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MovePicker: use EvalInfo to skip generating captures

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When we know already no captures are possible in a given
position.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2008-11-15 13:00:56 +01:00
parent f4758ced90
commit 20d7197a9b
5 changed files with 39 additions and 15 deletions
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41
src/movepick.cpp
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@@ -26,6 +26,7 @@
#include <cassert>
#include "history.h"
#include "evaluate.h"
#include "movegen.h"
#include "movepick.h"
#include "search.h"
@@ -44,7 +45,9 @@ namespace {
int MainSearchPhaseIndex;
int EvasionsPhaseIndex;
int QsearchWithChecksPhaseIndex;
int QsearchNoCapturesPhaseIndex;
int QsearchWithoutChecksPhaseIndex;
int NoMovesPhaseIndex;
}
@@ -62,9 +65,9 @@ namespace {
/// search captures, promotions and some checks) and about how important good
/// move ordering is at the current node.
MovePicker::MovePicker(const Position& p, bool pvnode, Move ttm, Move mk,
Move k1, Move k2, Depth d) : pos(p) {
pvNode = pvnode;
MovePicker::MovePicker(const Position& p, bool pv, Move ttm,
Move mk, Move k1, Move k2, Depth d, EvalInfo* ei) : pos(p) {
pvNode = pv;
ttMove = ttm;
mateKiller = (mk == ttm)? MOVE_NONE : mk;
killer1 = k1;
@@ -73,17 +76,25 @@ MovePicker::MovePicker(const Position& p, bool pvnode, Move ttm, Move mk,
movesPicked = 0;
numOfMoves = 0;
numOfBadCaptures = 0;
dc = p.discovered_check_candidates(p.side_to_move());
// With EvalInfo we are able to know how many captures are possible before
// generating them. So avoid generating them in case we know are zero.
Color us = pos.side_to_move();
Color them = opposite_color(us);
bool noAttacks = ei && (ei->attackedBy[us][0] & pos.pieces_of_color(them)) == 0;
bool noCaptures = noAttacks && (pos.ep_square() == SQ_NONE) && !pos.has_pawn_on_7th(us);
if (p.is_check())
phaseIndex = EvasionsPhaseIndex;
phaseIndex = EvasionsPhaseIndex;
else if (depth > Depth(0))
phaseIndex = MainSearchPhaseIndex;
phaseIndex = MainSearchPhaseIndex;
else if (depth == Depth(0))
phaseIndex = QsearchWithChecksPhaseIndex;
phaseIndex = (noCaptures ? QsearchNoCapturesPhaseIndex : QsearchWithChecksPhaseIndex);
else
phaseIndex = QsearchWithoutChecksPhaseIndex;
phaseIndex = (noCaptures ? NoMovesPhaseIndex : QsearchWithoutChecksPhaseIndex);
dc = p.discovered_check_candidates(us);
pinned = p.pinned_pieces(p.side_to_move());
finished = false;
@@ -493,8 +504,9 @@ MovePicker::MovegenPhase MovePicker::current_move_type() const {
/// MovePicker::init_phase_table() initializes the PhaseTable[],
/// MainSearchPhaseIndex, EvasionPhaseIndex, QsearchWithChecksPhaseIndex
/// and QsearchWithoutChecksPhaseIndex variables. It is only called once
/// during program startup, and never again while the program is running.
/// QsearchNoCapturesPhaseIndex, QsearchWithoutChecksPhaseIndex and
/// NoMovesPhaseIndex variables. It is only called once during program
/// startup, and never again while the program is running.
void MovePicker::init_phase_table() {
@@ -523,8 +535,17 @@ void MovePicker::init_phase_table() {
PhaseTable[i++] = PH_QCHECKS;
PhaseTable[i++] = PH_STOP;
// Quiescence search with checks only and no captures
QsearchNoCapturesPhaseIndex = i - 1;
PhaseTable[i++] = PH_QCHECKS;
PhaseTable[i++] = PH_STOP;
// Quiescence search without checks
QsearchWithoutChecksPhaseIndex = i - 1;
PhaseTable[i++] = PH_QCAPTURES;
PhaseTable[i++] = PH_STOP;
// Do not generate any move
NoMovesPhaseIndex = i - 1;
PhaseTable[i++] = PH_STOP;
}