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/mingw 7.3 on Ubuntu 18.04.
Read the FAQ or leave a comment.

!! latest version !!


Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Lolligerhans
Date: Sun Jan 17 09:35:59 2021 +0100
Timestamp: 1610872559

Add penalty for doubled pawns in agile structure

Give an additional penalty of S(20, 10) for any doubled pawn if none of
the opponent's pawns is facing any of our
- pawns or
- pawn attacks;
that means, each of their pawns can push at least one square without
being captured.
This ignores their non-pawns pieces and attacks.

One possible justification: Their pawns' ability to push freely provides
options to react to our threats by changing their pawn structure. Our
doubled pawns however will likely lead to an exploitable weakness, even
if the pawn structure is not yet fixed.

Note that the notion of "their pawns not being fixed" is symmetric for
both players: If all of their pawns can push freely so can ours. All
pawns being freely pushable might just be an early-game-indicator.
However, it can trigger during endgame pawns races, where doubled pawns
are especially hindering, too.

LTC
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 134976 W: 17964 L: 17415 D: 99597 Elo +1.41
Ptnml(0-2): 998, 12702, 39619, 13091, 1078
https://tests.stockfishchess.org/tests/view/5ffdd5316019e097de3ef281

STC
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 35640 W: 7219 L: 6904 D: 21517 Elo +3.07
Ptnml(0-2): 645, 4096, 8084, 4289, 706
https://tests.stockfishchess.org/tests/view/5ffda4a16019e097de3ef265

closes https://github.com/official-stockfish/Stockfish/pull/3302

Bench: 4363873
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Tomasz Sobczyk
Date: Wed Jan 13 22:59:54 2021 +0100
Timestamp: 1610575194

Optimize generate_moves

This change simplifies control flow in the generate_moves function which ensures the compiler doesn't duplicate work due to possibly not resolving pureness of the function calls. Also the biggest change is the removal of the unnecessary condition checking for empty b in a convoluted way. The rationale for removal of this condition is that computing attacks_bb with occupancy is not much more costly than computing pseudo attacks and overall the condition (also being likely unpredictable) is a pessimisation.

This is inspired by previous changes by @BM123499.

Passed STC:
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 88040 W: 8172 L: 7931 D: 71937 Elo +0.95
Ptnml(0-2): 285, 6128, 30957, 6361, 289
https://tests.stockfishchess.org/tests/view/5ffc28386019e097de3ef1c7

closes https://github.com/official-stockfish/Stockfish/pull/3300

No functional change.
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Mon Jan 11 19:42:31 2021 +0100
Timestamp: 1610390551

Bad Outpost Pawn Scale

Changed name from Bad Outpost to Uncontested Outpost
Scale Uncontested Outpost with number of pawns + Decrease Bishop PSQT values and general tuning

Credits for the decrease of the Bishop PSQT values: Fauzi
Credits for scaling Uncontested Outpost with number of pawns: Lolligerhans
Credits for the tunings: Fauzi

Passed STC:
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 32040 W: 6593 L: 6281 D: 19166 Elo +3.38
Ptnml(0-2): 596, 3713, 7095, 4015, 601
https://tests.stockfishchess.org/tests/view/5ffa43026019e097de3ef0f2

Passed LTC:
LLR: 2.95 (-2.94,2.94) {0.25,1.25}
Total: 84376 W: 11395 L: 10950 D: 62031 Elo +1.83
Ptnml(0-2): 652, 7930, 24623, 8287, 696
https://tests.stockfishchess.org/tests/view/5ffa6e7b6019e097de3ef0fd

closes https://github.com/official-stockfish/Stockfish/pull/3296

Bench: 4287509
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Vizvezdenec
Date: Mon Jan 11 19:36:07 2021 +0100
Timestamp: 1610390167

Refine stat based reductions

This patch separates stat based reductions for quiet moves in case of being in check and in case of not being in check.
We will be using sum of first continuation history and main history (similar to movepicker) instead of statScore for the first case.

passed STC
https://tests.stockfishchess.org/tests/view/5ff87b2f6019e097de3ef09b
LLR: 2.93 (-2.94,2.94) {-0.25,1.25}
Total: 63992 W: 5887 L: 5678 D: 52427 Elo +1.13
Ptnml(0-2): 201, 4561, 22305, 4686, 243

passed LTC
https://tests.stockfishchess.org/tests/view/5ff8b6206019e097de3ef0b2
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 81216 W: 3127 L: 2880 D: 75209 Elo +1.06
Ptnml(0-2): 46, 2544, 35176, 2801, 41

closes https://github.com/official-stockfish/Stockfish/pull/3293

bench 4395984
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: BM123499
Date: Mon Jan 11 19:31:22 2021 +0100
Timestamp: 1610389882

Rethink En Passant Evasion Capture

It now checks if it were a discovery attack instead of the attacking piece is the double-moved pawn.

