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.

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 Mar 31 10:48:27 2019 +0200
Timestamp: 1554022107

Replace std::mins/max with clamp function (#2062)

Adding a clamp function makes some of these range limitations a bit prettier and removes some #include's.

STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 28117 W: 6300 L: 6191 D: 15626 Elo +1.35
http://tests.stockfishchess.org/tests/view/5c9aa1df0ebc5925cfff8fcc

Non functional change.
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 Mar 31 10:44:55 2019 +0200
Timestamp: 1554021895

Remove duplication. (#2068)

always use the implementation of gives_check in position, no need to
hand-inline part of the implementation in search.

LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 57895 W: 12632 L: 12582 D: 32681 Elo +0.30
http://tests.stockfishchess.org/tests/view/5c9eaa4b0ebc5925cfffc9e3

No functional change.
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 Mar 31 10:43:20 2019 +0200
Timestamp: 1554021800

Accessor for SquareBB #2067

This is a non-functional code style change.

If we add an accessor function for SquareBB we can consolidate all of the asserts. This is also a bit cleaner because all SquareBB accesses go through this method making future changes easier to manage.

STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 63406 W: 14084 L: 14045 D: 35277 Elo +0.21
http://tests.stockfishchess.org/tests/view/5c9ea6100ebc5925cfffc9af

No functional change.
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 Mar 24 17:41:25 2019 +0100
Timestamp: 1553445685

Simplify pawn asymmetry (remove use of semiopen files). (#2054)

This is a functional simplification.

To me, the exclusive OR of semiopenFiles here is quite convoluted. Looks like it can be removed.

STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 43885 W: 9731 L: 9653 D: 24501 Elo +0.62
http://tests.stockfishchess.org/tests/view/5c9041680ebc5925cfff10ea

LTC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 68437 W: 11577 L: 11533 D: 45327 Elo +0.22
http://tests.stockfishchess.org/tests/view/5c9101740ebc5925cfff1cbf

bench 3575627
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 Mar 24 17:40:29 2019 +0100
Timestamp: 1553445629

Remove unneeded condition. (#2057)

This is covered by the line just before. If we would like to protect
against the piece value of e.g. a N == B, this could be done by an
assert, no need to do this at runtime.

No functional change.
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 Mar 24 17:37:38 2019 +0100
Timestamp: 1553445458

Simplify Passed Pawns (#2058)

This is a non-functional simplification/speedup.

The truth-table for popcount(support) >= popcount(lever) - 1 is:
------------------lever
------------------0-------1---------2
support--0------X-------X---------0
-----------1------X-------X---------X
-----------2------X-------X---------X

Thus, it is functionally equivalent to just do: support || !more_than_one(lever) which removes the expensive popcounts and the -1.

Result of 20 runs:
base (...h_master.exe) = 1451680 +/- 8202
test (./stockfish ) = 1454781 +/- 8604
diff = +3101 +/- 931

STC
LLR: 2.94 (-2.94,2.94) [-3.00,1.00]
Total: 35424 W: 7768 L: 7674 D: 19982 Elo +0.92
Http://tests.stockfishchess.org/tests/view/5c970f170ebc5925cfff5e28

No functional change.
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: Wed Mar 20 14:57:34 2019 +0100
Timestamp: 1553090254

Remove !extension check #2045

While looking at pruning using see_ge() (which is very valuable)
it became apparent that the !extension test is not adding any
value - simplify it away.

STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 56843 W: 12621 L: 12569 D: 31653 Elo +0.32
http://tests.stockfishchess.org/tests/view/5c8588cb0ebc5925cffe77f4

LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 78622 W: 13223 L: 13195 D: 52204 Elo +0.12
http://tests.stockfishchess.org/tests/view/5c8611cc0ebc5925cffe7f86

Further work could be to optimize the remaining see_ge() test. The idea of less pruning at higher depths is valuable, but perhaps the test (-PawnValueEg * depth) can be improved.

Bench: 3188688
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: CoffeeOne
Date: Wed Mar 20 14:50:41 2019 +0100
Timestamp: 1553089841

Skip skipping thread scheme (#1972)


Several simplification tests (all with the bounds [-3,1]) were run:
5+0.05 8 threads, failed very quickly:
http://tests.stockfishchess.org/tests/view/5c439a020ebc5902bb5d3970

20+0.2 8 threads, also failed, but needed a lot more games:
http://tests.stockfishchess.org/tests/view/5c44b1b70ebc5902bb5d4e34

60+0.6 8 threads passed:
http://tests.stockfishchess.org/tests/view/5c48bfe40ebc5902bca15325

60+0.6 4 threads passed:
http://tests.stockfishchess.org/tests/view/5c4b71a00ebc593af5d49904

No functional change.
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: Marco Costalba
Date: Tue Mar 12 08:35:10 2019 +0100
Timestamp: 1552376110

Increase thread stack for OS X (#2035)

On OS X threads other than the main thread are created with a reduced stack
size of 512KB by default, this is dangerously low for deep searches, so
adjust it to TH_STACK_SIZE. The implementation calls pthread_create() with
proper stack size parameter.

