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Chess engine: Stockfish 20011003

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Stockfish - UCI chess engine, compiled by Joost VandeVondele

 Update Elo estimates for terms in search

 This updates estimates from 1.5 year ago, and adds missing terms. All estimates from tests run on fishtest at 10+0.1 (STC), 20000 games, error bars +- 3 Elo, see the original message in the pull request for the full list of tests.
Noteworthy changes are step 7 (futility pruning) going from ~30 to ~50 Elo and step 13 (pruning at shallow depth) going from ~170 to ~200 Elo.

@Rocky640 made the suggestion to look at time control dependence of these terms. I picked two large terms (early futility pruning and singular extension), so with small relative error. It turns out it is actually quite interesting (see figure 1).
Contrary to my expectation, the Elo gain for early futility pruning is pretty time control sensitive, while singular extension gain is not.

Going back to the old measurement of futility pruning (30 Elo vs today 50 Elo), the code is actually identical but the margins have changed. It seems like a nice example of how connected terms in search really are, i.e. the value of early futility pruning increased significantly due to changes elsewhere in search.

 No functional change.


Rating JCER=3344

 Stockfish 20011003 - download


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