Author: Uri Blass
Date: 02:08:40 04/19/03
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On April 19, 2003 at 04:54:29, Tony Werten wrote: >On April 19, 2003 at 04:07:37, Uri Blass wrote: > >>On April 19, 2003 at 03:37:06, Tony Werten wrote: >> >>>On April 17, 2003 at 20:35:35, James Robertson wrote: >>> >>>>Out of curiosity I tested just the move generation and basic board functions of >>>>my bitboard chess program on several different computers. My home computer is a >>>>Pentium 933mhz, and the other computers I used were Athlons in the 1.6ghz range. >>>> >>>>My program's move generator runs at roughly the same speed on both systems. I >>>>was surprised and tested using several different compilers (VC5, VC6, .NET, >>>>gcc), under Windows and under Linux. To compare more easily, I wrote a simple >>>>non-bitboard move generator and tested this on all of the machines. The speed >>>>differences scaled with the speed of the processors, which seemed logical. >>>>However, I still cannot explain why the bitboard functions are so much slower on >>>>the faster computers. The only difference I can see is that my home computer is >>>>a pentium and the others are athlons. >>>> >>>>It seems strange that this would make such a large difference. Can anyone give >>>>any reasons why? I used no assembly, just C/C++ code, with all the default >>>>compiler options on all tests. >>> >>>I think it's because bitboards tend to fill up the caches, so memory becomes the >>>bottleneck. >>> >>>With other approaches this doesn't happen, ( until you add the big stuff like >>>eval ) so all things stay in chache wich makes it (almost) only processor >>>limited. >>> >>>Tony >> >>Does it mean that bitboard chess programs or programs with big evaluation are >>basically optimized for the old hardware because they cannot get much from new >>hardware? > >No, because you're doing more then, wich can go faster with faster hardware. ie >You don't reach the move generation bottleneck, but have others. > >But if all you are doing, has a memory bottleneck (wich happens when only >generating moves with bitboards ), a faster cpu won't help very much. > >Tony The question is how can I identify memory bottleneck. I use bitboards only for pawn structure but I have a big move generator(some thousands of C lines). Is the only way to buy fast hardware and see if my program is faster on faster hardware or is there a better way? Uri
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