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Restore pliesFromNull counter

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It is not equivalent because the check for the
50 moves rule get badly affected.

// Draw by the 50 moves rule?
if (st->rule50 > 100 || (st->rule50 == 100 && !is_check()))
    return true;

So we _really_ need two counters.

Thanks to Joona and Tord to be patience with a silly guy ;-)

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-10-09 10:08:42 +01:00
parent 06a5b602dc
commit f05d059b17
2 changed files with 9 additions and 6 deletions
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13
src/position.cpp
View file

@ -703,7 +703,7 @@ void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
// pointer to point to the new, ready to be updated, state.
struct ReducedStateInfo {
Key key, pawnKey, materialKey;
int castleRights, rule50;
int castleRights, rule50, pliesFromNull;
Square epSquare;
Value mgValue, egValue;
Value npMaterial[2];
@ -724,6 +724,7 @@ void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
// Increment the 50 moves rule draw counter. Resetting it to zero in the
// case of non-reversible moves is taken care of later.
st->rule50++;
st->pliesFromNull++;
if (move_is_castle(m))
{
@ -1238,11 +1239,11 @@ void Position::do_null_move(StateInfo& backupSt) {
// Note that differently from normal case here backupSt is actually used as
// a backup storage not as a new state to be used.
backupSt.key = st->key;
backupSt.rule50 = st->rule50;
backupSt.epSquare = st->epSquare;
backupSt.mgValue = st->mgValue;
backupSt.egValue = st->egValue;
backupSt.previous = st->previous;
backupSt.pliesFromNull = st->pliesFromNull;
st->previous = &backupSt;
// Save the current key to the history[] array, in order to be able to
@ -1258,7 +1259,8 @@ void Position::do_null_move(StateInfo& backupSt) {
sideToMove = opposite_color(sideToMove);
st->epSquare = SQ_NONE;
st->rule50 = 0;
st->rule50++;
st->pliesFromNull = 0;
gamePly++;
st->mgValue += (sideToMove == WHITE)? TempoValueMidgame : -TempoValueMidgame;
@ -1276,14 +1278,15 @@ void Position::undo_null_move() {
// Restore information from the our backup StateInfo object
StateInfo* backupSt = st->previous;
st->key = backupSt->key;
st->rule50 = backupSt->rule50;
st->epSquare = backupSt->epSquare;
st->mgValue = backupSt->mgValue;
st->egValue = backupSt->egValue;
st->previous = backupSt->previous;
st->pliesFromNull = backupSt->pliesFromNull;
// Update the necessary information
sideToMove = opposite_color(sideToMove);
st->rule50--;
gamePly--;
}
@ -1684,7 +1687,7 @@ bool Position::is_draw() const {
return true;
// Draw by repetition?
for (int i = 2; i < Min(gamePly, st->rule50); i += 2)
for (int i = 2; i < Min(Min(gamePly, st->rule50), st->pliesFromNull); i += 2)
if (history[gamePly - i] == st->key)
return true;

2
src/position.h
View file

@ -88,7 +88,7 @@ enum Phase {
struct StateInfo {
Key key, pawnKey, materialKey;
int castleRights, rule50;
int castleRights, rule50, pliesFromNull;
Square epSquare;
Value mgValue, egValue;
Value npMaterial[2];