Author: Tord Romstad
Date: 12:59:00 10/07/03
Go up one level in this thread
On October 07, 2003 at 13:08:28, Anthony Cozzie wrote: >On October 07, 2003 at 12:29:18, Tord Romstad wrote: > >>On October 07, 2003 at 08:27:40, Anthony Cozzie wrote: >> >>>On October 06, 2003 at 22:24:18, macaroni wrote: >>> >>>>What are the usualy ways of pruning the quiescent search. I don't use bitboard, >>>>so that cuts out some stuff, and makes a swap function heaps harder. At the >>>>moment, I just say a capture is no good if it doesn't increase the score above >>>>alpha-margin (50 centipawns for position stuff at the moment). Are there any >>>>other simple, or sort of simple ways? >>>>Cheers >>> >>>1. You stepped on a mine here. Your "I don't use bitboards, because ____" will >>>start a huge flamewar. Mark my words. >> >>He didn't say "I don't use bitboards, because ____", just "I don't use >>bitboards". Hence, no flamewar. :-) > >I'm sorta disappointed, actually. Then you should try to explain why you do or don't use bitboards yourself, preferably in a very provocative and annoying way. ;-) >>>2. When you say "swap-off" function, I think you mean a capture evaluator. >>>However, there is no reason you can't write a capture evaluator without >>>bitboards (actually, there isn't really a good way to do it _with_ bitboards >>>IMO). >> >>I agree. Writing a static exchange evaluator is more or less equally >>difficult in all common board representations. > >I think I said that it was harder with bitboards ;) OK, I probably didn't read carefully enough before answering. To me virtually everything seems harder or clumsier with bitboards, but I always assumed it was just because I'm too stupid. At least we agree that not using bitboards is not a reason to avoid trying to write a capture evaluator. >However, it is not exactly _easy_ to write in any representation. > >The logic runs like this: A big part of capture evaluation is xray: if I have >Ba1 + Qb2, my pawn at e5 is defended twice, not once. With bitboards, figuring >this stuff out is very annoying, because get_attacks_bishop(E5) will not find >the bishop. To make things even more annoying, imagine Pf6, Pe5, Qb2, and Ba1 - >now we have to deal with pawns as well. With a 64 byte or 0x88 board, you just >keep scanning. This is why Zappa's capture evaluation actually doesn't use the >bitboards (slight fib, but mainly it scans). I'm working on incremental attack >tables right now so that I don't have to mess with it. I use simple scanning myself on my 16x16 board. >P.S. I believe SEE refers to capture analysis in place of Q search, although >perhaps its meaning has changed somewhat. I have no idea -- perhaps I have always misused the term. Tord
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