Author: Gerd Isenberg
Date: 13:04:53 02/29/04
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On February 29, 2004 at 15:13:49, David Mitchell wrote: >On February 29, 2004 at 14:44:54, Martin Schreiber wrote: > >>Hi, >> >>I've two questions: >> >>1.) >>is using bitboards a necessary condition to write a strong chess engine? And if >>not so, what other good/fast solution we have for the board representation? >> >>2.) >>And are there strong freeware or commercial chess engines, which don't use >>bitboards? >>And what kind of board representation they use? >> >>Thanks for your comments >>Martin > >1. No, bitboards are not necessary in order to write a strong chess engine. >2. I would guess 0x88 is as fast as bitboards for 64 bit cpu's, and slightly >faster than bitboards on 32 bit cpu's. Hard to make a direct comparison because >with bitboards, you get more info your program can use later in the eval, etc. > >If you click on Computer Resource Center -> Chess links, and select Crafty, you >can find and d/l an excellent write up by Robert Hyatt on this subject. > >Bitboards take a while to learn to use well. Many commercial programs have not >used them in the past, but may in the future if the 64 bit cpu's become quite >popular, because of the 2x (at least) speed up bitboards achieve on them. Not per se with AMD64 or intel64. 64-bit instructions do have an additional prefix byte. So the codesize advantage may only 3/4 instead of 1/2. Latency of 64 bit instructions is sometimes worse (bsf, mul). Two independent 32-bit instructions are likely to gain more parallelism. It doesn't matter much, whether 1*64 or 2*32 bit are loaded/strored, considering some latency and internal bus widths. More important features with AMD64, and that is not only helpful for bitboards, are the doubled register-file size, the bigger 2.level cache, improved branch prediction, two more pipe stages and more. OTOH register hungry bitboard algorithms which are not efficiently possible with x86-32 became more interesting now. Gerd > >dave
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