Author: Steffen Jakob
Date: 08:51:38 07/08/01
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On July 08, 2001 at 10:02:27, Robert Hyatt wrote: >On July 08, 2001 at 08:56:32, Alvaro Jose Povoa Cardoso wrote: > >> >>My problems with mate scores adjustments are all gone now, thanks to the help of >>Dr. Hyatt and Bruce Moreland. >> >>In main.c of Crafty 16.18 there is the following notes: >>* A very interesting bug was found in storing mate bounds in the hash * >>* table, one I had not heard of before. I now store two MATE * >>* bounds, either > MATE-300, or < -MATE+300, which is conservative * >>* but safe. >> >>Could you please explain why should we do so? > > > >This had to do with the problem that the bound is an absolute thing that >says the score can not be less than X or it can not be greater than X. >But X depends on the ply depth and it caused problems when I tried to adjust >it like I adjust exact mate scores. That is all that I can really say here as >this was done several years ago and I don't recall the exact circumstance where >I got burned by this problem... I simply remember that it was a lot of >debugging (hash table problems are generally difficult to debug since you have >to follow a deep and complicated tree search). I can refresh your memory. At that time I did some work with the following position: [D]8/p7/P5p1/7p/7P/4kpK1/8/8 w When I showed it to you you said that crafty detected it was a mate in 5. In fact white gets mated in 6. This was the symptom of the mate bug. Greetings, Steffen.
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