Stockfish Development Versions are build automatically if there are changes on the master branch in the git repository (https://github.com/official-stockfish/Stockfish). Use it at your own risk.
They are compiled with gcc 11.2/mingw 10 on Ubuntu 22.04.

Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Vizvezdenec
Date: Mon Apr 13 09:16:54 2020 +0200
Timestamp: 1586762214

Scale up space weight with number of blocked pawns

This idea is loosely based on stockfish losses in closed positions in different tournaments. Space weight symmetrically increases for both sides the more blocked position is.

passed STC
https://tests.stockfishchess.org/tests/view/5e919eefaf0a0143109dc8ce
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 16994 W: 3389 L: 3172 D: 10433 Elo +4.44
Ptnml(0-2): 277, 1931, 3918, 2040, 331

passed LTC
https://tests.stockfishchess.org/tests/view/5e91d04faf0a0143109dc8ea
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 133386 W: 17316 L: 16763 D: 99307 Elo +1.44
Ptnml(0-2): 945, 12407, 39524, 12784, 1033

closes https://github.com/official-stockfish/Stockfish/pull/2626

Bench: 4966867
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Lolligerhans
Date: Mon Apr 13 08:50:25 2020 +0200
Timestamp: 1586760625

Remove candidate passers w/o feasible lever

+-------+
| o . . | o their pawns
| x . . | x our pawns
| . x . | <- Can sacrifice to create passer?
+-------+
yes

1 2 3 4 5
+-------+ +-------+ +-------+ +-------+ +-------+
| o . . | | o r . | | o r . | | o . b | | o . b | lowercase: theirs
| x b . | | x . . | | x . R | | x . R | | x . . | uppercase: ours
| . x . | | . x . | | . x . | | . x . | | . x B |
+-------+ +-------+ +-------+ +-------+ +-------+
no no yes no yes

The value of our top pawn depends on our ability to advance our bottom
pawn, levering their blocker. Previously, this pawn configuration was
always scored as passer (although a blocked one).

Add requirements for the square s above our (possibly) sacrificed pawn:
- s must not be occupied by them (1).
- If they attack s (2), we must attack s (3).
- If they attack s with a minor (4), we must attack s with a minor (5).
The attack from their blocker is ignored because it is inherent in the
structure; we are ok with sacrificing our bottom pawn.

LTC
LLR: 2.95 (-2.94,2.94) {0.25,1.75}
Total: 37030 W: 4962 L: 4682 D: 27386 Elo +2.63
Ptnml(0-2): 266, 3445, 10863, 3625, 316
https://tests.stockfishchess.org/tests/view/5e92a2b4be6ede5b954bf239

STC
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 40874 W: 8066 L: 7813 D: 24995 Elo +2.15
Ptnml(0-2): 706, 4753, 9324, 4890, 764
https://tests.stockfishchess.org/tests/view/5e922199af0a0143109dc90e

closes https://github.com/official-stockfish/Stockfish/pull/2624

Bench: 4828294
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Joost VandeVondele
Date: Sun Apr 12 20:38:47 2020 +0200
Timestamp: 1586716727

Extend irreversible moves

if these are ttMoves and played in positions with a high value of the rule50 counter. The unusual extension of 2 is safe in this context as awarding it will reset the rule50 counter, making sure it is awarded very rarely in a search path.

This patch partially addresses https://github.com/official-stockfish/Stockfish/issues/2620 as it should make it less likely to play a move that resets the counter, but that is worse than alternative moves after a slightly deeper search.

passed STC:
LLR: 2.96 (-2.94,2.94) {-0.50,1.50}
Total: 71658 W: 13840 L: 13560 D: 44258 Elo +1.36
Ptnml(0-2): 1058, 7921, 17643, 8097, 1110
https://tests.stockfishchess.org/tests/view/5e90d0f6754c3424c4cf9f41

passed LTC:
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 85082 W: 11069 L: 10680 D: 63333 Elo +1.59
Ptnml(0-2): 459, 6982, 27259, 7393, 448
https://tests.stockfishchess.org/tests/view/5e917470af0a0143109dc341

closes https://github.com/official-stockfish/Stockfish/pull/2623

Bench: 4432822
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: protonspring
Date: Sun Apr 12 20:34:50 2020 +0200
Timestamp: 1586716490

Always remember the ttMove

In master, if the received ttMove meets the prescribed conditions in the various MovePicker constructors, it is returned as the first move, otherwise we set it to MOVE_NONE. If set to MOVE_NONE, we no longer track what the ttMove was, and it will might be returned later in a list of generated moves. This may be a waste. With this patch, if the ttMove fails to meet the prescribed conditions, we simply skip the TT stages, but still store the move and make sure it's never returned.

