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>
Tord says that using a lower horizon at PV nodes
looks strange and inconsistent with the general
philosophy of our search (i.e. always being more
conservative at PV nodes). So set LMR at 3 also
on search_pv().
Test result after 601 games seems to confirm this.
Mod vs Orig +156 =318 -127 52.41% 315.0/601 +17 ELO
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Test extension of LMR horizon to 3 plies alone, without
touching null move search. To keep the patch minimal we still
don't change LMR horizon in PV search. This will be the object
of the next patch.
Result seems good after 998 games:
Mod vs Orig +252/=518/-228 51.20% 511.0/998 +8 ELO
So dynamic null move reduction seems a bit stronger then
fixed reduction even with LMR horizon set to 3.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Revert to LMR horizont of 2 plies. Only if parent move
is a null move increase to 3 so to avoid the bad combination
of null move reduction + LMR reduction. This is a more
aggressive patch then previous one, but it seems we are
going in the wromg direction.
After 531 games result is not good:
Mod vs Orig +123/=265/-143 48.12% 255.5/531 -13 ELO
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Set null move reduction to R=4, but increase the LMR horizon
to 3 plies. The two tweaks are related and should compensate
the combined effect of null move + LMR reduction at shallow
depths.
Idea from Tord.
After 999 games at 1+0
Mod vs Orig +251 =522 -225 51.30% + 9 ELO
On Tord iMac Core 2 Duo 2.8 GHz, one thread,
Mac OS X 10.6, at 1+0 time control we have:
Mod vs Orig 994-1006 -1.4 ELO
But Orig version is pgo compiled and Mod is not.
The PGO compiled version is about 8% faster, which
corresponds to about 7 Elo points. This means that
results are reasonably consistent.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
a static eval cached in the transposition table would always equal the static
eval of the current position. This is in general not true, because the cached
value could be from a previous search with different evaluation parameter
settings, or from a search from the opposite side (Stockfish's evaluation
function is assymmetric by default).
This feature makes sense during development, but
It doesn't seem to make sense for normal users.
Also fix a possible race where the GUI adjudicates
the game a fraction of second before the engine sets
looseOnTime flag so that it will bogusly waits until
it ran out of time at the beginning of the next new game.
The fix is to always reset looseOnTime at the beginning
of a new game.
Race condition spotted by Tord.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Mostly of times we are interested only in the sign of SEE,
namely if a capture is negative or not.
If the capturing piece is smaller then the captured one we
already know SEE cannot be negative and this information
is enough most of the times. And of course it is much
faster to detect then a full SEE.
Note that in case see_sign() is negative then the returned
value is exactly the see() value, this is very important,
especially for ordering capturing moves.
With this patch the calls to the costly see() are reduced
of almost 30%.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Some variables were global due to some old and now removed code,
but now can be moved in local scope.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Testing on Joona QUAD failed to give any
advantage. Actually we had a little loss:
Mod - Orig: 342.0 - 374.0
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Rename to move_is_promotion() to be more clear, also add
a new function move_promotion_piece() to get the
promotion piece type in the few places where is needed.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
When we are hunting for mate, transposition table is filled in
with mate scores. Current implemenatation of aspiration search
can't cope with this very well.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Move TT object away from heavy write accessed NodesSincePoll
and also, inside TT isolate the heavy accessed writes variable.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This was needed by an old optimization in sorting of
non-captures that is now obsoleted by new std::sort()
approach.
Remove also the unused depth member data. Interestingly
this has always been unused since the Glaurung days.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Also move NodesSincePoll away from the same cache line
of other heavy read accessed only variables.
Fortunatly we don't have anymore write access contention,
but still read access contention in some cases.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
They are always true anyway and are heavy used file scope
variables where there could be SMP contention. Although read only.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This reduces contention and reduce history trashing
effect especially at high search depths.
No functional change for single CPU case.
After 999 games at 1+0 on Dual Core Intel we have
Mod vs Orig +233 =526 -240 -2 ELO
We need to test at longer time controls and possibly with
a QUAD where we could foreseen an improvment.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This is a first step for future patches and in
any case seems a nice thing to do.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This should reduce concurrent accessing in SMP case.
Suggestion by Tord Romstad.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Both with added comment and changing the API to
reflect that only destination square and moved piece
is important for history.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Aspiration window search must be disabled for
multi-pv case.
We missed one point where aspiration window should
be disabled in this case.
Patch from Joona, with a little added edit by me.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Centralize in a single object all the global resources
management and avoid a bunch of sparse exit() calls.
This is more reliable and clean and more stick to C++ coding
practices.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Move closing of file in Book destructor. This
guarantees us against leaving the file open under
any case and simplifies also Book use.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Instead of a position because the key is all that we
need.
