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: Joost VandeVondele
Date: Mon Feb 10 09:12:07 2020 +0100
Timestamp: 1581322327

Fix wrong assert.

can trigger an abort when compiling with debug=yes, and using 7men TB.
The assert should check that less than 8 pieces are in the key for each
side, matching the assumption that underlies the FEN string construction.
Also take explicitly care of a 'v' character in material strings.

Fixes an issue reported in the forum:
https://groups.google.com/d/msg/fishcooking/yoVC7etIpz0/7mS7ntZMBAAJ

closes https://github.com/official-stockfish/Stockfish/pull/2547

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: Wed Feb 5 15:32:29 2020 +0100
Timestamp: 1580913149

Small cleanups.

closes https://github.com/official-stockfish/Stockfish/pull/2532

Bench: 4869669
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: Wed Feb 5 13:42:24 2020 +0100
Timestamp: 1580906544

Reintroduce king infiltration

This patch reintroduces the recently simplified king infiltration bonus
in initiative calculation, doubling its effect, and compensating more.

passed STC
http://tests.stockfishchess.org/tests/view/5e3476f630ae32da08941d5c
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 75323 W: 14434 L: 14140 D: 46749 Elo +1.36
Ptnml(0-2): 1231, 8729, 17528, 8826, 1331

passed LTC
http://tests.stockfishchess.org/tests/view/5e377353e70d848499f638c1
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 171466 W: 22223 L: 21561 D: 127682 Elo +1.34
Ptnml(0-2): 1204, 15951, 50831, 16397, 1312

closes https://github.com/official-stockfish/Stockfish/pull/2545

Brench: 4869669
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 Feb 2 07:11:49 2020 +0100
Timestamp: 1580623909

Simplify away king infiltration.

STC :
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 91438 W: 17496 L: 17438 D: 56504 Elo +0.22
Ptnml(0-2): 1573, 10711, 21067, 10790, 1563
https://tests.stockfishchess.org/tests/view/5e34812630ae32da08941d65

LTC :
LLR: 2.96 (-2.94,2.94) {-1.50,0.50}
Total: 40485 W: 5246 L: 5177 D: 30062 Elo +0.59
Ptnml(0-2): 289, 3818, 11976, 3812, 327
https://tests.stockfishchess.org/tests/view/5e354daee70d848499f6380c

closes https://github.com/official-stockfish/Stockfish/pull/2542

Bench: 5047825
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: Sat Feb 1 09:05:13 2020 +0100
Timestamp: 1580544313

Simplify Tweak late move reductions at root.

Revert change from Jan 15.

STC 10+0.1 :
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 65135 W: 12543 L: 12436 D: 40156 Elo +0.57
Ptnml(0-2): 1090, 7618, 14947, 7623, 1136
https://tests.stockfishchess.org/tests/view/5e334016708b13464ceea32e

LTC 60+0.6 :
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 17768 W: 2286 L: 2191 D: 13291 Elo +1.86
Ptnml(0-2): 128, 1602, 5273, 1679, 140
https://tests.stockfishchess.org/tests/view/5e34011e57e1ecae66ec2aab

closes https://github.com/official-stockfish/Stockfish/pull/2537

Bench: 4914050
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: Fri Jan 31 19:48:44 2020 +0100
Timestamp: 1580496524

Revert 5 recent patches

Revert 5 patches which were merged, but lead to a regression test that showed negative Elo gain:

http://tests.stockfishchess.org/tests/view/5e307251ab2d69d58394fdb9

This was discussed in depth in:

https://github.com/official-stockfish/Stockfish/issues/2531

Each patch was removed and tested as a simplification, full list below, and the whole combo as well.

After the revert the regression test showed a neutral result:

http://tests.stockfishchess.org/tests/view/5e334851708b13464ceea33c

As a result of this experience, the SPRT testing bounds will be made more strict.

