X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fendgame.cpp;h=e52f9939e3eea38180315735578cfc40ab7c5b97;hp=635ff4085382ad07f4d2ecc67a7fbcfacb615695;hb=67b0da83da343cb6046f2a2f088f7aa1a6276637;hpb=3cddb0c0765e7a4ecd66806d92b72e1faddac4c4

diff --git a/src/endgame.cpp b/src/endgame.cpp
index 635ff408..e52f9939 100644
--- a/src/endgame.cpp
+++ b/src/endgame.cpp
@@ -65,6 +65,21 @@ namespace {
   }
 #endif
 
+  // Map the square as if strongSide is white and strongSide's only pawn
+  // is on the left half of the board.
+  Square normalize(const Position& pos, Color strongSide, Square sq) {
+
+    assert(pos.count<PAWN>(strongSide) == 1);
+
+    if (file_of(pos.list<PAWN>(strongSide)[0]) >= FILE_E)
+        sq = mirror(sq);
+
+    if (strongSide == BLACK)
+        sq = ~sq;
+
+    return sq;
+  }
+
   // Get the material key of a Position out of the given endgame key code
   // like "KBPKN". The trick here is to first forge an ad-hoc fen string
   // and then let a Position object to do the work for us. Note that the
@@ -174,11 +189,11 @@ Value Endgame<KBNK>::operator()(const Position& pos) const {
 
   // 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.
+  // flip the kings so to drive enemy toward corners A8 or H1.
   if (opposite_colors(bishopSq, SQ_A1))
   {
-      winnerKSq = mirror(winnerKSq);
-      loserKSq = mirror(loserKSq);
+      winnerKSq = ~winnerKSq;
+      loserKSq  = ~loserKSq;
   }
 
   Value result =  VALUE_KNOWN_WIN
@@ -196,25 +211,12 @@ Value Endgame<KPK>::operator()(const Position& pos) const {
   assert(verify_material(pos, strongSide, VALUE_ZERO, 1));
   assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
 
-  Square wksq = pos.king_square(strongSide);
-  Square bksq = pos.king_square(weakSide);
-  Square psq  = pos.list<PAWN>(strongSide)[0];
-  Color  us   = pos.side_to_move();
+  // Assume strongSide is white and the pawn is on files A-D
+  Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
+  Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
+  Square psq  = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
 
-  if (strongSide == BLACK)
-  {
-      wksq = ~wksq;
-      bksq = ~bksq;
-      psq  = ~psq;
-      us   = ~us;
-  }
-
-  if (file_of(psq) >= FILE_E)
-  {
-      wksq = mirror(wksq);
-      bksq = mirror(bksq);
-      psq  = mirror(psq);
-  }
+  Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
 
   if (!Bitbases::probe_kpk(wksq, psq, bksq, us))
       return VALUE_DRAW;
@@ -235,18 +237,10 @@ Value Endgame<KRKP>::operator()(const Position& pos) const {
   assert(verify_material(pos, strongSide, RookValueMg, 0));
   assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
 
-  Square wksq = pos.king_square(strongSide);
-  Square bksq = pos.king_square(weakSide);
-  Square rsq  = pos.list<ROOK>(strongSide)[0];
-  Square psq  = pos.list<PAWN>(weakSide)[0];
-
-  if (strongSide == BLACK)
-  {
-      wksq = ~wksq;
-      bksq = ~bksq;
-      rsq  = ~rsq;
-      psq  = ~psq;
-  }
+  Square wksq = relative_square(strongSide, pos.king_square(strongSide));
+  Square bksq = relative_square(strongSide, pos.king_square(weakSide));
+  Square rsq  = relative_square(strongSide, pos.list<ROOK>(strongSide)[0]);
+  Square psq  = relative_square(strongSide, pos.list<PAWN>(weakSide)[0]);
 
