Date: Sun, 15 Aug 2021 18:29:08 +0200 From: "Stefan Kanthak" <stefan.kanthak@...go.de> To: "Rich Felker" <dalias@...c.org> Cc: "Szabolcs Nagy" <nsz@...t70.net>, <musl@...ts.openwall.com> Subject: Re: [PATCH #2] Properly simplified nextafter() Rich Felker <dalias@...c.org> wrote: > On Sun, Aug 15, 2021 at 05:19:05PM +0200, Stefan Kanthak wrote: >> Szabolcs Nagy <nsz@...t70.net> wrote: >> >> > * Stefan Kanthak <stefan.kanthak@...go.de> [2021-08-15 09:04:55 +0200]: >> >> Szabolcs Nagy <nsz@...t70.net> wrote: >> >>> you should benchmark, but the second best is to look >> >>> at the longest dependency chain in the hot path and >> >>> add up the instruction latencies. >> >> >> >> 1 billion calls to nextafter(), with random from, and to either 0 or +INF: >> >> run 1 against glibc, 8.58 ns/call >> >> run 2 against musl original, 3.59 >> >> run 3 against musl patched, 0.52 >> >> run 4 the pure floating-point variant from 0.72 >> >> my initial post in this thread, >> >> run 5 the assembly variant I posted. 0.28 ns/call >> > >> > thanks for the numbers. it's not the best measurment >> >> IF YOU DON'T LIKE IT, PERFORM YOUR OWN MEASUREMENT! > > The burden of performing a meaningful measurement is on the party who > says there's something that needs to be changed. I offered you two patches which speed a rather simple function by a measured factor of 5 and 7 respectively. IF YOU DOUBT THESE NUMBERS, PROVIDE YOUR OWN! Stefan
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