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 5.3.1/mingw 5.3.1 on Ubuntu 16.04.
2.Jan.2016: BMI build now slightly faster due to profiling.
Development builds for OS X are available at stockfishchess.de
Read the FAQ or leave a comment.

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!! latest version !!


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: Sun Sep 25 10:45:10 2016 +0200
Timestamp: 1474793110

Rename shift_bb() to shift()

Rename shift_bb() to shift(), and DELTA_S to SOUTH, etc.
to improve code readability, especially in evaluate.cpp
when they are used together:

old b = shift_bb<DELTA_S>(pos.pieces(PAWN))
new b = shift<SOUTH>(pos.pieces(PAWN))

While there fix some small code style issues.

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: joergoster
Date: Sat Sep 24 19:56:02 2016 +0200
Timestamp: 1474739762

Allowing singular extension in mate positions

Drop useless condition

abs(ttValue) < VALUE_KNOWN_WIN

And extend singular extension search to cases when ttValue
stores a mate score. This improves mate finding and does
not introduce any regression.

Yery tested this patch against current master on the 6500+
Chest mate suite with 200K fixed nodes:

shortest mates found: master: 1206 patch:1205
any mate found: master: 1903 patch: 2003

with 1 sec time:

shortest mates found: master: 2667 patch: 2628
any mate found: master: 3585 patch: 3646

Verified for no regression:

STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 25655 W: 4578 L: 4465 D: 16612

LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 66247 W: 8618 L: 8557 D: 49072

bench: 6335042
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 Sep 24 07:37:52 2016 +0200
Timestamp: 1474695472

Fix crash when passing a mate/stalemate position

Both Tablebases::filter_root_moves() and
extract_ponder_from_tt(9 were unable to handle
a mate/stalemate position.

Spotted and reported by Dann Corbit.

Added some mate/stalemate positions to bench so
to early catch this regression in the future.

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: Stéphane Nicolet
Date: Thu Sep 22 08:31:23 2016 +0200
Timestamp: 1474525883

Simplify pinners conditions in SEE()

Use the following transformations:

- to check that A is included in B, testing "(A & ~B) == 0" is faster
than "(A & B) == A"

- to remove the intersection of A and B from A, doing "A &= ~B;" is as
fast as "if (A & B) A &= ~B;" but is simpler.

Overall, the simpler patch version is 0.3% than current master.

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: Guenther Demetz
Date: Wed Sep 21 08:42:25 2016 +0200
Timestamp: 1474440145

Fix pin-aware SEE

Correct pinners calculation and fix bug with pinned
pieces giving check. With this patch 'pinners' only
returns sliders with exactly one defensive piece between
the slider and the attacked square (in other words, pinners
returns exact pinners).

This was a co-operation between Marco Costalba,


Special thanks to Ronald de Man for reporting the bug with
pinned pieces giving check, discussed here:
https://groups.google.com/forum/?fromgroups=#!topic/fishcooking/S_4E_Xs5HaE

STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 132118 W: 23578 L: 23645 D: 84895

LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 36424 W: 4770 L: 4670 D: 26984

bench: 6272231
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 Sep 18 08:13:34 2016 +0200
Timestamp: 1474179214

Use fixed depth bench to make PGO builds more reproducible

Discussed on fishcooking

proposal and objdump verification:
https://groups.google.com/d/msg/fishcooking/4_ausUwMXP0/EGPsMYqOFAAJ

verified no significant speed difference between depth and time:
https://groups.google.com/d/msg/fishcooking/4_ausUwMXP0/KazW5QZmFgAJ

stockfish_time - stats:
mean = 2207232.56 std = 7079.51 std/mean = 0.003207

stockfish_depth - stats:
mean = 2201783.57 std = 6356.69 std/mean = 0.002887

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: Sat Sep 17 10:14:28 2016 +0200
Timestamp: 1474100068

Fix a warning with MSVC

warning C4706: assignment within conditional expression

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: Stéphane Nicolet
Date: Sat Sep 17 09:56:36 2016 +0200
Timestamp: 1474098996

Swap mg and eg in internal representation of Score

Instrumentation shows that in make_score(mg, eg) calls, the mg value is
zero in 25,9% of the calls while the eg value is zero in 36,8% of the
calls.

