From: Marco Costalba <mcostalba@gmail.com>
Date: Sun, 25 Jul 2010 10:05:01 +0000 (+0100)
Subject: Introduce and use same_color_squares()
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=9b1d5bd5343540db412c50ae2944246e3f25d18b;hp=a84e4b20491f69d2b6f64e4f9738fc8ba3394990

Introduce and use same_color_squares()

No functional change.

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

diff --git a/src/endgame.cpp b/src/endgame.cpp
index e3cd2007..1be38441 100644
--- a/src/endgame.cpp
+++ b/src/endgame.cpp
@@ -152,7 +152,7 @@ Value EvaluationFunction<KBNK>::apply(const Position& pos) const {
   Square loserKSq = pos.king_square(weakerSide);
   Square bishopSquare = pos.piece_list(strongerSide, BISHOP, 0);
 
-  if (square_color(bishopSquare) == BLACK)
+  if (same_color_squares(bishopSquare, SQ_A1))
   {
       winnerKSq = flop_square(winnerKSq);
       loserKSq = flop_square(loserKSq);
@@ -398,7 +398,7 @@ ScaleFactor ScalingFunction<KBPsK>::apply(const Position& pos) const {
       Square queeningSq = relative_square(strongerSide, make_square(pawnFile, RANK_8));
       Square kingSq = pos.king_square(weakerSide);
 
-      if (   square_color(queeningSq) != square_color(bishopSq)
+      if (  !same_color_squares(queeningSq, bishopSq)
           && file_distance(square_file(kingSq), pawnFile) <= 1)
       {
           // The bishop has the wrong color, and the defending king is on the
@@ -675,12 +675,12 @@ ScaleFactor ScalingFunction<KBPKB>::apply(const Position& pos) const {
   // Case 1: Defending king blocks the pawn, and cannot be driven away
   if (   square_file(weakerKingSq) == square_file(pawnSq)
       && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
-      && (   square_color(weakerKingSq) != square_color(strongerBishopSq)
+      && (  !same_color_squares(weakerKingSq, strongerBishopSq)
           || relative_rank(strongerSide, weakerKingSq) <= RANK_6))
       return SCALE_FACTOR_ZERO;
 
   // Case 2: Opposite colored bishops
-  if (square_color(strongerBishopSq) != square_color(weakerBishopSq))
+  if (!same_color_squares(strongerBishopSq, weakerBishopSq))
   {
       // We assume that the position is drawn in the following three situations:
       //
@@ -724,7 +724,7 @@ ScaleFactor ScalingFunction<KBPPKB>::apply(const Position& pos) const {
   Square wbsq = pos.piece_list(strongerSide, BISHOP, 0);
   Square bbsq = pos.piece_list(weakerSide, BISHOP, 0);
 
-  if (square_color(wbsq) == square_color(bbsq))
+  if (same_color_squares(wbsq, bbsq))
       // Not opposite-colored bishops, no scaling
       return SCALE_FACTOR_NONE;
 
@@ -753,7 +753,7 @@ ScaleFactor ScalingFunction<KBPPKB>::apply(const Position& pos) const {
     // some square in the frontmost pawn's path.
     if (   square_file(ksq) == square_file(blockSq1)
         && relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1)
-        && square_color(ksq) != square_color(wbsq))
+        && !same_color_squares(ksq, wbsq))
         return SCALE_FACTOR_ZERO;
     else
         return SCALE_FACTOR_NONE;
@@ -763,14 +763,14 @@ ScaleFactor ScalingFunction<KBPPKB>::apply(const Position& pos) const {
     // in front of the frontmost pawn's path, and the square diagonally behind
     // this square on the file of the other pawn.
     if (   ksq == blockSq1
-        && square_color(ksq) != square_color(wbsq)
+        && !same_color_squares(ksq, wbsq)
         && (   bbsq == blockSq2
             || (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(BISHOP, weakerSide))
             || rank_distance(r1, r2) >= 2))
         return SCALE_FACTOR_ZERO;
 
     else if (   ksq == blockSq2
-             && square_color(ksq) != square_color(wbsq)
+             && !same_color_squares(ksq, wbsq)
              && (   bbsq == blockSq1
                  || (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(BISHOP, weakerSide))))
         return SCALE_FACTOR_ZERO;
@@ -804,7 +804,7 @@ ScaleFactor ScalingFunction<KBPKN>::apply(const Position& pos) const {
 
   if (   square_file(weakerKingSq) == square_file(pawnSq)
       && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
-      && (   square_color(weakerKingSq) != square_color(strongerBishopSq)
+      && (  !same_color_squares(weakerKingSq, strongerBishopSq)
           || relative_rank(strongerSide, weakerKingSq) <= RANK_6))
       return SCALE_FACTOR_ZERO;
 
diff --git a/src/position.cpp b/src/position.cpp
index 5e64975b..9af2d9d8 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -400,7 +400,7 @@ void Position::print(Move move) const {
           char c = (color_of_piece_on(sq) == BLACK ? '=' : ' ');
           Piece piece = piece_on(sq);
 
-          if (piece == EMPTY && square_color(sq) == BLACK)
+          if (piece == EMPTY && same_color_squares(sq, SQ_A1))
               piece = EMPTY_BLACK_SQ;
 
           cout << c << pieceLetters.from_piece(piece) << c << '|';
diff --git a/src/position.h b/src/position.h
index 4854b29d..d2132388 100644
--- a/src/position.h
+++ b/src/position.h
@@ -540,7 +540,7 @@ inline bool Position::opposite_colored_bishops() const {
 
   return   piece_count(WHITE, BISHOP) == 1
         && piece_count(BLACK, BISHOP) == 1
-        && square_color(piece_list(WHITE, BISHOP, 0)) != square_color(piece_list(BLACK, BISHOP, 0));
+        && !same_color_squares(piece_list(WHITE, BISHOP, 0), piece_list(BLACK, BISHOP, 0));
 }
 
 inline bool Position::has_pawn_on_7th(Color c) const {
diff --git a/src/square.h b/src/square.h
index aa3585c1..d35d72bf 100644
--- a/src/square.h
+++ b/src/square.h
@@ -139,6 +139,11 @@ inline Color square_color(Square s) {
   return Color((int(square_file(s)) + int(square_rank(s))) & 1);
 }
 
+inline bool same_color_squares(Square s1, Square s2) {
+  int s = int(s1) ^ int(s2);
+  return (((s >> 3) ^ s) & 1) == 0;
+}
+
 inline int file_distance(File f1, File f2) {
   return abs(int(f1) - int(f2));
 }