Author: Michel Langeveld
Date: 21:05:05 11/21/01
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On November 21, 2001 at 18:31:18, Gian-Carlo Pascutto wrote: >On November 21, 2001 at 18:23:08, Michel Langeveld wrote: > >>I build nullmove in my chessprogram and received a problem. >> >>The example which is on Bruce side seems not to work in certain positions. >>Especially positions where it's possible to give mate: >> >>[D] rnbq1bnr/pp2k3/2p1p1B1/3pP1p1/7p/4PQ2/PPPN1PPP/R3K1NR b KQ >> >>After Qc7 white doesn't see Qf7 anymore. >> >>It seems to be that the line: >> >>val = -AlphaBeta(depth - 1 - R, -beta, -beta + 1); >> >>Must be changed into: >> >>val = -AlphaBeta(depth - 1 - R, -beta+1, -beta); > >Nope. > >Due to the negamax recursive call, (-beta, -beta+1) >becomes (beta-1, beta) at the next level, which is >correct. > >(-beta+1, -beta) would become (beta, beta-1). These >last bounds are false. What is effectively beta there >(the second value), is smaller than alpha. > >I hope that makes sense. I'm not as good an explainer >as Bruce is. > >-- >GCP You explained it well :-) I see indeed that -beta+1, -beta is incorrect. I have changed this back to -beta, -beta+1 and even -beta, -alfa but I have still problems. I think this is because my nullmove can end immediatly in my QSearch. Or is this normal behaviour?
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