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FitzOReilly / fatalii

Chess engine
MIT License
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version 0.6.0 Alpha quickly finds tactics #199

Open tissatussa opened 8 months ago

tissatussa commented 8 months ago

just by chance i happened to test your new version v0.6.0 and the PR-192 alpha version , giving both this position :

r1q2k1r/p3R1pp/2n5/1p3pB1/2pp4/2P5/3Q1PPP/4R1K1 w - - 0 21

Fatalii-alpha-diff

here Bh6 is clearly best move. newest v0.6.0 finds it at depth 14 after 20 seconds, Alpha even at depth 11 after 4 seconds !?

i test in CuteChess with infinite time. a few strong engines do NOT find the "solution" to this position, or only after a long time.

i don't know if this can help you in any way. it just happened here and i want to share it. is LMR involved ? i have no clue ..

[ i'm on Xubuntu 22.04 ]

FitzOReilly commented 7 months ago

Interesting position. Thanks for letting me know!

I tested it with a few older versions: Both 0.4.0 and 0.5.0 find it at depth 9. It's probably due to pruning. Version 0.6.0 adds late move reductions and futility + reverse futility pruning at higher depths.

tissatussa commented 7 months ago

here are 3 other puzzle positions which i used to test engines - they all have a "solution" which is clearly best. see the results for Fatalii v0.6.0 and its Alpha below. i attached my ZIPped screenshots, which give evaluation details when depth is climbing : 3-puzzles.zip

r1bqk2r/pp1n2bp/2p3p1/4pp2/2P5/2N1PNP1/PPQ2PP1/2KR1B1R w kq - 0 1

0_White-to-move-g4-best-move

solution : g4 (=clearly best move) 0.6.0 finds it after 9 minutes at depth 17 Alpha finds it after 3 seconds at depth 9 (and 10,11) BUT then it finds OTHER moves to be best..

7Q/p2r4/kp6/4Bp2/P3b3/KP1q4/8/2R5 w - - 0 1

0_position-White-to-move

solution: Rd1 (=clearly best move) 0.6.0 finds it after 2 seconds at depth 13 Alpha finds it after 27 seconds at depth 15

4k3/2p1np2/p4qrp/3Bp3/4P1b1/2P1Q3/Pr1N1PP1/1R2R1K1 b - - 0 1

0_position-Black-to-play

solution: Nxd5 (=clearly best move) 0.6.0 finds it after 94 seconds at depth 17 btw. BUT after 7 minutes at depth 18 it sees this move is CLEARLY better for Black. Alpha finds it within 3 minutes at depth 14 btw. BUT after 13 minutes at depth 17 it sees this move is CLEARLY better for Black.