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.
Read the FAQ or leave a comment.

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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 May 28 14:57:58 2016 +0200
Timestamp: 1464440278

Pins or discovered attacks on the opponent's queen

Bonus for pins or discovered attacks on the opponent's queen

STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 32020 W: 5914 L: 5652 D: 20454

LTC:
LLR: 2.97 (-2.94,2.94) [0.00,5.00]
Total: 10946 W: 1530 L: 1375 D: 8041

Bench: 7031649
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 May 28 14:52:21 2016 +0200
Timestamp: 1464439941

Teach check_blockers to check also non-king pieces

This is a prerequisite for next 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: Stéphane Nicolet
Date: Thu May 26 12:33:44 2016 +0200
Timestamp: 1464258824

Simplify doubled pawn

Only use doubled pawn malus when the doubled pawns are on consecutive squares.

Passed STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 7678 W: 1469 L: 1325 D: 4884

And LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 26739 W: 3562 L: 3449 D: 19728

Bench: 8211685
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: Leonid Pechenik
Date: Fri May 20 19:44:50 2016 +0200
Timestamp: 1463766290

More detailed dependence of time allocation on the magnitude of score change

10+0.1:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 5657 W: 1130 L: 979 D: 3548

60+0.6:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 36884 W: 5002 L: 4762 D: 27120

bench: 8428997
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: loco-loco
Date: Fri May 20 19:34:49 2016 +0200
Timestamp: 1463765689

Assorted pruning tweaks

LTC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 38257 W: 5206 L: 4961 D: 28090

STC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 16550 W: 3110 L: 2914 D: 10526

Bench: 8428997
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: mstembera
Date: Sat May 14 21:34:55 2016 +0200
Timestamp: 1463254495

Fix a multiPV bug in lazy SMP

Where the helper threads were not doing multiPV at all.

Regression tested sprt @ 5+0.05 th 7

LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 73918 W: 11891 L: 11853 D: 50174

bench: 8716243
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 May 13 13:01:59 2016 +0200
Timestamp: 1463137319

Double pawn simplification

Try doubled pawn simplification, with psq
table compensation.

STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 36094 W: 6558 L: 6463 D: 23073

LTC:
LLR: 2.94 (-2.94,2.94) [-3.00,1.00]
Total: 102352 W: 13417 L: 13404 D: 75531

Bench: 8716243
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: loco-loco
Date: Tue May 10 18:15:16 2016 +0200
Timestamp: 1462896916

Merge good and bad quiets

STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 58613 W: 10779 L: 10723 D: 37111

LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 33608 W: 4539 L: 4436 D: 24633

Bench: 9441294
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: Fri May 6 20:04:57 2016 +0200
Timestamp: 1462557897

Unsafe checks

Introducing a new multi-purpose penalty related to King safety, which
includes all kind of potential checks (from unsafe or unavailable
squares currently occupied by some other piece)

This will indirectly detect and reward some pins, discovered checks, and
motifs such as square vacation, or rook behind its pawn and aligned with
King (example Black Rg8, g7 against Kg1),
and penalize some pawn blockers (if they move, it allows a discovered
check by the pawn).

And since it looks also at protected squares, it detects some potential
defense overloading.

Finally, the rook contact checks had been removed some time ago. This
test will give a small bonus for them, as well as for bishop contact
checks.

Passed STC
http://tests.stockfishchess.org/tests/view/5729ec740ebc59301a354b36
LLR: 2.94 (-2.94,2.94) [0.00,5.00]
Total: 13306 W: 2477 L: 2296 D: 8533

and LTC
http://tests.stockfishchess.org/tests/view/572a5be00ebc59301a354b65
LLR: 2.97 (-2.94,2.94) [0.00,5.00]
Total: 20369 W: 2750 L: 2565 D: 15054

bench: 9298175
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 May 5 09:09:07 2016 +0200
Timestamp: 1462432147

Retire __popcnt64 intrinsic

Just use _mm_popcnt_u64() that is available
both for MSVC abd Intel compiler.