STC
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 66424 W: 12903 L: 12806 D: 40715 Elo +0.51
Ptnml(0-2): 1195, 7730, 15230, 7897, 1160

LTC
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 45682 W: 5989 L: 5926 D: 33767 Elo +0.48
Ptnml(0-2): 329, 4361, 13443, 4334, 374

closes https://github.com/official-stockfish/Stockfish/pull/2616

Bench 4928928
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Joost VandeVondele
Date: Sun Apr 12 20:30:08 2020 +0200
Timestamp: 1586716208

Small cleanups

closes https://github.com/official-stockfish/Stockfish/pull/2606

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Vizvezdenec
Date: Tue Apr 7 17:47:01 2020 +0200
Timestamp: 1586274421

Introduce capture history pruning

This patch introduces a heuristic that is similar to countermove based pruning but for captures - capture history pruning. The idea is that we can (almost) safely prune really late captures with negative history if they don't give check so will most likely not produce some king-attacking tactic.

passed STC
https://tests.stockfishchess.org/tests/view/5e8c60d40ffd2be7f15e5470
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 23748 W: 4758 L: 4529 D: 14461 Elo +3.35
Ptnml(0-2): 421, 2712, 5400, 2899, 442

passed LTC
https://tests.stockfishchess.org/tests/view/5e8c72bf0ffd2be7f15e547f
LLR: 2.96 (-2.94,2.94) {0.25,1.75}
Total: 17330 W: 2415 L: 2190 D: 12725 Elo +4.51
Ptnml(0-2): 126, 1561, 5107, 1704, 167

closes https://github.com/official-stockfish/Stockfish/pull/2618

bench 4417023
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Vizvezdenec
Date: Sun Apr 5 08:44:25 2020 +0200
Timestamp: 1586069065

Further increase reductions with increasing number of threads

This patch doubles the reduction increase with thread count.

passed STC
https://tests.stockfishchess.org/tests/view/5e874f5a4411759d9d098696
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 9162 W: 1558 L: 1385 D: 6219 Elo +6.56
Ptnml(0-2): 90, 958, 2343, 1069, 121

passed LTC
https://tests.stockfishchess.org/tests/view/5e8762804411759d9d09869f
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 79364 W: 9541 L: 9159 D: 60664 Elo +1.67
Ptnml(0-2): 462, 6880, 24661, 7172, 507

closes https://github.com/official-stockfish/Stockfish/pull/2615

bench 4831963
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: 31m059
Date: Sun Apr 5 08:39:00 2020 +0200
Timestamp: 1586068740

Retire candidate passed pawns

Before this commit, some pawns were considered "candidate" passed pawns and given half bonus. After this commit, all of these pawns are scored as passed pawns, and they do not receive less bonus.

STC:
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 21806 W: 4320 L: 4158 D: 13328 Elo +2.58
Ptnml(0-2): 367, 2526, 5001, 2596, 413
https://tests.stockfishchess.org/tests/view/5e86b4724411759d9d098639

LTC:
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 12590 W: 1734 L: 1617 D: 9239 Elo +3.23
Ptnml(0-2): 96, 1187, 3645, 1238, 129
https://tests.stockfishchess.org/tests/view/5e86d2874411759d9d098640

This PR and commit are dedicated to our colleague Stefan Geschwentner (@locutus2), one of the most respected and accomplished members of the Stockfish developer community. Stockfish is a volunteer project and has always thrived because of Stefan's talent, insight, generosity, and dedication. Welcome back, Stefan!

closes https://github.com/official-stockfish/Stockfish/pull/2613

Bench: 4831963
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: protonspring
Date: Sun Apr 5 08:35:31 2020 +0200
Timestamp: 1586068531

remove KNPK endgame code

In more than 100k local KNPK games, there is no discernible difference between master and master with this endgame removed: master:42971, patch:42973, draws: 3969. Removal does not seem to regress in normal games.

