Author: Vincent Diepeveen
Date: 04:38:41 08/08/03
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On August 08, 2003 at 02:35:00, Joost Buijs wrote: >Vincent, > >Have you ever tried bitboards? why don't you try this code and find out it is 2.2 times faster than what crafty has. i measured this against crafty. please don't complain about L2 cache needs of crafty's move generator because when you generate semi legal move list for a few million times then crafty's move generator is within L1 cache even. In fact this is 0.6% system time so you would save out 2.4% directly. But if you remove the 'if' condition to put the move in the movelist, then you will notice that this is completely branchless code for 1 piece with exception of the loop. So where 0.6% system time in move generator already saves me out 0.6% system time which is worth the effort of some months of fulltime programming as you know, even more important is that all scans in my evaluation that involve semi legal moves, is completely branchless. And there you have a major winner in system time as you already noticed. I can scan more and i can scan it faster than most other software. And there is your answer. Such code like this is a lot cleaner. Bitboards is not easier to evaluate. It is much harder. Also my code is trace cache friendly so to speak. If i evaluate a pattern i prefer general code which works both for white and black. That is not always easy to write and in not all cases it gets done, but which single bitboard program is using such general code? the only use i see in bitboards is a pawn bitboard so that complex pawn patterns require just one 'if' instead of a bunch. I feel your decision was wrong. With this code you can get 2 times faster in 32 bits. Also the advantage is you might get again interested in improving the evaluation function. Best regards, Vincent >I agree that on a 32 bit machine it takes a tiny bit longer to generate all the >moves with a bitboard engine. The whole move generation process takes ~3% from >the time the engine needs to determine a move, so thats is not important at all. > >The evaluation fuction is much cleaner and more convenient to handle when using >bitboards, probably you can gain a lot here. > >About two years ago I rewrote my old engine completely, and since that time it >is using bitboards. I still think I made a good decision by doing so. >In fact my program runs even faster after the conversion to bitboards. All other >things like the search and evaluation parameters are exactly the same as in the >old 1991 engine, so I am really comparing apples to apples here. > >B.T.W. I think the move generation is not that slow at all, for instance a perft >6 from the starting position takes here 6.24 sec. on a fast Athlon-XP, that's >about 8.5 million moves/s. Can you tell me what your numbers are with respect to >this? I'm really curious about this. > >Next year I will certainly get a dual or quad Opteron, I think my bitboard >engine will really scream on such a machine. > >The development of my engine has been frozen for 10 year or so, simply because I >was very busy doing other things. But recently I decided to start developing it >further. This year I won't attend the CSVN tourney, but I certainly want to be >there next spring. > >Groetjes, >Joost
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