UCI chess engine reading Polyglot books
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Stockfish Polyglot 2019-01-06

Stockfish Polyglot is none but the very own Stockfish with the only addition of the possibility to use Polyglot (.bin) books. In order to do that I used the library polybook.h and the C++ file polybook.cpp from Brainfish adding them to the Stockfish code with few other changes to make the polybook functions working. No functional changes to the original Stockfish algorythms were made. Stockfish Polyglot features also the 'OwnBook' checkbox, so that the user can easily switch from the Polyglot book to the local CTG book (Chessbase softwares) or ABK book (Arena GUI). I've wandered through GitHub to recover the 'OwnBook' checkbox code (it needed just two mere rows..), luckily I've managed to find it and extract the part I needed to use.

Stockfish Polyglot 2019-01-11 https://chess.massimilianogoi.com

For feedbacks or suggestions please write me at https://chess.massimilianogoi.com/contacts/


Since this program is under the GPU license you can do whatever you want with it, included uploading it on other websites, as far as its source is cited (the Stockfish crew, Thomas Zipproth for Brainfish and me (Massimiliano Goi) for this project).


This distribution is the expansion of Stockfish beta having timestamp: 1547135164 - Remove pvExact

The variable pvExact now overlaps with the pvHit concept. So you simplify the logic with small code tweaks to have pvHit trigger where pvExact previously triggered.

passed STC: LLR: 2.96 (-2.94,2.94) [-3.00,1.00] Total: 20558 W: 4497 L: 4373 D: 11688 Elo +2.10 http://tests.stockfishchess.org/tests/view/5c36e9fd0ebc596a450c7885

passed LTC: LLR: 2.95 (-2.94,2.94) [-3.00,1.00] Total: 23482 W: 3888 L: 3772 D: 15822 Elo +1.72 http://tests.stockfishchess.org/tests/view/5c37072d0ebc596a450c7a52

Bench: 3739723


Author: mstembera Date: Thu Jan 10 16:36:59 2019 +0100 Timestamp: 1547134619

Minor cleanup to recent 'Flag critical search tree in hash table' patch

No functional change

Author: Joost VandeVondele Date: Wed Jan 9 16:57:24 2019 +0100 Timestamp: 1547049444

Small improvements to the CI infrastructure

  • avoid inlining for the debug testing so that suppressions work
  • provide more output for triggered errors

No functional change.

Author: MJZ1977 Date: Wed Jan 9 15:05:33 2019 +0100 Timestamp: 1547042733

Flag critical search tree in hash table

Introducing new concept, saving principal lines into the transposition table to generate a "critical search tree" which we can reuse later for intelligent pruning/extension decisions.

For instance in this patch we just reduce reduction for these lines. But a lot of other ideas are possible.

To go further : tune some parameters, how to add or remove lines from the critical search tree, how to use these lines in search choices, etc.

STC : LLR: 2.94 (-2.94,2.94) [0.50,4.50] Total: 59761 W: 13321 L: 12863 D: 33577 Elo +2.66 http://tests.stockfishchess.org/tests/view/5c34da5d0ebc596a450c53d3

LTC : LLR: 2.96 (-2.94,2.94) [0.00,3.50] Total: 26826 W: 4439 L: 4191 D: 18196 Elo +3.21 http://tests.stockfishchess.org/tests/view/5c35ceb00ebc596a450c65b2

Special thanks to Miguel Lahoz for his help in transposition table in/out.

Bench: 3399866

Author: Miguel Lahoz Date: Sun Jan 6 16:02:31 2019 +0100 Timestamp: 1546786951

Introduce Multi-Cut

This was inspired after reading about Multi-Cut.

We now do non-singular cut node pruning. The idea is to prune when we have a "backup plan" in case our expected fail high node does not fail high on the ttMove.

For singular extensions, we do a search on all other moves but the ttMove. If this fails high on our original beta, this means that both the ttMove, as well as at least one other move was proven to fail high on a lower depth search. We then assume that one of these moves will work on a higher depth and prune.

STC: LLR: 2.96 (-2.94,2.94) [0.50,4.50] Total: 72952 W: 16104 L: 15583 D: 41265 Elo +2.48 http://tests.stockfishchess.org/tests/view/5c3119640ebc596a450c0be5

LTC: LLR: 2.95 (-2.94,2.94) [0.00,3.50] Total: 27103 W: 4564 L: 4314 D: 18225 Elo +3.20 http://tests.stockfishchess.org/tests/view/5c3184c00ebc596a450c1662

Bench: 3145487

Terms of use

Stockfish is free, and distributed under the GNU General Public License (GPL). Essentially, this means that you are free to do almost exactly what you want with the program, including distributing it among your friends, making it available for download from your web site, selling it (either by itself or as part of some bigger software package), or using it as the starting point for a software project of your own.

The only real limitation is that whenever you distribute Stockfish in some way, you must always include the full source code, or a pointer to where the source code can be found. If you make any changes to the source code, these changes must also be made available under the GPL.

For full details, read the copy of the GPL found in the file named Copying.txt.