Reverted patches:

1 Dynamic Complexity 6d0eabd5fe2961551477820ab7619e2c31e01ffd :

STC 10+0.1 https://tests.stockfishchess.org/tests/view/5e31fcacec661e2e6a340d08 :
LLR: 2.97 (-2.94,2.94) {-1.50,0.50}
Total: 38130 W: 7326 L: 7189 D: 23615 Elo +1.25
Ptnml(0-2): 677, 4346, 8843, 4545, 646

LTC 60+0.6 https://tests.stockfishchess.org/tests/view/5e32c18fec661e2e6a340d73 :
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 38675 W: 4941 L: 4866 D: 28868 Elo +0.67
Ptnml(0-2): 270, 3556, 11429, 3584, 291

3 More bonus for bestMoves on past PV nodes 71e0b5385e2717679a57c6b77d8c7ac5fff3b89f :

STC 10+0.1 https://tests.stockfishchess.org/tests/view/5e31fe93ec661e2e6a340d10 :
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 46100 W: 8853 L: 8727 D: 28520 Elo +0.95
Ptnml(0-2): 796, 5297, 10749, 5387, 813

LTC 60+0.6 https://tests.stockfishchess.org/tests/view/5e32c187ec661e2e6a340d71 :
LLR: 2.96 (-2.94,2.94) {-1.50,0.50}
Total: 16920 W: 2161 L: 2055 D: 12704 Elo +2.18
Ptnml(0-2): 115, 1498, 5006, 1569, 130

4 Tweak Restricted Piece Bonus 0ae00454ba6928d181b46103e5c83e6d58fcebe5 :

STC 10+0.1 https://tests.stockfishchess.org/tests/view/5e31fefaec661e2e6a340d15 :
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 88328 W: 17060 L: 16997 D: 54271 Elo +0.25
Ptnml(0-2): 1536, 10446, 20169, 10422, 1581

LTC 60+0.6 https://tests.stockfishchess.org/tests/view/5e32c17aec661e2e6a340d6f :
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 34784 W: 4551 L: 4466 D: 25767 Elo +0.85
Ptnml(0-2): 255, 3279, 10061, 3345, 262

5 History update for pruned captures 01b6088af39902001d2d6844561b6a2faa549282 :

STC 10+0.1 https://tests.stockfishchess.org/tests/view/5e31ff5eec661e2e6a340d1a :
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 29541 W: 5735 L: 5588 D: 18218 Elo +1.73
Ptnml(0-2): 483, 3445, 6820, 3469, 545

LTC 60+0.6 https://tests.stockfishchess.org/tests/view/5e32c196ec661e2e6a340d75 :
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 22177 W: 2854 L: 2757 D: 16566 Elo +1.52
Ptnml(0-2): 143, 2005, 6555, 2055, 164

6 Tweak trapped rook penalty 18fc21eba0368fd5e3c4c4b8ee1000c9ac445425 :

STC 10+0.1 https://tests.stockfishchess.org/tests/view/5e31ffb1ec661e2e6a340d1c :
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 24476 W: 4727 L: 4569 D: 15180 Elo +2.24
Ptnml(0-2): 390, 2834, 5659, 2933, 417

LTC 60+0.6 https://tests.stockfishchess.org/tests/view/5e32c19eec661e2e6a340d77 :
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 97332 W: 12492 L: 12466 D: 72374 Elo +0.09
Ptnml(0-2): 690, 9107, 28738, 9034, 720

All 5 as one simplification :
LTC 60+0.6 https://tests.stockfishchess.org/tests/view/5e334098708b13464ceea330 :
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 7829 W: 1079 L: 964 D: 5786 Elo +5.10
Ptnml(0-2): 52, 690, 2281, 781, 65

Bench: 5153165
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: Wed Jan 29 07:25:18 2020 +0100
Timestamp: 1580279118

Fix compilation on android

Fall back to the default implementation of aligned_ttmem_alloc, which
was introduced as part of 39437f4e55aaa26ef9f0d5a1c762e560e9ffde32

Fixes #2524

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: joergoster
Date: Tue Jan 28 19:25:39 2020 +0100
Timestamp: 1580235939

Simplify hashfull calculation.

We can simplify the calculation of the hashfull info by looping over exact 1,000 entries,
and then divide the result by ClusterSize. Somewhat memory accesses, somewhat more accurate.

Passed non-regression LTC
https://tests.stockfishchess.org/tests/view/5e30079dab2d69d58394fd5d
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 30125 W: 3987 L: 3926 D: 22212 Elo +0.70
Ptnml(0-2): 177, 2504, 9558, 2642, 141

closes https://github.com/official-stockfish/Stockfish/pull/2523

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: Guenther Demetz
Date: Tue Jan 28 16:28:56 2020 +0100
Timestamp: 1580225336

More bonus for bestMoves on past PV nodes

It looks like it is important to keep past PV (ttPv) nodes as close as possible to current PV nodes.
Credits to Mark Tenzer (31m059) & Stefan Geschwentner who first tried ideas on ttPv nodes.

