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Use a union to fast and simply backup info in do_move()

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This nice union trick let us optimize the speed and
remove the now unuseful backup() and restore() functions.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-02-20 11:13:19 +01:00
parent 95cfc0e306
commit 1dc27f3232
2 changed files with 16 additions and 65 deletions
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59
src/position.cpp
View file

@ -669,60 +669,6 @@ bool Position::move_is_capture(Move m) const {
}
/// Position::backup() is called when making a move. All information
/// necessary to restore the position when the move is later unmade
/// is saved to an UndoInfo object. The function Position::restore
/// does the reverse operation: When one does a backup followed by
/// a restore with the same UndoInfo object, the position is restored
/// to the state before backup was called.
void Position::backup(UndoInfo& u) const {
for (Color c = WHITE; c <= BLACK; c++)
{
u.pinners[c] = pinners[c];
u.pinned[c] = pinned[c];
u.dcCandidates[c] = dcCandidates[c];
}
u.checkersBB = checkersBB;
u.key = key;
u.pawnKey = pawnKey;
u.materialKey = materialKey;
u.castleRights = castleRights;
u.rule50 = rule50;
u.epSquare = epSquare;
u.lastMove = lastMove;
u.mgValue = mgValue;
u.egValue = egValue;
u.capture = NO_PIECE_TYPE;
}
/// Position::restore() is called when unmaking a move. It copies back
/// the information backed up during a previous call to Position::backup.
void Position::restore(const UndoInfo& u) {
for (Color c = WHITE; c <= BLACK; c++)
{
pinners[c] = u.pinners[c];
pinned[c] = u.pinned[c];
dcCandidates[c] = u.dcCandidates[c];
}
checkersBB = u.checkersBB;
key = u.key;
pawnKey = u.pawnKey;
materialKey = u.materialKey;
castleRights = u.castleRights;
rule50 = u.rule50;
epSquare = u.epSquare;
lastMove = u.lastMove;
mgValue = u.mgValue;
egValue = u.egValue;
// u.capture is restored in undo_move()
}
/// Position::update_checkers() is a private method to udpate chekers info
template<PieceType Piece>
@ -758,7 +704,8 @@ void Position::do_move(Move m, UndoInfo& u) {
// Back up the necessary information to our UndoInfo object (except the
// captured piece, which is taken care of later.
backup(u);
u = undoInfoUnion;
u.capture = NO_PIECE_TYPE;
// Save the current key to the history[] array, in order to be able to
// detect repetition draws.
@ -1219,7 +1166,7 @@ void Position::undo_move(Move m, const UndoInfo &u) {
// Restore information from our UndoInfo object (except the captured piece,
// which is taken care of later)
restore(u);
undoInfoUnion = u;
if (move_is_castle(m))
undo_castle_move(m);

22
src/position.h
View file

@ -240,8 +240,6 @@ public:
bool square_is_weak(Square s, Color c) const;
// Doing and undoing moves
void backup(UndoInfo &u) const;
void restore(const UndoInfo &u);
void do_move(Move m, UndoInfo &u);
void undo_move(Move m, const UndoInfo &u);
void do_null_move(UndoInfo &u);
@ -345,13 +343,19 @@ private:
File initialKFile, initialKRFile, initialQRFile;
// Info backed up in do_move()
mutable Bitboard pinners[2], pinned[2], dcCandidates[2];
Bitboard checkersBB;
Key key, pawnKey, materialKey;
int castleRights, rule50;
Square epSquare;
Move lastMove;
Value mgValue, egValue;
union {
UndoInfo undoInfoUnion;
struct { // Must have the same layout of UndoInfo
mutable Bitboard pinners[2], pinned[2], dcCandidates[2];
Bitboard checkersBB;
Key key, pawnKey, materialKey;
int castleRights, rule50;
Square epSquare;
Move lastMove;
Value mgValue, egValue;
PieceType capture;
};
};
// Static variables
static int castleRightsMask[64];