As a side effect, certain illegal fens have different, and slightly more logical move generation.
There is no intend to maintain particular behavior for such non-reachable fens.

Passed STC:
LLR: 2.93 (-2.94,2.94) {-1.25,0.25}
Total: 47912 W: 4327 L: 4285 D: 39300 Elo +0.30
Ptnml(0-2): 144, 3312, 17012, 3334, 154
https://tests.stockfishchess.org/tests/view/5ff890946019e097de3ef0a5

closes https://github.com/official-stockfish/Stockfish/pull/3292

closes / fixes https://github.com/official-stockfish/Stockfish/issues/3270

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Dieter Dobbelaere
Date: Mon Jan 11 19:23:05 2021 +0100
Timestamp: 1610389385

Fix static_assert.

With a hard-coded true, this declaration has no effect.

closes https://github.com/official-stockfish/Stockfish/pull/3295

No functional change.
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Dieter Dobbelaere
Date: Mon Jan 11 19:19:39 2021 +0100
Timestamp: 1610389179

Use correct chess terms + fix spelling.

- "discovered check" (instead of "discovery check")
- "en passant" (instead of "en-passant")
- "pseudo-legal" before a noun (instead of "pseudo legal")
- "3-fold" (instead of "3fold")

closes https://github.com/official-stockfish/Stockfish/pull/3294

No functional change.
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Vizvezdenec
Date: Mon Jan 11 19:17:03 2021 +0100
Timestamp: 1610389023

Small code cleanup in LMR

In a recent patch we added comparing capture history to a number for LMR of captures.
Calling it via thisThread-> is not needed since capture history was already declared by this time -
so removing makes code slightly shorter and easier to follow.

closes https://github.com/official-stockfish/Stockfish/pull/3297

No functional change.
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: MaximMolchanov
Date: Mon Jan 11 18:54:18 2021 +0100
Timestamp: 1610387658

Affine transform robust implementation

Size of the weights in the last layer is less than 512 bits. It leads to wrong data access for AVX512. There is no error because in current implementation it is guaranteed that there is an array of zeros after weights so zero multiplied by something is returned and sum is correct. It is a mistake that can lead to unexpected bugs in the future. Used AVX2 instructions for smaller input size.

No measurable slowdown on avx512.

closes https://github.com/official-stockfish/Stockfish/pull/3298

No functional change.
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: bmc4
Date: Mon Jan 11 18:41:47 2021 +0100
Timestamp: 1610386907

Remove Condition from Generate_Move Loop

it seems it's faster to handle blockers_for_king(~Us) outside loops

Passed STC:
LLR: 2.96 (-2.94,2.94) {-0.25,1.25}
Total: 22184 W: 2063 L: 1919 D: 18202 Elo +2.26
Ptnml(0-2): 63, 1485, 7855, 1623, 66
https://tests.stockfishchess.org/tests/view/5ffbee2f6019e097de3ef18d

closes https://github.com/official-stockfish/Stockfish/pull/3299

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Joost VandeVondele
Date: Fri Jan 8 17:04:23 2021 +0100
Timestamp: 1610121863

Update copyright years

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Vizvezdenec
Date: Fri Jan 8 16:57:26 2021 +0100
Timestamp: 1610121446

Reorder conditions in LMR and pruning

Make code logic somewhat easier to follow.

closes https://github.com/official-stockfish/Stockfish/pull/3285

No functional change.
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: MaximMolchanov
Date: Fri Jan 8 16:35:44 2021 +0100
Timestamp: 1610120144

Affine transform refactoring.

