Author: Stuart Cracraft
Date: 15:48:29 03/07/06
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On March 07, 2006 at 15:36:11, Robert Hyatt wrote: >On March 07, 2006 at 03:49:47, Richard Pijl wrote: > >>>If one's results do not rotate approximately as described >>>for the four positions and you say the evaluation is an >>>issue, what kinds of evaluation issues have you seen that >>>could explain it?!? >> >>I had this problem long time ago in the Baron as well. To be able to detect >>these issues I created a little tool that reads a large PGN file, and for every >>position in the PGN file calls the static evaluation function for that position >>mirror the position and call static eval again. Whenever that didn't give >>exactly the same score for both positions, I print both fens, and continue. >>Usually, if there is an evaluation mirroring bug, it doesn't take long for it to >>find it. >> >>Richard. > > >I've also had this forever it seems, in the "evtest" code in crafty. I have >'flip' (reverse board, make white pieces black and vice-versa, then copy >exchange ranks 1 and 8, 2 and 7, etc. I also have a "flop" command that just >exchanges files a and h, b ahd g, etc, but doesn't change the color. I then do >something like: > >s1 = evaluate() > >flip > >s2 = evaluate() > >flop > >s3 = evaluate() > >flip > >s4 = evaluate() > >and the scores must match, except that after a flip the sign must change since >the pieces are changing. My current code will run through several thousand FEN >positions with nary a complaint since I no longer have any asymmetry >whatsoever... Congratulations - not just on the truly great description but on your perfect multi-lateral symmetry. Is this what it means to be balanced? Stuart
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