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>
Marco Costalba