Simpler stalemate check.
parent
0347339970
commit
b46bf2950f
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@ -22,6 +22,7 @@
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#include "bitcount.h"
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#include "endgame.h"
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#include "movegen.h"
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using std::string;
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@ -82,21 +83,6 @@ namespace {
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template<typename M>
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void delete_endgame(const typename M::value_type& p) { delete p.second; }
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// Fast stalemate detection with lone king
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bool is_kxk_stalemate(const Position &pos, const Color c) {
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if ( pos.side_to_move() == c &&
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!pos.in_check()) {
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const Square from = pos.king_square(c);
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Bitboard b = pos.attacks_from<KING>(from);
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while (b) {
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// Assume there are no pinned pieces, as it is a lone king
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if (pos.pl_move_is_legal(make_move(from, pop_1st_bit(&b)), 0))
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return false;
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}
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return true;
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}
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return false;
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}
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} // namespace
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@ -147,7 +133,10 @@ Value Endgame<KXK>::operator()(const Position& pos) const {
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assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
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assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO);
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if (is_kxk_stalemate(pos, weakerSide)) {
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// Stalemate detection with lone king
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if ( pos.side_to_move() == weakerSide
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&& !pos.in_check()
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&& !MoveList<MV_LEGAL>(pos).size()) {
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return VALUE_DRAW;
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}
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