Marco Costalba [Sat, 10 Apr 2010 09:32:17 +0000 (10:32 +0100)]
Avoid TT cutoffs at root of null zugzwang verification
This patch fixes an issue with zugzwang well explained by Tord:
"Assume that a zugzwang position occurs at iteration N,
at a search depth d, with d < 6*OnePly. The null move search
fails high, and no verification search is done, because the
depth is too small. The position gets stored in the transposition
table with a good score and a depth of d.
Now, consider what happens when the same position occurs at iteration
N+1, this time with a depth of d+OnePly (i.e. one ply deeper than at
the previous iteration). Once again, the null move search fails
high. The point is that the verification search will also fail high,
because of an instant transposition table cutoff caused by the value
stored in the TT during the previous iteration."
With this patch we simply do not allow TT cutoffs at the root node
of a null move verification search if the TT value was found by a
null search.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Marco Costalba [Sat, 3 Apr 2010 07:54:21 +0000 (08:54 +0100)]
Store score in TT when null search fails high
Use full depth, not reduced one. This allows
to avoid to do a null search when in the same
position and at the same or bigger depth the
null search failed high.
A very small increase, if any.
After 963 games at 1+0
Mod vs Orig: +158 =657 -147 +4 ELO
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Tord Romstad [Tue, 30 Mar 2010 13:15:01 +0000 (15:15 +0200)]
Remove several unnecessary UCI options: All king safety options
except "Aggressiveness" and "Cowardice", and "UCI_ShowCurrLine".
No functional change compared to the previous version with the
default settings.
Marco Costalba [Sat, 20 Mar 2010 10:59:22 +0000 (11:59 +0100)]
Remove castleRightsMask[] hack
Array castleRightsMask[] is not static because it can
be different for different positions, so let it be
a Position member data. This allows to remove tricky
hacks to take in account that although it was defined
static it could change.
Theoretically now copying a position is a bit slower because
we need to copy also an array of 64 integers, but because in
split() we don't copy the position anymore, but just keep the
pointer, the added burden is not mesurable even in MP case.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Marco Costalba [Wed, 17 Mar 2010 17:09:37 +0000 (18:09 +0100)]
Fix POPCNT detection gcc compile error
Also don't use __cpuid() intrinsic for Intel under
Linux because gives wrong results when detecting HT,
use the gcc version instead. Finally clean up the code.
Error was due to changed __cpuid() signature for
gcc compiler.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Marco Costalba [Tue, 9 Mar 2010 14:46:20 +0000 (15:46 +0100)]
Reduce increase progression of aspiration window
Currently, in case of fail high/low we research with
a window increased by 2*AspirationDelta at first
attempt, this patch instead makes the research be
done with an increase of just AspirationDelta size,
in case of a consecutive fail we will widen to
2*AspirationDelta and so on.
After Joona's test:
Orig - Mod: 850 - 890
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Marco Costalba [Sun, 7 Mar 2010 08:02:34 +0000 (10:02 +0200)]
Use separated research counters in root_search()
One for failing highs and one for failing lows, this
should reduce average window size in case of positions
that fail first high and then low (or the contrary).
After ~2000 games on Joona's quad we have:
Mod - Orig: 1012- 975 (+6 elo)
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Marco Costalba [Sat, 6 Mar 2010 10:43:31 +0000 (11:43 +0100)]
Sort again root moves after a fail low
Currently we use original sorting after a fail low to
research at wider window. This patch instead sorts the
moves according to the last available move's scores.
Strangely no functional change, but should be.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Marco Costalba [Sun, 28 Feb 2010 10:53:29 +0000 (11:53 +0100)]
We don't need lpThreadId parameter in CreateThread()
Under Windows we use CreateThread() to setup threads and
we pass a pointer to a variable that receives the thread
identifier, but this parameter is optional and we don't
use it, so remove it.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Marco Costalba [Sat, 27 Feb 2010 11:01:07 +0000 (12:01 +0100)]
Remove an incorrect assert in wake_sleeping_threads()
Currently there is no guarantee that threads are sleeping
when calling wake_sleeping_threads() because put_threads_to_sleep()
returns without waiting for threads to actually sleep.
Assert can be easily triggered calling put_threads_to_sleep() and
wake_sleeping_threads() in a tight loop.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Joona Kiiski [Tue, 23 Feb 2010 10:05:26 +0000 (12:05 +0200)]
Do not wait for threads falling asleep
I cannot see any reason to do this. Even this is not enough to fix
theoretical race case on Windows which doesn't seem to cause any
problems in practice anyhow
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Marco Costalba [Sat, 20 Feb 2010 22:56:02 +0000 (23:56 +0100)]
Revert "Recursive lock"
Joona says that sp_update_pv() does not pass the split point
boundaries, so there is no risk to corrupt data from another
split point. Also the race on thread_should_stop() is harmless
because of this.
So revert the patch and come back to single lock.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Marco Costalba [Sat, 20 Feb 2010 17:36:07 +0000 (18:36 +0100)]
Revert small state change optimization in idle_loop()
Joona says:
1. We should not be afraid of "AllThreadsShouldExit" flag.
Because when this is set to true we _must_not_ be searching (= All
splits must have been undone).
And if we are not searching it's impossible that some other thread
could give us work to do. So setting state to THREAD_AVAILABLE
doesn't do any harm. If you want to add check for this, you could do
it like this:
if (threads[threadID].state == THREAD_WORKISWAITING)
{
+ assert(!AllThreadsShouldExit)
threads[threadID].state = THREAD_SEARCHING;
2a. If waitSp->cpus == 0, setting state to THREAD_AVAILABLE makes
no harm either, because helpful master concept dictates that _only_
our own slave can book us. If we don't have any slaves, noone has the
right to book us.
2b. If point (2a) is not correct then your extra check only adds extra race:
In smp code checking for waitSp->cpus > 0 is not enough. It's possible that
our slave immediately exits and another thread
books us as a slave when our state is still
THREAD_AVAILABLE. So instead of adding extra level of security we have
just introduced extra race.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Marco Costalba [Sat, 20 Feb 2010 17:29:53 +0000 (18:29 +0100)]
Recursive lock all split point's chain
When we found a cut-off then lock all the split point chain,
not only current one to avoid races in case two threads running
on different split points where one is ancestor then the other,
find a beta cut-off at the same time, in this case we want only
one to call sp_update_pv().
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Marco Costalba [Sat, 20 Feb 2010 16:52:09 +0000 (17:52 +0100)]
Retire per-thread stopRequest flag
This is a per split-point request, not per-thread. When we find
a beta cut-off in current thread's split point or in or in some
ancestor of the current split point then threads should stop
immediately the search and return to idle_loop().
The check is done by thread_should_stop() that now looks only
at split point's chain.
No functional change and a good semplification.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
projects / stockfish / log