Verified on MSVC that the produced assembly
has the hardware 'popcnt' instruction.

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: Thu May 5 08:53:50 2016 +0200
Timestamp: 1462431230

Simplify History LMR Formula

STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 41713 W: 7589 L: 7504 D: 26620

LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 41353 W: 5484 L: 5391 D: 30478

Bench: 8946983
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 May 1 15:10:33 2016 +0200
Timestamp: 1462108233

Fix a warning with MSVC

Introduced by 2dd24dc4e618dc7b ("Use popcount intrinsic with Intel")

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: Sun May 1 14:30:50 2016 +0200
Timestamp: 1462105850

Fix LazySMP when searching to a fixed depth.

Currently, helper threads will only search up to the
specified depth limit. Now let them search until the
main thread has finished the specified depth.

On the other hand, we don't want to pick a thread with
a higher search depth.

This may be considered cheating. ;-)

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: erbsenzaehler
Date: Sun May 1 14:18:16 2016 +0200
Timestamp: 1462105096

Use popcount intrinsic with Interl compiler

It seems that icc used our fallback version of popcount.
Now use intrinsics.

icc version 16.0.2 (gcc version 5.3.0 compatibility)
bmi2 compile
uname -r 4.5.1-1-ARCH

20xbench gives a nice speedup
./stockfish-icc-master 2161515 +- 34462
./stockfish-icc-sse42 2260857 +- 50349
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: Krgp
Date: Sun May 1 14:11:28 2016 +0200
Timestamp: 1462104688

Remove useless -mbmi flag in Makefile

I could not find anything documented that is necessary that prepending -mbmi to -mbmi2 gives some benefit.
Instead at
https://gcc.gnu.org/onlinedocs/gcc/x86-Built-in-Functions.html#x86-Built-in-Functions

The following built-in functions are available when -mbmi is used. All of them generate the machine instruction that is part of the name.
unsigned int __builtin_ia32_bextr_u32(unsigned int, unsigned int);
unsigned long long __builtin_ia32_bextr_u64 (unsigned long long, unsigned long long);

The following built-in functions are available when -mbmi2 is used. All of them generate the machine instruction that is part of the name.
unsigned int _bzhi_u32 (unsigned int, unsigned int)
unsigned int _pdep_u32 (unsigned int, unsigned int)
unsigned int _pext_u32 (unsigned int, unsigned int)
unsigned long long _bzhi_u64 (unsigned long long, unsigned long long)
unsigned long long _pdep_u64 (unsigned long long, unsigned long long)
unsigned long long _pext_u64 (unsigned long long, unsigned long long)

and at
https://gcc.gnu.org/ml/gcc/2014-02/msg00204.html

( "... The real optimization comes from being able to use pext
(parallel bit extract), which can implement several bextr expressions in
parallel.")

Apart from that we don't use all -msse -msse2 -msse3 -msse4.2 etc. but just -msse3 (or -msse4.2) only.

As regards to the speedup within noise level - this pull request is actually reversal of mcostalba#198 wherein prepending -mbmi to -mbmi2 was claimed to be 0.3% faster and here (removing -mbmi) gives 0.4% speed gain.
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 Apr 30 22:23:22 2016 +0100
Timestamp: 1462051402

Isolated pawn simplification

STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 117822 W: 21697 L: 21744 D: 74381

LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 92307 W: 12330 L: 12305 D: 67672

Bench: 8813983

Resolves #659
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: Sun Apr 24 01:00:58 2016 +0100
Timestamp: 1461456058

Use FMHs to assist with LMR formula.

