Author: Bas Hamstra
Date: 01:22:06 01/13/03
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On January 12, 2003 at 21:01:01, Russell Reagan wrote: >On January 12, 2003 at 20:25:01, Bas Hamstra wrote: >>I test it with all pieces being still on the board, while the square in >>question is not attacked. So a worst case scenario. > >In that case, the bitboards should perform about equally fast in any position >whether there is an attack or not. The 0x88 isn't the same though. It will be >slower if there is no attack, and faster if there is. So if you used more >positions (not just a few, but a lot, like during a search) you might find it\ >to be faster overall. Gerbil is faster than Crafty, sometimes almost twice as >fast, and so that speed has to come from somewhere. Thanks for your data about Gerbil, this motivates me again :-) It is difficult to predict how fast a program is going to be. I remember the GNU guys tested all critical functions when they switched to bitboards, and they were faster than the old versions. But when the rewrite was finished, the nps went *down* somewhat. Yes, where does gerbil's high nps come from? I have a few ideas without knowing Gerbil too well. - it probably does not do SEE sorting in the qsearch (?), which Crafty does do, this really kills nps but not overall searchdepth. In Tao I assign SEE scores to ALL captures which is even worse than Bob does (he does not calculate SEE if Defender > Attacker or a capture is considered "futile"). - Gerbil has less eval, mostly piece-square stuff - 0x88 is more cache-friendly Another thing is that Bruce probably uses a more efficient InCheck detection than SquareAttacked. >>No, but my BB program (Tao) does typically around 400k nps where Crafty does >>600k on my hardware, so slower. The new 0x88 toy doesn't even have a search >>yet, >>but I aim for at least 1M nps in the midgame for piece/square plus extensive >>pawn eval. > >Gerbil, on my PC (PIII 733 MHz), gets between 500knps and 800knps in the games >I have played with it. For comparison, Crafty gets between 300knps and >500knps. My computer is certainly not the newest fastest thing, so I imagine >Gerbil could get 1Mnps easily on a faster machine, and so could your 0x88 >program. Thanks for this interesting data. Best regards, Bas. >> Yes, I thought about that. I don't see a point in looping through 8 pawns to >> see if one square is attacked, that's why I put the conditionals in, which >> saves about half of the piece-loop and should be faster overall, I would >> suspect. > >Good point. I didn't consider that. > >Russell
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