X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fposition.cpp;h=cb63cf9537775848cdc222856a87dfdddc445ef3;hp=feb185cfb39b4ac9739745915aad42dbd0d22130;hb=a28f4a56d31c9e7f7c5ce28a93e2b2b9ca9be5e5;hpb=4350d9e8a6c979c5631d05ecb645834882701e4c diff --git a/src/position.cpp b/src/position.cpp index feb185cf..cb63cf95 100644 --- a/src/position.cpp +++ b/src/position.cpp @@ -91,6 +91,12 @@ Score Position::PieceSquareTable[16][64]; static PieceLetters pieceLetters; +// Material values used by SEE, indexed by PieceType +const Value Position::seeValues[] = { + VALUE_ZERO, PawnValueMidgame, KnightValueMidgame, BishopValueMidgame, + RookValueMidgame, QueenValueMidgame, QueenValueMidgame*10 +}; + /// Constructors @@ -1339,12 +1345,6 @@ void Position::undo_null_move() { /// move, and one which takes a 'from' and a 'to' square. The function does /// not yet understand promotions captures. -int Position::see(Square to) const { - - assert(square_is_ok(to)); - return see(SQ_NONE, to); -} - int Position::see(Move m) const { assert(move_is_ok(m)); @@ -1369,82 +1369,50 @@ int Position::see_sign(Move m) const { int Position::see(Square from, Square to) const { - // Material values - static const int seeValues[18] = { - 0, PawnValueMidgame, KnightValueMidgame, BishopValueMidgame, - RookValueMidgame, QueenValueMidgame, QueenValueMidgame*10, 0, - 0, PawnValueMidgame, KnightValueMidgame, BishopValueMidgame, - RookValueMidgame, QueenValueMidgame, QueenValueMidgame*10, 0, - 0, 0 - }; - - Bitboard attackers, stmAttackers, b; + Bitboard occ, attackers, stmAttackers, b; + int swapList[32], slIndex = 1; + PieceType capturedType, pt; + Color stm; - assert(square_is_ok(from) || from == SQ_NONE); + assert(square_is_ok(from)); assert(square_is_ok(to)); - // Initialize colors - Color us = (from != SQ_NONE ? color_of_piece_on(from) : opposite_color(color_of_piece_on(to))); - Color them = opposite_color(us); - - // Initialize pieces - Piece piece = piece_on(from); - Piece capture = piece_on(to); - Bitboard occ = occupied_squares(); + capturedType = type_of_piece_on(to); // King cannot be recaptured - if (type_of_piece(piece) == KING) - return seeValues[capture]; + if (capturedType == KING) + return seeValues[capturedType]; + + occ = occupied_squares(); // Handle en passant moves if (st->epSquare == to && type_of_piece_on(from) == PAWN) { - assert(capture == PIECE_NONE); + Square capQq = (side_to_move() == WHITE) ? (to - DELTA_N) : (to - DELTA_S); - Square capQq = (side_to_move() == WHITE)? (to - DELTA_N) : (to - DELTA_S); - capture = piece_on(capQq); + assert(capturedType == PIECE_TYPE_NONE); assert(type_of_piece_on(capQq) == PAWN); // Remove the captured pawn clear_bit(&occ, capQq); + capturedType = PAWN; } - while (true) - { - // Find all attackers to the destination square, with the moving piece - // removed, but possibly an X-ray attacker added behind it. - clear_bit(&occ, from); - attackers = (rook_attacks_bb(to, occ) & pieces(ROOK, QUEEN)) - | (bishop_attacks_bb(to, occ) & pieces(BISHOP, QUEEN)) - | (attacks_from(to) & pieces(KNIGHT)) - | (attacks_from(to) & pieces(KING)) - | (attacks_from(to, WHITE) & pieces(PAWN, BLACK)) - | (attacks_from(to, BLACK) & pieces(PAWN, WHITE)); - - if (from != SQ_NONE) - break; - - // If we don't have any attacker we are finished - if ((attackers & pieces_of_color(us)) == EmptyBoardBB) - return 0; - - // Locate the least valuable attacker to the destination square - // and use it to initialize from square. - stmAttackers = attackers & pieces_of_color(us); - PieceType pt; - for (pt = PAWN; !