STC:
LLR: 2.99 (-2.94,2.94) [0.00,5.00]
Total: 52232 W: 9654 L: 9304 D: 33274

LTC:
LLR: 2.97 (-2.94,2.94) [0.00,5.00]
Total: 115988 W: 15550 L: 15049 D: 85389

Bench: 7890808

Resolves #651
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: erbsenzaehler
Date: Sun Apr 24 00:55:56 2016 +0100
Timestamp: 1461455756

Use -O3 for all compilers (including ICC)

There seems to be no benefit from using -fast over -O3 with icc.
So use -O3 everywhere.

No functional change

Resolves #652
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: DU-jdto
Date: Sat Apr 23 02:04:28 2016 +0100
Timestamp: 1461373468

Remove some pointless micro-optimizations

Seems to give around 1% speed-up for CPUs with popcnt support.
Seems to give a very minor speed-up for CPUs without popcnt.

No functional change

Resolves #646
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: Mon Apr 18 00:13:16 2016 +0200
Timestamp: 1460931196

Fix incorrect draw detection

In this position we should have draw for repetition:

position fen rnbqkbnr/2pppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1 moves g1f3 g8f6 f3g1
go infinite

But latest patch broke it.

Actually we had two(!) very subtle bugs, the first is that Position::set()
clears the passed state and in particular 'previous' member, so
that on passing setupStates, 'previous' pointer was reset.

Second bug is even more subtle: SetupStates was based on std::vector
as container, but when vector grows, std::vector copies all its contents
to a new location invalidating all references to its entries. Because
all StateInfo records are linked by 'previous' pointer, this made pointers
go stale upon adding more element to setupStates. So revert to use a
std::deque that ensures references are preserved when pushing back new
elements.

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: loco-loco
Date: Sun Apr 17 15:19:20 2016 +0100
Timestamp: 1460902760

Add a second level of follow-up moves

STC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 6438 W: 1229 L: 1077 D: 4132

LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 4000 W: 605 L: 473 D: 2922

bench: 7378965

Resolves #636
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 Apr 17 08:29:33 2016 +0200
Timestamp: 1460874573

StateInfo is usually allocated on the stack by search()

And passed in do_move(), this ensures maximum efficiency and
speed and at the same time unlimited move numbers.

The draw back is that to handle Position init we need to
reserve a StateInfo inside Position itself and use at
init time and when copying from another Position.

After lazy SMP we don't need anymore this gimmick and we can
get rid of this special case and always pass an external
StateInfo to Position object.

Also rewritten and simplified Position constructors.

Verified it does not regress with a 3 threads SMP test:
ELO: -0.00 +-12.7 (95%) LOS: 50.0%
Total: 1000 W: 173 L: 173 D: 654

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: Niklas Fiekas
Date: Sat Apr 16 10:22:36 2016 +0100
Timestamp: 1460798556

Fix last search info carried over to mate position

When starting search in a mate or stalemate position, Stockfish does not
even care to reinitialize and start worker threads. However after search
all threads are checked for the best move.

This can lead to bestmove and info beeing carried over from the last
search.

Example session:

setoption name threads value 7
go movetime 4000
position startpos moves f2f3 e7e5 g2g4 d8h4
go movetime 4000

Actual output is like (almost always):

[...]
bestmove e2e4
info depth 0 score mate 0
info depth 20 seldepth 29 multipv 1 score cp 28 [...] pv e2e4
bestmove e2e4

Expected output / output after fix:

[...]
bestmove e2e4 ponder e7e6
info depth 0 score mate 0
bestmove (none)

Resolves #623
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 Apr 9 10:42:04 2016 +0200
Timestamp: 1460191324

Hide global visibility when not needed

Also move PieceValue definition in psqt.cpp,
where it is initialized.

Fix a warning in popcount16() with Intel compiler

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 Apr 9 09:35:19 2016 +0200
Timestamp: 1460187319

Fix Travis Cl

Broken after "32-bit/64-bit Makefile fix" commit.

Ubuntu "Precise" 12.04.5 supports multilib only until
g++ 4.6 that is not enough to compile Stockfish.

So move to Ubuntu 14.04.4 LTS (Trusty Tahr)

No functional change.

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