STC
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 46390 W: 8998 L: 8884 D: 28508 Elo +0.85
Ptnml(0-2): 707, 5274, 11163, 5300, 751
https://tests.stockfishchess.org/tests/view/5e83b18ee42a5c3b3ca2ef02

LTC
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 44768 W: 5863 L: 5814 D: 33091 Elo +0.38
Ptnml(0-2): 251, 3918, 14028, 3905, 282
https://tests.stockfishchess.org/tests/view/5e84a82a4411759d9d0984f4

In tests with a book of endgames that can convert into KNPK, no significant difference can be seen either

```
TC 1.0+0.01
Score of patch vs master: 6131 - 6188 - 27681 [0.499] 40000
Elo difference: -0.5 +/- 1.9, LOS: 30.4 %, DrawRatio: 69.2 %

TC 2.0+0.02
Score of patch vs master: 5740 - 5741 - 28519 [0.500] 40000
Elo difference: -0.0 +/- 1.8, LOS: 49.6 %, DrawRatio: 71.3 %
``

closes https://github.com/official-stockfish/Stockfish/pull/2611

Bench 4512059
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Vizvezdenec
Date: Thu Apr 2 15:11:16 2020 +0200
Timestamp: 1585833076

Increase reduction for captures.

The idea behind this patch is that if static eval is really bad so capturing of current piece on spot will still produce a position with an eval much lower than alpha then our best chance is to create some kind of king attack. So captures without check are mostly worse than captures with check and can be reduced more.

passed STC
https://tests.stockfishchess.org/tests/view/5e8514b44411759d9d098543
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 46196 W: 9039 L: 8781 D: 28376 Elo +1.94
Ptnml(0-2): 750, 5412, 10628, 5446, 862

passed LTC
https://tests.stockfishchess.org/tests/view/5e8530134411759d9d09854c
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 23462 W: 3228 L: 2988 D: 17246 Elo +3.55
Ptnml(0-2): 186, 2125, 6849, 2405, 166

close https://github.com/official-stockfish/Stockfish/pull/2612

bench 4742598
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: 31m059
Date: Thu Apr 2 14:56:30 2020 +0200
Timestamp: 1585832190

Simplify a candidate passer condition.

STC:
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 31528 W: 6208 L: 6061 D: 19259 Elo +1.62
Ptnml(0-2): 541, 3673, 7205, 3788, 557
https://tests.stockfishchess.org/tests/view/5e825db0e42a5c3b3ca2ee21

LTC:
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 38546 W: 5083 L: 5009 D: 28454 Elo +0.67
Ptnml(0-2): 299, 3628, 11362, 3668, 316
https://tests.stockfishchess.org/tests/view/5e826ec7e42a5c3b3ca2ee2a

closes https://github.com/official-stockfish/Stockfish/pull/2607

Bench: 5139561
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: mstembera
Date: Thu Apr 2 14:54:47 2020 +0200
Timestamp: 1585832087

No voting for TB loss / mate.

Just as we pick the shortest mate also make sure we stave off mate as long as possible.

https://github.com/official-stockfish/Stockfish/pull/2603

bench: 5138771
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: protonspring
Date: Thu Apr 2 14:40:03 2020 +0200
Timestamp: 1585831203

Limit array access in Position

This is a non-functional code style change that routes all position array accesses to single methods, and adds an assert to check correctness.

Passed STC
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 37312 W: 7378 L: 7246 D: 22688 Elo +1.23
Ptnml(0-2): 606, 4280, 8762, 4392, 616
https://tests.stockfishchess.org/tests/view/5e7c0c69e42a5c3b3ca2eb3d

closes https://github.com/official-stockfish/Stockfish/pull/2595

No functional change.
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Joost VandeVondele
Date: Mon Mar 30 22:46:07 2020 +0200
Timestamp: 1585601167

Small cleanups

https://github.com/official-stockfish/Stockfish/pull/2584

No functional change.
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Praveen tummala
Date: Mon Mar 30 22:41:22 2020 +0200
Timestamp: 1585600882

Movecount pruning reduction logic

This patch refines search reduction logic in case the position is not a former PV node and is pruned based on move count.

passed STC
https://tests.stockfishchess.org/tests/view/5e8092bde42a5c3b3ca2ed35
