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Fix incorrect StateInfo

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We use Position::set() to set root position across
threads. But there are some StateInfo fields (previous,
pliesFromNull, capturedPiece) that cannot be deduced
from a fen string, so set() clears them and to not lose
the info we need to backup and later restore setupStates->back().
Note that setupStates is shared by threads but is accessed
in read-only mode.

This fixes regression introduced by df6cb446ea

Tested with 3 threads at STC:
LLR: 2.95 (-2.94,2.94) [-4.00,0.00]
Total: 14436 W: 2304 L: 2196 D: 9936

Bench: 5608839
This commit is contained in:
Marco Costalba 2017-08-14 09:12:16 -07:00
parent c3e964f35e
commit 232c50fed0
1 changed files with 7 additions and 5 deletions
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12
src/thread.cpp
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@ -158,10 +158,12 @@ void ThreadPool::start_thinking(Position& pos, StateListPtr& states,
if (states.get())
setupStates = std::move(states); // Ownership transfer, states is now empty
// We use Position::set() to set root position across threads. So we
// need to save and later to restore st->previous, cleared by set().
// Note that setupStates is shared by threads but is accessed in read-only mode.
StateInfo* previous = setupStates->back().previous;
// We use Position::set() to set root position across threads. But there are
// some StateInfo fields (previous, pliesFromNull, capturedPiece) that cannot
// be deduced from a fen string, so set() clears them and to not lose the info
// we need to backup and later restore setupStates->back(). Note that setupStates
// is shared by threads but is accessed in read-only mode.
StateInfo tmp = setupStates->back();
for (Thread* th : Threads)
{
@ -171,7 +173,7 @@ void ThreadPool::start_thinking(Position& pos, StateListPtr& states,
th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th);
}
setupStates->back().previous = previous;
setupStates->back() = tmp;
main()->start_searching();
}