X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fmovegen.cpp;h=d821f0fad2e0ce56ccf6e03e6d22850b02ddb0b5;hb=ae2f5f25cd8a6bc2762eefc032436052c0db679e;hp=e1e6a54b72aa718c55c9c51bc38416f0d13a4e25;hpb=4c3a000211bea046dd9506bae748576ecf6368fa;p=stockfish

diff --git a/src/movegen.cpp b/src/movegen.cpp
index e1e6a54b..d821f0fa 100644
--- a/src/movegen.cpp
+++ b/src/movegen.cpp
@@ -217,7 +217,7 @@ MoveStack* generate<MV_NON_CAPTURE_CHECK>(const Position& pos, MoveStack* mlist)
   while (b)
   {
      from = pop_1st_bit(&b);
-     switch (pos.type_of_piece_on(from))
+     switch (piece_type(pos.piece_on(from)))
      {
       case PAWN:   /* Will be generated togheter with pawns direct checks */     break;
       case KNIGHT: mlist = generate_discovered_checks<KNIGHT>(pos, mlist, from); break;
@@ -265,19 +265,24 @@ MoveStack* generate<MV_EVASION>(const Position& pos, MoveStack* mlist) {
       checkersCnt++;
       checksq = pop_1st_bit(&b);
 
-      assert(pos.color_of_piece_on(checksq) == opposite_color(us));
+      assert(piece_color(pos.piece_on(checksq)) == opposite_color(us));
 
-      switch (pos.type_of_piece_on(checksq))
+      switch (piece_type(pos.piece_on(checksq)))
       {
       case BISHOP: sliderAttacks |= BishopPseudoAttacks[checksq]; break;
       case ROOK:   sliderAttacks |= RookPseudoAttacks[checksq];   break;
       case QUEEN:
-          // In case of a queen remove also squares attacked in the other direction to
-          // avoid possible illegal moves when queen and king are on adjacent squares.
-          if (RookPseudoAttacks[checksq] & (1ULL << ksq))
-              sliderAttacks |= RookPseudoAttacks[checksq] | pos.attacks_from<BISHOP>(checksq);
+          // If queen and king are far we can safely remove all the squares attacked
+          // in the other direction becuase are not reachable by the king anyway.
+          if (squares_between(ksq, checksq) || (RookPseudoAttacks[checksq] & (1ULL << ksq)))
+              sliderAttacks |= QueenPseudoAttacks[checksq];
+
+          // Otherwise, if king and queen are adjacent and on a diagonal line, we need to
+          // use real rook attacks to check if king is safe to move in the other direction.
+          // For example: king in B2, queen in A1 a knight in B1, and we can safely move to C1.
           else
               sliderAttacks |= BishopPseudoAttacks[checksq] | pos.attacks_from<ROOK>(checksq);
+
       default:
           break;
       }