   Square queeningSq = file_of(psq) | RANK_1;
   Value result;
@@ -486,31 +480,12 @@ ScaleFactor Endgame<KRPKR>::operator()(const Position& pos) const {
   assert(verify_material(pos, strongSide, RookValueMg, 1));
   assert(verify_material(pos, weakSide,   RookValueMg, 0));
 
-  Square wksq = pos.king_square(strongSide);
-  Square bksq = pos.king_square(weakSide);
-  Square wrsq = pos.list<ROOK>(strongSide)[0];
-  Square wpsq = pos.list<PAWN>(strongSide)[0];
-  Square brsq = pos.list<ROOK>(weakSide)[0];
-
-  // Orient the board in such a way that the stronger side is white, and the
-  // pawn is on the left half of the board.
-  if (strongSide == BLACK)
-  {
-      wksq = ~wksq;
-      wrsq = ~wrsq;
-      wpsq = ~wpsq;
-      bksq = ~bksq;
-      brsq = ~brsq;
-  }
-
-  if (file_of(wpsq) > FILE_D)
-  {
-      wksq = mirror(wksq);
-      wrsq = mirror(wrsq);
-      wpsq = mirror(wpsq);
-      bksq = mirror(bksq);
-      brsq = mirror(brsq);
-  }
+  // Assume strongSide is white and the pawn is on files A-D
+  Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
+  Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
+  Square wrsq = normalize(pos, strongSide, pos.list<ROOK>(strongSide)[0]);
+  Square wpsq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
+  Square brsq = normalize(pos, strongSide, pos.list<ROOK>(weakSide)[0]);
 
   File f = file_of(wpsq);
   Rank r = rank_of(wpsq);
@@ -852,15 +827,11 @@ ScaleFactor Endgame<KNPK>::operator()(const Position& pos) const {
   assert(verify_material(pos, strongSide, KnightValueMg, 1));
   assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
 
-  Square pawnSq = pos.list<PAWN>(strongSide)[0];
-  Square weakKingSq = pos.king_square(weakSide);
-
-  if (   pawnSq == relative_square(strongSide, SQ_A7)
-      && square_distance(weakKingSq, relative_square(strongSide, SQ_A8)) <= 1)
-      return SCALE_FACTOR_DRAW;
+  // Assume strongSide is white and the pawn is on files A-D
+  Square pawnSq     = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
+  Square weakKingSq = normalize(pos, strongSide, pos.king_square(weakSide));
 
-  if (   pawnSq == relative_square(strongSide, SQ_H7)
-      && square_distance(weakKingSq, relative_square(strongSide, SQ_H8)) <= 1)
+  if (pawnSq == SQ_A7 && square_distance(SQ_A8, weakKingSq) <= 1)
       return SCALE_FACTOR_DRAW;
 
   return SCALE_FACTOR_NONE;
@@ -896,25 +867,12 @@ ScaleFactor Endgame<KPKP>::operator()(const Position& pos) const {
   assert(verify_material(pos, strongSide, VALUE_ZERO, 1));
   assert(verify_material(pos, weakSide,   VALUE_ZERO, 1));
 
-  Square wksq = pos.king_square(strongSide);
-  Square bksq = pos.king_square(weakSide);
-  Square psq  = pos.list<PAWN>(strongSide)[0];
-  Color  us   = pos.side_to_move();
-
-  if (strongSide == BLACK)
-  {
-      wksq = ~wksq;
-      bksq = ~bksq;
-      psq  = ~psq;
-      us   = ~us;
-  }
+  // Assume strongSide is white and the pawn is on files A-D
+  Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
+  Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
+  Square psq  = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
 
-  if (file_of(psq) >= FILE_E)
-  {
-      wksq = mirror(wksq);
-      bksq = mirror(bksq);
-      psq  = mirror(psq);
-  }
+  Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
 
   // If the pawn has advanced to the fifth rank or further, and is not a
   // rook pawn, it's too dangerous to assume that it's at least a draw.