Interface is more clear and also very very little bit faster.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
We don't want to return unproven null move fails high, so
that if a position is so good that null move fails high we
want to check this with real do_move() / undo_move() test,
not just razoring the position because, from the opponent
point of view, is very bad.
These are tests results at 1+0
Mod vs Orig +252 -264 =483 49.40%
Mod vs Toga II 1.4.1SE +365 -325 =309 52.00%
So it seems a very slightly regression regarding orig version (but
withing error bar) and a nice increase against Toga that is what we
are interested most. Orig version scores 49.75% against Toga, so
we welcome this change ;-)
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It is bogusly assigned from moves[i].move instead of mlist[i].move
or equivalently to moves[count].move that it seem more clear to me.
Bug is hidden while all the moves are included, in this default case
moves[i].move and mlist[i].move are the same variable.
Also a bit of cleanup while there.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
After proof testing on 3 different engines these
are the results:
Stockfish - Toga II 1.4.1SE +130 -132 =132 49.75%
Stockfish - Deep Sieng 3.0 +145 -110 =150 54.45%
Stockfish - HIARCS 12 MP +94 -149 =150 43.00%
So it seems no regressions occurs, although also no
improvment. But anyhow this patch increases Stockfish
strenght against itself, so merge it.
Note that this patch not only adds back razoring at depth
one, but also increases razor depth limit from 3 to 4
because hard coded depth 4 limit is no more overwritten
by UCI parameter that otherwise defaults to 3.
Because futility margins array has a fixed size we cannot
arbitrarly choose or change the SelectiveDepth parameter,
otherwise we have a crash for values bigger then array size.
On the other hand tweaking of this parameter requires some
modification to the hardcoded margins, so makes sense to hard
code also this very bounded one.
Who wants to experiment is of course free to change the sources.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Currently futility is allowed when depth < SelectiveDepth
and SelectiveDepth is 7*OnePly, so the comprison is
always true.
Patch could introduce a functional change only if
we choose to increase SelectiveDepth.
Currently no functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
When testing at 1'+0" time control results are still
reasonably good. We have made two sessions on two
different PC.
After 840 games Mod - Orig: +221 -194 =425 +10 ELO (two CPU)
After 935 games Mod - Orig: +246 -222 =467 +9 ELO (single CPU)
So it seems that with fast CPU and/or longer time controls
benefits of the patch are a bit reduced. This could be due
to the fact that only 3% of nodes are pruned by razoring at
depth one and these nodes are very swallow ones, mostly get
pruned anyway with only a slightly additional cost, even
without performing any do_move() call.
Another reason is that sometime (0,3%% of cases) a possible
good move is missed typically in positions when moving side
gives check, as example in the following one
3r2k1/pbpp1nbp/1p6/3P3q/6RP/1P4P1/P4Pb1/3Q2K1 w - -
The winning move Rxg7+ is missed.
Bottom line is that patch seems good for blitz times, perhaps
also for longer times. We should test against a third engine
(Toga ?) to have a final answer regarding this new setup.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Some time ago it was found by Marco Costalba that it's better
to disable razoring at depth one, because given the very low
evaluation of the node, futility pruning would already do
the job at very low cost and avoiding missing important moves.
Now enable razoring there again, but only when our quickly evaluated
material advantage is more than a rook. The idea is to try razoring
only when it's extremely likely that it will succeed.
Extreme lightning speed test show promising result:
Orig - Mod: +1285 =1495 -1348
This needs to be tested with longer time controls though.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Restructure RazorMargins and FutilityMargins arrays so that their
values can be more easily tuned.
Add RazorApprMargins array which replaces razorAtDepthOne concept,
because setting RazorApprMargin very high value at ply one is
same as not razoring there at all.
Comment out setting razoring and futility margins through uci to
avoid errors while tuning.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
If a variable will be populated reading an UCI option
then do not hard code its default values.
This avoids misleadings when reading the sources.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
And upon reentering the same position try it as first.
Normally qsearch moves order is already very good, first move
is the cut off in almost 90% of cases. With this patch, we get
a cut off on TT move of 98%.
Another good side effect is that we don't generate captures
and/or checks when we already have a TT move.
Unfortunatly we found a TT move only in 1% of cases. So real
impact of this patch is relatively low.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Restore old behaviour that after search is aborted we call insert_pv,
before breaking out from the iterative deepening loop.
Remove one useless FIXME and document other better.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Check all fail highs in assumed PV with greater care (fruit/Toga already does this).
Add a flag when aspiration search fails high at ply 1 to prevent search to
be terminated prematurely.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This reverts commit 55dd98f7c717b94a659931cd20e088334b1cf7a6.
Revert fallback-system for root_search
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
However also this patch is immediately reverted. For three reasons:
1) the case it affects is very rare (and then we are likely to lose anyway),
so we can well live without this.
