Author: Robert Hyatt
Date: 08:02:05 01/21/01
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On January 21, 2001 at 09:12:59, Ricardo Gibert wrote: >[D]8/P6p/1P5P/8/8/4k3/5r2/4K3 b - - 0 0 >[D]8/1P5p/P6P/8/8/4k3/5r2/4K3 b - - 0 0 > >If Crafty encounters these as leaf node positions, what evalution does it >return? It would think white is winning. However, if it encounters a position like win at chess #141 at a leaf position it might think black is winning, when white has a forced mate in 6. In this position I would agree with Crafty's evaluation. It seems to me that if anybody wins at all, white wins. The non-ending checks/mate threats make this an exception. But then _all_ chess programs have that exception for deep checking lines. A quick check would be to leave white's two pawns where they are, but enumerate _all_ the possible places you can put the white king and black king and rook, and then compute the percentage of the time the current eval is wrong, and the percent it is right. If it is right > 50% of the time (it will be) then this is the right thing to do. If it is wrong > 50% of the time, this is bad. I would expect it to be right in > 90% of the cases. Which means not doing this would be wrong in 90% of the cases. Which side of that fence would you rather be on? I didn't do this eval term to find wac#2. I did it because in very fast games on ICC I was getting whacked by two connected passers that reached the 6th, even when it was possible to prevent them from getting there if it had only known that preventing this would be worth giving up a pawn to accomplish. I haven't seen this term lose a single game that I can recall. At least not since it was refined a year or two ago. That is the main way I evaluate the effectiveness of such evaluation terms...
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