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)
}
}
?
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
>>> */
>>>
>>
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