Author: Bruce Moreland
Date: 10:49:50 09/10/99
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On September 10, 1999 at 13:07:02, Robert Hyatt wrote: >On September 10, 1999 at 12:58:13, Bruce Moreland wrote: > >>Store all mate scores as bounds and see what happens. I'll tell you what will >>happen. You'll find this in a few seconds and there won't be any bugs. >> >>bruce > > >It didn't help a bit, unless I modified the bounds as I mentioned. I was always >updating a true mate score, and getting rid of this didn't help a bit, as I >expected when playing around yesterday. The problem was those "mate in N" >bounds that get stored... they can be wrong if they aren't adjusted. I now >store true mate scores as always, but mate bounds are reduced to just say >"< -MATE+300 or > MATE-300. I use 300 because of the large tablebase mate >scores that get stored. But I am still storing actual mate scores as I have >never had a problem with that (i adjust them to mate-in-N from the current >ply of course.) > >But those bound mates were causing this particular problem to blow up, because >I would store > MATE-10 (mate in 5) at position X, ply 8, then look that up at >ply=10 or 12 and make a wrong decision. It was _very_ hard to find in a tree >of 1M nodes... I should clarify. Convert as follows: Mate in N becomes >= Mate in 500 -Mate in N becomes <= -Mate in 500 >= Mate in N becomes >= Mate in 500 <- This is our point of dispute. <= -Mate in N becomes <= -Mate in 500 <- So is this. <= Mate in N is simply not stored. <- A nasty case. >= -Mate in N is simply not stored. <- Likewise. This should confidently fix every bug known to man, it short-circuits all of the problems you mention above, it will take you five minutes to implement, and the only place you have special-case code for mate scores in the hash table is in the hash table store code, you don't have to have weird stuff in your probe code. bruce
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