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.

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Linux x64
Author: noobpwnftw
Date: Mon Dec 24 11:24:29 2018 +0100
Timestamp: 1545647069

Simplify SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX loop (#1892)

When iterating through 'SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX' structure, do not use structure member beyond known size.

API is guaranteed to provide us at lease one element upon successful, and no element in the structure can have a zero size.

No functional change.
Windows x64 for Haswell CPUs
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Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: noobpwnftw
Date: Mon Dec 24 11:20:14 2018 +0100
Timestamp: 1545646814

Fix crash in best_group() (#1891)

This pull request fixes a rare crashing bug on Windows inside our NUMA code, first
reported by Dann Corbit in the following forum thread (thanks!):
https://groups.google.com/forum/?fromgroups=#!topic/fishcooking/gA6aoMEuOwg

The fix is to not use structure member beyond known size when iterating through
'SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX' structure. We note that the Microsoft
API is guaranteed to provide us at least one element upon successful, and no
element in the structure can have a zero size.

No functional change.
Windows x64 for Haswell CPUs
Windows x64 for modern computers
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Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Joost VandeVondele
Date: Mon Dec 24 11:06:47 2018 +0100
Timestamp: 1545646007

Extend stack to ss-5, and remove conditions

The `&& (ss-1)->killers[0] ` conditions are there seemingly to protect
accessing ss-5.

This is unneeded and not so intuitive (as the killer is checked for equality
with currentMove, and that one is non-zero once we're high enough in the stack,
this protects access to ss-5). We can just extend the stack from ss-4 to ss-5,
so we can call update_continuation_histories(ss-1, ..) always in search.

This goes a bit further than #1881 and addresses a comment in #1878.

passed STC:
http://tests.stockfishchess.org/tests/view/5c1aa8d50ebc5902ba127ad0
LLR: 3.12 (-2.94,2.94) [-3.00,1.00]
Total: 53515 W: 11734 L: 11666 D: 30115 Elo +0.44

passed LTC:
http://tests.stockfishchess.org/tests/view/5c1b272c0ebc5902ba12858d
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 140176 W: 23123 L: 23192 D: 93861 Elo -0.17

Bench: 3451321
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: Mon Dec 24 10:44:38 2018 +0100
Timestamp: 1545644678

Improve endgame KBN vs K (#1877)

Even when playing without endgame table bases, this particular endgame should
be a win 100% of the time when Stockfish is given a KRBK position, assuming
there are enough moves remaining in the FEN to finish the game without hitting
the 50 move rule.

PROBLEM: The issue with master here is that the PushClose difference per square
is 20, however, the difference in squares for the PushToCorners array is usually
less. Thus, the engine prefers to move the kings closer together rather than pushing
the weak king to the correct corner.

What happens is if the weak king is in a safe corner, SF still prefers pushing the
kings together. Occasionally, the strong king traps the weak king in the safe corner.
It takes a while for SF to figure it out, but often draws the game by the 50 move rule
(on shorter time controls).

This patch increases the PushToCorners values to correct this problem. We also added
an assert to catch any overflow problem if anybody would want to increase the array
values again in the future.

It was tested in a couple of matches starting with random KRBK positions and showed
increased winning rates, see https://github.com/official-stockfish/Stockfish/pull/1877

No functional change
Windows x64 for Haswell CPUs
Windows x64 for modern computers
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Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: erbsenzaehler
Date: Sun Dec 23 18:17:44 2018 +0100
Timestamp: 1545585464

Update our continuous integration machinery (#1889)

* Update our continuous integration machinery

Ubuntu 16.04 can now be used with travis. Updating all the other stuff
when there.
Invoking the lld linker seems to save 5 minutes with clang on linux.

No functional change.

* fix
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Linux x64
Author: mstembera
Date: Sun Dec 23 16:10:07 2018 +0100
Timestamp: 1545577807

Use a bit less code to calculate hashfull() (#1830)

* Use a bit less code to calculate hashfull(). Change post increment to preincrement as is more standard
in the rest of stockfish. Scale result so we report 100% instead of 99.9% when completely full.