Verified for no regression at STC enabling the patch on all platforms where
pthread is supported.

LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 50873 W: 9768 L: 9700 D: 31405 Elo +0.46

No functional change.
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 Mar 10 10:53:39 2019 +0100
Timestamp: 1552211619

Remove popcount16() (#2038)

This is a non-functional simplification / code-style change.

This popcount16 method does nothing but initialize the PopCnt16 arrays.

This can be done in a single bitset line, which is less lines and more clear. Performance for this code is moot.

No functional change.
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 10 10:47:42 2019 +0100
Timestamp: 1552211262

Simplify failedLow away #1986

FailedLow doesn't seem to add any value so remove it.

STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 43915 W: 9682 L: 9604 D: 24629 Elo +0.62
http://tests.stockfishchess.org/tests/view/5c5339770ebc592fc7baef74

LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 58515 W: 9670 L: 9609 D: 39236 Elo +0.36
http://tests.stockfishchess.org/tests/view/5c53cc840ebc592fc7baf6c1

Ideas for further work:

Tune the values in the revised fallingEval calculation
Consider adding a term using delta, e.g. c * (delta - 20) as an indicator of eval instability

Bench: 3318033
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: Marco Costalba
Date: Sat Mar 9 13:28:11 2019 +0100
Timestamp: 1552134491

Revert "Allowing singular extension in mate positions"

It was causing an assert: value > -VALUE_INFINITE
under some conditions.

See https://github.com/official-stockfish/Stockfish/issues/2036

Bench: 3318033
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: Tue Mar 5 20:48:29 2019 +0100
Timestamp: 1551815309

Remove FutilityMoveCounts array. (#2024)

This is a functional simplification that removes the FutilityMoveCounts array with a simple equation using only ints.

LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 14175 W: 3123 L: 2987 D: 8065 Elo +3.33

LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 9900 W: 1735 L: 1597 D: 6568 Elo +4.84

Bench: 3380343

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: Tue Mar 5 19:02:04 2019 +0100
Timestamp: 1551808924

Shrink Reductions[] array to one dimension

This is a non-functional patch which shrinks the reductions array.
This saves about 8Kb of memory.

The only slow part of master's reductions array is the calculation
of the log values, so using a separate array for those values and
calculating the rest real-time appears to be just as fast as master.

STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 63245 W: 13906 L: 13866 D: 35473 Elo +0.22
http://tests.stockfishchess.org/tests/view/5c7b571f0ebc5925cffdc104

No funcional change.
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: SFisGOD
Date: Tue Mar 5 14:54:25 2019 +0100
Timestamp: 1551794065

Pawn value tweak

STC:
LLR: 2.96 (-2.94,2.94) [0.00,4.00]
Total: 47166 W: 10664 L: 10311 D: 26191 Elo +2.60
http://tests.stockfishchess.org/tests/view/5c7dfc370ebc5925cffdf830

LTC:
LLR: 2.95 (-2.94,2.94) [0.00,4.00]
Total: 35439 W: 6034 L: 5767 D: 23638 Elo +2.62
http://tests.stockfishchess.org/tests/view/5c7e41020ebc5925cffdfe9b

Bench: 3470519
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: Marco Costalba
Date: Tue Mar 5 11:13:02 2019 +0100
Timestamp: 1551780782

Assorted trivial cleanups 2/2019

No functional change.
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 5 11:10:10 2019 +0100
Timestamp: 1551780610

Add continuation history 5

Original patch passed STC:
http://tests.stockfishchess.org/tests/view/5c7439ff0ebc5925cffd3e64
LLR: 2.95 (-2.94,2.94) [0.50,4.50]
Total: 26348 W: 5926 L: 5632 D: 14790 Elo +3.88

and LTC:
http://tests.stockfishchess.org/tests/view/5c745a8b0ebc5925cffd41a8
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 198411 W: 33238 L: 32510 D: 132663 Elo +1.27

But had undefined behavior.
After fixing (thx to @vondele )

passed LTC:
http://tests.stockfishchess.org/tests/view/5c763c7c0ebc5925cffd5de2
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 112253 W: 18711 L: 18225 D: 75317 Elo +1.50

bench 3049229
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 27 13:36:48 2019 +0100
Timestamp: 1551271008

Remove skipQuiets with mate fix. (#2021)

This removes the skipQuiets variable, as was done in an earlier round by
@protonspring, but fixes an oversight which led to wrong mate
announcements. Quiets can only be pruned when there is no mate score, so
set moveCountPruning at the right spot.

tested as a fix at STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 66321 W: 14690 L: 14657 D: 36974 Elo +0.17
http://tests.stockfishchess.org/tests/view/5c74f3170ebc5925cffd4b3c

and as the full patch at LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 25903 W: 4341 L: 4228 D: 17334 Elo +1.52
http://tests.stockfishchess.org/tests/view/5c7540030ebc5925cffd506f

Bench: 3292342
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: Marco Costalba
Date: Tue Feb 26 13:23:09 2019 +0100
Timestamp: 1551183789

Revert "Remove skipQuiets variable in search()"

This reverts commit 76d2f5b94a0df20d84ccf922bd1c0fcf1c779090.

