in not working for arrays is silly, change my view

[aliak]

On Monday, 2 March 2020 at 23:27:22 UTC, Steven Schveighoffer 
wrote:
>
> What I think is happening is that it determines nobody is using 
> the result, and the function is pure, so it doesn't bother 
> calling that function (probably not even the lambda, and then 
> probably removes the loop completely).
>
> I'm assuming for some reason, the binary search is not flagged 
> pure, so it's not being skipped.

Apparently you're right: 
https://github.com/dlang/phobos/blob/5e13653a6eb55c1188396ae064717a1a03fd7483/std/range/package.d#L11107

>
> If I change to this to ensure side effects:
>
> bool makeImpure; // TLS variable outside of main
>
> ...
>
>     auto results = benchmark!(
>         () => makeImpure = r1.canFind(max),
>         () => makeImpure = r2.contains(max),
>         () => makeImpure = r3.canFind(max),
>     )(5_000);
>
> writefln("%(%s\n%)", results); // modified to help with the 
> comma confusion
>
> I now get:
> 4 secs, 428 ms, and 3 hnsecs
> 221 μs and 9 hnsecs
> 4 secs, 49 ms, 982 μs, and 5 hnsecs
>
> More like what I expected!

Ahhhh damn! And here I was thinking that branch prediction made a 
HUGE difference! Ok, I'm taking my tail and slowly moving away 
now :) Let us never speak of this again.

>
> -Steve