Joona Kiiski [Sun, 25 Jan 2015 22:03:57 +0000 (22:03 +0000)]
Stockfish 6 Release Candidate 3
- Fix a skill level problem: Don't allow move pruning at root node
- Revert "Fix profile build for gcc on Mac OSX". Results for a faster binary in x86-64.
- Fix a MSVC warning
Marco Costalba [Tue, 20 Jan 2015 21:17:22 +0000 (22:17 +0100)]
Don't use _pext_u64() directly
This intrinsic to call BMI2 PEXT instruction is
defined in immintrin.h. This header should be
included only when USE_PEXT is defined, otherwise
we define _pext_u64 as 0 forcing a nop.
But under some mingw platforms, even if we don't
include the header, immintrin.h gets included
anyhow through an include chain that starts with
STL <algorithm> header. So we end up both defining
_pext_u64 function and at the same time defining
_pext_u64 as 0 leading to a compile error.
The correct solution is of not using _pext_u64 directly.
This patch fixes a compile error with some mingw64
package when compiling with x86-64.
Marco Costalba [Tue, 20 Jan 2015 08:13:30 +0000 (09:13 +0100)]
Try hard to retrieve a ponder move
In case we stop the search during a fail-high
it is possible we return to GUI without a ponder
move. This patch try harder to find a ponder move
retrieving it from TT. This is important in games
played with 'ponder on'.
Marco Costalba [Wed, 21 Jan 2015 18:53:26 +0000 (19:53 +0100)]
Document how to enable PEXT with MSVC
When not using Makefile, e.g. with MSVC, if hardware
supports BMI2 instructions, then USE_PEXT should be
added in project configuration to enable pext support.
Marco Costalba [Tue, 20 Jan 2015 21:17:22 +0000 (22:17 +0100)]
Don't use _pext_u64() directly
This intrinsic to call BMI2 PEXT instruction is
defined in immintrin.h. This header should be
included only when USE_PEXT is defined, otherwise
we define _pext_u64 as 0 forcing a nop.
But under some mingw platforms, even if we don't
include the header, immintrin.h gets included
anyhow through an include chain that starts with
STL <algorithm> header. So we end up both defining
_pext_u64 function and at the same time defining
_pext_u64 as 0 leading to a compile error.
The correct solution is of not using _pext_u64 directly.
This patch fixes a compile error with some mingw64
package when compiling with x86-64.
Marco Costalba [Sun, 18 Jan 2015 09:41:56 +0000 (10:41 +0100)]
Fix a coverity scan warning
Coverity scan warns about uninitialized 'sf' argument when
calling probe(). Actually it is a false positive because
argument is passed by reference and assigned inside
probe(). Nevertheless it is a hint that fucntion signature
is a bit tricky, so rewrite it in a more conventional way,
assigning 'sf' from probe() return value.
Marco Costalba [Sat, 3 Jan 2015 09:51:38 +0000 (10:51 +0100)]
Assorted work in uci.cpp
- Change UCI::value() signature
This function should only return the value,
lowerbound and upperbound info is up to the
caller because it requires external knowledge,
out of the scope of this little helper.
- Retire 'key' command
It is not an UCI command and is absolutely
useless: never used.
All king safety related terms (shelterweakness, stormdanger,
attackunits, ..) was tuned together. Additionally for attack units a
finer granularity (factor 4) is used.
ShelterWeakness and Stormdanger array are now indexed additionally by
file pair (a/h,b/g,c/f,d/e). The special case of king blocking a pawn
is incorporated in the StormDanger array. Finally the 93 parameters
are tuned by SPSA on LTC.
mstembera [Thu, 18 Dec 2014 19:56:00 +0000 (03:56 +0800)]
Change profile-build options to produce 1% to 2% faster executables.
The "@rm ucioption.gc*" line is necessary to avoid a gcc 4.7.x bug.
