From: Marco Costalba <mcostalba@gmail.com>
Date: Thu, 23 Oct 2008 19:43:48 +0000 (+0100)
Subject: Unify pinned and discovery checks code
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=1ac2f501452ebd9249437b338c98ec398776b71a;ds=sidebyside

Unify pinned and discovery checks code

Templates are our friends here. No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---

diff --git a/src/position.cpp b/src/position.cpp
index e33b65fc..111f5cea 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -296,86 +296,66 @@ void Position::copy(const Position &pos) {
 }
 
 
-/// Position:pinned_pieces<>() returns a bitboard of all pinned (against the
-/// king) pieces for the given color and for the given pinner type.
-template<PieceType Piece>
-Bitboard Position::pinned_pieces(Color c, Square ksq) const {
+/// Position:pinned_pieces() returns a bitboard of all pinned (against the
+/// king) pieces for the given color.
+Bitboard Position::pinned_pieces(Color c) const {
+
+  Square ksq = king_square(c);
+  return hidden_checks<ROOK, true>(c, ksq) | hidden_checks<BISHOP, true>(c, ksq);
+}
+
+
+/// Position:discovered_check_candidates() returns a bitboard containing all
+/// pieces for the given side which are candidates for giving a discovered
+/// check.  The code is almost the same as the function for finding pinned
+/// pieces.
+
+Bitboard Position::discovered_check_candidates(Color c) const {
+
+  Square ksq = king_square(opposite_color(c));
+  return hidden_checks<ROOK, false>(c, ksq) | hidden_checks<BISHOP, false>(c, ksq);
+}
+
+
+/// Position:hidden_checks<>() returns a bitboard of all pinned (against the
+/// king) pieces for the given color and for the given pinner type. Or, when
+/// template parameter FindPinned is false, the pinned pieces of opposite color
+/// that are, indeed, the pieces candidate for a discovery check.
+template<PieceType Piece, bool FindPinned>
+Bitboard Position::hidden_checks(Color c, Square ksq) const {
 
   Square s;
-  Bitboard sliders, pinned = EmptyBoardBB;
+  Bitboard sliders, result = EmptyBoardBB;
   
   if (Piece == ROOK) // Resolved at compile time
-      sliders = rooks_and_queens(opposite_color(c)) & RookPseudoAttacks[ksq];
+      sliders = rooks_and_queens(FindPinned ? opposite_color(c) : c) & RookPseudoAttacks[ksq];
   else
-      sliders = bishops_and_queens(opposite_color(c)) & BishopPseudoAttacks[ksq];
+      sliders = bishops_and_queens(FindPinned ? opposite_color(c) : c) & BishopPseudoAttacks[ksq];
 
-  if (sliders && (sliders & ~checkersBB))
+  if (sliders && (!FindPinned || (sliders & ~checkersBB)))
   {
-       // Our king blockers are candidate pinned pieces
+       // King blockers are candidate pinned pieces
       Bitboard candidate_pinned = piece_attacks<Piece>(ksq) & pieces_of_color(c);
 
       // Pinners are sliders, not checkers, that give check when 
       // candidate pinned are removed.
-      Bitboard pinners =  sliders & ~checkersBB;
+      Bitboard pinners = (FindPinned ? sliders & ~checkersBB : sliders);
+
       if (Piece == ROOK)
           pinners &= rook_attacks_bb(ksq, occupied_squares() ^ candidate_pinned);
       else
           pinners &= bishop_attacks_bb(ksq, occupied_squares() ^ candidate_pinned);
 
-      // Finally for each pinner find the corresponding pinned piece
-      // among the candidates.
+
+      // Finally for each pinner find the corresponding pinned piece (if same color of king)
+      // or discovery checker (if opposite color) among the candidates.
       while (pinners)
       {
           s = pop_1st_bit(&pinners);
-          pinned |= (squares_between(s, ksq) & candidate_pinned);
+          result |= (squares_between(s, ksq) & candidate_pinned);
       }
   }
-  return pinned;
-}
-
-
-/// Position:pinned_pieces() returns a bitboard of all pinned (against the
-/// king) pieces for the given color.
-Bitboard Position::pinned_pieces(Color c) const {
-
-  Square ksq = king_square(c);
-  return pinned_pieces<ROOK>(c, ksq) | pinned_pieces<BISHOP>(c, ksq);
-}
-
-
-/// Position:discovered_check_candidates() returns a bitboard containing all
-/// pieces for the given side which are candidates for giving a discovered
-/// check.  The code is almost the same as the function for finding pinned
-/// pieces.
-
-Bitboard Position::discovered_check_candidates(Color c) const {
-  Bitboard b1, b2, dc, checkers, sliders;
-  Square ksq = king_square(opposite_color(c)), s;
-
-  dc = EmptyBoardBB;
-  b1 = occupied_squares();
-
-  sliders = rooks_and_queens(c);
-  if(sliders & RookPseudoAttacks[ksq]) {
-    b2 = piece_attacks<ROOK>(ksq) & pieces_of_color(c);
-    checkers = rook_attacks_bb(ksq, b1 ^ b2) & sliders;
-    while(checkers) {
-      s = pop_1st_bit(&checkers);
-      dc |= (squares_between(s, ksq) & b2);
-    }
-  }
-
-  sliders = bishops_and_queens(c);
-  if(sliders & BishopPseudoAttacks[ksq]) {
-    b2 = piece_attacks<BISHOP>(ksq) & pieces_of_color(c);
-    checkers = bishop_attacks_bb(ksq, b1 ^ b2) & sliders;
-    while(checkers) {
-      s = pop_1st_bit(&checkers);
-      dc |= (squares_between(s, ksq) & b2);
-    }
-  }
-
-  return dc;
+  return result;
 }
 
 
diff --git a/src/position.h b/src/position.h
index 5ae75655..f77b368a 100644
--- a/src/position.h
+++ b/src/position.h
@@ -197,8 +197,6 @@ public:
   // Bitboards for pinned pieces and discovered check candidates
   Bitboard discovered_check_candidates(Color c) const;
   Bitboard pinned_pieces(Color c) const;
-  template<PieceType Piece>
-  Bitboard pinned_pieces(Color c, Square ksq) const;
 
   // Checking pieces
   Bitboard checkers() const;
@@ -307,6 +305,9 @@ private:
   void undo_ep_move(Move m);
   void find_checkers();
 
+  template<PieceType Piece, bool FindPinned>
+  Bitboard hidden_checks(Color c, Square ksq) const;
+
   // Computing hash keys from scratch (for initialization and debugging)
   Key compute_key() const;
   Key compute_pawn_key() const;