If after the first tried 2 + int(depth) moves we still
have no any move that takes us out of a mate then do
not prune the following move, it is more important to
escape mate then speed up search.
This fixes an odd behaviour regarding mates, as example
the following diagram is a mate in 4, not in 3 as bogusly
reported before this patch.
1B2n3/8/2R5/5p2/3kp1n1/4p3/B3K3/8 w - - bm #4;
The performance impact should be minimal, the increment
in searched nodes is less then 0.1 %%
Idea and patch by Joona
After 999 games at 1+0
Mod vs Orig +193 =604 -202 -3 ELO
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
In this case we call evaluate() being in check and this
is not allowed.
Bug found testing with reduced PLY_MAX value as suggested
by Miguel A. Ballicora on talkchess.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
When pondering InfiniteSearch == false but myTime == 0 so that
NodesBetweenPolls = 1000 instead of the standard.
The patch fixes the bug and is more robust because checks
directly myTime for a non-zero value, without relying on
an indirect test (InfiniteSearch in this case).
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Instead of checking the time every 100 nodes in the last second,
and every 1000 nodes in the last five seconds, Stockfish now checks
every 1000 nodes in the last second and every 5000 nodes in the last
five seconds. This was tested in 1036 games at a time control of
40 moves/10 seconds, and no losses on time occured.
Also fixed a bug pointed out by Marco: In infinite mode, myTime
is actually 0, but of course we still don't want to check the time
more frequently than the standard once per 30000 nodes in this
case.
In RootMoveList c'tor we allocate a search stack and then
call directly qsearch.
There is called init_node() that clears all the fields of the search
stack array that refers to current ply but not the the killer moves.
The killer moves cleared correspond to ply+2.
In id_loop() this is not a problem because killer moves of
corresponding ply are cleared anyway few instructions later,
but in RootMoveList c'tor we leave them uninitialized.
This patch fixes this very old bug. It comes direclty
from Glaurung age.
Bug spotted by Valgrind.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
In particular don't use an array of StateInfo, this
avoids a possible overflow and is in any case redundant.
Also pass as argument the pv[] array size to avoid a second
possible overflow on this one.
Fix suggested by Joona.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This satisfies a specific user request of 28/8/2009
"The only issue I have is that during multiPV analysis, the depth 1
best move score is not reported by the engine (reporting for the best
move begins at depth 2). I need it at depth 1 also. Would it be
possible to make this modification in future versions? This would be
of great help as otherwise I will have to use a lesser engine.
The goal of my project is to calculate the ELO performance in a game
and also the ELO rating of individual moves. For this I need depth 1
scores for lower rated performances. I intend to distribute the program
for free upon completion.
Thanks, Jack Welbourne"
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Remove a bunch of difficult and tricky code to test
legality of castle and ep moves and instead use a slower
but simpler check against the list of generated legal moves.
Because these moves are very rare the performance impact
is small but code semplification is ver big: almost 100 lines
of difficult code removed !
No functionality change. No performance change (strangely enough
there is no even minimal performance regression in pgo builds but
instead a slightly and unexpected increase).
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
When a node fails low and bestValue is still equal to
the original static node evaluation, then save this
in TT along with usual info.
This will allow us to avoid a future costly evaluation() call.
This patch extends to failed low nodes what we already do
for failed high ones.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Still not clear if it helps and, especially, how it
helps. So revert for now to avoid any influence on
future feature now under test.
With this patch we come back to be functional
equivalent to patch e33c94883 F_53.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
After 828 games at 1+0
Mod vs Orig +191 =447 -190 50.06% 414.5/828
So almost no difference. Patch is committed more for
documentation purposes then for other reasons.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It is in line with attackers_to() and is shorter and
piece is already redundant because is passed as template
parameter anyway.
Integrate also pawn_attacks_from() in the attacks_from()
family so to have an uniform attack info API.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It is a bit longer but much easier to understand especially
for people new to the sources. I remember it was not trivial
for me to understand the returned attack bitboard refers to
attacks launched from the given square and not attacking the
given square.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Most of them are not required to be public and are
used in one place only so remove them and use its
definitions.
Also rename piece_attacks_square() in piece_attacks()
to be aligned to the current naming policy.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
These functions return bitboard of attacking pieces,
not the attacks themselfs so reflect this in the name.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It seems that it works better without compensation
of drifted value when saving static evaluation in TT.