(stmAttackers & pieces(pt)); pt++) - assert(pt < KING); - - from = first_1(stmAttackers & pieces(pt)); - piece = piece_on(from); - } + // Find all attackers to the destination square, with the moving piece + // removed, but possibly an X-ray attacker added behind it. + clear_bit(&occ, from); + attackers = (rook_attacks_bb(to, occ) & pieces(ROOK, QUEEN)) + | (bishop_attacks_bb(to, occ) & pieces(BISHOP, QUEEN)) + | (attacks_from(to) & pieces(KNIGHT)) + | (attacks_from(to) & pieces(KING)) + | (attacks_from(to, WHITE) & pieces(PAWN, BLACK)) + | (attacks_from(to, BLACK) & pieces(PAWN, WHITE)); // If the opponent has no attackers we are finished - stmAttackers = attackers & pieces_of_color(them); + stm = opposite_color(color_of_piece_on(from)); + stmAttackers = attackers & pieces_of_color(stm); if (!stmAttackers) - return seeValues[capture]; - - attackers &= occ; // Remove the moving piece + return seeValues[capturedType]; // The destination square is defended, which makes things rather more // difficult to compute. We proceed by building up a "swap list" containing @@ -1452,12 +1420,8 @@ int Position::see(Square from, Square to) const { // destination square, where the sides alternately capture, and always // capture with the least valuable piece. After each capture, we look for // new X-ray attacks from behind the capturing piece. - int lastCapturingPieceValue = seeValues[piece]; - int swapList[32], n = 1; - Color c = them; - PieceType pt; - - swapList[0] = seeValues[capture]; + swapList[0] = seeValues[capturedType]; + capturedType = type_of_piece_on(from); do { // Locate the least valuable attacker for the side to move. The loop @@ -1470,35 +1434,35 @@ int Position::see(Square from, Square to) const { // and scan for new X-ray attacks behind the attacker. b = stmAttackers & pieces(pt); occ ^= (b & (~b + 1)); - attackers |= (rook_attacks_bb(to, occ) & pieces(ROOK, QUEEN)) + attackers |= (rook_attacks_bb(to, occ) & pieces(ROOK, QUEEN)) | (bishop_attacks_bb(to, occ) & pieces(BISHOP, QUEEN)); - attackers &= occ; + attackers &= occ; // Cut out pieces we've already done // Add the new entry to the swap list - assert(n < 32); - swapList[n] = -swapList[n - 1] + lastCapturingPieceValue; - n++; + assert(slIndex < 32); + swapList[slIndex] = -swapList[slIndex - 1] + seeValues[capturedType]; + slIndex++; // Remember the value of the capturing piece, and change the side to move // before beginning the next iteration - lastCapturingPieceValue = seeValues[pt]; - c = opposite_color(c); - stmAttackers = attackers & pieces_of_color(c); + capturedType = pt; + stm = opposite_color(stm); + stmAttackers = attackers & pieces_of_color(stm); // Stop after a king capture if (pt == KING && stmAttackers) { - assert(n < 32); - swapList[n++] = QueenValueMidgame*10; + assert(slIndex < 32); + swapList[slIndex++] = QueenValueMidgame*10; break; } } while (stmAttackers); // Having built the swap list, we negamax through it to find the best // achievable score from the point of view of the side to move - while (--n) - swapList[n-1] = Min(-swapList[n], swapList[n-1]); + while (--slIndex) + swapList[slIndex-1] = Min(-swapList[slIndex], swapList[slIndex-1]); return swapList[0]; } @@ -1713,7 +1677,6 @@ Value Position::compute_non_pawn_material(Color c) const { /// Position::is_draw() tests whether the position is drawn by material, /// repetition, or the 50 moves rule. It does not detect stalemates, this /// must be done by the search. -// FIXME: Currently we are not handling 50 move rule correctly when in check bool Position::is_draw() const { @@ -1723,7 +1686,7 @@ bool Position::is_draw() const { return true; // Draw by the 50 moves rule? - if (st->rule50 > 100 || (st->rule50 == 100 && !is_check())) + if (st->rule50 > 99 && (st->rule50 > 100 || !is_mate())) return true; // Draw by repetition?