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.
No functional change.
Import C++11 branch from:
https://github.com/mcostalba/Stockfish/tree/c++11
The version imported is teh last one as of today:
6670e93e50
Branch is fully equivalent with master but syzygy
tablebases that are missing (but will be added with
next commit).
bench: 8080602
On platforms where size_t is 32 bit, we
can have an overflow in this expression:
(mbSize * 1024 * 1024)
Fix it setting max hash size of 2GB on platforms
where size_t is 32 bit.
A small rename while there: now struct Cluster
is definied inside class TranspositionTable so
we should drop the redundant TT prefix.
No functional change.
On Android-ARM current TB code crashes at
random times even in single thread mode.
Reported, debugged, fixed and verified
by Peter Osterlund.
No functional change.
Resolves#201
This optimization is aimed at old hardware only (withouth popcount), and even on
non popcount compile (ARCH=x86-64), it provides no mesurable speedup:
stat test master diff
mean 2,341,779 2,354,699 -12,920
stdev 12,910 14,770 18,150
speedup -0.55%
P(speedup>0) 23.8%
No functional change.
Resolves#187
- 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.
- Comments fixing and other trivia
No functional change.
And reshuffle a bit the functions to place
them in a consistent order.
To be on the safe side, patch has been
validated for no regression/crashes with
a small 8K games test with 3 threads:
ELO: 3.98 +-4.4 (95%) LOS: 96.3%
Total: 8388 W: 1500 L: 1404 D: 5484
No functional change.
It is up to material (and pawn) table look up
code to know where the per-thread tables are,
so change API to reflect this.
Also some comment fixing while there
No functional change.
Move all in evaluation.
Simplify the code and concentrate in a single place
all the logic behind space evaluation, making it much
more clear.
Verified also at STC it does not regress due to a possible
slow down:
LLR: 3.91 (-2.94,2.94) [-3.00,1.00]
Total: 65744 W: 13285 L: 13194 D: 39265
No functional change.
Commenst are obsolete now, an updated description
would be quite obscure, so better let the code
to talk and remove them all together.
No functional change.
Use the same template of other pawns moves generation,
make the code more uniform, simplify generate_promotions
that has now been renamed.
No functional change (verified also with perft).
In some UNIX systems "rm" prompts user for confirmation.
However "rm -f" is always a guaranteed forced deletion.
Also move gcc profiling hack under the correct target
No Functional change
Resolves#168
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.
STC
ELO: 3.46 +-2.2 (95%) LOS: 99.9%
Total: 40000 W: 8275 L: 7877 D: 23848
LTC
LLR: 2.96 (-2.94,2.94) [0.00,6.00]
Total: 10311 W: 1876 L: 1721 D: 6714
Bench: 9498821
Resolves#163
The evaluation is already done by the specialized
function, don't need to add something elese later.
With this patch following positions are evaluated
correctly as draws:
8/6p1/1Pkp1p1p/2nNn2P/2P1K1P1/8/8/3B4 w - - 7
8/1k4p1/1P1p1p1p/3NnK1P/2P3P1/1n6/4B3/8 w - -
Verified it not regress with an STC test:
LLR: 3.15 (-2.94,2.94) [-3.00,1.00]
Total: 49812 W: 10095 L: 10016 D: 29701
Reported by Arjun Temurnikar.
bench: 8289983
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.
No functional change.
Resolves#157
In some cases we want to go direcly to the moves loop
without checking for early return. The patch make this
logic more clear and consistent.
Tested for no regression, passed STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 25282 W: 5136 L: 5022 D: 15124
and LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 72007 W: 12133 L: 12095 D: 47779
bench: 9316798
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.
Paper: http://xorshift.di.unimi.it/
Reference source code (public domain):
http://xorshift.di.unimi.it/xorshift64star.c
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%
Xorshift64*, old seed
key16 64918 = 99.057%
low18 179994 = 99.225%
low32 305350 = 99.993%
Xorshift64*, new seed
key16 65027 = 99.223%
low18 181118 = 99.845%
low32 305371 = 100.000%
Bench: 9324905
Resolves#148
