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- 18 commits
- 57 files changed
- 9 contributors
Commits on Feb 20, 2021
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Tune search parameters (with Unai Corzo)
The values used in this patch are taken from a SPSA parameter tuning session originated by Unai Corzo (@unaiic), but the final difference of his tune was multiplied x2 by hand. Most of the credits should go to him :-) STC: https://tests.stockfishchess.org/tests/view/602f03d07f517a561bc49d40 LLR: 2.94 (-2.94,2.94) {-0.25,1.25} Total: 67664 W: 6252 L: 6035 D: 55377 Ptnml(0-2): 256, 4799, 23527, 4972, 278 LTC: https://tests.stockfishchess.org/tests/view/602f41697f517a561bc49d5a LLR: 2.96 (-2.94,2.94) {0.25,1.25} Total: 26256 W: 1034 L: 906 D: 24316 Ptnml(0-2): 10, 804, 11377, 922, 15 Closes #3363 Bench: 3957653
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Introduce ProbCut for check evasions
The idea of this patch can be described as follows: if we are in check and the transposition table move is a capture that returns a value far above beta, we can assume that the opponent just blundered a piece by giving check, and we return the transposition table value. This is similar to the usual probCut logic for quiet moves, but with a different threshold. Passed STC LLR: 2.94 (-2.94,2.94) {-0.25,1.25} Total: 33440 W: 3056 L: 2891 D: 27493 Ptnml(0-2): 110, 2338, 11672, 2477, 123 https://tests.stockfishchess.org/tests/view/602cd1087f517a561bc49bda Passed LTC LLR: 2.98 (-2.94,2.94) {0.25,1.25} Total: 10072 W: 401 L: 309 D: 9362 Ptnml(0-2): 2, 288, 4365, 378, 3 https://tests.stockfishchess.org/tests/view/602ceea57f517a561bc49bf0 The committed version has an additional fix to never return unproven wins in the tablebase range or the mate range. This fix passed tests for non- regression at STC and LTC: STC: LLR: 2.93 (-2.94,2.94) {-1.25,0.25} Total: 26240 W: 2354 L: 2280 D: 21606 Ptnml(0-2): 85, 1763, 9372, 1793, 107 https://tests.stockfishchess.org/tests/view/602d86a87f517a561bc49c7a LTC: LLR: 2.95 (-2.94,2.94) {-0.75,0.25} Total: 35304 W: 1299 L: 1256 D: 32749 Ptnml(0-2): 14, 1095, 15395, 1130, 18 https://tests.stockfishchess.org/tests/view/602d98d17f517a561bc49c83 Closes #3362 Bench: 3830215
Commits on Feb 26, 2021
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We introduce a metric for each internal node in search, called DistanceFromPV. This distance indicated how far the current node is from the principal variation. We then use this distance to search the nodes which are close to the PV a little deeper (up to 4 plies deeper than the PV): this improves the quality of the search at these nodes and bring better updates for the PV during search. STC: LLR: 2.96 (-2.94,2.94) {-0.25,1.25} Total: 54936 W: 5047 L: 4850 D: 45039 Ptnml(0-2): 183, 3907, 19075, 4136, 167 https://tests.stockfishchess.org/tests/view/6037b88e7f517a561bc4a392 LTC: LLR: 2.95 (-2.94,2.94) {0.25,1.25} Total: 49608 W: 1880 L: 1703 D: 46025 Ptnml(0-2): 22, 1514, 21555, 1691, 22 https://tests.stockfishchess.org/tests/view/6038271b7f517a561bc4a3cb Closes #3369 Bench: 5037279
Commits on Mar 7, 2021
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Clean functions returning by const values
The codebase contains multiple functions returning by const-value. This patch is a small cleanup making those function returns by value instead, removing the const specifier. closes #3328 No functional change
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Deal with commented lines in UCI input
commands starting with '#' as the first character will be ignored closes #3378 No functional change
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Use Bitboard over Square in movegen
It uses pos.checkers() on target when movegen is the type of EVASION. It simplify the code. And it's also expected a slightly speed up, because Bitboard is more direct when doing bitwise. Passed STC: LLR: 2.93 (-2.94,2.94) {-1.25,0.25} Total: 28176 W: 2506 L: 2437 D: 23233 Ptnml(0-2): 80, 1904, 10063, 1949, 92 https://tests.stockfishchess.org/tests/view/60421d18ddcba5f0627bb6a9 Passed LTC: LLR: 2.93 (-2.94,2.94) {-0.75,0.25} Total: 9704 W: 402 L: 341 D: 8961 Ptnml(0-2): 3, 279, 4230, 334, 6 https://tests.stockfishchess.org/tests/view/60422823ddcba5f0627bb6ae closes #3383 No functional change
Commits on Mar 10, 2021
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Change advanced pawn push threshold
A pawn push is now considered to be "advanced" if the relative destination rank is > 6 (previously it was > 5). This affects the search heuristic. Also remove an assert concerning en passant moves in qsearch(). STC: LLR: 2.97 (-2.94,2.94) {-0.25,1.25} Total: 46744 W: 4224 L: 4040 D: 38480 Ptnml(0-2): 165, 3206, 16451, 3380, 170 https://tests.stockfishchess.org/tests/view/604746082433018de7a3872e LTC: LLR: 2.94 (-2.94,2.94) {0.25,1.25} Total: 107840 W: 4198 L: 3892 D: 99750 Ptnml(0-2): 58, 3472, 46557, 3772, 61 https://tests.stockfishchess.org/tests/view/60475eae2433018de7a38737 Closes #3389 Bench: 4796780
Commits on Mar 16, 2021
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Introduce least_significant_square_bb()