STC:
https://tests.stockfishchess.org/tests/view/5e2ff5efab2d69d58394fd52
LLR: 2.95 (-2.94,2.94) {-1.00,3.00}
Total: 13302 W: 2647 L: 2507 D: 8148 Elo +3.66
Ptnml(0-2): 237, 1540, 2956, 1632, 260

LTC:
https://tests.stockfishchess.org/tests/view/5e2fff38ab2d69d58394fd55
LLR: 2.95 (-2.94,2.94) {0.00,2.00}
Total: 15797 W: 2137 L: 1960 D: 11700 Elo +3.89
Ptnml(0-2): 96, 1443, 4628, 1547, 130

closes https://github.com/official-stockfish/Stockfish/pull/2529

bench: 5545845
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: Tue Jan 28 10:31:25 2020 +0100
Timestamp: 1580203885

Less NMP if the position was previously in PV.

The intention of the patch is to avoid aggressive null move pruning (NMP)
in positions that have previously been found to be important (PV nodes).
If we already do not apply NMP for current PV nodes, it makes sense to apply
it less often for positions that have previously been PV nodes too.

STC:
LLR: 2.96 (-2.94,2.94) {-1.00,3.00}
Total: 14959 W: 2921 L: 2782 D: 9256 Elo +3.23
Ptnml(0-2): 254, 1679, 3493, 1762, 282
http://tests.stockfishchess.org/tests/view/5e2f6637ab2d69d58394fcfd

LTC:
LLR: 2.95 (-2.94,2.94) {0.00,2.00}
Total: 6442 W: 899 L: 753 D: 4790 Elo +7.88
Ptnml(0-2): 42, 549, 1885, 659, 61
http://tests.stockfishchess.org/tests/view/5e2f767bab2d69d58394fd04

closes https://github.com/official-stockfish/Stockfish/pull/2525

Bench: 4725546
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: Alain SAVARD
Date: Mon Jan 27 18:14:10 2020 +0100
Timestamp: 1580145250

Dynamic Complexity based on psqt

Adjust initiative score by psqt/2 instead of materialScore/2 which simplifies #2516

Passed STC
http://tests.stockfishchess.org/tests/view/5e2e667dab2d69d58394fc73
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 23198 W: 4506 L: 4353 D: 14339 Elo +2.29
Ptnml(0-2): 396, 2615, 5380, 2728, 418

Passed LTC
http://tests.stockfishchess.org/tests/view/5e2ed75cab2d69d58394fcbf
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 8519 W: 1179 L: 1062 D: 6278 Elo +4.77
Ptnml(0-2): 50, 775, 2472, 843, 74

closes https://github.com/official-stockfish/Stockfish/pull/2522

Bench: 4684459
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: Sami Kiminki
Date: Mon Jan 27 11:16:10 2020 +0100
Timestamp: 1580120170

Advise the kernel to use huge pages (Linux)

Align the TT allocation by 2M to make it huge page friendly and advise the
kernel to use huge pages.

Benchmarks on my i7-8700K (6C/12T) box: (3 runs per bench per config)

vanilla (nps) hugepages (nps) avg
==================================================================================
bench | 3012490 3024364 3036331 3071052 3067544 3071052 +1.5%
bench 16 12 20 | 19237932 19050166 19085315 19266346 19207025 19548758 +1.1%
bench 16384 12 20 | 18182313 18371581 18336838 19381275 19738012 19620225 +7.0%

On my box, huge pages have a significant perf impact when using a big
hash size. They also speed up TT initialization big time:

vanilla (s) huge pages (s) speed-up
=======================================================================
time stockfish bench 16384 1 1 | 5.37 1.48 3.6x

In practice, huge pages with auto-defrag may always be enabled in the
system, in which case this patch has no effect. This
depends on the values in /sys/kernel/mm/transparent_hugepage/enabled
and /sys/kernel/mm/transparent_hugepage/defrag.

closes https://github.com/official-stockfish/Stockfish/pull/2463

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: Alain SAVARD
Date: Mon Jan 27 09:05:55 2020 +0100
Timestamp: 1580112355

Dynamic complexity

Instead of computing the initiative bonus on the material score + dynamic score
compute it on (material score/2) + dynamic score,

