTimer()
>> for i := 0; i < b.N; i++ {
>> s3 = InsertVerbose_b(x, k, y...)
>> }
>> }
>>
>> var s4 []int
>> func Benchmark_InsertVerbose_c(b *testing.B) {
>> var x = make([]int, N)
>> var y = make([]int, N/2)
>> var k = N/2
>> b.ResetTimer()
>> for i := 0; i < b.N; i++ {
>> s4 = InsertVerbose_c(x, k, y...)
>> }
>> }
>>
>>
>> The result:
>>
>> $ go test -bench=. -benchtime=3s
>> ==================== N = 1615119
>> goos: linux
>> goarch: amd64
>> pkg: a.y/bench/sliceinsert
>> cpu: Intel(R) Core(TM) i5-4210U CPU @ 1.70GHz
>> Benchmark_InsertOneline-4 693 4741509 ns/op
>> Benchmark_InsertOneline_Disassemble-4 871 4194142 ns/op
>> Benchmark_InsertVerbose-4 764 4627334 ns/op
>> Benchmark_InsertVerbose_b-4 769 4958537 ns/op
>> Benchmark_InsertVerbose_c-4 661 4855514 ns/op
>>
>
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