Author: Robert Hyatt
Date: 20:25:12 05/03/00
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On May 03, 2000 at 13:27:04, John Coffey wrote: >Where can I find more info on killer moves? How is a killer move determined and >where is it used? > >John You 'find' it in one of two ways: At the current ply, you try a move and it produces a value >= beta, so that you can stop searching right now, without searching the remainder of the moves. Remember this move as "good" and try it early whenever you search again at this ply. At the current ply you complete the search, and the score is > alpha (we know it is less than beta or we would have failed high). Remeber the 'best' move at this ply as a 'killer'. You use it in move ordering. The best example was given in Slate/Atkin's article in "Chess Skill in Man and Machine". In a position they gave, black was threatened by Nc7+, forking king and rook. Most of black's moves don't defend against this, so for each 'lemon' black move, we try Nc7+ to see if it still wins an exchange. This move will usually refute the black move and we are done after one move, rather than having to search most of the white moves to stumble into Nc7.
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