Author: Robert Hyatt
Date: 06:48:25 12/03/03
Go up one level in this thread
On December 02, 2003 at 18:32:08, macaroni wrote: >this is the analasys from the re-write of my engine from the first position in >WAC. >[D]2rr3k/pp3pp1/1nnqbN1p/3pN3/2pP4/2P3Q1/PPB4P/R4RK1 w - - 0 1 >-->"WAC001", best=Qg6 >stage=middlegame, playing as WHITE, nullmove is ON, Using >ply=1, value=-200, nodes=113, kNps=0, best=Ne5xc6 >ply=2, value=-200, nodes=2546, kNps=11, best=Ne5xc6 >ply=3, value=-200, nodes=7708, kNps=18, best=Ne5xc6 >ply=4, value=10000, nodes=129225, kNps=88, best=Qg3-g6 >ply=5, value=100, nodes=224379, kNps=105, best=Nf6-e8 >ply=6, value=10000, nodes=658686, kNps=125, best=Qg3-g6 >ply=6, value=10000, nodes=1012767, kNps=129, best=Qg3-g6 > >it's a very easy mate in 2, and the computer, as expected, finds it at ply 4, >but then disregards it at ply 5, for Ne8, which also just about wins. It is >nullmoving that has caused this, is there any way I can avoid this sort of >problem? it arises, because after playing Qg6, it nullmoves, and calls a 1 ply, >or 0 ply search, in both of these searches, black is better by 200 points, it >doesn't fail in the ply 4 search because there is nothing better, it DOES fail >in the ply 5 search because Ne8 is also good, so beta is 100, not -200. >cheers >tor This really can't be a null-move related issue, it is a search bug. You are somehow letting a worse score overwrite a mate score, which should be impossible if you do the alpha/beta test correctly. That tree should be small enough to dump and see just how the mate score is getting replaced, manually.
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