Author: Gian-Carlo Pascutto
Date: 15:44:36 09/27/01
Go up one level in this thread
On September 27, 2001 at 18:15:29, Nolan Denson wrote: >In the >context of whole application, speedup is obviously limited by the fraction >of the execution time spent in vector loops (Amdahl's law). Hmm, that would be ... 0 ? >Besides, >vectorization alone is not always the way to befenit from P4. This processor >has other rich features that our compiler can exploit to boost performance. Really? Then why is everything running so slow? >Another note. SSE2 *does* support integer operations, in fact it is a full >extension of 64-bit MMX(tm) technology into 128-bits. So tell your friends! >SSE/SSE2 is not just FP alone, it is also integers. Too bad chessboards dont have 128 squares eh? Maybe it's possible to do bitboards ops in them with a bearable penalty, but all data structures will also double in size, and the P4 doesn't exactly have huge caches. As a comparisation, I rewrote the popcount function of crafty in optimized MMX assembly for the Athlon and the net speed gain was...1% I don't know what speedup, if any, people with a P4 saw with it. I don't think SSE has 'first bit set' or 'last bit set' function either. That would require continous packing/unpacking from the SSE code to normal integer registers. Horrors. >Crafty, indeed is very hard to optimize, and vectorization has not given us >any benefit at all so far. But maybe you are happy to hear that our team has >two chess hobbyist as well, and that our near future focus will be on >improving integer performance. I keep you posted if we have something >interesting to report. >Aart 'Near future'...nothing concrete of course. Interesting that although the vast majority of code out there is integer and they appearently didn't care for it (or already gave up ;). You mailed Intel. What did you expect? They can't say: 'sorry but the P4 just sucks (for chess)' _and_ keep their jobs ;) -- GCP
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.