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Use a circular buffer to keep track of setup states

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This fixes a regression on real games due to the fact that
we have some mismatches:

    history[st->gamePly - i] != stp->key

when st->gamePly - i == 0,this is due to a nasty bug I have
introduced when using std::vector<> as StateInfo backup. The
point is that StateInfo keeps inside a pointer to the previous
StateInfo in a kind of linked list. But when std::vector<> is
resized reallocates a larger chunk of memory and moves the
data there so these pointers became stale.

This patch fixes the issue.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2011-07-23 12:52:49 +01:00
parent 03ad183384
commit 5f7eb20090
1 changed files with 8 additions and 6 deletions
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14
src/uci.cpp
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@ -38,8 +38,9 @@ namespace {
const string StartPositionFEN = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
// Keep track of position keys along the setup moves (from start position to the
// position just before to start searching). This is needed by draw detection.
std::vector<StateInfo> SetupState(200, StateInfo());
// position just before to start searching). This is needed by draw detection
// where, due to 50 moves rule, we need to ckeck at most 100 plies back.
StateInfo StateRingBuf[102], *SetupState = StateRingBuf;
// UCIParser is a class for parsing UCI input. The class
// is actually a string stream built on a given input string.
@ -144,13 +145,14 @@ namespace {
}
else return;
SetupState.clear();
// Parse move list (if any)
while (up >> token && (m = move_from_uci(pos, token)) != MOVE_NONE)
{
SetupState.push_back(StateInfo());
pos.do_move(m, SetupState.back());
pos.do_move(m, *SetupState);
// Increment pointer to StateRingBuf circular buffer
if (++SetupState - StateRingBuf >= 102)
SetupState = StateRingBuf;
}
}