Penalty for all enemy pawns xrayed by our bishop.

[stockfish] / src / endgame.cpp

diff --git a/src/endgame.cpp b/src/endgame.cpp
index 0a2b02ad6c96305dcb6833e5ccdc97c20859c91e..e232da6243a32f0e2c9e647bf1814e0c916689bd 100644 (file)
--- a/src/endgame.cpp
+++ b/src/endgame.cpp
@@ -24,8 +24,6 @@
 #include "endgame.h"
 #include "movegen.h"
 
-using std::string;
-
 namespace {
 
   // Used to drive the king towards the edge of the board
@@ -81,8 +79,6 @@ namespace Endgames {
     add<KQKR>("KQKR");
     add<KNNKP>("KNNKP");
 
-    add<KNPK>("KNPK");
-    add<KNPKB>("KNPKB");
     add<KRPKR>("KRPKR");
     add<KRPKB>("KRPKB");
     add<KBPKB>("KBPKB");
@@ -326,23 +322,23 @@ ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
   // No assertions about the material of weakSide, because we want draws to
   // be detected even when the weaker side has some pawns.
 
-  Bitboard strongpawns = pos.pieces(strongSide, PAWN);
-  Bitboard allpawns = pos.pieces(PAWN);
+  Bitboard strongPawns = pos.pieces(strongSide, PAWN);
+  Bitboard allPawns = pos.pieces(PAWN);
 
   // All strongSide pawns are on a single rook file?
-  if (!(strongpawns & ~FileABB) || !(strongpawns & ~FileHBB))
+  if (!(strongPawns & ~FileABB) || !(strongPawns & ~FileHBB))
   {
       Square bishopSq = pos.square<BISHOP>(strongSide);
-      Square queeningSq = relative_square(strongSide, make_square(file_of(lsb(strongpawns)), RANK_8));
-      Square weakkingSq = pos.square<KING>(weakSide);
+      Square queeningSq = relative_square(strongSide, make_square(file_of(lsb(strongPawns)), RANK_8));
+      Square weakKingSq = pos.square<KING>(weakSide);
 
       if (   opposite_colors(queeningSq, bishopSq)
-          && distance(queeningSq, weakkingSq) <= 1)
+          && distance(queeningSq, weakKingSq) <= 1)
           return SCALE_FACTOR_DRAW;
   }
 
   // If all the pawns are on the same B or G file, then it's potentially a draw
-  if ((!(allpawns & ~FileBBB) || !(allpawns & ~FileGBB))
+  if ((!(allPawns & ~FileBBB) || !(allPawns & ~FileGBB))
       && pos.non_pawn_material(weakSide) == 0
       && pos.count<PAWN>(weakSide) >= 1)
   {
@@ -356,8 +352,8 @@ ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
       // There's potential for a draw if our pawn is blocked on the 7th rank,
       // the bishop cannot attack it or they only have one pawn left
       if (   relative_rank(strongSide, weakPawnSq) == RANK_7
-          && (strongpawns & (weakPawnSq + pawn_push(weakSide)))
-          && (opposite_colors(bishopSq, weakPawnSq) || !more_than_one(strongpawns)))
+          && (strongPawns & (weakPawnSq + pawn_push(weakSide)))
+          && (opposite_colors(bishopSq, weakPawnSq) || !more_than_one(strongPawns)))
       {
           int strongKingDist = distance(weakPawnSq, strongKingSq);
           int weakKingDist = distance(weakPawnSq, weakKingSq);
@@ -588,11 +584,9 @@ ScaleFactor Endgame<KPsK>::operator()(const Position& pos) const {
   Square ksq = pos.square<KING>(weakSide);
   Bitboard pawns = pos.pieces(strongSide, PAWN);
 
-  // If all pawns are ahead of the king, on a single rook file and
-  // the king is within one file of the pawns, it's a draw.
-  if (   !(pawns & ~forward_ranks_bb(weakSide, ksq))
-      && !((pawns & ~FileABB) && (pawns & ~FileHBB))
-      &&  distance<File>(ksq, lsb(pawns)) <= 1)
+  // If all pawns are ahead of the king on a single rook file, it's a draw.
+  if (!((pawns & ~FileABB) || (pawns & ~FileHBB)) &&
+      !(pawns & ~passed_pawn_span(weakSide, ksq)))
       return SCALE_FACTOR_DRAW;
 
   return SCALE_FACTOR_NONE;
@@ -615,8 +609,7 @@ ScaleFactor Endgame<KBPKB>::operator()(const Position& pos) const {
   Square weakKingSq = pos.square<KING>(weakSide);
 
   // Case 1: Defending king blocks the pawn, and cannot be driven away
-  if (   file_of(weakKingSq) == file_of(pawnSq)
-      && relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq)
+  if (   (forward_file_bb(strongSide, pawnSq) & weakKingSq)
       && (   opposite_colors(weakKingSq, strongBishopSq)
           || relative_rank(strongSide, weakKingSq) <= RANK_6))
       return SCALE_FACTOR_DRAW;
@@ -719,46 +712,6 @@ ScaleFactor Endgame<KBPKN>::operator()(const Position& pos) const {
 }
 
 
-/// KNP vs K. There is a single rule: if the pawn is a rook pawn on the 7th rank
-/// and the defending king prevents the pawn from advancing, the position is drawn.
-template<>
-ScaleFactor Endgame<KNPK>::operator()(const Position& pos) const {
-
-  assert(verify_material(pos, strongSide, KnightValueMg, 1));
-  assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
-
-  // Assume strongSide is white and the pawn is on files A-D
-  Square pawnSq     = normalize(pos, strongSide, pos.square<PAWN>(strongSide));
-  Square weakKingSq = normalize(pos, strongSide, pos.square<KING>(weakSide));
-
-  if (pawnSq == SQ_A7 && distance(SQ_A8, weakKingSq) <= 1)
-      return SCALE_FACTOR_DRAW;
-
-  return SCALE_FACTOR_NONE;
-}
-
-
-/// KNP vs KB. If knight can block bishop from taking pawn, it's a win.
-/// Otherwise the position is drawn.
-template<>
-ScaleFactor Endgame<KNPKB>::operator()(const Position& pos) const {
-
-  assert(verify_material(pos, strongSide, KnightValueMg, 1));
-  assert(verify_material(pos, weakSide, BishopValueMg, 0));
-
-  Square pawnSq = pos.square<PAWN>(strongSide);
-  Square bishopSq = pos.square<BISHOP>(weakSide);
-  Square weakKingSq = pos.square<KING>(weakSide);
-
-  // King needs to get close to promoting pawn to prevent knight from blocking.
-  // Rules for this are very tricky, so just approximate.
-  if (forward_file_bb(strongSide, pawnSq) & pos.attacks_from<BISHOP>(bishopSq))
-      return ScaleFactor(distance(weakKingSq, pawnSq));
-
-  return SCALE_FACTOR_NONE;
-}
-
-
 /// KP vs KP. This is done by removing the weakest side's pawn and probing the
 /// KP vs K bitbase: If the weakest side has a draw without the pawn, it probably
 /// has at least a draw with the pawn as well. The exception is when the stronger