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Subject: perft results (how accurate is accurate enough ?)

Author: Roman Hartmann

Date: 13:58:33 09/23/04


hello all,

while testing my move generator (10x12 array, only legal moves) and comparing
the perft result from Crafty and my own results I noticed that my results differ
for some positions a bit. As the results start to differ only at some depth it's
not that easy to track this bug. Although I'm quite certain that the problem is
somehow related to EP-moves I wasn't able to solve this riddle yet.

By searching the web I found some websites with perft results from other chess
engines with numbers even more off than the results from my move generator.

some results -total nodes- from my move generator (proper Results from Crafty):
rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
perft 4: 20603 ok
perft 5: 5072212 ok
perft 6: 124132506 (124132536) differ

r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq -
perft 3: 99949 ok
perft 4: 4185800 (4185552) differ
perft 5: 197909832 (197876242) differ

8/2p5/3p4/KP5r/1R3p1k/8/4P1P1/8 w - -
perft 3: 3017 ok
perft 4: 46264 (46255) differ
perft 5: 720964 (720879) differ
perft 6: 11761790 (11750962) differ

8/PPP4k/8/8/8/8/4Kppp/8 w - -
perft 5: 1840260 ok
perft 6: 36177037 ok

Well, as searching for this bug has allready consumed much more time than I ever
expected it would I'm not sure -after having seen this sites- that the the move
generator has to be perfect in order to create a working chess engine. On the
other hand my move generating process is quite complicated and I'm not sure if I
will still understand all the parts of it in a few months like I do understand
them now.

What should I do about that? Try to track down this bug at any price or just go
on an do some work on other parts of the engine and fix this bug later? Or
should I just forget about the bug at all?
Thanks for all suggestions in advance.

Best regards
Roman



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