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Make contempt dependent on the current score of the root position. The idea is that we now use a linear formula like the following to decide on the contempt to use during a search : contempt = x + y * eval where x is the base contempt set by the user in the "Contempt" UCI option, and y * eval is the dynamic part which adapts itself to the estimation of the evaluation of the root position returned by the search. In this patch, we use x = 18 centipawns by default, and the y * eval correction can go from -20 centipawns if the root eval is less than -2.0 pawns, up to +20 centipawns when the root eval is more than 2.0 pawns. To summarize, the new contempt goes from -0.02 to 0.38 pawns, depending if Stockfish is losing or winning, with an average value of 0.18 pawns by default. STC: LLR: 2.95 (-2.94,2.94) [0.00,5.00] Total: 110052 W: 24614 L: 23938 D: 61500 http://tests.stockfishchess.org/tests/view/5a72e6020ebc590f2c86ea20 LTC: LLR: 2.97 (-2.94,2.94) [0.00,5.00] Total: 16470 W: 2896 L: 2705 D: 10869 http://tests.stockfishchess.org/tests/view/5a76c5b90ebc5902971a9830 A second match at LTC was organised against the current master: ELO: 1.45 +-2.9 (95%) LOS: 84.0% Total: 19369 W: 3350 L: 3269 D: 12750 http://tests.stockfishchess.org/tests/view/5a7acf980ebc5902971a9a2e Finally, we checked that there is no apparent problem with multithreading, despite the fact that some threads might have a slightly different contempt level that the main thread. Match of this version against master, both using 5 threads, time control 30+0.3: ELO: 2.18 +-3.2 (95%) LOS: 90.8% Total: 14840 W: 2502 L: 2409 D: 9929 http://tests.stockfishchess.org/tests/view/5a7bf3e80ebc5902971a9aa2 Include suggestions from Marco Costalba, Aram Tumanian, Ronald de Man, etc. Bench: 5207156
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this test was supposed to be 40k games, but it has already surpassed that
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http://tests.stockfishchess.org/tests/view/5a7defef0ebc5902971a9c00
Indeed, I suppose that it ran 40000 games, then the first worker result was purged (idx 0 was red and is now missing), and now it runs over 40000 games, this is funny :-)
What's more, the machine mgrabiak in slot 45 is posting a result which means that SF9 is losing Elo compared to SF8, this is funny too.
I propose to let it run to see how this will develop...
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Moreover, when mgrabiak-3cores-15 is busy running in this regression test, it does not pollute the other tests. Time to have some green patches :-)