Futility captures alone does not seem an improvment.
Perhaps is a combination of stand pat + futility that is winning,
so revert for now and continue testing starting from a standard
base until we find the correct receipe.
After 999 games at 1+0
Mod vs Orig +231 0506 -201 +10 ELO
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Not a biggie but is a reduced pruned patch that doesn't
seems to hurt, so it is welcomed ;-)
After 999 games at 1+0
Mod vs Orig +207 =601 -191 +6 ELO
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
At ply == OnePly (common case) we avoid some useless
floating point computation.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Joona new aspiration window. Main idea is to always
research aspiration fail highs/low at the same
ply and use much smaller aspiration window than previously.
Testing result is very positive.
1CPU:
953-1149
4CPU:
545 - 656
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Avoid to take the lock two times in a tight sequence, the first
in get_next_move() and the second to update sp->moves.
Do all with one lock and so retire the now useless locked version
of get_next_move().
Also fix some theorical race due to comparison sp->bestValue < sp->beta
is done out of lock protection. Finally fix another (harmless but time
waster) race that coudl occur because thread_should_stop() is also
called outside of lock protection.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
In debug run with 2 threads it happens to be following
assert after some minutes:
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
in search(), line 1615.
I am not able to understand why, anyhow reverted for the moment.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This avoid us to forget some very needed tests now that
futility has changed in a whole big chunk we need to fine
tuning every splitted change.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This will be useful to use gains table in move
ordering along with history table.
No functional change and big code remove.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
With current search control system, I can see absolutely no
reason to classify fixed time search as infinite search.
So remove old dated hack
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
In less then 1% of cases value > sp->bestValue, so avoid
an useless lock in the common case. This is the same change
already applied to sp_search().
Also SplitPoint futilityValue is not volatile because
never changes after has been assigned in split()
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
When we have more then 2 threads then we do an array
access with index 'Threads[slave].activeSplitPoints - 1'
This should be >= 0 because we tested the variable just
few statements before, but because is a shared variable
it could be that the 'slave' thread set the value to zero
just after we test it, so that when we use the decremented
variable for array access we crash.
Bug spotted by Bruno Causse.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Unify start loop for master and slave threads. Also guarantee
that all the 'stop' flags are set to false before first slave
is started, should be no harm because only master thread can
reset 'stop' flag of slaves to true, so should be no race but
better safe then sorry.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Only pure blocking evasions are candidate
for pruning.
After 998 games at 1+0
Mod vs Orig +215 =596 -187 +10 ELO
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
When pondering threads are put to sleep, but when thinking
the threads are parked in idle_loop in a tight polling loop
checking for workIsWaiting falg.
So before we set the slave's flag workIsWaiting we have to
guarantee that all the slave data is already setup because
slave can start in any moment from there.
Rearrange the last loop to fix this race.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Once we have allocated our slave threads and we have removed
master from available threads we can safely remove the lock
so that the lenghty search stack copy operation will not
impact lock contention.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
A pointer is enough because after a split point has been
setup master and slaves thread end up calling sp_search() or
sp_search_pv() and here a full copy of split point position is
done again, note that even master does another copy (of itself)
and this is done before any do_move() call so that master Position
is never updated between split() and sp_search().
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
And detach splitPoint Position from the master one.
So we duplicate StateInfo only once in split() instead
of one for each thread in sp_search
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Renamed a bit the functions to be more clear what
we actually are doing when we craete a Position object
and explained how StateInfo works.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Only the previous, the current and the next ply SearchStack
are copied.
This reduces split overhead especially at low depth (high ply)
and with many threads.
Possibly no functional change (it is not easy to prove in SMP)
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
The init_eval() function corrupted the static array castleRightsMask[]
in the Position class, resulting in instant crashes in most Chess960
games. Fixed by repairing the damage directly after the function is
called. Also modified the Position::to_fen() function to display
castle rights correctly for Chess960 positions, and added sanity checks
for uncastled rook files in Position::is_ok().
It is a good programming practice to verify a system
call has indeed succeed.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
When a search fails high then sp->alpha is increased and
slave threads are requested to stop.
So we have to check for a stop request before to start a search
otherwise we could end up with sp->alpha >= sp->beta
leading to an assert in debug run in search_pv().
This patch fixes the assert and get rid of some of possible races.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
maximum depth during a "go movetime ..." search. This prevents
Stockfish from hanging forever after finding a mate in two or
three while running a test suite at a level of a few seconds
per move.
No functional change when playing games at normal time controls.
In qsearch() try to get a cutoff with the help of an
extra check if we are already very near.
Small increase in actual games but a good result in tactical
test sets where this patch makes SF more tactical.
Mod vs Orig +197 =620 -181 +6 ELO
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Value is never used un-initialized, but MSVC is not
smart enough to detect itself :-(
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Now that we have position static score we don't
need to call evaluate() a second time.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This will allow to have wider access to attack
information, for instance from MovePicker.
Note that 'eval' field become obsolete, it is kept
just becasue when we get a position score from TT
we update 'eval' even without an EvalInfo object.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
In sp_search_pv() we do a LMR search using sp->alpha, at the end
we detect a fail high with condition (value > sp->alpha), but if
another thread has increased sp->alpha during our LMR search we
could miss to detect a fail high event becasue value will be equal
to old alpha and so smaller then new one.
This patch fixes this SMP-bug and changes also the non SMP versions
of the search to keep code style in sync.
Bug spotted by Bruno Causse.
No functional change (for single CPU case)
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