Reordered weights in such a way that accumulated sum fits to output.
Weights are grouped in blocks of four elements because four
int8 (weight type) corresponds to one int32 (output type).
No horizontal additions.
Grouped AVX512, AVX2 and SSSE3 implementations.
Repeated code was removed.

An earlier version passed STC:

LLR: 2.97 (-2.94,2.94) {-0.25,1.25}
Total: 15336 W: 1495 L: 1355 D: 12486 Elo +3.17
Ptnml(0-2): 44, 1054, 5350, 1158, 62
https://tests.stockfishchess.org/tests/view/5ff60e106019e097de3eefd5

Speedup depends on the architecture, up to 4% measured on a NNUE only bench.

closes https://github.com/official-stockfish/Stockfish/pull/3287

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Thu Dec 31 18:03:33 2020 +0100
Timestamp: 1609434213

WeakUnopposed penalty for backwards on file A or H

Do not give the WeakUnopposed penalty for backwards on file A or H

The original idea comes from Lolligerhans, and a series of tunings and tests done by Fauzi.

Passed STC:
LLR: 2.96 (-2.94,2.94) {-0.25,1.25}
Total: 140864 W: 28127 L: 27660 D: 85077 Elo +1.15
Ptnml(0-2): 2529, 16660, 31735, 16831, 2677
https://tests.stockfishchess.org/tests/view/5fe39dec3932f79192d39673

Passed LTC:
LLR: 2.95 (-2.94,2.94) {0.25,1.25}
Total: 67568 W: 8993 L: 8590 D: 49985 Elo +2.07
Ptnml(0-2): 523, 6176, 19983, 6579, 523
https://tests.stockfishchess.org/tests/view/5fe3dd1b3932f79192d39693

closes https://github.com/official-stockfish/Stockfish/pull/3275

Bench: 4109336
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Unai Corzo
Date: Thu Dec 31 17:51:14 2020 +0100
Timestamp: 1609433474

Remove razoring

has become ineffective now.

STC https://tests.stockfishchess.org/tests/view/5fe653403932f79192d3981a
LLR: 2.95 (-2.94,2.94) {-1.25,0.25}
Total: 63448 W: 5965 L: 5934 D: 51549 Elo +0.17
Ptnml(0-2): 230, 4738, 21769, 4745, 242

LTC https://tests.stockfishchess.org/tests/view/5fe6f0f03932f79192d39856
LLR: 2.93 (-2.94,2.94) {-0.75,0.25}
Total: 65368 W: 2485 L: 2459 D: 60424 Elo +0.14
Ptnml(0-2): 33, 2186, 28230, 2192, 43

closes https://github.com/official-stockfish/Stockfish/pull/3278

bench: 4493379
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Unai Corzo
Date: Thu Dec 31 17:48:47 2020 +0100
Timestamp: 1609433327

Simplify away late irreversible move extension

Late irreversible move extension seems to be useless now.

STC https://tests.stockfishchess.org/tests/view/5fe75c5c3932f79192d398ca
LLR: 2.93 (-2.94,2.94) {-1.25,0.25}
Total: 196192 W: 18111 L: 18278 D: 159803 Elo -0.30
Ptnml(0-2): 681, 14097, 68652, 14040, 626

LTC https://tests.stockfishchess.org/tests/view/5fe875e23932f79192d39952
LLR: 2.96 (-2.94,2.94) {-0.75,0.25}
Total: 28080 W: 1105 L: 1053 D: 25922 Elo +0.64
Ptnml(0-2): 13, 904, 12158, 948, 17

closes https://github.com/official-stockfish/Stockfish/pull/3279

bench: 4144640
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Unai Corzo
Date: Thu Dec 31 17:44:15 2020 +0100
Timestamp: 1609433055

Assorted parameter tweak

Parameter tweak from various tunes and patches.

STC https://tests.stockfishchess.org/tests/view/5fec2ae36019e097de3ee94a
LLR: 2.97 (-2.94,2.94) {-0.25,1.25}
Total: 41976 W: 4032 L: 3848 D: 34096 Elo +1.52
Ptnml(0-2): 147, 3086, 14341, 3264, 150

LTC https://tests.stockfishchess.org/tests/view/5fec5c3c6019e097de3ee973
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 23936 W: 970 L: 844 D: 22122 Elo +1.83
Ptnml(0-2): 14, 749, 10319, 869, 17

closes https://github.com/official-stockfish/Stockfish/pull/3281

bench: 4354546
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stefan Geschwentner
Date: Thu Dec 31 17:41:34 2020 +0100
Timestamp: 1609432894

Tweak capture LMR.

