Simplify SEE pruning for captures

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index e51e2f4dae122310673d40cfced2c5afaea79129..970b0f4764b9ac5f234955bfc21aeda492cb4433 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -989,28 +989,9 @@ moves_loop: // When in check, search starts here
                    + captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] / 7 < alpha)
                   continue;
 
-              Bitboard occupied;
-              // SEE based pruning (~11 Elo)
-              if (!pos.see_ge(move, occupied, Value(-205) * depth))
-              {
-                 if (depth < 2 - capture)
-                    continue;
-                 // Don't prune the move if opponent Queen/Rook is under discovered attack after the exchanges
-                 // Don't prune the move if opponent King is under discovered attack after or during the exchanges
-                 Bitboard leftEnemies = (pos.pieces(~us, KING, QUEEN, ROOK)) & occupied;
-                 Bitboard attacks = 0;
-                 occupied |= to_sq(move);
-                 while (leftEnemies && !attacks)
-                 {
-                      Square sq = pop_lsb(leftEnemies);
-                      attacks |= pos.attackers_to(sq, occupied) & pos.pieces(us) & occupied;
-                      // Don't consider pieces that were already threatened/hanging before SEE exchanges
-                      if (attacks && (sq != pos.square<KING>(~us) && (pos.attackers_to(sq, pos.pieces()) & pos.pieces(us))))
-                         attacks = 0;
-                 }
-                 if (!attacks)
-                    continue;
-              }
+              // SEE based pruning for captures and checks (~11 Elo)
+              if (!pos.see_ge(move, Value(-205) * depth))
+                  continue;
           }
           else
           {