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Pick best moves one per cycle instead of sorting

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When the move list is very small, like captures normally
are, it is faster to pick the best move with a linear
scan, one per cycle.

This has the added advantage that the picked capture move is
very possibly a cut-off move, so that other searches are
avoided. For non-captures it is still faster to sort in
advance.

Because scan-and-pick alghortim is not stable, node count
has changed.

After 885 games at 1+0
Mod vs Orig +196 =510 -179 50.96%  451.0/885

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-10-20 11:38:20 +01:00
parent 51c3af9dd0
commit cf4df0327a
2 changed files with 33 additions and 7 deletions
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21
src/move.h
View file

@ -86,6 +86,27 @@ inline void sort_moves(T* firstMove, T* lastMove)
}
}
// Picks up the best move in range [curMove, lastMove), one per cycle.
// It is faster then sorting all the moves in advance when moves are few,
// as normally are the possible captures. Note that is not a stable alghoritm.
template<typename T>
inline T pick_best(T* curMove, T* lastMove)
{
T bestMove, tmp;
bestMove = *curMove;
while (++curMove != lastMove)
{
if (*curMove < bestMove)
{
tmp = *curMove;
*curMove = bestMove;
bestMove = tmp;
}
}
return bestMove;
}
////
//// Inline functions
////

19
src/movepick.cpp
View file

@ -122,7 +122,6 @@ void MovePicker::go_next_phase() {
case PH_GOOD_CAPTURES:
lastMove = generate_captures(pos, moves);
score_captures();
sort_moves(moves, lastMove);
return;
case PH_KILLERS:
@ -141,20 +140,17 @@ void MovePicker::go_next_phase() {
// to get SEE move ordering.
curMove = badCaptures;
lastMove = lastBadCapture;
sort_moves(badCaptures, lastMove);
return;
case PH_EVASIONS:
assert(pos.is_check());
lastMove = generate_evasions(pos, moves, pinned);
score_evasions();
sort_moves(moves, lastMove);
return;
case PH_QCAPTURES:
lastMove = generate_captures(pos, moves);
score_captures();
sort_moves(moves, lastMove);
return;
case PH_QCHECKS:
@ -267,17 +263,17 @@ Move MovePicker::get_next_move() {
{
while (curMove != lastMove)
{
move = (curMove++)->move;
switch (phase) {
case PH_TT_MOVES:
move = (curMove++)->move;
if ( move != MOVE_NONE
&& move_is_legal(pos, move, pinned))
return move;
break;
case PH_GOOD_CAPTURES:
move = pick_best(curMove++, lastMove).move;
if ( move != ttMoves[0].move
&& move != ttMoves[1].move
&& pos.pl_move_is_legal(move, pinned))
@ -297,6 +293,7 @@ Move MovePicker::get_next_move() {
break;
case PH_KILLERS:
move = (curMove++)->move;
if ( move != MOVE_NONE
&& move != ttMoves[0].move
&& move != ttMoves[1].move
@ -306,6 +303,7 @@ Move MovePicker::get_next_move() {
break;
case PH_NONCAPTURES:
move = (curMove++)->move;
if ( move != ttMoves[0].move
&& move != ttMoves[1].move
&& move != killers[0].move
@ -316,11 +314,18 @@ Move MovePicker::get_next_move() {
case PH_EVASIONS:
case PH_BAD_CAPTURES:
move = pick_best(curMove++, lastMove).move;
return move;
case PH_QCAPTURES:
move = pick_best(curMove++, lastMove).move;
if ( move != ttMoves[0].move
&& pos.pl_move_is_legal(move, pinned))
return move;
break;
case PH_QCHECKS:
// Maybe postpone the legality check until after futility pruning?
move = (curMove++)->move;
if ( move != ttMoves[0].move
&& pos.pl_move_is_legal(move, pinned))
return move;