Author: Uri Blass
Date: 01:27:57 02/08/04
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On February 07, 2004 at 23:37:31, Robert Hyatt wrote: >On February 07, 2004 at 18:26:00, Uri Blass wrote: > >>I started to work on having some evaluation about endgame and >>I wrote something to detect draws in KP vs K. >> >>It does not detect every possible draw but at least hopefully when it detect >>draw it is correct if I have no bugs. >> >>Tablebases is not a solution because they are too slow and I believe that >>generally functions are better because even in case of having tablebases if I do >>not probe them in the qsearch I may get KP vs K that I need to evaluate without >>tablebases and I want to return correct score without looking in tablebases. >> >>I read that yace is using bitbases even for 4 piece endgames when the bitbases >>give only win draw loss information and I guess that the bitbases were >>calculated from nalimov tablebases. >> >>I wonder what other people do in KP vs K endgame in case of not looking in >>tablebases(because the program does not support tablebases or because it is a >>qsearch node). > >I have special code. that handles two rules: > >1. If the king is one square in front of the pawn, and has the opposition, >then the pawn queens. > >2. If the king is two squares in front of the pawn, then the pawn queens no >matter what. > >A couple of special exception cases to make sure that the opponent can't capture >the pawn instantly, and you are done... Just try Crafty with KP vs K and no >tables, to see what I mean... I started by having rules to find draws so later I do not need to check if the king can capture the pawn instantely except cases when the pawn is in the second rank because it is one of the cases when draw should be detected based on distances. Note that I already checked if this rule is correct and I found that it is not correct [D]8/K7/8/5k2/8/3P4/8/8 w - - 0 1 In this position my latest version plays d4 with draw score when Kb6 is winning but is evaluated as a draw because the black king is closer to the pawn relative to the white king and it is black to move and the pawn is not in the second rank. I still think that it is possible to have always correct rules based on distance but it is not so simple. Maybe distance to block the pawn is better but in this case I need to check that the pawn is not in the 7th because in these cases the king can block the pawn and still lose. Uri
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