Due to a bug, see https://github.com/official-stockfish/Stockfish/issues/2019

Bench: 3516616
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: Kurtbusch
Date: Thu Feb 21 19:53:03 2019 +0100
Timestamp: 1550775183

Add KNNvKP Endgame Heuristic

This is a somewhat different patch. It fixes blindspots for
two knights vs pawn endgame.

With local testing starting from random KNNvKP positions where the
pawn has not advanced beyond the 4th rank (thanks @protonspring !)
at 15+0.15 (4 cores), this went +105=868-27 against master. All except
two losses were won in reverse.

The heuristic is simple but effective - the strategy in these endgames
is to push the opposing king to the corner, then move the knight that's
blocking the pawn in for the checkmate while the pawn is free to move
and prevents stalemate. This patch gives SF the little boost it needs
to search the relevant king-cornering mating lines.

See the discussion in pull request 1939 for some more good results for
this test in independant tests:
https://github.com/official-stockfish/Stockfish/pull/1939

Bench: 3310239
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: MJZ1977
Date: Thu Feb 21 19:36:48 2019 +0100
Timestamp: 1550774208

ProbCutCount limit dependancy to cutNode

Use the ProbCutCount limit `2 + 2 * cutNode` instead of constant 3.

STC
LLR: -2.95 (-2.94,2.94) [0.50,4.50]
Total: 61812 W: 13599 L: 13459 D: 34754 Elo +0.79
http://tests.stockfishchess.org/tests/view/5c6d19240ebc5925cffca07a

LTC
LLR: 2.96 (-2.94,2.94) [0.00,3.50]
Total: 27549 W: 4614 L: 4363 D: 18572 Elo +3.17
http://tests.stockfishchess.org/tests/view/5c6d45c10ebc5925cffca7a6

Closes https://github.com/official-stockfish/Stockfish/pull/2015

Bench: 3368889
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 Feb 21 19:24:02 2019 +0100
Timestamp: 1550773442

Remove PvNode dimension from Reductions array

This is a functional simplification: if we simply subtract one to Reductions[]
when PvNode is set, we can remove this dimension of the multidimensional array.
I think this saves about 8K of memory.

STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 10118 W: 2282 L: 2138 D: 5698 Elo +4.95
http://tests.stockfishchess.org/tests/view/5c6332b60ebc5925cffbdfed

LTC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 70765 W: 11617 L: 11575 D: 47573 Elo +0.21
http://tests.stockfishchess.org/tests/view/5c63379e0ebc5925cffbe0de

Closes https://github.com/official-stockfish/Stockfish/pull/2010

Bench 3261078
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 Feb 21 19:18:02 2019 +0100
Timestamp: 1550773082

Remove skipQuiets variable in search()

This is a functional simplification. The moveCountPruning variable and the
skipQuiets variable are similar enough in function that they can be combined.
This removes the skipQuiets variable in search.

STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 23278 W: 5210 L: 5091 D: 12977 Elo +1.78
http://tests.stockfishchess.org/tests/view/5c65dc490ebc5925cffc12e9

LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 77107 W: 12792 L: 12761 D: 51554 Elo +0.14
http://tests.stockfishchess.org/tests/view/5c65e4360ebc5925cffc1490

Closes https://github.com/official-stockfish/Stockfish/pull/2011

bench 3640330
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: Fri Feb 8 10:31:28 2019 +0100
Timestamp: 1549618288

Change outposts to single value #1946

This is a functional simplification of the Outposts array
moving it to a single value. This is a duplicate PR because
I couldn't figure out how to fix the original one.

The idea is from @31m059 with formatting recommendations by @snicolet.

See #1940 for additional information.

STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 23933 W: 5279 L: 5162 D: 13492 Elo +1.70
http://tests.stockfishchess.org/tests/view/5c3575800ebc596a450c5ecb

LTC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 41718 W: 6919 L: 6831 D: 27968 Elo +0.73
http://tests.stockfishchess.org/tests/view/5c358c440ebc596a450c6117

bench 3783543
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: Marco Costalba
Date: Fri Feb 8 10:20:43 2019 +0100
Timestamp: 1549617643

Assorted trivial cleanups 1/2019

To address #1862

No functional change.

< prev page next page >