Author: Peter McKenzie
Date: 19:00:21 04/11/03
[D] 6k1/7p/4Q1p1/3pP1P1/p6q/Pp1r2R1/1P5P/7K b - - 0 1 This position was posted a while ago, and it was noted that some programs (eg. Hiarcs, Warp) still report a very big score for white after a very long search. On the other hand, other programs like Crafty, Yace, and movei seem to see the draw (or close to it) within 10-12 ply. I decided to investigate this a bit further, starting with the hypothesis that the main differentiator here is the effectiveness of a program's main hash table. I modified Warp's replacement scheme with a little hack, telling it never to replace a draw score with a non-draw score. With this change, Warp can see the draw at depth 11 while previously it was still showing +4.8 at depth 15! While its unlikely this little hack will help overall strength, it does indicate that its the hashing scheme which is critical here. I use a single hash table, with 4 probes. Its basically an always replace strategy, where I replace the record with the lowest draft (of the records probed). Interested in how others get on with this position, and if the hack gives similar results if your program has trouble with it. cheers, Peter
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