No functional change.
Windows x64 for Haswell CPUs
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Linux x64 for modern computers
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Author: mstembera
Date: Sun Dec 23 16:09:03 2018 +0100
Timestamp: 1545577743

Turn on random access for Syzygy files in Windows (#1840)

* This is the Windows version of
https://github.com/official-stockfish/Stockfish/pull/1829

No functional change.

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Author: protonspring
Date: Sun Dec 23 16:05:24 2018 +0100
Timestamp: 1545577524

Simplify generate_castling (#1885)

Although this is a compile-time constant, we stick the castlingSide into a CastlingRight, then pull it out again. This seems unecessarily complex.

No functional change.
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Linux x64
Author: protonspring
Date: Thu Dec 20 10:47:18 2018 +0100
Timestamp: 1545299238

Simplify KBNK endgame implementation

We do not need to change the winnerKSq variable, so we can simplify
a little bit the logic of the code by changing only the loserKSq
variable when it is necessary. Also consolidate and clarify comments.

See the pull request thread for a proof that the code is correct:
https://github.com/official-stockfish/Stockfish/pull/1854

No functional change
Windows x64 for Haswell CPUs
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Linux x64
Author: Guenther Demetz
Date: Tue Dec 18 09:38:06 2018 +0100
Timestamp: 1545122286

Tweak main killer penalty

Apply refuted main killer penalty also on early TT cut-offs. This
makes penalty logic more consistent with the logic at normal search.

Failed STC:
http://tests.stockfishchess.org/tests/view/5c121e730ebc5902ba11aad8
LLR: -2.95 (-2.94,2.94) [0.00,5.00]
Total: 72193 W: 15848 L: 15625 D: 40720 Elo +1.07

Passed LTC:
http://tests.stockfishchess.org/tests/view/5c17b1b10ebc5902ba123c24
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 35073 W: 5886 L: 5625 D: 23562 Elo +2.59

Closes https://github.com/official-stockfish/Stockfish/pull/1878

bench: 3393939
Windows x64 for Haswell CPUs
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Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: mstembera
Date: Tue Dec 18 08:51:25 2018 +0100
Timestamp: 1545119485

New voting formula for threads

We now use a quadratic formula during the vote for threads
when deciding on which thread to pick a move from.

time control 5+0.05, with 8 threads:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 20202 W: 4031 L: 3813 D: 12358 Elo +3.75
http://tests.stockfishchess.org/tests/view/5c16c8e60ebc5902ba1223e2

time control 20+0.2, with 8 threads:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 14330 W: 2290 L: 2115 D: 9925 Elo +4.24
http://tests.stockfishchess.org/tests/view/5c16efca0ebc5902ba122993

20000 games match at time control 5+0.05, with 31 threads:
ELO: 5.63 +-2.8 (95%) LOS: 100.0%
Total: 20000 W: 3539 L: 3215 D: 13246 Elo +5.63
http://tests.stockfishchess.org/tests/view/5c16f07a0ebc5902ba122a20

Closes https://github.com/official-stockfish/Stockfish/pull/1876

No functional change (in simple thread mode)
Windows x64 for Haswell CPUs
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Linux x64
Author: 31m059
Date: Sun Dec 16 10:04:49 2018 +0100
Timestamp: 1544951089

Use stronglyProtected

~stronglyProtected is quite similar to ~attackedBy[Them][PAWN] & ~attackedBy2[Them],
the only difference appears to be that the former includes squares attacked twice
by both sides. The resulting logic is simpler, and the change appears to be at least
Elo-neutral at both STC and LTC.

STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 35924 W: 7978 L: 7885 D: 20061 Elo +0.90
http://tests.stockfishchess.org/tests/view/5c14a5c00ebc5902ba11ed72

LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 37078 W: 6125 L: 6030 D: 24923 Elo +0.89
http://tests.stockfishchess.org/tests/view/5c14ae880ebc5902ba11eed8

Bench: 3646542
Windows x64 for Haswell CPUs
Windows x64 for modern computers
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Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Alain SAVARD
Date: Sun Dec 16 09:57:43 2018 +0100
Timestamp: 1544950663

Refactor king ring calculation

Compute the "double protection by pawns" expression only once
in initialize(), instead of once for each piece in the piece loop.