Confirmed for gcc 4.7.4, 4.8.1, and 4.9.1
Suggested by Kiran Panditrao on fishcooking forum.
https://groups.google.com/forum/?fromgroups=#!topic/fishcooking/AY8gN53nG18
Marco Costalba [Sat, 13 Dec 2014 08:27:39 +0000 (09:27 +0100)]
Coding style in TT code
In particular seems more natural to return
bool and TTEntry on the same line, actually
we should pass and return them as a pair,
but due to limitations of C++ and not wanting
to use std::pair this can be an acceptable
compromise.
Ernesto Gatti [Mon, 8 Dec 2014 00:10:57 +0000 (08:10 +0800)]
Simpler PRNG and faster magics search
This patch replaces RKISS by a simpler and faster PRNG, xorshift64* proposed
by S. Vigna (2014). It is extremely simple, has a large enough period for
Stockfish's needs (2^64), requires no warming-up (allowing such code to be
removed), and offers slightly better randomness than MT19937.
The patch also simplifies how init_magics() searches for magics:
- Old logic: seed the PRNG always with the same seed,
then use optimized bit rotations to tailor the RNG sequence per rank.
- New logic: seed the PRNG with an optimized seed per rank.
This has two advantages:
1. Less code and less computation to perform during magics search (not ROTL).
2. More choices for random sequence tuning. The old logic only let us choose
from 4096 bit rotation pairs. With the new one, we can look for the best seeds
among 2^64 values. Indeed, the set of seeds[][] provided in the patch reduces
the effort needed to find the magics:
64-bit SF:
Old logic -> 5,783,789 rand64() calls needed to find the magics
New logic -> 4,420,086 calls
32-bit SF:
Old logic -> 2,175,518 calls
New logic -> 1,895,955 calls
In the 64-bit case, init_magics() take 25 ms less to complete (Intel Core i5).
Finally, when playing with strength handicap, non-determinism is achieved
by setting the seed of the static RNG only once. Afterwards, there is no need
to skip output values.
The bench only changes because the Zobrist keys are now different (since they
are random numbers straight out of the PRNG).
The RNG seed has been carefully chosen so that the
resulting Zobrist keys are particularly well-behaved:
1. All triplets of XORed keys are unique, implying that it
would take at least 7 keys to find a 64-bit collision
(test suggested by ceebo)
2. All pairs of XORed keys are unique modulo 2^32
3. The cardinality of { (key1 ^ key2) >> 48 } is as close
as possible to the maximum (65536)
Point 2 aims at ensuring a good distribution among the bits
that determine an TT entry's cluster, likewise point 3
among the bits that form the TT entry's key16 inside a
cluster.
Details:
Bitset card(key1^key2)
------ ---------------
RKISS
key16 64894 = 99.020% of theoretical maximum
low18 180117 = 99.293%
low32 305362 = 99.997%
Marco Costalba [Sun, 30 Nov 2014 13:59:09 +0000 (14:59 +0100)]
Explicitly pass RootMoves to TB probes
Currently Search::RootMoves is accessed and even
modified by TB probing functions in a hidden
and sneaky way.
This is bad practice and makes the code tricky.
Instead explicily pass the vector as function
argument so to clarify that the vector is modified
inside the functions.
Marco Costalba [Sat, 15 Nov 2014 04:36:49 +0000 (05:36 +0100)]
Use DEPTH_MAX instead of MAX_PLY
When comparing to a Depth it is more
consistent to use DEPTH_MAX instead
of a int.
This is a subtle difference because we use
ply and depth almost interchangably in SF,
but they are different. FOr counting plies
makes ense to continue using ints, while
for Depth we have our specific enum.
Gary Linscott [Wed, 12 Nov 2014 21:13:55 +0000 (16:13 -0500)]
100% accurate PV display
This gives SF accurate PVs, such that the evaluation of the leaf node in
the PV matches the score backed up to the root (99% of the time.
q-search will use the value stored in the hash table instead of the eval
value sometimes).
One drawback is that fail-high/low only get a minimal 2 move PV.
It doesn't add any additional overhead to the non-PV codepath except an
extra eight bytes to the SearchStack structure in multi-threaded
searches.
A core part of this is not pruning based on TT score in PV nodes. This
was measured as not being a regression at multiple TCs, except for one
exception, fast TC with huge hash, which is not realistic for longer
searches.