diff --git a/src/endgame.cpp b/src/endgame.cpp index d458cd66..ec54d4e6 100644 --- a/src/endgame.cpp +++ b/src/endgame.cpp @@ -22,6 +22,7 @@ #include "bitcount.h" #include "endgame.h" +#include "movegen.h" using std::string; @@ -132,6 +133,13 @@ Value Endgame::operator()(const Position& pos) const { assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO); assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO); + // Stalemate detection with lone king + if ( pos.side_to_move() == weakerSide + && !pos.in_check() + && !MoveList(pos).size()) { + return VALUE_DRAW; + } + Square winnerKSq = pos.king_square(strongerSide); Square loserKSq = pos.king_square(weakerSide); @@ -142,9 +150,9 @@ Value Endgame::operator()(const Position& pos) const { if ( pos.piece_count(strongerSide, QUEEN) || pos.piece_count(strongerSide, ROOK) - || pos.piece_count(strongerSide, BISHOP) > 1) - // TODO: check for two equal-colored bishops! - result += VALUE_KNOWN_WIN; + || pos.both_color_bishops(strongerSide)) { + result += VALUE_KNOWN_WIN; + } return strongerSide == pos.side_to_move() ? result : -result; } diff --git a/src/position.h b/src/position.h index bcbfc850..8229e71b 100644 --- a/src/position.h +++ b/src/position.h @@ -189,6 +189,7 @@ public: template bool is_draw() const; int startpos_ply_counter() const; bool opposite_colored_bishops() const; + bool both_color_bishops(Color c) const; bool has_pawn_on_7th(Color c) const; bool is_chess960() const; @@ -432,6 +433,12 @@ inline bool Position::opposite_colored_bishops() const { && opposite_colors(pieceList[WHITE][BISHOP][0], pieceList[BLACK][BISHOP][0]); } +inline bool Position::both_color_bishops(Color c) const { + // Assumes that there are only two bishops + return pieceCount[c][BISHOP] >= 2 && + opposite_colors(pieceList[c][BISHOP][0], pieceList[c][BISHOP][1]); +} + inline bool Position::has_pawn_on_7th(Color c) const { return pieces(PAWN, c) & rank_bb(relative_rank(c, RANK_7)); }