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Split killer moves from non-captures

Browse source 
In MovePicker consider killer moves as a separate
phase from non-capture picking.

Note that this change guarantees that killer1 is always
tried before killer2. Until now, because scoring difference
of the two moves was just 1 point, if psqt tables of killer1
gave a lower value then killer2, the latter was tried as first.

After 999 games at 1+0 we have
Mod vs Orig: +245 =527 -227 +6 ELO

Not a lot but patch is anyhow something worth to have.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-05-25 07:49:50 +01:00
parent 1b0888708d
commit bdb1bfecfb
3 changed files with 29 additions and 22 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
src/movegen.cpp
View file

@ -392,7 +392,6 @@ bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
assert(pinned == pos.pinned_pieces(pos.side_to_move()));
Color us = pos.side_to_move();
Color them = opposite_color(us);
Square from = move_from(m);
Piece pc = pos.piece_on(from);
@ -401,6 +400,7 @@ bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
if (color_of_piece(pc) != us)
return false;
Color them = opposite_color(us);
Square to = move_to(m);
// En passant moves

43
src/movepick.cpp
View file

@ -74,6 +74,7 @@ MovePicker::MovePicker(const Position& p, bool pv, Move ttm,
movesPicked = 0;
numOfMoves = 0;
numOfBadCaptures = 0;
checkKillers = checkLegal = false;
if (p.is_check())
phaseIndex = EvasionsPhaseIndex;
@ -139,6 +140,25 @@ 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) )
moves[numOfMoves++].move = killer2;
break;
case PH_NONCAPTURES:
checkKillers = (numOfMoves != 0); // previous phase is PH_KILLERS
numOfMoves = generate_noncaptures(pos, moves);
score_noncaptures();
std::sort(moves, moves + numOfMoves);
movesPicked = 0;
checkLegal = true;
break;
case PH_BAD_CAPTURES:
@ -146,13 +166,6 @@ Move MovePicker::get_next_move() {
movesPicked = 0;
break;
case PH_NONCAPTURES:
numOfMoves = generate_noncaptures(pos, moves);
score_noncaptures();
std::sort(moves, moves + numOfMoves);
movesPicked = 0;
break;
case PH_EVASIONS:
assert(pos.is_check());
numOfMoves = generate_evasions(pos, moves, pinned);
@ -258,13 +271,7 @@ void MovePicker::score_noncaptures() {
for (int i = 0; i < numOfMoves; i++)
{
m = moves[i].move;
if (m == killer1)
hs = HistoryMax + 2;
else if (m == killer2)
hs = HistoryMax + 1;
else
hs = H.move_ordering_score(pos.piece_on(move_from(m)), move_to(m));
hs = H.move_ordering_score(pos.piece_on(move_from(m)), move_to(m));
// Ensure history is always preferred to pst
if (hs > 0)
@ -320,13 +327,15 @@ Move MovePicker::pick_move_from_list() {
switch (PhaseTable[phaseIndex]) {
case PH_GOOD_CAPTURES:
case PH_KILLERS:
case PH_NONCAPTURES:
while (movesPicked < numOfMoves)
{
Move move = moves[movesPicked++].move;
if ( move != ttMove
&& move != mateKiller
&& pos.pl_move_is_legal(move, pinned))
&& (!checkKillers || (move != killer1 && move != killer2))
&& (!checkLegal || pos.pl_move_is_legal(move, pinned)))
return move;
}
break;
@ -381,9 +390,7 @@ void MovePicker::init_phase_table() {
PhaseTable[i++] = PH_TT_MOVE;
PhaseTable[i++] = PH_MATE_KILLER;
PhaseTable[i++] = PH_GOOD_CAPTURES;
// PH_KILLER_1 and PH_KILLER_2 are not yet used.
// PhaseTable[i++] = PH_KILLER_1;
// PhaseTable[i++] = PH_KILLER_2;
PhaseTable[i++] = PH_KILLERS;
PhaseTable[i++] = PH_NONCAPTURES;
PhaseTable[i++] = PH_BAD_CAPTURES;
PhaseTable[i++] = PH_STOP;

6
src/movepick.h
View file

@ -57,10 +57,9 @@ public:
PH_TT_MOVE, // Transposition table move
PH_MATE_KILLER, // Mate killer from the current ply
PH_GOOD_CAPTURES, // Queen promotions and captures with SEE values >= 0
PH_BAD_CAPTURES, // Queen promotions and captures with SEE values < 0
PH_KILLER_1, // Killer move 1 from the current ply (not used yet).
PH_KILLER_2, // Killer move 2 from the current ply (not used yet).
PH_KILLERS, // Killer moves from the current ply
PH_NONCAPTURES, // Non-captures and underpromotions
PH_BAD_CAPTURES, // Queen promotions and captures with SEE values < 0
PH_EVASIONS, // Check evasions
PH_QCAPTURES, // Captures in quiescence search
PH_QCHECKS, // Non-capture checks in quiescence search
@ -91,6 +90,7 @@ private:
int phaseIndex;
int numOfMoves, numOfBadCaptures;
int movesPicked;
bool checkKillers, checkLegal;
bool finished;
};