Passed STC
http://tests.stockfishchess.org/tests/view/5e2c4945ab2d69d58394fa8f
LLR: 2.94 (-2.94,2.94) {-1.00,3.00}
Total: 39387 W: 7594 L: 7386 D: 24407 Elo +1.83
Ptnml(0-2): 658, 4519, 9165, 4649, 697

Passed LTC
http://tests.stockfishchess.org/tests/view/5e2c85ccab2d69d58394faa7
LLR: 2.95 (-2.94,2.94) {0.00,2.00}
Total: 32588 W: 4206 L: 3986 D: 24396 Elo +2.35
Ptnml(0-2): 244, 2909, 9738, 3111, 253

closes https://github.com/official-stockfish/Stockfish/pull/2516

Bench: 4765486
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: Sat Jan 25 09:44:09 2020 +0100
Timestamp: 1579941849

Tweak RestrictedPiece bonus

Double the "RestrictedPiece" bonus for restricted moves targeting
occupied squares.

STC LLR: 3.58 (-2.94,2.94) {-1.00,3.00}
Total: 25504 W: 4887 L: 4697 D: 15920 Elo +2.59
Ptnml(0-2): 387, 2935, 5947, 3051, 422
https://tests.stockfishchess.org/tests/view/5e2aa15dab2d69d58394f94d

LTC LLR: 2.94 (-2.94,2.94) {0.00,2.00}
Total: 28572 W: 3826 L: 3621 D: 21125 Elo +2.49
Ptnml(0-2): 224, 2609, 8403, 2791, 239
https://tests.stockfishchess.org/tests/view/5e2ae7f4ab2d69d58394f9a6

Bench: 4719086
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: Stefan Geschwentner
Date: Thu Jan 23 19:12:48 2020 +0100
Timestamp: 1579803168

History update for pruned captures

Use a SEE pruned capture move for history updates: this patch collects
pruned capture moves also in the failed captures list, so that they get
an update in capture history.

STC:
LLR: 2.95 (-2.94,2.94) {-1.00,3.00}
Total: 11124 W: 2222 L: 2089 D: 6813 Elo +4.15
Ptnml(0-2): 186, 1280, 2506, 1381, 200
http://tests.stockfishchess.org/tests/view/5e28995fc3b97aa0d75bc294

LTC:
LLR: 2.94 (-2.94,2.94) {0.00,2.00}
Total: 25552 W: 3418 L: 3211 D: 18923 Elo +2.81
Ptnml(0-2): 168, 2354, 7538, 2490, 200
http://tests.stockfishchess.org/tests/view/5e2943734744cfa4d6af415b

Closes https://github.com/official-stockfish/Stockfish/pull/2511

Bench: 4810202
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 Jan 23 19:03:25 2020 +0100
Timestamp: 1579802605

Tweak trapped rook penalty

This patch greatly increases the endgame penalty for having a trapped rook.
Idea was a result of witnessing Stockfish losing some games at CCCC exchanging
pieces in the position with a trapped rook which directly lead to a lost endgame.
This patch should partially fix such behavior making this penalty high even in
deep endgames.

Passed STC
http://tests.stockfishchess.org/tests/view/5e279d7cc3b97aa0d75bc1c4
LLR: 2.94 (-2.94,2.94) {-1.00,3.00}
Total: 8528 W: 1706 L: 1588 D: 5234 Elo +4.81
Ptnml(0-2): 133, 957, 1985, 1024, 159

Passed LTC
http://tests.stockfishchess.org/tests/view/5e27aee4c3b97aa0d75bc1e1
LLR: 2.95 (-2.94,2.94) {0.00,2.00}
Total: 88713 W: 11520 L: 11130 D: 66063 Elo +1.53
Ptnml(0-2): 646, 8170, 26342, 8492, 676

Closes https://github.com/official-stockfish/Stockfish/pull/2510

Bench: 4964462

----------------------

Comment by Malcolm Campbell:

Congrats! I think this might be a common pattern - scores that seem to mainly apply
to the midgame are often better with a similar (or at least fairly big) endgame value
as well. Maybe there are others eval parameters we can tweak like this...
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: Stefan Geschwentner
Date: Thu Jan 23 18:53:50 2020 +0100
Timestamp: 1579802030

Less reduction for escape moves at ttPv nodes

At expected PV nodes or nodes which marked as PV node in the hash table,
reduce escape moves even one ply less.

