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>
