Author: Bruce Moreland
Date: 09:27:52 07/09/01
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On July 09, 2001 at 11:24:22, Miguel A. Ballicora wrote: >I do something like this: > > if (is_mate_value(best)) > return best-1; > else > return best; > >So, the value is adjusting when it comes back from the leaves. In this way, >the values do not depend on the distance to root, depend on the distance >to leaves, which is correct. I can come back to this position any time, pick the >value from the table and the value is always meaningful. Mate in 5 will be >always mate in five no matter how I reach this position. Any comments on this? >Is it right? any drawbacks? > >In theory, I should not have problems with storing exact values but I am not >100% sure. Extensions make this value not perfectly correct since I can find >a mate in 8 with checks faster than a mate in 5 with silent moves. >Maybe that is the reason why I see oscilations in the evaluation when I am >detecting mates. May be I should store bounds like >= MATE in 8, or maybe >I should do Bruce's approach and forget about all this. I agree with Bruce, when >a Mate is found the most important thing is not to have bugs. The game is >decided generally at this point... as long as there is no bug. > >All I can say is that I haven't seen serious problems so far with the way I do >it. When a mate is found is eventually delivered. > >Regards, >Miguel There's an issue about what you store in the hash table when you have a mate score, and what you do when you get it out. There are also issues involving how bounds (>= mate in 7) are handled. I'd expect that eventually a program with bugs could deliver mate. But it's annoying watching a bug that causes the thing to return a different mate score in every iteration. The place to notice this stuff is when you have endgame databases hooked up, and you probe them in the tree. That causes all kinds of hell unless you have things working properly. bruce
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