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Add psqt ordering when there is no history

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This seems to increase strenght (about 15 ELO),
still to test some variations on this theme that
could increase ELO even more.

Idea from Rebel (http://members.home.nl/matador/chess840.htm)

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2008-10-15 07:18:05 +01:00
parent cb76e4a814
commit 644db060ae
2 changed files with 35 additions and 8 deletions
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37
src/movepick.cpp
View file

@ -246,15 +246,36 @@ void MovePicker::score_captures() {
}
void MovePicker::score_noncaptures() {
for(int i = 0; i < numOfMoves; i++) {
Move m = moves[i].move;
if(m == killer1)
moves[i].score = HistoryMax + 2;
else if(m == killer2)
moves[i].score = HistoryMax + 1;
else
moves[i].score = H.move_ordering_score(pos->piece_on(move_from(m)), m);
bool all_zero = true;
for (int i = 0; i < numOfMoves; i++)
{
Move m = moves[i].move;
if (m == killer1)
{
moves[i].score = HistoryMax + 2;
all_zero = false;
}
else if (m == killer2)
{
moves[i].score = HistoryMax + 1;
all_zero = false;
}
else
{
moves[i].score = H.move_ordering_score(pos->piece_on(move_from(m)), m);
if (all_zero && moves[i].score != 0)
all_zero = false;
}
}
if (!all_zero)
return;
// If we don't have at least one history score then
// try to order using psq tables difference between
// from square and to square.
for (int i = 0; i < numOfMoves; i++)
moves[i].score = pos->mg_pst_delta(moves[i].move);
}
void MovePicker::score_evasions() {

6
src/position.h
View file

@ -278,6 +278,7 @@ public:
Value eg_value() const;
Value non_pawn_material(Color c) const;
Phase game_phase() const;
Value mg_pst_delta(Move m) const;
// Game termination checks
bool is_mate();
@ -681,6 +682,11 @@ inline Value Position::mg_pst(Color c, PieceType pt, Square s) const {
return MgPieceSquareTable[piece_of_color_and_type(c, pt)][s];
}
inline Value Position::mg_pst_delta(Move m) const {
return MgPieceSquareTable[piece_on(move_from(m))][move_to(m)]
-MgPieceSquareTable[piece_on(move_from(m))][move_from(m)];
}
inline Value Position::eg_pst(Color c, PieceType pt, Square s) const {
return EgPieceSquareTable[piece_of_color_and_type(c, pt)][s];
}