Swapping the internal fields of mg and eg in the internal
representation of Score allows the compiler to optimize away the shift
in (eg << 16) + mg in more cases, thus resulting in a 0.3% speed-up
overall.

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: Sat Sep 17 09:51:20 2016 +0200
Timestamp: 1474098680

Fix indentation in struct FromToStats

And other little trivial stuff.

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: Stéphane Nicolet
Date: Fri Sep 16 08:30:06 2016 +0200
Timestamp: 1474007406

Retire KingDanger array

Rescales the king danger variables in evaluate_king() to
suppress the KingDanger[] array. This avoids the cost of
the memory accesses to the array and simplifies the non-linear
transformation used.

Full credits to "hxim" for the seminal idea and implementation,
see pull request #786.
https://github.com/official-stockfish/Stockfish/pull/786

Passed STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 9649 W: 1829 L: 1689 D: 6131

Passed LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 53494 W: 7254 L: 7178 D: 39062

Bench: 6116200
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 Sep 16 08:15:07 2016 +0200
Timestamp: 1474006507

Use per-thread counterMoveHistory

Drops a scalability bottleneck due to memory contention
of a single shared table across threads. The effect starts
to be sensible with a high number of threads. Specifically
we have a small regression with 7 threads both at 60 and
180 seconds TC:

10000 @ 60+0.6 th 7
ELO: -2.46 +-3.2 (95%) LOS: 6.5%
Total: 9896 W: 1037 L: 1107 D: 7752

5000 @ 180+0.6 th 7
ELO: -1.95 +-4.1 (95%) LOS: 17.7%
Total: 5000 W: 444 L: 472 D: 4084

We have a regression because counterMoveHistory table is
quite big and it takes time for a single thread to fill it.
Sharing the table yields to a higher fill rate and better
quality of moves and up to 7 threads the benefits of sharing
more then compensate the loss in speed due to contention.
Interestingly even with a 3X longer TC, so with more time
for the single thread to catch up, the improvment is quite
limited and below noise level. It seems we really need much
longer TC to saturate the table.

When we move to high threads number it's another story:

5000 @ 60+0.6 th 22
ELO: 3.49 +-4.3 (95%) LOS: 94.6%
Total: 4880 W: 490 L: 441 D: 3949

2000 @ 60+0.6 th 32
ELO: 8.34 +-6.9 (95%) LOS: 99.1%
Total: 2000 W: 229 L: 181 D: 1590

As expected the speed-up more than compensates the filling
rate, and we expect that with tournament TC, where single
thread is able to saturate the table, the difference will
be even stronger. For instance for TCEC 9 super-final time
control will be 180 minutes + 15 seconds and this scalability
improvement seems definitely the way to go.

So, summarizing:

GOOD:

Measured big improvement in high core scenario

Suitable for TCEC 9 superfinal (big hardware, very long TC)

Consistent and natural patch that extends to counterMoveHistory
what we already do for remaining history tables, that are all per-thread

Non functional change for the common case of a single core

Very simple (just 6 lines modified, no added ones)

BAD:

Small regression (within 2-3 ELO) with few threads and short TC

bench: 5341477
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: Thu Sep 15 09:07:49 2016 +0200
Timestamp: 1473923269

Renaming in MovePicker

Rename stages and simplify a bit the code.

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: Wed Sep 14 15:43:56 2016 +0200
Timestamp: 1473860636

Retire MovePicker::see_sign()

No more used after last patch.

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: VoyagerOne
Date: Wed Sep 14 15:38:38 2016 +0200
Timestamp: 1473860318

Tweak SEE margin in pruning conditions

Use 35 * depth^2 to calculate see_margin.

STC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 22636 W: 4212 L: 3990 D: 14434

LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 47241 W: 6314 L: 6041 D: 34886

The Movepick SEE is now dead code, retire it.

