Marcel Duchamp endgame "splits" engines / hash phe
Posted: Mon Feb 19, 2018 10:04 pm
The final long section of an article on Marcel Duchamp which I wrote for the Gödel's Lost Letter weblog https://rjlipton.wordpress.com/2018/02/ ... f-duchamp/ covers his only known composed endgame problem---different from the "corresponding squares" position which is the only other Duchamp endgame discussion I've found by searching here:
[d]1r6/1PR5/5p2/1P5p/5K2/8/6k1/8 w - - 0 1
This gives widely different results for Houdini, Komodo, and Stockfish versions run on 1 core thread with various power-of-2 hash table sizes. Houdini versions tend to all settle down to a stable eval under +0.40 around depth 26 in under a minute. Komodo versions settle around +3.00 but sometimes go haywire up near +7.00. Stockfish versions gyrate most of all, and often the result changes wildly if you keep the same hash size but change to one of the three mirror FENs:
8/1K6/8/2k5/P5p1/2P5/5rp1/6R1 b - - 0 1
8/6K1/8/5k2/1p5P/5P2/1pr5/1R6 b - - 0 1
6r1/5RP1/2p5/p5P1/2K5/8/1k6/8 w - - 0 1
My post tabulates analysis just for depths 37--40. I could post clips of UCI analysis output here but my real purpose is just to ask for input on the issue of hash table effects. I'm aware of things like the Hyatt-Cozzie results
http://www.craftychess.com/hyatt/collisions.html showing they don't usually degrade play, and this is distinct from the issue of positions that are still tough for engines such as in Dann Corbitt's post on Saturday. The "art" is to find positions where the presence of long forcing lines and opportunities to delay the horizon enhance the propagation of spurious evals in hash.
[d]1r6/1PR5/5p2/1P5p/5K2/8/6k1/8 w - - 0 1
This gives widely different results for Houdini, Komodo, and Stockfish versions run on 1 core thread with various power-of-2 hash table sizes. Houdini versions tend to all settle down to a stable eval under +0.40 around depth 26 in under a minute. Komodo versions settle around +3.00 but sometimes go haywire up near +7.00. Stockfish versions gyrate most of all, and often the result changes wildly if you keep the same hash size but change to one of the three mirror FENs:
8/1K6/8/2k5/P5p1/2P5/5rp1/6R1 b - - 0 1
8/6K1/8/5k2/1p5P/5P2/1pr5/1R6 b - - 0 1
6r1/5RP1/2p5/p5P1/2K5/8/1k6/8 w - - 0 1
My post tabulates analysis just for depths 37--40. I could post clips of UCI analysis output here but my real purpose is just to ask for input on the issue of hash table effects. I'm aware of things like the Hyatt-Cozzie results
http://www.craftychess.com/hyatt/collisions.html showing they don't usually degrade play, and this is distinct from the issue of positions that are still tough for engines such as in Dann Corbitt's post on Saturday. The "art" is to find positions where the presence of long forcing lines and opportunities to delay the horizon enhance the propagation of spurious evals in hash.