Author: Brian Richardson
Date: 13:08:35 08/14/05
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On August 14, 2005 at 15:33:00, Robert Hyatt wrote: >On August 14, 2005 at 14:57:50, Brian Richardson wrote: > >>Just wondering if others see this behavior or not. >> >>In the position below, Tinker prefers Qc7 after a bit. >> >>[D]5rk/3b2p/1q1p1p1p/2p1p/1pP1P1P/1P1PQP/r2N2KR/7R/ b 0 1 >> >>However, in the "flipped" position (horizontally around a rank axis) >>it does not like Qc2 (I think the flip is correct) >> >>[D]7r/R2n2kr/1p1pqp/1Pp1p1p/2P1P/1Q1P1P1P/3B2P/5RK/ w 0 1 >> >>When I ran this test with Crafty, and flipping, the moves are also a bit >>different, as are the scores for each full ply. >> >>So, I'm wondering if this is an asymmetrical evaluation problem, or search >>instability, or no big deal. >> >>Thanks > > >Here's the thing for crafty. > >It is 100% symmetrical if you just flip the board along either axis. I test >this all the time. But if you do a search, it might not be, because my move >generator generates moves in a specific order, and if you flip the board, the >move order will change (think about FirstOne() applied to a bitboard that is >rotated, you get a different first or last bit set, etc... > >a 1-ply search should be perfect unless there are two moves with the same score, >and flipping the board causes the generator to produce a different order for the >two moves in questio... > >My "rule of thumb" is _everything_ is a big deal, until properly explained... Thanks for the reply. I can understand different search trees based on different move generation order and such, but shouldn't the final score for each full ply be exactly the same either way? Perhaps you could see if Crafty does this for you, or not, in which case I'm just missing something. Thanks again.
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