Bench: 5341477
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: syzygy
Date: Tue Sep 13 07:14:09 2016 +0200
Timestamp: 1473743649

Integrate next_stage() logic into next_move()

Measured bench speed up goes from 0,7% to 2%,
given the unreliable measure a reverse simmplification
test was done on fishtest:

master vs patch
LLR: -2.94 (-2.94,2.94) [-3.00,1.00]
Total: 15499 W: 2685 L: 2867 D: 9947

Test result is positive, master is weaker.

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: Guenther Demetz
Date: Mon Sep 12 15:45:00 2016 +0200
Timestamp: 1473687900

Simplify code for pinaware SEE

This is the most compact and neatest version
is was able to produce.

On normal builds I have a small slowdown:
normal builds base vs. simplification (gcc 4.8.1 Win7-64 i7-3770 @ 3.4GHz x86-64-modern)
Results for 20 tests for each version:

Base Test Diff
Mean 1974744 1969333 5411
StDev 11825 10281 5874
p-value: 0,178
speedup: -0,003

On pgo-builds however I measure a nice 1.1% speedup

pgo-builds base vs. simplification
Results for 20 tests for each version:

Base Test Diff
Mean 1974119 1995444 -21325
StDev 8703 5717 4623
p-value: 1
speedup: 0,011

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: Guenther Demetz
Date: Mon Sep 12 09:31:09 2016 +0200
Timestamp: 1473665469

Pinned aware SEE

Don't allow pinned pieces to attack the exchange-square as long all
pinners (this includes also potential ones) are on their original
square.
As soon a pinner moves to the exchange-square or get captured on it, we
fall back to standard SEE behaviour.

This correctly handles the majority of cases with absolute pins.

bench: 6883133
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: Stefano Cardanobile
Date: Sun Sep 11 07:42:12 2016 +0200
Timestamp: 1473572532

Reorder evaluation start

In evaluate, we start by initializing the pos.psq_score
and adding the material imbalance. After that, we check
whether a specialized eval exists and if yes we return
that value and discard whatever we have computed until now.

It sounds more logical to first probe material entry and
return if we have a specialized eval, and only if it is
not the case initialize eval with some values. There is
no measurable speed-difference on my computer.

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: Marco Costalba
Date: Fri Sep 9 17:11:54 2016 +0200
Timestamp: 1473433914

Use Movepick SEE value in search

This halves the calls to the costly pos.see_sign(),
speed up is about 1-1.3%

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: Marco Costalba
Date: Thu Sep 8 06:02:42 2016 +0200
Timestamp: 1473307362

Refactor previous patch

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: ajithcj
Date: Thu Sep 8 05:55:10 2016 +0200
Timestamp: 1473306910

Prune dangerous moves at low depth

At very low depths prune captures,
promotions and checks if see is negative.

STC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 6772 W: 1328 L: 1173 D: 4271

LTC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 8917 W: 1270 L: 1122 D: 6525

bench: 6024713
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: Sun Sep 4 15:33:17 2016 +0200
Timestamp: 1472995997

Syntactic sugar to loop across pieces

Also add some comments to the new operator~(Piece).

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: syzygy
Date: Sun Sep 4 09:22:09 2016 +0200
Timestamp: 1472973729

Change from [Color][PieceType] to [Piece]

Speed up of almost 1% in both normal and
pgo builds.

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: Sat Sep 3 08:21:05 2016 +0200
Timestamp: 1472883665

Fix syzygy with partial TB

In case we have installed a not complete set of 6-men tables and
there is 6 piece position on board, but no corresponding
tablebase engine is not using any syzygy at all.

Reported by Jouni Uski, fix by Peter Österlund,
confirmed as a bug by Ronald de Man.

bench: 7591630
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 Sep 3 00:04:20 2016 +0200
Timestamp: 1472853860

Space bonus in presence of open files

If the opponent has a cramped position, opening a file often
helps him/her to exchange pieces, so it makes sense to reduce
the space bonus if there are open files.

Credits: Leonardo Ljubičić for the strategic idea, Alain Savard for the
implementation of the open files calculation, "CrunchyNYC" for the
compensation of the numerator.

STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 49112 W: 9239 L: 8900 D: 30973

LTC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 89415 W: 12014 L: 11601 D: 65800

Bench: 7591630

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