/// Position::see() is a static exchange evaluator: It tries to estimate the
-/// material gain or loss resulting from a move. There are three versions of
-/// this function: One which takes a destination square as input, one takes a
-/// move, and one which takes a 'from' and a 'to' square. The function does
-/// not yet understand promotions captures.
+/// material gain or loss resulting from a move. Parameter 'asymmThreshold' takes
+/// tempi into account. If the side who initiated the capturing sequence does the
+/// last capture, he loses a tempo and if the result is below 'asymmThreshold'
+/// the capturing sequence is considered bad.
int Position::see_sign(Move m) const {
return see(m);
}
-int Position::see(Move m) const {
- return do_see<false>(m, 0);
-}
-
-/// Position::see_asymm() takes tempi into account.
-/// If the side who initiated the capturing sequence does the last capture,
-/// he loses a tempo. In this case if the result is below asymmThreshold
-/// the capturing sequence is considered bad.
-
-int Position::see_asymm(Move m, int asymmThreshold) const
-{
- return do_see<true>(m, asymmThreshold);
-}
-
-template <bool Asymmetric>
-int Position::do_see(Move m, int asymmThreshold) const {
+int Position::see(Move m, int asymmThreshold) const {
Square from, to;
Bitboard occupied, attackers, stmAttackers;
} while (stmAttackers);
// If we are doing asymmetric SEE evaluation and the same side does the first
- // and the last capture, he loses a tempo and gain must be at least worth "asymmThreshold".
- // If not, we replace the score with a very low value, before negamaxing.
- if (Asymmetric)
- {
- for (int i = 0; i < slIndex ; i += 2)
- {
+ // and the last capture, he loses a tempo and gain must be at least worth
+ // 'asymmThreshold', otherwise we replace the score with a very low value,
+ // before negamaxing.
+ if (asymmThreshold)
+ for (int i = 0; i < slIndex; i += 2)
if (swapList[i] < asymmThreshold)
- swapList[i] = - QueenValueMg * 16;
- }
- }
+ swapList[i] = - QueenValueMg * 16;
// Having built the swap list, we negamax through it to find the best
// achievable score from the point of view of the side to move.
void undo_null_move();
// Static exchange evaluation
- int see(Move m) const;
+ int see(Move m, int asymmThreshold = 0) const;
int see_sign(Move m) const;
- int see_asymm(Move m, int asymmThreshold) const;
// Accessing hash keys
Key key() const;
// Helper functions
void do_castle(Square kfrom, Square kto, Square rfrom, Square rto);
- template<bool Asymmetric> int do_see(Move m, int asymmThreshold) const;
template<bool FindPinned> Bitboard hidden_checkers() const;
// Computing hash keys from scratch (for initialization and debugging)
continue;
}
- // Prune moves with negative or equal SEE.
- // Also prune moves with positive SEE where capturing loses a tempo and SEE < beta - futilityBase.
+ // Prune moves with negative or equal SEE and also moves with positive
+ // SEE where capturing piece loses a tempo and SEE < beta - futilityBase.
if ( futilityBase < beta
&& depth < DEPTH_ZERO
- && pos.see_asymm(move, beta - futilityBase) <= 0)
+ && pos.see(move, beta - futilityBase) <= 0)
{
bestValue = std::max(bestValue, futilityBase);
continue;