From 33c608e140b7fd7ced99086488e82a9bbe22e8e3 Mon Sep 17 00:00:00 2001 From: Marco Costalba Date: Wed, 11 Feb 2009 17:21:03 +0100 Subject: [PATCH] Final touches to generate_evasions() Small code tidy up and a little optimization to avoid calling generate_piece_blocking_evasions() when blockSquares is empty (30% of cases). Signed-off-by: Marco Costalba --- src/movegen.cpp | 78 +++++++++++++++++++++++++------------------------ 1 file changed, 40 insertions(+), 38 deletions(-) diff --git a/src/movegen.cpp b/src/movegen.cpp index 134127eb..0fc68436 100644 --- a/src/movegen.cpp +++ b/src/movegen.cpp @@ -200,9 +200,8 @@ int generate_checks(const Position& pos, MoveStack* mlist, Bitboard dc) { /// generate_evasions() generates all check evasions when the side to move is -/// in check. Unlike the other move generation functions, this one generates -/// only legal moves. It returns the number of generated moves. This -/// function is very ugly, and needs cleaning up some time later. FIXME +/// in check. Unlike the other move generation functions, this one generates +/// only legal moves. It returns the number of generated moves. int generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) { @@ -218,8 +217,8 @@ int generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) { assert(pos.piece_on(ksq) == king_of_color(us)); // The bitboard of occupied pieces without our king - Bitboard b2 = pos.occupied_squares(); - clear_bit(&b2, ksq); + Bitboard b_noKing = pos.occupied_squares(); + clear_bit(&b_noKing, ksq); // Find squares attacked by slider checkers, we will // remove them from king evasions set so to avoid a couple @@ -231,14 +230,14 @@ int generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) { while (b) { from = pop_1st_bit(&b); - checkersAttacks |= bishop_attacks_bb(from, b2); + checkersAttacks |= bishop_attacks_bb(from, b_noKing); } b = checkers & (pos.queens() | pos.rooks()); while (b) { from = pop_1st_bit(&b); - checkersAttacks |= rook_attacks_bb(from, b2); + checkersAttacks |= rook_attacks_bb(from, b_noKing); } // Generate evasions for king @@ -247,7 +246,7 @@ int generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) { { to = pop_1st_bit(&b1); // Note that we can use square_is_attacked() only because we - // have already removed sliders checkers. + // have already removed slider checkers. if (!pos.square_is_attacked(to, them)) (*mlist++).move = make_move(ksq, to); } @@ -297,39 +296,42 @@ int generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) { assert((pos.occupied_squares() & blockSquares) == EmptyBoardBB); - // Pieces moves - mlist = generate_piece_blocking_evasions(pos, mlist, us, pinned, blockSquares); - mlist = generate_piece_blocking_evasions(pos, mlist, us, pinned, blockSquares); - mlist = generate_piece_blocking_evasions(pos, mlist, us, pinned, blockSquares); - mlist = generate_piece_blocking_evasions(pos, mlist, us, pinned, blockSquares); - mlist = generate_piece_blocking_evasions(pos, mlist, us, pinned, blockSquares); - } + if (blockSquares != EmptyBoardBB) + { + // Pieces moves + mlist = generate_piece_blocking_evasions(pos, mlist, us, pinned, blockSquares); + mlist = generate_piece_blocking_evasions(pos, mlist, us, pinned, blockSquares); + mlist = generate_piece_blocking_evasions(pos, mlist, us, pinned, blockSquares); + mlist = generate_piece_blocking_evasions(pos, mlist, us, pinned, blockSquares); + mlist = generate_piece_blocking_evasions(pos, mlist, us, pinned, blockSquares); + } + } - // Finally, the ugly special case of en passant captures. An en passant - // capture can only be a check evasion if the check is not a discovered - // check. If pos.ep_square() is set, the last move made must have been - // a double pawn push. If, furthermore, the checking piece is a pawn, - // an en passant check evasion may be possible. - if (pos.ep_square() != SQ_NONE && (checkers & pos.pawns(them))) - { - to = pos.ep_square(); - b1 = pos.pawn_attacks(them, to) & pos.pawns(us); + // Finally, the special case of en passant captures. An en passant + // capture can only be a check evasion if the check is not a discovered + // check. If pos.ep_square() is set, the last move made must have been + // a double pawn push. If, furthermore, the checking piece is a pawn, + // an en passant check evasion may be possible. + if (pos.ep_square() != SQ_NONE && (checkers & pos.pawns(them))) + { + to = pos.ep_square(); + b1 = pos.pawn_attacks(them, to) & pos.pawns(us); - // The checking pawn cannot be a discovered (bishop) check candidate - // otherwise we were in check also before last double push move. - assert(!bit_is_set(pos.discovered_check_candidates(them), checksq)); - assert(count_1s(b1) == 1 || count_1s(b1) == 2); + // The checking pawn cannot be a discovered (bishop) check candidate + // otherwise we were in check also before last double push move. + assert(!bit_is_set(pos.discovered_check_candidates(them), checksq)); + assert(count_1s(b1) == 1 || count_1s(b1) == 2); - b1 &= ~pinned; - while (b1) - { - from = pop_1st_bit(&b1); - // Move is always legal because checking pawn is not a discovered - // check candidate and our capturing pawn has been already tested - // against pinned pieces. - (*mlist++).move = make_ep_move(from, to); - } - } + b1 &= ~pinned; + while (b1) + { + from = pop_1st_bit(&b1); + // Move is always legal because checking pawn is not a discovered + // check candidate and our capturing pawn has been already tested + // against pinned pieces. + (*mlist++).move = make_ep_move(from, to); + } + } } return int(mlist - mlist_start); } -- 2.39.2