STC:
LLR: 2.94 (-2.94,2.94) {-1.00,3.00}
Total: 31795 W: 6140 L: 5953 D: 19702 Elo +2.04
Ptnml(0-2): 525, 3625, 7455, 3695, 583
http://tests.stockfishchess.org/tests/view/5e25d77fc3b97aa0d75bc013

LTC:
LLR: 2.94 (-2.94,2.94) {0.00,2.00}
Total: 43975 W: 5708 L: 5454 D: 32813 Elo +2.01
Ptnml(0-2): 314, 4012, 13070, 4242, 325
http://tests.stockfishchess.org/tests/view/5e2618c1c3b97aa0d75bc03c

Closes https://github.com/official-stockfish/Stockfish/pull/2505

Bench: 4475583
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: Guenther Demetz
Date: Thu Jan 23 18:43:47 2020 +0100
Timestamp: 1579801427

Use (strict) greater-than-operator for 'improving'

Currently on a normal bench run in ~0,7% of cases 'improving' is set to
true although the static eval isn't improving at all, just keeping
equal. It looks like the strict gt-operator is more appropriate here,
since it returns to 'improving' its literal meaning without sideffects.

STC {-1.00,3.00} failed yellow:
https://tests.stockfishchess.org/tests/view/5e1ec38c8fd5f550e4ae1c28
LLR: -2.93 (-2.94,2.94) {-1.00,3.00}
Total: 53155 W: 10170 L: 10109 D: 32876 Elo +0.40
Ptnml(0-2): 863, 6282, 12251, 6283, 892

non-regression LTC passed:
https://tests.stockfishchess.org/tests/view/5e1f1c0d8fd5f550e4ae1c41
LLR: 2.98 (-2.94,2.94) {-1.50,0.50}
Total: 23961 W: 3114 L: 3018 D: 17829 Elo +1.39
Ptnml(0-2): 163, 2220, 7114, 2298, 170

CLoses https://github.com/official-stockfish/Stockfish/pull/2496

bench: 4561386
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: Chess13234
Date: Thu Jan 23 18:33:01 2020 +0100
Timestamp: 1579800781

Minor fixes for misc.cpp

Fixes conflict with tune.h STRINGIFY macro.

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: protonspring
Date: Thu Jan 23 18:20:11 2020 +0100
Timestamp: 1579800011

Use a std::bitset for KPKBitbase

This is a non-functional simplification. Looks like std::bitset works good
for the KPKBitbase. Thanks for Jorg Oster for helping get the speed up
(the [] accessor is faster than test()).

Speed testing: 10k calls to probe:
master 9.8 sec
patch 9.8 sec.

STC
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 100154 W: 19025 L: 18992 D: 62137 Elo +0.11
Ptnml(0-2): 1397, 11376, 24572, 11254, 1473
http://tests.stockfishchess.org/tests/view/5e21e601346e35ac603b7d2b

Closes https://github.com/official-stockfish/Stockfish/pull/2502

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: protonspring
Date: Thu Jan 23 17:59:03 2020 +0100
Timestamp: 1579798743

Determine opposite colors mathematically

This is a non-functional speed-up: master has to access SquareBB twice while this patch
determines opposite_colors just using the values of the squares. It doesn't seem to change
the overall speed of bench, but calling opposite_colors(...) 10 Million times:

master: 39.4 seconds
patch: 11.4 seconds.

The only data point I have (other than my own tests), is a quite old failed STC test:
LLR: -2.93 (-2.94,2.94) [-1.50,4.50]
Total: 24308 W: 5331 L: 5330 D: 13647 Elo +0.01
Ptnml(0-2): 315, 2577, 6326, 2623, 289
http://tests.stockfishchess.org/tests/view/5e010256c13ac2425c4a9a67

Closes https://github.com/official-stockfish/Stockfish/pull/2498

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: protonspring
Date: Thu Jan 23 17:49:10 2020 +0100
Timestamp: 1579798150

Simplify KPK classify

This is a non-functional simplification. If we use the "side to move" of the entry
instead of the template, one of the classify methods goes away. Furthermore, I've
resolved the colors in some of the statements (we're already assuming direction
using NORTH), and used stm (side to move) instead of "us," since this is much clearer
to me.

This is not tested because it is non-functional, only applies building the bitbase
and there are no changes to the binary (on my machine).