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 78848 W: 15480 L: 15170 D: 48198 Elo +1.37
Ptnml(0-2): 1406, 9310, 17773, 9438, 1497

passed LTC
https://tests.stockfishchess.org/tests/view/5e80bb13e42a5c3b3ca2ed4b
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 86596 W: 11451 L: 11033 D: 64112 Elo +1.68
Ptnml(0-2): 624, 7993, 25687, 8329, 665

closes https://github.com/official-stockfish/Stockfish/pull/2605

Bench: 5138771
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Vizvezdenec
Date: Sun Mar 29 19:48:01 2020 +0200
Timestamp: 1585504081

Count only the most advanced passed pawn for each file.

This patch adjusts definition of passed pawns - if there is a pawn of our color in the same file in front of a current pawn it's no longer counts as passed.

passed STC
https://tests.stockfishchess.org/tests/view/5e802037e42a5c3b3ca2ed07
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 215296 W: 41843 L: 41341 D: 132112 Elo +0.81
Ptnml(0-2): 3688, 25313, 49304, 25495, 3848

passed LTC
https://tests.stockfishchess.org/tests/view/5e806441e42a5c3b3ca2ed2b
LLR: 2.95 (-2.94,2.94) {0.25,1.75}
Total: 74050 W: 9761 L: 9379 D: 54910 Elo +1.79
Ptnml(0-2): 510, 6838, 22025, 7064, 588

closes https://github.com/official-stockfish/Stockfish/pull/2602

bench: 4902237
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: xoto10
Date: Sun Mar 29 19:44:07 2020 +0200
Timestamp: 1585503847

Remove previousScore adjustment of delta.

STC:
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 14580 W: 2904 L: 2731 D: 8945 Elo +4.12
Ptnml(0-2): 243, 1665, 3339, 1762, 281
https://tests.stockfishchess.org/tests/view/5e7d080ae42a5c3b3ca2ebc6

LTC:
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 60338 W: 7870 L: 7831 D: 44637 Elo +0.22
Ptnml(0-2): 451, 5596, 18018, 5671, 433
https://tests.stockfishchess.org/tests/view/5e7d11b3e42a5c3b3ca2ebd3

closes https://github.com/official-stockfish/Stockfish/pull/2598

Bench 5247262
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Lyudmil Antonov
Date: Thu Mar 26 17:49:28 2020 +0100
Timestamp: 1585241368

Tuned history reduction

Value after a long Bayesian tuning, using a home-made classification approach.

STC
https://tests.stockfishchess.org/tests/view/5e7c7b16e42a5c3b3ca2eb66
LLR: 2.96 (-2.94,2.94) {-0.50,1.50}
Total: 45472 W: 8992 L: 8732 D: 27748 Elo +1.99
Ptnml(0-2): 795, 5276, 10352, 5500, 813

LTC
https://tests.stockfishchess.org/tests/view/5e7c8be7e42a5c3b3ca2eb75
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 22744 W: 3085 L: 2849 D: 16810 Elo +3.61
Ptnml(0-2): 156, 2090, 6658, 2298, 170

closes https://github.com/official-stockfish/Stockfish/pull/2597

Bench 5030855
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: xoto10
Date: Thu Mar 26 17:46:51 2020 +0100
Timestamp: 1585241211

Remove passed_count from almostUnwinnable.

This simplification allows the almostUnwinnable flag to match endgames where the pawns are all on the same flank but are not symmetrical.

STC:
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 23356 W: 4543 L: 4395 D: 14418 Elo +2.20
Ptnml(0-2): 346, 2651, 5582, 2707, 392
https://tests.stockfishchess.org/tests/view/5e7b8f57e42a5c3b3ca2eb09

LTC:
LLR: 2.96 (-2.94,2.94) {-1.50,0.50}
Total: 31778 W: 4097 L: 4023 D: 23658 Elo +0.81
Ptnml(0-2): 199, 2853, 9729, 2891, 217
https://tests.stockfishchess.org/tests/view/5e7ba5ade42a5c3b3ca2eb16

closes https://github.com/official-stockfish/Stockfish/pull/2596

Bench 4777139
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: protonspring
Date: Wed Mar 25 21:42:33 2020 +0100
Timestamp: 1585168953

Remove KNPKB endgame.

This is a functional simplification that removes the KNPKB endgame.

Testing on only KNPKB positions suggests that this removal actually gains Elo:

Score of patch vs master: 3380 - 3035 - 33585 [0.504] 40000
Elo difference: 3.0 +/- 1.4, LOS: 100.0 %, DrawRatio: 84.0 %

Score of patch vs master: 290 - 36 - 39674 [0.503] 40000
Elo difference: 2.2 +/- 0.3, LOS: 100.0 %, DrawRatio: 99.2 %

removal also doesn't cause a regression with the standard book:

STC
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 71376 W: 13794 L: 13719 D: 43863 Elo +0.37
