Messages in this thread | | | From | Daniel Phillips <> | Subject | Re: [RFC][PATCH] Faster generic_fls | Date | Thu, 1 May 2003 03:02:14 +0200 |
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On Wednesday 30 April 2003 22:59, Willy Tarreau wrote: > On Wed, Apr 30, 2003 at 09:15:33PM +0200, Daniel Phillips wrote: > > In the dawn of time, before God gave us Cache, my version would have been > > the fastest, because it executes the fewest instructions. In the misty > > future, as cache continues to scale and processors sprout more parallel > > execution units, it will be clearly better once again. > > Daniel, > > I must acknowledge that your simple code was not easy to beat ! You can try > this one on your PIII, I could only test it on an athlon mobile and a P4. > With gcc 2.95.3, it gives me a boost of about 25%, because it seems as gcc > cannot optimize shifts efficiently. On 3.2.3, however, it's between 0 and > 5% depending on optimization/CPU.
Was something ifdef'd incorrectly? Otherwise, there is something the PIII hates about that code. I got 107 seconds on the PIII, vs 53 seconds for my posted code at O3, and virtually no difference at O2. (gcc 3.2.3)
Regards,
Daniel
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