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Simplify locking in sp_search and sp_search_pv

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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>
This commit is contained in:
Marco Costalba
2010-01-27 17:29:34 +01:00
parent 307909bed8
commit bb968fd42a
4 changed files with 25 additions and 33 deletions
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36
src/search.cpp
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@@ -1874,28 +1874,29 @@ namespace {
SearchStack* ss = sp->sstack[threadID];
Value value = -VALUE_INFINITE;
Move move;
int moveCount;
bool isCheck = pos.is_check();
bool useFutilityPruning = sp->depth < SelectiveDepth
&& !isCheck;
const int FutilityMoveCountMargin = 3 + (1 << (3 * int(sp->depth) / 8));
while ( sp->bestValue < sp->beta
while ( lock_grab_bool(&(sp->lock))
&& sp->bestValue < sp->beta
&& !thread_should_stop(threadID)
&& (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE)
&& (move = sp->mp->get_next_move()) != MOVE_NONE)
{
moveCount = ++sp->moves;
lock_release(&(sp->lock));
assert(move_is_ok(move));
bool moveIsCheck = pos.move_is_check(move, ci);
bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
lock_grab(&(sp->lock));
int moveCount = ++sp->moves;
lock_release(&(sp->lock));
ss[sp->ply].currentMove = move;
// Decide the new search depth.
// Decide the new search depth
bool dangerous;
Depth ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, false, false, &dangerous);
Depth newDepth = sp->depth - OnePly + ext;
@@ -1982,7 +1983,7 @@ namespace {
}
}
lock_grab(&(sp->lock));
/* Here we have the lock still grabbed */
// If this is the master thread and we have been asked to stop because of
// a beta cutoff higher up in the tree, stop all slave threads.
@@ -2015,24 +2016,25 @@ namespace {
CheckInfo ci(pos);
SearchStack* ss = sp->sstack[threadID];
Value value = -VALUE_INFINITE;
int moveCount;
Move move;
while ( sp->alpha < sp->beta
while ( lock_grab_bool(&(sp->lock))
&& sp->alpha < sp->beta
&& !thread_should_stop(threadID)
&& (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE)
&& (move = sp->mp->get_next_move()) != MOVE_NONE)
{
bool moveIsCheck = pos.move_is_check(move, ci);
bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
moveCount = ++sp->moves;
lock_release(&(sp->lock));
assert(move_is_ok(move));
lock_grab(&(sp->lock));
int moveCount = ++sp->moves;
lock_release(&(sp->lock));
bool moveIsCheck = pos.move_is_check(move, ci);
bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
ss[sp->ply].currentMove = move;
// Decide the new search depth.
// Decide the new search depth
bool dangerous;
Depth ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, false, &dangerous);
Depth newDepth = sp->depth - OnePly + ext;
@@ -2131,7 +2133,7 @@ namespace {
}
}
lock_grab(&(sp->lock));
/* Here we have the lock still grabbed */
// If this is the master thread and we have been asked to stop because of
// a beta cutoff higher up in the tree, stop all slave threads.