Simplification of SEE verification logic

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 3a7f85a85e1f67fa18308a60c2854139219430ec..5205fb5729b5799e96310b70682607fdac73ce03 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1006,17 +1006,15 @@ moves_loop: // When in check, search starts here
               {
                   if (depth < 2 - capture)
                       continue;
-                  // Don't prune the move if opp. King/Queen/Rook is attacked by a slider after the exchanges.
-                  // Since in see_ge we don't update occupied when the king recaptures, we also don't prune the
-                  // move when the opp. King gets a discovered slider attack DURING the exchanges.
-                  Bitboard leftEnemies = pos.pieces(~us, ROOK, QUEEN, KING) & occupied;
+                  // Don't prune the move if opp. King/Queen/Rook gets a discovered attack during or after the exchanges
+                  Bitboard leftEnemies = pos.pieces(~us, KING, QUEEN, ROOK);
                   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;
-                      // Exclude Queen/Rook(s) which were already threatened before SEE
+                      // Exclude Queen/Rook(s) which were already threatened before SEE (opp King can't be in check when it's our turn)
                       if (attacks && sq != pos.square<KING>(~us) && (pos.attackers_to(sq, pos.pieces()) & pos.pieces(us)))
                           attacks = 0;
                   }