Apply the recently added LMR condition for captures at nodes which are not PV or former PV nodes only if capture history is not too good.

STC:
LLR: 2.96 (-2.94,2.94) {-0.25,1.25}
Total: 95296 W: 8917 L: 8660 D: 77719 Elo +0.94
Ptnml(0-2): 323, 6871, 33045, 7044, 365
https://tests.stockfishchess.org/tests/view/5feca7f46019e097de3ee9ae

LTC:
LLR: 2.95 (-2.94,2.94) {0.25,1.25}
Total: 29216 W: 1172 L: 1034 D: 27010 Elo +1.64
Ptnml(0-2): 11, 946, 12568, 1060, 23
https://tests.stockfishchess.org/tests/view/5fecf1786019e097de3ee9d5

closes https://github.com/official-stockfish/Stockfish/pull/3283

Bench: 4006138
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Vizvezdenec
Date: Fri Dec 25 10:21:00 2020 +0100
Timestamp: 1608888060

Do more LMR for captures

This patch enables LMR for all captures at allNodes that were not in PV.
Currently we do LMR for all captures at cutNodes so this is an expansion of this logic:
now we do LMR for all captures almost at all non-pv nodes,
excluding only allNodes that were in PV.

passed STC
https://tests.stockfishchess.org/tests/view/5fe50b9d3932f79192d3973c
LLR: 2.95 (-2.94,2.94) {-0.25,1.25}
Total: 83128 W: 7606 L: 7368 D: 68154 Elo +0.99
Ptnml(0-2): 292, 5905, 28939, 6129, 299

passed LTC
https://tests.stockfishchess.org/tests/view/5fe552e43932f79192d39744
LLR: 2.92 (-2.94,2.94) {0.25,1.25}
Total: 13968 W: 568 L: 466 D: 12934 Elo +2.54
Ptnml(0-2): 5, 418, 6043, 506, 12

closes https://github.com/official-stockfish/Stockfish/pull/3273

Bench: 4194835
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Moez Jellouli
Date: Wed Dec 23 20:20:24 2020 +0100
Timestamp: 1608751224

Correct Outflanking calculations in classical eval

Take signed value of rank difference between kings squares instead absolute value in outflanking calculation. This change correct evaluation of endgames with one king invading opponent last ranks.

Passed STC:
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 122240 W: 24326 L: 23896 D: 74018 Elo +1.22
Ptnml(0-2): 2101, 14139, 28236, 14517, 2127
https://tests.stockfishchess.org/tests/view/5fdfc33a3932f79192d394b8

Passed LTC:
LLR: 2.97 (-2.94,2.94) {0.25,1.25}
Total: 157416 W: 20870 L: 20292 D: 116254 Elo +1.28
Ptnml(0-2): 973, 13954, 48333, 14418, 1030
https://tests.stockfishchess.org/tests/view/5fe07a453932f79192d39502

closes https://github.com/official-stockfish/Stockfish/pull/3271

Bench: 4162769
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Wed Dec 23 20:17:57 2020 +0100
Timestamp: 1608751077

Tweak the formulas for unsafeSquares

We give more bonus for a special case: If there are some enemy squares occupied
or attacked by the enemy on the passed pawn span,
but if they are all attacked by our pawn, use new intermediate factor 30.

The main credit goes to Rocky for the idea, with additional tuning and tests.

Passed STC:
LLR: 2.95 (-2.94,2.94) {-0.25,1.25}
Total: 96464 W: 19233 L: 18834 D: 58397 Elo +1.44
Ptnml(0-2): 1683, 11327, 21950, 11452, 1820
https://tests.stockfishchess.org/tests/view/5fdd21ab3932f79192d39357

Passed LTC:
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 81320 W: 10784 L: 10352 D: 60184 Elo +1.85
Ptnml(0-2): 602, 7524, 24044, 7820, 670
https://tests.stockfishchess.org/tests/view/5fddec983932f79192d393a4

closes https://github.com/official-stockfish/Stockfish/pull/3268

Bench: 4338972
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: pb00067
Date: Fri Dec 18 21:19:46 2020 +0100
Timestamp: 1608322786

Simplify condition for assigning static-eval based bonus

for quiet move ordering and simplify bonus formula.