Passed STC
http://tests.stockfishchess.org/tests/view/5c1506380ebc5902ba11f3b4
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 9494 W: 2191 L: 2045 D: 5258 Elo +5.34

Inspired by Nick Pelling's test
http://tests.stockfishchess.org/tests/view/5c144d110ebc5902ba11e4af
and an older test of mine
http://tests.stockfishchess.org/tests/view/5c0402810ebc5902bcee1fc8

Non functional change.
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Linux x64
Author: Joost VandeVondele
Date: Sun Dec 16 09:53:11 2018 +0100
Timestamp: 1544950391

Fix a segfault.

this patch fixes a rare but reproducible segfault observed playing a
multi-threaded match, it is discussed somewhat in fishcooking.

From the core file, it could be observed that the issue was in qsearch, namely:

````
ss->pv[0] = MOVE_NONE;
````

and the backtrace shows the it arrives there via razoring, called from the rootNode:

````
(gdb) bt
alpha=-19, beta=682, depth=DEPTH_ZERO) at search.cpp:1247
````

Indeed, ss->pv can indeed by a nullptr at the rootNode. However, why is the
segfault so rare ?

The reason is that the condition that guards razoring:

````
(depth < 2 * ONE_PLY && eval <= alpha - RazorMargin)
````

is almost never true, since at the root alpha for depth < 5 is -VALUE_INFINITE.

Nevertheless with the new failHigh scheme, this is not guaranteed, and rootDepth > 5,
can still result in a depth < 2 search at the rootNode. If now another thread,
via the hash, writes a new low eval to the rootPos qsearch can be entered.
Rare but not unseen... I assume that some of the crashes in fishtest recently
might be due to this.

Closes https://github.com/official-stockfish/Stockfish/pull/1860

No functional change
Windows x64 for Haswell CPUs
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Linux x64
Author: Joost VandeVondele
Date: Sun Dec 16 09:41:09 2018 +0100
Timestamp: 1544949669

Start a TT resize only after search finished.

As noticed in the forum, a crash in extract_ponder_from_tt could result
if hash size is set before the ponder move is printed. While it is arguably
a GUI issue (but it got me on the cli), it is easy to avoid this issue.

Closes https://github.com/official-stockfish/Stockfish/pull/1856

No functional change.
Windows x64 for Haswell CPUs
Windows x64 for modern computers
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Linux x64
Author: 31m059
Date: Sun Dec 16 09:32:37 2018 +0100
Timestamp: 1544949157

Remove Null Move Pruning material threshold

On November 30th, @xoto10 experimented with removing this threshold,
but the simplification barely failed LTC. I was inspired to try various
[0, 4] tweaks to increase its value, which would narrow the effects of
this threshold without removing it entirely. Various values repeatedly
led to Elo gains at both STC and LTC, most of which were insufficient
to pass.

After a couple of weeks, I tried again to find an Elo-gaining tweak
but noticed that I could raise the threshold higher and higher without
regression. I decided to try removing it entirely--forgetting that
@xoto10 had already attempted this. However, this now performs much
better at both STC and LTC, producing a STC Elo gain and also potentially
a smaller LTC one.

The reason appears to be a recent change in master (e8ffca3) near
this code, which interacts with this patch. This simplification
governs the conditions under which that patch's effects are applied.
Something non-obvious about that change has significantly improved
the performance of this simplification.

I recognize and thank @xoto10, who originally had this idea. Since
I ran several LTCs recently (to determine whether to open this PR,
or one for a related [0, 4]), I would also like to acknowledge the
other developers and CPU donors for their patience. Thank you all!

STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 13445 W: 3000 L: 2862 D: 7583 Elo +3.57
http://tests.stockfishchess.org/tests/view/5c11f01b0ebc5902ba11a6b8

LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 33868 W: 5663 L: 5563 D: 22642 Elo +1.03
http://tests.stockfishchess.org/tests/view/5c11ffe90ebc5902ba11a8a9

Closes https://github.com/official-stockfish/Stockfish/pull/1870

Bench: 3343286
Windows x64 for Haswell CPUs
Windows x64 for modern computers
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Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: SFisGOD
Date: Thu Dec 13 13:35:35 2018 +0100
Timestamp: 1544704535

A combo of parameter tweaks

Joint work by SFisGOD, xoroshiro and Chess13234.

This combo consists of the following tweaks:
Assorted bonuses and penalties by SFisGOD
Bishop and Rook PSQT by SFisGOD
Tempo Value by xoroshiro
Futility pruning by Chess13234

STC:
LLR: 2.95 (-2.94,2.94) [0.00,4.00]
Total: 9005 W: 2082 L: 1882 D: 5041 Elo +7.72
http://tests.stockfishchess.org/tests/view/5c11628c0ebc5902ba119e90

LTC:
LLR: 2.95 (-2.94,2.94) [0.00,4.00]
Total: 44207 W: 7451 L: 7157 D: 29599 Elo +2.31
http://tests.stockfishchess.org/tests/view/5c1172a40ebc5902ba119fa3

Bench: 3332460
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: Kurt
Date: Thu Dec 13 13:20:31 2018 +0100
Timestamp: 1544703631

Asymmetrical 8x8 Pawn PSQT

STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 13323 W: 3015 L: 2818 D: 7490 Elo +5.14
http://tests.stockfishchess.org/tests/view/5c00a2520ebc5902bcedd41b

LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 52294 W: 9093 L: 8756 D:34445
http://tests.stockfishchess.org/tests/view/5c00b2c40ebc5902bcedd596

Some obvious followups to this are to further tune this PSQT, or
try 8x8 for other pieces. As of now I don't plan on trying this
for other pieces as I think the majority of the ELO it brings is
for pawns and kings.

Looking at the new values, the differences between kingside and
queenside are quite significant. I am very hopeful that this a
llows SF to understand and plan pawn structures even better than
it already does. Cheers!

Closes https://github.com/official-stockfish/Stockfish/pull/1839

Bench: 3569243
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 Dec 11 13:47:56 2018 +0100
Timestamp: 1544532476

Changes identified in RENAME/REFORMATTING thread (#1861)

I've gone through the RENAME/REFORMATTING thread and changed everything I could find, plus a few more. With this, let's close the previous issue and open another.

No functional change.

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Linux x64
Author: VoyagerOne
Date: Sun Dec 9 13:11:13 2018 +0100
Timestamp: 1544357473

Tweak CMH pruning

STC: (yellow)
LLR: -2.94 (-2.94,2.94) [0.00,5.00]
Total: 48919 W: 10625 L: 10517 D: 27777 Elo +0.77
http://tests.stockfishchess.org/tests/view/5c07e6a20ebc5902bcee7395

LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 50360 W: 8424 L: 8102 D: 33834 Elo +2.22
http://tests.stockfishchess.org/tests/view/5c0812450ebc5902bcee76f4

Bench: 3775064
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 Dec 9 12:59:57 2018 +0100
Timestamp: 1544356797

remove extra line.
Windows x64 for Haswell CPUs
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Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: protonspring
Date: Sun Dec 9 12:59:57 2018 +0100
Timestamp: 1544356797

remove parenthesis.
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Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: protonspring
Date: Sun Dec 9 12:59:57 2018 +0100
Timestamp: 1544356797

add paren.
Windows x64 for Haswell CPUs
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Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: protonspring
Date: Sun Dec 9 12:59:57 2018 +0100
Timestamp: 1544356797

simplify opposite_colors
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Linux x64
Author: Stéphane Nicolet
Date: Thu Dec 6 15:04:04 2018 +0100
Timestamp: 1544105044

Revert "pseudo_legal() and MOVE_NONE"

This reverts commit 33d95482182e459eb033de47a31f142880aa9afb ,
which crashed in DEBUG mode because of the following assert in position.h

````
Assertion failed: (is_ok(m)), function capture, file ./position.h, line 369.
````

No functional change

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