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Final touches to generate_evasions()

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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 <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-02-11 17:21:03 +01:00
parent ff60dafe8d
commit 33c608e140
1 changed files with 40 additions and 38 deletions
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78
src/movegen.cpp
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@ -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<PAWN>(pos, mlist, us, pinned, blockSquares);
mlist = generate_piece_blocking_evasions<KNIGHT>(pos, mlist, us, pinned, blockSquares);
mlist = generate_piece_blocking_evasions<BISHOP>(pos, mlist, us, pinned, blockSquares);
mlist = generate_piece_blocking_evasions<ROOK>(pos, mlist, us, pinned, blockSquares);
mlist = generate_piece_blocking_evasions<QUEEN>(pos, mlist, us, pinned, blockSquares);
}
if (blockSquares != EmptyBoardBB)
{
// Pieces moves
mlist = generate_piece_blocking_evasions<PAWN>(pos, mlist, us, pinned, blockSquares);
mlist = generate_piece_blocking_evasions<KNIGHT>(pos, mlist, us, pinned, blockSquares);
mlist = generate_piece_blocking_evasions<BISHOP>(pos, mlist, us, pinned, blockSquares);
mlist = generate_piece_blocking_evasions<ROOK>(pos, mlist, us, pinned, blockSquares);
mlist = generate_piece_blocking_evasions<QUEEN>(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);
}