2) Because the case is so rare it's hard to test this change properly.
3) To perform fallback search, we must reset so many global variables that this
patch is very likely both buggy and extremely bad style.
Consider including this again if we clean-up global variables one day...
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
However just after finished writing this patch I realized that this
is not the way to go. So this will be immediately reverted.
(Just save this here in git in case I change my mind later :) )
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Implement system where aspiration search window is calculated using
values from previous iterations.
And then some crazy experimental stuff: If search fails low at the root,
don't widen window, but continue and hope we will find a better move
with given window. If search fails high at the root, cut immediately,
add some more time and start new iteration.
Note: this patch is not complete implementation, but a first test
for this idea. There are many FIXMEs left around. Most importantly
how to deal with the situation when we don't have any move!
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
In null move search do not jump directly in
qsearch() from depth(4*OnePly), but only
from depth(3*OnePly).
After 999 games at 1+0: +248 -224 =527 +8ELO
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It doesn't seem to work against Toga. After more then 400 games
we are at -13 ELO while, without it we are at + 5 ELO after 1000
games.
So revert for now to keep code simple.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Strangely enough it seems that optimization doesn't work.
After 760 games at 1+0: +155 -184 =421 -13 ELO
Probably the overhead, although small, for setting the flag
is not compensated by the saved evaluation call.
This could be due to the fact that after a TT value is stored,
if and when we hit the position again the stored TT value is
actually used as a cut-off so that we don't need to go on
with another search and evaluation is avoided in any case.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
When the stored TT value equals the static value set a
proper flag so to not call evaluation() if we hit the
same position again but use the stored TT value instead.
This is another trick to avoid calling costly evaluation()
in qsearch.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
After testing it seems patch is bad:
After 999 games 1+0: +242 -271 =486 -10 ELO
So restore saving of TT at the end but using new Joona
idea of storing as VALUE_TYPE_UPPER/VALUE_TYPE_LOWER instead
of VALUE_TYPE_EXACT.
Some optimization is still possible but better test new ideas
one by one.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Instead of just drop evaluation score after stand pat
logic save it in TT so to be reused if the same position
occurs again.
Note that we NEVER use the cached value apart to avoid an
evaluation call, in particulary we never return to caller
after a succesful tt hit.
To accomodate this a new value type VALUE_TYPE_EVAL has been
introduced so that ok_to_use_TT() always returns false.
With this patch we cut about 15% of total evaluation calls.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It is now disabled by default due to bad results
against a pool of engines...more testing is needed tough.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This is the only "correct" exact value we can store.
Otherwise there could be spurious failed high/low nodes.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
I have just made a new rule that no modification
that increases pruning is allowed if after 1000 games
ELO is not increased by at least 10 point (was +5 in this case)
Yes, I like this kind of nosense rules :-)
Previous setup didn't change anything
After 996 games 1+0: +267 -261 =468 +2 ELO
Now with this new setup we have
After 999 games 1+0: +277 -245 =477 +11 ELO
Seems reasonable...
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Reduce of two plies near the leafs and when we still
have enough depth to go so to limit horizon effects.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Note that some pawns and material info has been switched
to int from int8_t.
This is a waste of space but it is not clear if we have a
faster or slower code (or nothing changed), some test should be
needed.
Few warnings still are alive.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It does not seem to clearly improve things and
in any case is disabled by default, so retire for now.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Prune more moves after a null search because of
a lower beta limit then in main search.
In test positions reduces the searched nodes of 30% !!!!
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It is slower the previous uglier but faster code.
So completely restore old one for now :-(
Just leave in the rework of status backup/restore in do_move().
We will cherry pick bits of previous work once we are sure
we have fixed the performance regression.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
We don't backup anymore but use the renamed StateInfo
argument passed in do_move() to store the new position
state when doing a move.
Backup is now just revert to previous StateInfo that we know
because we store a pointer to it.
Note that now backing store is up to the caller, Position is
stateless in that regard, state is accessed through a pointer.
This patch will let us remove all the backup/restore copying,
just a pointer switch is now necessary.
Note that do_null_move() still uses StateInfo as backup.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
We store it now in the same UndoInfo struct as 'previous'
field, so when doing a move we also know where to get
the previous info when undoing the back the move.
This is needed for future patches and is a nice cleanup anyway.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Pass value as an argument instead or recalculating it.
Altough call is cheap this is a very hot path so with
this patch total time spent for move_is_capture() is almost
halved.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This is somewhat taken from Stockfish 1.2 Default,
only the razoring thresold are updated, not the
razoring depth.
At the end razoring is a bit more aggressive. Results
seems slightly positive.
After 999 games +239 =536 -224 Elo +5
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Optimistic razoring settings. It is stronger with
most engines but weaker with someones.
The default is instead more solid and uniform with all
the opponents.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Add also the possibility to razor at ply one.
