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55b6464)
Do not calculate SEE on all the moves in MovePicker::score_captures()
but delay until pick_move_from_list() when only the best ones are
double checked against their see value.
If a beta cut-off occurs then we avoid calculating SEE on all
the moves, but just the picked ones.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
// Suprisingly, this appears to perform slightly better than SEE based
// move ordering. The reason is probably that in a position with a winning
// capture, capturing a more valuable (but sufficiently defended) piece
// Suprisingly, this appears to perform slightly better than SEE based
// move ordering. The reason is probably that in a position with a winning
// capture, capturing a more valuable (but sufficiently defended) piece
- // first usually doesn't hurt. The opponent will have to recapture, and
+ // first usually doesn't hurt. The opponent will have to recapture, and
// the hanging piece will still be hanging (except in the unusual cases
// where it is possible to recapture with the hanging piece). Exchanging
// big pieces before capturing a hanging piece probably helps to reduce
// the hanging piece will still be hanging (except in the unusual cases
// where it is possible to recapture with the hanging piece). Exchanging
// big pieces before capturing a hanging piece probably helps to reduce
+ // the subtree size. Instead of calculating SEE here to filter out
+ // loosing captures, we delay the filtering in pick_move_from_list()
for (int i = 0; i < numOfMoves; i++)
{
m = moves[i].move;
for (int i = 0; i < numOfMoves; i++)
{
m = moves[i].move;
- seeValue = pos.see(m);
- if (seeValue >= 0)
- {
- if (move_promotion(m))
- moves[i].score = QueenValueMidgame;
- else
- moves[i].score = int(pos.midgame_value_of_piece_on(move_to(m)))
- -int(pos.type_of_piece_on(move_from(m)));
- } else
- moves[i].score = seeValue;
+ if (move_promotion(m))
+ moves[i].score = QueenValueMidgame;
+ else
+ moves[i].score = int(pos.midgame_value_of_piece_on(move_to(m)))
+ -int(pos.type_of_piece_on(move_from(m)));
while (movesPicked < numOfMoves)
{
while (movesPicked < numOfMoves)
{
- int bestScore = -10000000;
- bestIndex = -1;
- for (int i = movesPicked; i < numOfMoves; i++)
+ bestIndex = find_best_index();
+
+ if (bestIndex != -1) // Found a possibly good capture
- if (moves[i].score < 0)
+ move = moves[bestIndex].move;
+ int seeValue = pos.see(move);
+ if (seeValue < 0)
{
// Losing capture, move it to the badCaptures[] array
assert(numOfBadCaptures < 63);
{
// Losing capture, move it to the badCaptures[] array
assert(numOfBadCaptures < 63);
- badCaptures[numOfBadCaptures++] = moves[i];
- moves[i--] = moves[--numOfMoves];
- }
- else if (moves[i].score > bestScore)
- {
- bestIndex = i;
- bestScore = moves[i].score;
+ moves[bestIndex].score = seeValue;
+ badCaptures[numOfBadCaptures++] = moves[bestIndex];
+ moves[bestIndex] = moves[--numOfMoves];
+ continue;
- }
- if (bestIndex != -1) // Found a good capture
- {
- move = moves[bestIndex].move;
moves[bestIndex] = moves[movesPicked++];
if ( move != ttMove
&& move != mateKiller
moves[bestIndex] = moves[movesPicked++];
if ( move != ttMove
&& move != mateKiller