Due to clamping the bonus to relative low values the impact on high
depths is minimal, thus the restriction to low depths seems not
necessary.
Also the condition of movecount in previous node seems to be not
determinant.

Passed STC:
LLR: 2.95 (-2.94,2.94) {-1.25,0.25}
Total: 14600 W: 1424 L: 1323 D: 11853 Elo +2.40
Ptnml(0-2): 55, 1033, 5020, 1140, 52
https://tests.stockfishchess.org/tests/view/5fd67b381ac16912018885ec

Passed LTC:
LLR: 2.95 (-2.94,2.94) {-0.75,0.25}
Total: 85008 W: 3218 L: 3206 D: 78584 Elo +0.05
Ptnml(0-2): 49, 2840, 36700, 2880, 35
https://tests.stockfishchess.org/tests/view/5fd6af041ac16912018885f8

closes https://github.com/official-stockfish/Stockfish/pull/3265

bench: 4524994
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Fri Dec 18 21:17:34 2020 +0100
Timestamp: 1608322654

Adjust definition of unsafeSquares

and adjust related bonus values. The bonus is now not given whenever
there is an enemy piece in front of the pawn.

Passed STC:
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 109472 W: 22097 L: 21673 D: 65702 Elo +1.35
Ptnml(0-2): 2111, 12800, 24482, 13240, 2103
https://tests.stockfishchess.org/tests/view/5fd8d3740c5870924361ffad

Passed LTC:
LLR: 2.95 (-2.94,2.94) {0.25,1.25}
Total: 39384 W: 5334 L: 4990 D: 29060 Elo +3.03
Ptnml(0-2): 279, 3648, 11535, 3910, 320
https://tests.stockfishchess.org/tests/view/5fd971ab0c5870924361fff0

closes https://github.com/official-stockfish/Stockfish/pull/3266

Bench: 4488955
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Vizvezdenec
Date: Mon Dec 14 07:52:02 2020 +0100
Timestamp: 1607928722

Increase reduction in case of stable best move

The idea of this patch is pretty simple - we already do more reductions
for non-PV and root nodes in case of stable best move for depth > 10.
This patch makes us do so if root depth if > 10 instead, which
is logical since best move changes (thus instability of it) is
counted at root, so it makes a lot of sense to use depth of the root.

passed STC
https://tests.stockfishchess.org/tests/view/5fd643271ac16912018885c5
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 13232 W: 1308 L: 1169 D: 10755 Elo +3.65
Ptnml(0-2): 39, 935, 4535, 1062, 45

passed LTC
https://tests.stockfishchess.org/tests/view/5fd68db11ac16912018885f0
LLR: 2.96 (-2.94,2.94) {0.25,1.25}
Total: 14024 W: 565 L: 463 D: 12996 Elo +2.53
Ptnml(0-2): 3, 423, 6062, 517, 7

closes https://github.com/official-stockfish/Stockfish/pull/3263

Bench: 4050630
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: pb00067
Date: Mon Dec 14 07:48:48 2020 +0100
Timestamp: 1607928528

Merge static history into main history,

thus simplifying and reducing the memory footprint.
I believe using static diff for better move ordering is more suited for
low depths, so restrict writing to low depths.

Todo: probably the condition for writing can be simplified

LTC:
LLR: 2.95 (-2.94,2.94) {-0.75,0.25}
Total: 18752 W: 768 L: 705 D: 17279 Elo +1.17
Ptnml(0-2): 7, 635, 8034, 688, 12
https://tests.stockfishchess.org/tests/view/5fd631791ac169120188859e

STC:
LLR: 2.95 (-2.94,2.94) {-1.25,0.25}
Total: 36504 W: 3380 L: 3313 D: 29811 Elo +0.64
Ptnml(0-2): 116, 2667, 12645, 2682, 142
https://tests.stockfishchess.org/tests/view/5fd5ed861ac1691201888569

closes https://github.com/official-stockfish/Stockfish/pull/3262

bench: 4018036
see source

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