From: Marco Costalba Date: Thu, 23 Jul 2009 06:13:06 +0000 (+0100) Subject: Delay costly SEE call during captures ordering in MovePicker X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=20224a5bbf2844b5b64eec1de199c2d51b8d93d4 Delay costly SEE call during captures ordering in MovePicker When ordering moves we push all captures with negative SEE values to badCaptures[] array during the scoring phase. This patch delays the costly SEE call up to when the move has been picked up in pick_move_from_list(), this way we save some SEE calls in case we get a cutoff. It seems we have a speed gain of about 1-1.5 % in terms of nodes/sec and profiling seems to confirm the small but real speed increase. Idea from Pablo Vazquez on talkchess.com http://www.talkchess.com/forum/viewtopic.php?t=29018&start=20 It would be a no functional change but actually it is not because now sorting set is different and so std::sort(), that is not a stable sort, does not guarantees the order of same scored moves to remain the same as before. After 952 games at 1+0 we are below error bar, almost equal just 6 games of difference (+2 ELO) Signed-off-by: Marco Costalba --- diff --git a/src/movepick.cpp b/src/movepick.cpp index 25cbdefd..af530c5c 100644 --- a/src/movepick.cpp +++ b/src/movepick.cpp @@ -141,12 +141,10 @@ Move MovePicker::get_next_move() { score_captures(); std::sort(moves, moves + numOfMoves); movesPicked = 0; - checkLegal = true; break; case PH_KILLERS: movesPicked = numOfMoves = 0; - checkLegal = false; if (killer1 != MOVE_NONE && move_is_legal(pos, killer1, pinned) && !pos.move_is_capture(killer1)) moves[numOfMoves++].move = killer1; if (killer2 != MOVE_NONE && move_is_legal(pos, killer2, pinned) && !pos.move_is_capture(killer2) ) @@ -155,16 +153,16 @@ Move MovePicker::get_next_move() { case PH_NONCAPTURES: checkKillers = (numOfMoves != 0); // previous phase is PH_KILLERS + checkLegal = true; numOfMoves = generate_noncaptures(pos, moves); score_noncaptures(); std::sort(moves, moves + numOfMoves); movesPicked = 0; - checkLegal = true; break; case PH_BAD_CAPTURES: - // Bad captures SEE value is already calculated by score_captures() - // so just sort them to get SEE move ordering. + // Bad captures SEE value is already calculated so just sort them + // to get SEE move ordering. std::sort(badCaptures, badCaptures + numOfBadCaptures); movesPicked = 0; break; @@ -179,7 +177,7 @@ Move MovePicker::get_next_move() { case PH_QCAPTURES: numOfMoves = generate_captures(pos, moves); - score_qcaptures(); + score_captures(); std::sort(moves, moves + numOfMoves); movesPicked = 0; break; @@ -229,38 +227,28 @@ Move MovePicker::get_next_move(Lock &lock) { void MovePicker::score_captures() { // Winning and equal captures in the main search are ordered by MVV/LVA. // Suprisingly, this appears to perform slightly better than SEE based - // move ordering. The reason is probably that in a position with a winning + // 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 subtree size. - // While scoring captures it moves all captures with negative SEE values - // to the badCaptures[] array. + // In main search we want to push captures with negative SEE values to + // badCaptures[] array, but instead of doing it now we delay till when + // the move has been picked up in pick_move_from_list(), this way we save + // some SEE calls in case we get a cutoff (idea from Pablo Vazquez). Move m; - int seeValue; + // Use MVV/LVA ordering for (int i = 0; i < numOfMoves; i++) { m = moves[i].move; - seeValue = pos.see_sign(m); - if (seeValue >= 0) - { - if (move_is_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))); - } + if (move_is_promotion(m)) + moves[i].score = QueenValueMidgame; else - { - // Losing capture, move it to the badCaptures[] array - assert(numOfBadCaptures < 63); - moves[i].score = seeValue; - badCaptures[numOfBadCaptures++] = moves[i]; - moves[i--] = moves[--numOfMoves]; - } + moves[i].score = int(pos.midgame_value_of_piece_on(move_to(m))) + -int(pos.type_of_piece_on(move_from(m))); } } @@ -304,20 +292,6 @@ void MovePicker::score_evasions() { } } -void MovePicker::score_qcaptures() { - - // Use MVV/LVA ordering - for (int i = 0; i < numOfMoves; i++) - { - Move m = moves[i].move; - if (move_is_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))); - } -} - /// MovePicker::pick_move_from_list() picks the move with the biggest score /// from a list of generated moves (moves[] or badCaptures[], depending on @@ -333,6 +307,26 @@ Move MovePicker::pick_move_from_list() { switch (PhaseTable[phaseIndex]) { case PH_GOOD_CAPTURES: + while (movesPicked < numOfMoves) + { + Move move = moves[movesPicked++].move; + if ( move != ttMove + && move != mateKiller + && pos.pl_move_is_legal(move, pinned)) + { + // Check for a non negative SEE now + int seeValue = pos.see_sign(move); + if (seeValue >= 0) + return move; + + // Losing capture, move it to the badCaptures[] array, note + // that move has now been already checked for legality. + assert(numOfBadCaptures < 63); + badCaptures[numOfBadCaptures].move = move; + badCaptures[numOfBadCaptures++].score = seeValue; + } + } + break; case PH_KILLERS: case PH_NONCAPTURES: while (movesPicked < numOfMoves) @@ -349,18 +343,11 @@ Move MovePicker::pick_move_from_list() { case PH_EVASIONS: if (movesPicked < numOfMoves) return moves[movesPicked++].move; - break; case PH_BAD_CAPTURES: - while (movesPicked < numOfBadCaptures) - { - Move move = badCaptures[movesPicked++].move; - if ( move != ttMove - && move != mateKiller - && pos.pl_move_is_legal(move, pinned)) - return move; - } + if (movesPicked < numOfBadCaptures) + return badCaptures[movesPicked++].move; break; case PH_QCAPTURES: diff --git a/src/movepick.h b/src/movepick.h index bcd5eb14..920a9757 100644 --- a/src/movepick.h +++ b/src/movepick.h @@ -77,7 +77,6 @@ private: void score_captures(); void score_noncaptures(); void score_evasions(); - void score_qcaptures(); Move pick_move_from_list(); const Position& pos;