Author: Uri Blass
Date: 03:24:08 08/04/04
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On August 04, 2004 at 05:46:24, Tord Romstad wrote: >Hi Cesar! > >On August 03, 2004 at 15:04:54, Cesar Contreras wrote: > >>I'm working on extended futility prunning and it's not working, it seems to >>make a node reduction, but it plays worse than without it. >> >>My question is, do any of you have seen good improvement using extended >>futility prunning? > >Yes, I use something very similar to extended futility pruning, with good >results. The technique as explained by Heinz didn't work for me, but with >some extra conditions added it performed much better. > >I never prune if there was an extension in one of the last two moves in >the current line. This little extra condition, by the way, is useful >also with many other pruning and reduction techniques. It greatly >improves the program's tactical accuracy. > >I also never prune checks, passed pawn pushes to the 7th or 8th rank, >or moves which threaten a valuable enemy piece. I don't prune if the >side not to move has very bad king safety. > >>what normal futility margin do you use? >>what extended futility margin do you use? > >2 pawns and 5 pawns, but around the result of the last iteration rather than >around alpha. > >Tord I see no reason to use constants. I have another pruning condition that is also similiar to futility pruning but I use a function instead of constants and I use beta and not alpha but maybe it is because of the fact that I prune after making moves and not before making them so my beta means your alpha. if (evalfull[ply]>=beta+calculatemargin(depth)) return beta; evalfull[ply] is the evaluation and calculatemargin is a function that can be improved(it is using a lot of global varaibles except depth) maybe it is better not to use beta but score of last iteration and I did not try it. Uri
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