Introducing least_significant_square_bb(). It is a function that returns a value equal to square_bb(lsb(bb)), but it uses fewer instruction. It should speed up more on older processors like armv7-a Clang. Passed STC: LLR: 2.93 (-2.94,2.94) {-0.25,1.25} Total: 213200 W: 19171 L: 18753 D: 175276 Ptnml(0-2): 680, 14513, 75831, 14861, 715 https://tests.stockfishchess.org/tests/view/604bc7632433018de7a38982 Closes #3391 No functional change -
Simplify move generation (1/2)
STC: LLR: 2.95 (-2.94,2.94) {-1.25,0.25} Total: 29792 W: 2611 L: 2545 D: 24636 Ptnml(0-2): 94, 1982, 10659, 2086, 75 https://tests.stockfishchess.org/tests/view/604fe5b62433018de7a38ba8 LTC: LLR: 2.92 (-2.94,2.94) {-0.75,0.25} Total: 22040 W: 826 L: 777 D: 20437 Ptnml(0-2): 8, 646, 9664, 693, 9 https://tests.stockfishchess.org/tests/view/604fec892433018de7a38bac Closes #3399 No functional change -
Simplify move generation (2/2)
STC: LLR: 2.97 (-2.94,2.94) {-1.25,0.25} Total: 39352 W: 3551 L: 3493 D: 32308 Ptnml(0-2): 143, 2695, 13928, 2781, 129 https://tests.stockfishchess.org/tests/view/6050007a2433018de7a38bbb LTC: LLR: 2.96 (-2.94,2.94) {-0.75,0.25} Total: 44944 W: 1629 L: 1596 D: 41719 Ptnml(0-2): 22, 1319, 19762, 1342, 27 https://tests.stockfishchess.org/tests/view/60500e892433018de7a38bc4 Closes #3399 No functional change
Commits on Mar 17, 2021
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Continuation of work by @topologist: we now do futility pruning and movecount pruning in qsearch() for pawn pushes up to the 7th rank. So the condition to avoid the pruning is if the move is a promotion or not. This allows to get rid of the advanced_pawn_push() function in position.h alltogether. Passed STC https://tests.stockfishchess.org/tests/view/6048c5842433018de7a387e6 LLR: 2.93 (-2.94,2.94) {-1.25,0.25} Total: 34424 W: 3081 L: 3015 D: 28328 Ptnml(0-2): 110, 2442, 12052, 2488, 120 Passed LTC https://tests.stockfishchess.org/tests/view/6048f7d22433018de7a387f0 LLR: 2.94 (-2.94,2.94) {-0.75,0.25} Total: 142024 W: 5170 L: 5202 D: 131652 Ptnml(0-2): 50, 4678, 61613, 4596, 75 Closes #3390 Bench: 4339126
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Change definition of between_bb()
We remark that in current master, most of our use cases for between_bb() can be optimized if the second parameter of the function is added to the segment. So we change the definition of between_bb(s1, s2) such that it excludes s1 but includes s2. We also use a precomputed array for between_bb() for another small speed gain (see https://tests.stockfishchess.org/tests/view/604d09f72433018de7a389fb). Passed STC: LLR: 2.96 (-2.94,2.94) {-0.25,1.25} Total: 18736 W: 1746 L: 1607 D: 15383 Ptnml(0-2): 61, 1226, 6644, 1387, 50 https://tests.stockfishchess.org/tests/view/60428c84ddcba5f0627bb6e4 Yellow LTC: LTC: LLR: -3.00 (-2.94,2.94) {0.25,1.25} Total: 39144 W: 1431 L: 1413 D: 36300 Ptnml(0-2): 13, 1176, 17184, 1178, 21 https://tests.stockfishchess.org/tests/view/605128702433018de7a38ca1 Closes #3397 --------- Verified for correctness by running perft on the following position: ./stockfish position fen 4rrk1/1p1nq3/p7/2p1P1pp/3P2bp/3Q1Bn1/PPPB4/1K2R1NR w - - 40 21 go perft 6 Nodes searched: 6136386434 -------- No functional change
Commits on Mar 19, 2021
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Add a specific FRC correction from classical to NNUE
our net currently is not trained on FRC games, and so doesn't know about the important pattern of a bishop that is cornered in FRC. This patch introduces a term we have in the classical evaluation for this case, and adds it to the NNUE eval. Since fishtest doesn't support FRC right now, the patch was tested locally at STC conditions, starting from the book of FRC starting positions. Score of master vs patch: 993 - 2226 - 6781 [0.438] 10000 Which corresponds to approximately 40 Elo The patch passes non-regression testing for traditional chess (where it adds one branch). passed STC: https://tests.stockfishchess.org/tests/view/604fa2532433018de7a38b67 LLR: 2.95 (-2.94,2.94) {-1.25,0.25} Total: 30560 W: 2701 L: 2636 D: 25223 Ptnml(0-2): 88, 2056, 10921, 2133, 82 passed STC also in an earlier version: https://tests.stockfishchess.org/tests/view/604f61282433018de7a38b4d closes #3398 No functional change
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Use reference instead of pointer for pop_lsb() signature
This patch changes the pop_lsb() signature from Square pop_lsb(Bitboard*) to Square pop_lsb(Bitboard&). This is more idomatic for C++ style signatures. Passed a non-regression STC test: LLR: 2.93 (-2.94,2.94) {-1.25,0.25} Total: 21280 W: 1928 L: 1847 D: 17505 Ptnml(0-2): 71, 1427, 7558, 1518, 66 https://tests.stockfishchess.org/tests/view/6053a1e22433018de7a38e2f We have verified that the generated binary is identical on gcc-10. Closes #3404 No functional change.
Commits on Mar 24, 2021
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With help of @BM123499, @mstembera, @gvreuls, @noobpwnftw and @Fanael Thanks! Closes #3405 No functional change
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