Hi Kortschak,
That's interesting! I've actually never had use for 3 index slicing in the
past, so I didn't think of this. It definitely achieves the desired result,
but also forces two allocations. I still find creating with the full
capacity in one go and copying / appending to be faster.
func BenchmarkCombine4(b *testing.B) {
n := New("one", "two")
with := New("three")
for i := 0; i < b.N; i++ {
_ = append(n[:len(n):len(n)], with...)
}
}
func BenchmarkCombine5(b *testing.B) {
n := New("one", "two")
with := New("three")
for i := 0; i < b.N; i++ {
test := make(Namespace, 0, len(n)+len(with))
test = append(test, n...)
test = append(test, with...)
}
}
func BenchmarkCombine6(b *testing.B) {
n := New("one", "two")
with := New("three")
for i := 0; i < b.N; i++ {
test := make(Namespace, len(n), len(n)+len(with))
copy(test, n)
test = append(test, with...)
}
}
Of those three benchmarks, the 3rd consistently benchmarks lower. Not by
huge margins, but enough:
BenchmarkCombine4-4 10000000 161 ns/op
BenchmarkCombine5-4 10000000 147 ns/op
BenchmarkCombine6-4 10000000 145 ns/op
Since my full use case (wasn't included in the original post) requires
appending more than one thing in a loop, that exaggerates this issue
further.
Thanks!
Evan
On Sunday, 17 July 2016 16:31:33 UTC-7, kortschak wrote:
>
> On Sun, 2016-07-17 at 09:09 -0700, Evan Digby wrote:
> > For now the solution is to explicitly make copies, which was the desired
> result in the first place.
> >
> > The code I posted earlier works as desired.
>
> You don't need to make explicit copies. If you use three index slicing,
> you get the behaviour you want.
>
> https://play.golang.org/p/ENpRmubQV4
>
>
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