After 818 games at 1+0
Mod vs Orig +217 =429 -172 52.75% 431.5/818 +19 ELO
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
After 934 games at 1+0
Mod vs Orig +228 =493 -213 50.80% 474.5/934 +6 ELO
So it seems not negative and there is also the added
benefit to unify LMRPVMoves use in search_pv() and in
root list.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Because of a hard-to-spot single-character bug in connected_moves(),
the discovered check code had no effect whatsoever. The condition
in the if (...) statement at the beginning of the code would always
return false.
Thanks to Edsel Apostol for pointing out this bug!
It is more clear that only in that case the move number is
correct, otherwise is only a partial quantity: the number of
moves of that phase.
In case of PH_EVASIONS instead we have only one phase.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It seems that pos.has_mate_threat() changes the position !
So that calling MovePicker c'tor before or after the
has_mate_threat() call changes the things !
Bug was unhidden by previous patch that makes MovePicker c'tor
to generate, score and sort good captures under some circumstances.
Because scoring the captures is position dependent it seems that
the moves returned by MovePicker are different when c'tor is
called before has_mate_threat()
Of course this is only a workaround because the real bug is still
hidden :-(
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Does not seem to improve on the standard, latest results
from Joona after 2040 games are negative:
Orig - Mod: 454 - 424 - 1162
And is more or less the same I got few days ago.
So revert for now.
Verified same functionality of 595a90dfd
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This avoids calculating the array entry position
at each access and gives another boost of almost 1%.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Try good captures before null move when depth < 3 * OnePly.
Use this kind of null move also in Depth == OnePly.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Explicitly write the conditions for pawn to 7th
and passed pawn instead of wrapping in redundant
helpers.
Also retire the now unused move_is_pawn_push_to_7th()
and the never used move_was_passed_pawn_push() and
move_is_deep_pawn_push()
Function extension() is so time critical that this
simple patch speeds up the pgo compile of 0.5% and
it is also more clear what actually happens there.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This fix a compile error under Linux with gcc when
there aren't the intel dev libraries.
Also simplify the previous patch moving TT definition
from search.cpp to tt.cpp so to avoid using passing a
pointer to TT to the current position.
Finally simplify do_move(), now we miss a prefetch in the
rare case of setting an en-passant square but code is
much cleaner and performance penalty is almost zero.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Move prefetching code inside do_move() so to allow a
very early prefetching and to put as many instructions
as possible between prefetching and following retrieve().
With this patch retrieve() times are cutted of another 25%
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
TT.retrieve() is the most time consuming function
because almost always involves a very slow RAM access.
TT table is so big that is never cached. This patch
prefetches TT data just after a move is done, so that
subsequent TT.retrieve will be very fast.
Profiling with VTune shows that TT:retrieve() times are
almost cutted in half !
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Current formula enable LMR when
i + MultiPV >= LMRPVMoves
It means that, for instance, if MultiPV == 1 then LMR
will be started to be considered at move i = LMRPVMoves - 1,
while if MultiPV == 3 then it will start before,
at move i = LMRPVMoves - 3.
With this patch the formula becomes
i >= MultiPV + LMRPVMoves - 2
So that LMR will always start after LMRPVMoves - 1 moves
from the last PV move.
No functional change when MultiPV == 1
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
down the transposition table.
When the search was stopped before a fail high at the root was
resolved, Stockfish would often print a very short PV, sometimes
consisting of just a single move. This was not only a little
user-unfriendly, but also harmed the strength a little in
ponder-on games: Single-move PVs mean that there is no ponder
move to search.
It is perhaps worth considering to remove the pv[][] array
entirely, and always build the entire PV from the transposition
table. This would simplify the source code somewhat and probably
make the program infinitesimally faster, at the expense of
sometimes getting shorter PVs or PVs with rubbish moves near
the end.
Added the UCI_LimitStrength and the UCI_Elo options, with an Elo
range of 2100-2900. When UCI_LimitStrength is enabled, the number
of threads is set to 1, and the search speed is slowed down according
to the chosen Elo level.
Todo:
1. Implement Elo levels below 2100 by blundering on purpose and/or
crippling the evaluation.
2. Automatically calibrate the maximum Elo by measuring the CPU speed
during program initialization, perhaps by doing some bitboard
computations and measuring the time taken.
No functional change when UCI_LimitStrength is false (the default).
Small micro-optimization in this very
time critical function.
Use bitwise 'or' instead of logic 'or' to avoid branches
in the assembly and use the result to skip an handful of checks.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
We do not accept null search returned mate values,
but we always do a full search in those cases.
So the variable mateThreat that is set only if null move
search returns a mate value is always false.
Restore the functionality of mateThreat moving the
assignement where it can be triggered.
After 999 games at 1+0
Mod vs Orig +253 =517 -229 51.20% +8 ELO
Bug reported by xiaozhi
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
