Author: Gian-Carlo Pascutto
Date: 11:13:26 09/27/01
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On September 27, 2001 at 11:50:12, Nolan Denson wrote: >Now keep in mind I am only a hobbyist ... but from my readings and looking at >the presentation .... they gave examples of where codes can be improved upon. >Basically it seems where you seen hot spots in the Vtune software .. i believe >this analyzer is indicating areas in which the code can be improved upon. I >seen many area's in crafty that this program was indicating had hot spots. They >presentation went on to say that if such area's exist it a program it could be >as simple as optimizing with the correct switches or part of the code needs to >be rewritten to take advantage of the vectoring. It seems as if they were saying >vector's speed up the code. So if you see area's that need to do it to take >advantage of this feature ... you may have to rewrite some of the code. The 'hot spots' that are shown are just the areas where the CPU spends most of its time. _If_ you can rewrite them in a faster way, the program will gain (some) speed. The problem is that it's simply not possible, and if it is, the speed gain is laughable. This is why the P4-optimized versions of some chessprograms are hardly faster than the normal versions. The 'vectorizing' that you are talking about (SSE/SSE2) is _useless_ for chessprograms. In fact, it's useless for nearly everything except some signal processing applications (MPEG/DivX encoding/decoding for example, or certain kind of 3D graphics) MMX is something that _could_ help bitboard-based chessprograms, but the P4 has bad support for it. I repeat, the P4 _sucks_ for chessprograms, and most other applications too. If you don't believe me, take a look at the SPEC2000 numbers for crafty on a P4 and an Athlon. Those numbers represent the _best_ Intels _own _engineers could do to get crafty to run faster by 'analyzing hotspots' or 'vectorizing code'. If you look at them, and compare them to the Athlon's, you'll see just why the P4 sucks. -- GCP
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