On Tuesday, June 27, 2017 at 6:20:42 PM UTC-4, peterGo wrote:
>
> T L,
>
> For equivalency, why did you write,
>
> func Benchmark_CloneWithCopy(b *testing.B) {
> for i := 0; i < b.N; i++ {
> t := make([]Element, N)
> copy(t, x)
> y = t
> }
> }
>
> instaed of
>
> func Benchmark_CloneWithCopy(b *testing.B) {
> for i := 0; i < b.N; i++ {
> y = make([]Element, N)
> copy(y, x)
> }
> }
>
> ?
>
The two have not big difference.
>
> Peter
>
> On Tuesday, June 27, 2017 at 5:59:25 PM UTC-4, peterGo wrote:
>>
>> T L,
>>
>> Why didn't you show us the output from
>>
>> $ go tool compile -m -m clone_test.go
>>
>> ?
>>
>> Peter
>>
>> On Tuesday, June 27, 2017 at 11:33:30 AM UTC-4, T L wrote:
>>>
>>> Ok, I think there are two reasons why the copy version is slower:
>>> 1. the copy version initializes each element twice actutally.
>>> 2. alloc a new slice by using make is slow than by using append. But why
>>> this?
>>>
>>> package main
>>>
>>> import (
>>> "testing"
>>> )
>>>
>>> const N = 1024 * 1024 // number of elements
>>> type Element int64
>>> var x = make([]Element, N)
>>> var y []Element
>>>
>>> func Benchmark_AllocWithMake(b *testing.B) {
>>> for i := 0; i < b.N; i++ {
>>> y = make([]Element, N)
>>> }
>>> }
>>>
>>> func Benchmark_AllocWithAppend(b *testing.B) {
>>> for i := 0; i < b.N; i++ {
>>> y = append([]Element(nil), x...)
>>> }
>>> }
>>>
>>> func Benchmark_CloneWithCopy(b *testing.B) {
>>> for i := 0; i < b.N; i++ {
>>> t := make([]Element, N)
>>> copy(t, x)
>>> y = t
>>> }
>>> }
>>>
>>> func Benchmark_CloneWithAppend(b *testing.B) {
>>> for i := 0; i < b.N; i++ {
>>> y = append([]Element(nil), x...)
>>> }
>>> }
>>>
>>> Benchmark_AllocWithMake-4 1000 1223666 ns/op
>>> Benchmark_AllocWithAppend-4 2000 725361 ns/op
>>> Benchmark_CloneWithCopy-4 1000 1813321 ns/op
>>> Benchmark_CloneWithAppend-4 2000 735011 ns/op
>>>
>>> On Tuesday, June 27, 2017 at 10:58:28 PM UTC+8, T L wrote:
>>>>
>>>>
>>>> package main
>>>>
>>>> import (
>>>> "testing"
>>>> )
>>>>
>>>> const N = 1024 * 1024 // number of elements
>>>> type Element int64
>>>> var x = make([]Element, N)
>>>> var y []Element
>>>>
>>>>
>>>> func Benchmark_CloneWithAppend(b *testing.B) {
>>>> for i := 0; i < b.N; i++ {
>>>> y = append([]Element(nil), x...)
>>>> }
>>>> }
>>>>
>>>> func Benchmark_CloneWithCopy(b *testing.B) {
>>>> b.ResetTimer()
>>>> for i := 0; i < b.N; i++ {
>>>> t := make([]Element, N)
>>>> copy(t, x)
>>>> y = t
>>>> }
>>>> }
>>>>
>>>> /*
>>>> $ go test -bench=.
>>>> Benchmark_CloneWithAppend-4 2000 738281 ns/op
>>>> Benchmark_CloneWithCopy-4 1000 1822462 ns/op
>>>> */
>>>>
>>>
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
