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Fix asserts due to TT access races

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In multi-threads runs with debug on we experience some
asserts due to the fact that TT access is intrinsecally
racy and its contents cannot be always trusted so must
be validated before to be used and this is what the
patch does.

No functional case.
This commit is contained in:
Marco Costalba 2012-10-26 12:33:58 +02:00
parent c594b989c0
commit 4c7a71a44b
1 changed files with 21 additions and 12 deletions
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33
src/search.cpp
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@ -553,13 +553,13 @@ namespace {
// smooth experience in analysis mode. We don't probe at Root nodes otherwise
// we should also update RootMoveList to avoid bogus output.
if ( !RootNode
&& tte && tte->depth() >= depth
&& tte
&& tte->depth() >= depth
&& ttValue != VALUE_NONE // Only in case of TT access race
&& ( PvNode ? tte->type() == BOUND_EXACT
: ttValue >= beta ? (tte->type() & BOUND_LOWER)
: (tte->type() & BOUND_UPPER)))
{
assert(ttValue != VALUE_NONE); // Due to depth > DEPTH_NONE
TT.refresh(tte);
ss->currentMove = ttMove; // Can be MOVE_NONE
@ -580,16 +580,22 @@ namespace {
else if (tte)
{
assert(tte->static_value() != VALUE_NONE);
assert(ttValue != VALUE_NONE || tte->type() == BOUND_NONE);
// Following asserts are valid only in single thread condition because
// TT access is always racy and its contents cannot be trusted.
assert(tte->static_value() != VALUE_NONE || Threads.size() > 1);
assert(ttValue != VALUE_NONE || tte->type() == BOUND_NONE || Threads.size() > 1);
ss->staticEval = eval = tte->static_value();
ss->evalMargin = tte->static_value_margin();
if (eval == VALUE_NONE || ss->evalMargin == VALUE_NONE) // Due to a race
eval = ss->staticEval = evaluate(pos, ss->evalMargin);
// Can ttValue be used as a better position evaluation?
if ( ((tte->type() & BOUND_LOWER) && ttValue > eval)
|| ((tte->type() & BOUND_UPPER) && ttValue < eval))
eval = ttValue;
if (ttValue != VALUE_NONE)
if ( ((tte->type() & BOUND_LOWER) && ttValue > eval)
|| ((tte->type() & BOUND_UPPER) && ttValue < eval))
eval = ttValue;
}
else
{
@ -1118,13 +1124,13 @@ split_point_start: // At split points actual search starts from here
// only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
ttDepth = inCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
: DEPTH_QS_NO_CHECKS;
if ( tte && tte->depth() >= ttDepth
if ( tte
&& tte->depth() >= ttDepth
&& ttValue != VALUE_NONE // Only in case of TT access race
&& ( PvNode ? tte->type() == BOUND_EXACT
: ttValue >= beta ? (tte->type() & BOUND_LOWER)
: (tte->type() & BOUND_UPPER)))
{
assert(ttValue != VALUE_NONE); // Due to ttDepth > DEPTH_NONE
ss->currentMove = ttMove; // Can be MOVE_NONE
return ttValue;
}
@ -1140,10 +1146,13 @@ split_point_start: // At split points actual search starts from here
{
if (tte)
{
assert(tte->static_value() != VALUE_NONE);
assert(tte->static_value() != VALUE_NONE || Threads.size() > 1);
ss->staticEval = bestValue = tte->static_value();
ss->evalMargin = tte->static_value_margin();
if (ss->staticEval == VALUE_NONE || ss->evalMargin == VALUE_NONE) // Due to a race
ss->staticEval = bestValue = evaluate(pos, ss->evalMargin);
}
else
ss->staticEval = bestValue = evaluate(pos, ss->evalMargin);