It is disable dby default but it seems stronger
against Stockfish itself. It is still not clear if
is stronger against other engines. By now leave
disabled.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Less prune at the bottom and at the middle, a bit more
at the top.
After 747 games: +215 =345 -187 +13 elo
Also introduced a vector of margins, now that start to be a lot
it is a more flexible solution.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Because razoring verification after qsearch() cuts more
then 40% of candidates, do not waste a costly qsearch for
nodes at depth one that will be probably discarded anyway
by futility.
Also tight razoring conditions to keep dangerous false
negatives below 0,05%. Still not clear if it is enough.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Bug fix merged from Glaurung 2.2 for search_pv()
Added the same fix also to sp_search_pv() where
was missing.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Use a margin to compare with beta so that positions
that after the verifying qsearch have gained a lot of points
are not discarded just becasue not above beta.
Also remove the second condition on depth <= OnePly, it
was too risky and added only a 2% more of pruned nodes.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Fix the logic in search_pv and sp_search_pv
An additional issue to consider is that a castle move
is not a capture but destination square is not empty.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Instead of number of searched nodes use the number of
opponent beta-cutoff occurred under the move subtree.
After 570 games 1+0 we have: +150 =288 -132 (+11 ELO)
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
When a null move fails low due to a capture, try
to detect if without the capture we are above beta,
in this case there is a good possibility this is
a cut-node and the capture is just a null move
artifact due to side to move change. So if we still
don't have a TT move it's a good time to start an IID.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Null move can fail low because of a capture artifact due
to the side to move change. Try to detect this condition
and fail high instead.
This pruning is very powerful, around 7% of nodes, but is
still experimental so is disabled by default.
Set UseNullCapturePruning to true to enable.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Strength increase was due to an hidden bug introduced
by the patch, namely the time per move to /30 instead
of /40 (see previous patch).
After testing this feature do not add any substantial
increase so is removed.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Cleanup and document.
The real functional change is that not mate threat
moves are never pruned, as could happen before.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
We can have depth(0) also in problematic cases
according to how extensions are tweaked by the user.
In any case we don't want to prune these moves.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Add infrastructure to threat killer moves as a vector,
this will allow us to easily parametrize the number of
killer moves, instead of hardcode this value to two as is now.
This patch just add the infrastructure, no functional
change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It is erroneusly considered a capture because king
moves on the same square of the rook.
Use the correct function Position::move_is_capture()
instead of the open coded (and buggy) one.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Killers should not be captures, but checks are not
and are produced also in qsearch.
Use this information, will be useful for move ordering.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Is set during the last iteration.
Sometime also during the second last.
During the last iteration is set in the 95% of cases.
During the second last is set in the 40% of cases.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Allow a seacrh to take a bit more time if needed.
This reduces the chanches of wast all the search time
for the last iteration and also allow to start the last
iteration when we have less time remaining.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It seems that "few moves" works because we extend the good
captures at the last ply of PV, so code it directly.
This version seems defenitly stronger then previous one.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
When an engine is in deep trouble at few
seconds from time limit then giveup without
fighting anymore.
This is used to reduce "lucky draws" and time pressure
blunders noises that can obfuscate results during tests
blitz games (typical one minute games).
Goal of this technique is to reduce number of matches
needed to reliably prove then an engine A is stronger
then an opponent B.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Razor on ply one if the advantage is more then a pawn,
the only way to gap the advantage is to capture, so
go directly in quiesce.
This seems to have a positive effect.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
A bunch of Intel C++ warnings removed, other silent out.
Still few remaining but need deeper look.
Also usual whitespace crap removal noise.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Because razoring is reached 10% of times and about 50% of time
first two conditions are met we can save 5% of calls to the fairly
costly evaluate().
On the other side statistics have shown 95% of nodes that pass
the first two razoring conditions pass also the evaluate() test.
So the risk of dropping the third condition seems low enough.
Testing seems to validate this.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Now I/O is fully done with C++ iostreams.
The only exception is in non-windows version
of Bioskey() in misc.cpp
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This patch modifies think() signature to accept
also opponent time. This is needed for future
changes to time managment.
Still no functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
When a move produces a beta-cut off is marked as
success in history and all the remaining ones are
marked as failures.
The loop across the searched moves, that is used
to register failures, does not skip the good one,
that is then registered as a failure too.
The patch fixes the bug and cleanup the code.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
sort() and sort_multipv() are almost the same, so
use only one implementation.
Also introduce the natural RootMove::operator<() to
compare the moves instead of compare_root_moves(),
this will allow to use std::sort instead of our
home grown bubble-sort.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Moves are already sorted, so just consider the best
and the second one.
Some trailing whitespace remove noise crept in due
to my editor removes it before to save.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Tord Romstad