Closes https://github.com/official-stockfish/Stockfish/pull/2485

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: protonspring
Date: Thu Jan 23 17:31:45 2020 +0100
Timestamp: 1579797105

Simplify signature of remove_piece()

This is a non-functional simplification. Instead of passing the piece type
for remove_piece, we can rely on the board. The only exception is en-passant
which must be explicitly set because the destination square for the capture
is not the same as the piece to remove.

Verified also in the Chess960 castling case by running a couple of perft, see
the pull request discussion: https://github.com/official-stockfish/Stockfish/pull/2460

STC
LLR: 2.94 (-2.94,2.94) [-3.00,1.00]
Total: 18624 W: 4147 L: 4070 D: 10407 Elo +1.44
Ptnml(0-2): 223, 1933, 4945, 1938, 260
http://tests.stockfishchess.org/tests/view/5dfeaa93e70446e17e451163

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: Stéphane Nicolet
Date: Thu Jan 23 17:17:26 2020 +0100
Timestamp: 1579796246

Restore development version

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: Stéphane Nicolet
Date: Sat Jan 18 01:44:37 2020 +0100
Timestamp: 1579308277

Stockfish 11

Official release version of Stockfish 11.

Bench: 5156767

-----------------------

It is our pleasure to release Stockfish 11 to our fans and supporters.

Downloads are freely available at http://stockfishchess.org/download/

This version 11 of Stockfish is 50 Elo stronger than the last version, and
150 Elo stronger than the version which famously lost a match to AlphaZero
two years ago. This makes Stockfish the strongest chess engine running on
your smartphone or normal desktop PC, and we estimate that on a modern four
cores CPU, Stockfish 11 could give 1:1000 time odds to the human chess champion
having classical time control, and be on par with him. More specific data,
including nice cumulative curves for the progression of Stockfish strength
over the last seven years, can be found on [our progression page][1], at
[Stefan Pohl site][2] or at [NextChessMove][3].

In October 2019 Stockfish has regained its crown in the TCEC competition,
beating in the superfinal of season 16 an evolution of the neural-network
engine Leela that had won the previous season. This clash of style between an
alpha-beta and an neural-network engine produced spectacular chess as always,
with Stockfish [emerging victorious this time][0].

Compared to Stockfish 10, we have made hundreds of improvements to the
[codebase][4], from the evaluation function (improvements in king attacks,
middlegame/endgame transitions, and many more) to the search algorithm (some
innovative coordination methods for the searching threads, better pruning of
unsound tactical lines, etc), and fixed a couple of bugs en passant.

Our testing framework [Fishtest][5] has also seen its share of improvements
to continue propelling Stockfish forward. Along with a lot of small enhancements,
Fishtest has switched to new SPRT bounds to increase the chance of catching Elo
gainers, along with a new testing book and the use of pentanomial statistics to
be more resource-efficient.

Overall the Stockfish project is an example of open-source at its best, as
its buzzing community of programmers sharing ideas and daily reviewing their
colleagues' patches proves to be an ideal form to develop innovative ideas for
chess programming, while the mathematical accuracy of the testing framework
allows us an unparalleled level of quality control for each patch we put in
the engine. If you wish, you too can help our ongoing efforts to keep improving
it, just [get involved][6] :-)

Stockfish is also special in that every chess fan, even if not a programmer,
[can easily help][7] the team to improve the engine by connecting their PC to
Fishtest and let it play some games in the background to test new patches.
Individual contributions vary from 1 to 32 cores, but this year Bojun Guo
made it a little bit special by plugging a whole data center during the whole
year: it was a vertiginous experience to see Fishtest spikes with 17466 cores
connected playing [25600 games/minute][8]. Thanks Guo!

The Stockfish team

[0]: <http://mytcecexperience.blogspot.com/2019/10/season-16-superfinal-games-91-100.html>
[1]: <https://github.com/glinscott/fishtest/wiki/Regression-Tests>
[2]: <https://www.sp-cc.de/index.htm>
[3]: <https://nextchessmove.com/dev-builds>
[4]: <https://github.com/official-stockfish/Stockfish>
[5]: <https://tests.stockfishchess.org/tests>
[6]: <https://stockfishchess.org/get-involved/>
[7]: <https://github.com/glinscott/fishtest/wiki>
[8]: <https://groups.google.com/forum/?fromgroups=#!topic/fishcooking/lebEmG5vgng%5B1-25%5D>
see source

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