Author: Robert Hyatt
Date: 19:55:09 03/16/99
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On March 16, 1999 at 18:36:08, Peter Kasinski wrote: >On March 16, 1999 at 16:58:09, Robert Hyatt wrote: > >>On March 16, 1999 at 12:04:51, Dann Corbit wrote: >> >>>On March 16, 1999 at 02:50:20, Cristian Zaslo wrote: >>> >>>>Hi everybody ! >>>>Will anyone be so kind and briefly explain me what sort of >>>>advantages would (not) have a chess programmer to implement >>>>a SEE in his code. >>>>Much obliged to you, >>>>Cristian >>>Er.... >>>What's a SEE? I've been programming 33 years and I have never heard of one. >> >> >>Stands for "Static Exchange Evaluator". It is a procedure that analyzes all >>captures on a single square and returns a value indicating who comes out >>ahead. >> > >>It can be used to order captures so that you try QxP where the pawn is free, >>before you try QxR where the R is defended. It can also be used to discard >>some captures in the q-search such as QxR where the R is defended and you are >>guaranteed to lose material. >> >>Used correctly it is possible to cut the size of the tree being searched by >>50% or more. > > >Bob, I looked at Swap() in Crafty where this is implemented. >Not using bitmaps I don't have a cheap way to determine what pieces attack a >given square. Would it still be profitable for me to compute these attacks in >order to use SEE? > >thank you, >PK There are far more non-bitboard programs than bitboard programs. And SEE works just fine. It will cost a little more probably, because there are loops that don't exist in bitmaps, but I had such a function in Cray Blitz. The idea is to take the target square, and first find out what pawns are attacking the square, then bishops, knights, rooks, queens and finally kings. Then the 'minimax' code at the bottom of my Swap() can be taken directly...
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