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Reorder evasions

Always try ttMove as first. Then try good captures ordered
by MVV/LVA, then non-captures if destination square is not
under attack, ordered by history value, and at the end
bad-captures and non-captures with a negative SEE. This
last group is ordered by the SEE score.

After 999 games at 1+0
Mod vs Orig +254 =546 -199 +19 ELO

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
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1 parent dddaeff commit 70b7404a63b74a57d4e1d0b9192b00837e9a1af8 @mcostalba committed Oct 31, 2009
Showing with 14 additions and 8 deletions.
  1. +14 −8 src/movepick.cpp
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22 src/movepick.cpp
@@ -197,8 +197,8 @@ void MovePicker::score_captures() {
if (move_is_promotion(m))
cur->score = QueenValueMidgame;
else
- cur->score = int(pos.midgame_value_of_piece_on(move_to(m)))
- -int(pos.type_of_piece_on(move_from(m)));
+ cur->score = pos.midgame_value_of_piece_on(move_to(m))
+ - pos.type_of_piece_on(move_from(m));
}
}
@@ -229,19 +229,25 @@ void MovePicker::score_noncaptures() {
}
void MovePicker::score_evasions() {
-
+ // Always try ttMove as first. Then try good captures ordered
+ // by MVV/LVA, then non-captures if destination square is not
+ // under attack, ordered by history value, and at the end
+ // bad-captures and non-captures with a negative SEE. This
+ // last group is ordered by the SEE score.
Move m;
+ int seeScore;
for (MoveStack* cur = moves; cur != lastMove; cur++)
{
m = cur->move;
if (m == ttMoves[0].move)
cur->score = 2 * HistoryMax;
- else if (!pos.square_is_empty(move_to(m)))
- {
- int seeScore = pos.see(m);
- cur->score = seeScore + (seeScore >= 0 ? HistoryMax : 0);
- } else
+ else if ((seeScore = pos.see_sign(m)) < 0)
+ cur->score = seeScore;
+ else if (pos.move_is_capture(m))
+ cur->score = pos.midgame_value_of_piece_on(move_to(m))
+ - pos.type_of_piece_on(move_from(m)) + HistoryMax;
+ else
cur->score = H.move_ordering_score(pos.piece_on(move_from(m)), move_to(m));
}
}

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