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Re: [PATCH] Inline C99 math functions
- From: "Carlos O'Donell" <carlos at redhat dot com>
- To: OndÅej BÃlka <neleai at seznam dot cz>, Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- Cc: libc-alpha at sourceware dot org
- Date: Tue, 16 Jun 2015 15:54:35 -0400
- Subject: Re: [PATCH] Inline C99 math functions
- Authentication-results: sourceware.org; auth=none
- References: <001201d0a75b$921d9860$b658c920$ at com> <alpine dot DEB dot 2 dot 10 dot 1506151431490 dot 26683 at digraph dot polyomino dot org dot uk> <001701d0a789$f2ab86f0$d80294d0$ at com> <20150615185201 dot GA3023 at domone> <alpine dot DEB dot 2 dot 10 dot 1506152127340 dot 9772 at digraph dot polyomino dot org dot uk> <20150616050045 dot GA8021 at domone> <55801706 dot 4010109 at linaro dot org> <20150616134331 dot GA7016 at domone>
On 06/16/2015 09:43 AM, OndÅej BÃlka wrote:
>> So to make this proposal to move forward, how exactly do you propose to
>> create a benchtest for such scenario? I get this is tricky and a lot of
>> variables may apply, but I do agree with Joseph that we shouldn't quite
>> aim for optimal performance, imho using compiler builtins with reasonable
>> performance is a gain in code maintainability.
>>
> As I said before about these they are hard to measure and I could
> argue also versus my benchmark that its inaccurate as it doesn't measure
> effect of cpu pipeline when function does other computation. Answer is
> don't do microbenchmark.
That's not an answer, an answer is "Here's a patch to extend the libm testing
to show how isinf/isnan/signbit/isfinite/isnormal/fpclassify impact performance."
I agree that microbenchmarks can be misleading if interpreted by automated
systems, but we aren't talking about that yet, we are talking about experts
using these tools to discuss patches in an objective fashion.
Cheers,
Carlos.