What you are doing is what sync.Once was invented for:
https://play.golang.org/p/erZqwFYgIR
On Tue, Oct 17, 2017 at 11:37 PM, Juliusz Chroboczek <j...@irif.fr> wrote:
> > The answer depends on whether you have just one value or many. For a
> single
> > value (sometimes known as a "future"), I tend to pair a chan of struct{}
> > with a value to be set. To make the value available, set it, then close
> the
> > channel. Readers wait on the channel, then read the value.
>
> That's an interesting idea. Surprisingly enough, it turns out to be
> only slightly slower than the obvious implementation with a mutex, and
> (even more suprisignly) actually faster when using hardware threading.
> This is on a 2-core hyperthreaded SandyBridge (4 hardware threads):
>
> BenchmarkMutexFuture 100000000 22.2 ns/op
> BenchmarkMutexFuture-2 50000000 39.9 ns/op
> BenchmarkMutexFuture-4 20000000 86.0 ns/op
> BenchmarkAtomicFuture 200000000 7.01 ns/op
> BenchmarkAtomicFuture-2 500000000 3.69 ns/op
> BenchmarkAtomicFuture-4 1000000000 2.69 ns/op
> BenchmarkChannelFuture 50000000 29.7 ns/op
> BenchmarkChannelFuture-2 50000000 54.6 ns/op
> BenchmarkChannelFuture-4 20000000 64.4 ns/op
>
> Code here: https://play.golang.org/p/Wm71o50HJ8
>
> -- Juliusz
>
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