Ptnml(0-2): 1066, 8092, 17290, 8181, 1059
https://tests.stockfishchess.org/tests/view/5e76c3d5e42a5c3b3ca2e8be

LTC
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 28394 W: 3731 L: 3662 D: 21001 Elo +0.84
Ptnml(0-2): 167, 2339, 9116, 2408, 167
https://tests.stockfishchess.org/tests/view/5e76e5eae42a5c3b3ca2e8d3

closes https://github.com/official-stockfish/Stockfish/pull/2594

Bench 5480811
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Vizvezdenec
Date: Fri Mar 20 21:07:37 2020 +0100
Timestamp: 1584734857

Adjust singular extension search depth

This patch applies a different singular extension search logic in case the position is ttPv && !PvNode.
It changes the depth of this search, higher for this types of nodes, and lower for other nodes.

passed STC
http://tests.stockfishchess.org/tests/view/5e72bbaae42a5c3b3ca2e75e
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 12692 W: 2608 L: 2389 D: 7695 Elo +6.00
Ptnml(0-2): 238, 1414, 2839, 1601, 254

passed LTC
http://tests.stockfishchess.org/tests/view/5e731c07e42a5c3b3ca2e770
LLR: 2.96 (-2.94,2.94) {0.25,1.75}
Total: 145716 W: 19218 L: 18626 D: 107872 Elo +1.41
Ptnml(0-2): 1100, 13605, 42899, 14111, 1143

closes https://github.com/official-stockfish/Stockfish/pull/2590

Bench: 5398277
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Vizvezdenec
Date: Tue Mar 17 19:34:47 2020 +0100
Timestamp: 1584470087

Adjust singular LMR for positions seen in PV

This patch continues work on altering search for ttPv nodes, using recent idea to alter it more in not PvNodes. Previous tweak based on this idea adjusted singularBeta - this one adjusts value of singularLMR, so they are both related to singular extension search.

passed STC
http://tests.stockfishchess.org/tests/view/5e700737e42a5c3b3ca2e659
LLR: 2.95 (-2.94,2.94) {-0.50,1.50}
Total: 140608 W: 27053 L: 26659 D: 86896 Elo +0.97
Ptnml(0-2): 2425, 16337, 32439, 16625, 2478

passed LTC
http://tests.stockfishchess.org/tests/view/5e7068eae42a5c3b3ca2e687
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 79318 W: 10463 L: 10064 D: 58791 Elo +1.75
Ptnml(0-2): 567, 7416, 23359, 7685, 632

closes https://github.com/official-stockfish/Stockfish/pull/2588

Bench: 4952322
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Stéphane Nicolet
Date: Tue Mar 17 19:20:37 2020 +0100
Timestamp: 1584469237

Anchored bishops

Reduce the "bad bishop" penalty when the bishop is protected by
one of our pawns, as it may indicate that the bishop has found
a safe spot outside the pawn chain.

STC:
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 176942 W: 34142 L: 33696 D: 109104 Elo +0.88
Ptnml(0-2): 3129, 20422, 40919, 20876, 3125
http://tests.stockfishchess.org/tests/view/5e6f61aae42a5c3b3ca2e62d

LTC:
LLR: 2.95 (-2.94,2.94) {0.25,1.75}
Total: 42252 W: 5615 L: 5322 D: 31315 Elo +2.41
Ptnml(0-2): 308, 3881, 12500, 4084, 353
http://tests.stockfishchess.org/tests/view/5e701382e42a5c3b3ca2e661

closes https://github.com/official-stockfish/Stockfish/pull/2587

Bench: 4963440
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Joost VandeVondele
Date: Sat Mar 14 17:04:50 2020 +0100
Timestamp: 1584201890

Small cleanups

closes https://github.com/official-stockfish/Stockfish/pull/2567

No functional change.
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: pb00067
Date: Sat Mar 14 16:30:17 2020 +0100
Timestamp: 1584199817

Simplify futility pruning parent node

only continuation histories seem needed for this purpose.

STC:
http://tests.stockfishchess.org/tests/view/5e6b88dfe42a5c3b3ca2e4ab
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 113356 W: 21725 L: 21696 D: 69935 Elo +0.09
Ptnml(0-2): 1999, 13255, 26163, 13240, 2021

LTC:
http://tests.stockfishchess.org/tests/view/5e6babbfe42a5c3b3ca2e4c2
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 22164 W: 2917 L: 2821 D: 16426 Elo +1.50
Ptnml(0-2): 173, 2040, 6548, 2160, 161

closes https://github.com/official-stockfish/Stockfish/pull/2583

bench: 4839496
see source

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