Fix KBNK endgame

Broken by recent patch. Also better document what's
happening there.

Verified to restore original behaviour.

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

diff --git a/src/endgame.cpp b/src/endgame.cpp
index 1be3844..24c8c5d 100644 (file)
--- a/src/endgame.cpp
+++ b/src/endgame.cpp
@@ -152,7 +152,10 @@ Value EvaluationFunction<KBNK>::apply(const Position& pos) const {
   Square loserKSq = pos.king_square(weakerSide);
   Square bishopSquare = pos.piece_list(strongerSide, BISHOP, 0);
 
-  if (same_color_squares(bishopSquare, SQ_A1))
+  // kbnk_mate_table() tries to drive toward corners A1 or H8,
+  // if we have a bishop that cannot reach the above squares we
+  // mirror the kings so to drive enemy toward corners A8 or H1.
+  if (!same_color_squares(bishopSquare, SQ_A1))
   {
       winnerKSq = flop_square(winnerKSq);
       loserKSq = flop_square(loserKSq);

diff --git a/src/position.cpp b/src/position.cpp
index 879e969..183530f 100644 (file)
--- 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 == NO_PIECE && same_color_squares(sq, SQ_A1))
+          if (piece == NO_PIECE && square_color(sq) == DARK)
               piece = NO_PIECE_DARK_SQ;
 
           cout << c << pieceLetters.from_piece(piece) << c << '|';