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movegen: Introduce generate_pawn_checks()

This greatly simplify redundant code.

Perhaps slihtly slower. Test needed.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2008-10-18 15:36:58 +02:00
parent 5abe8a0816
commit 34a515f20b

View file

@ -41,6 +41,23 @@ namespace {
int generate_piece_checks(PieceType pce, const Position& pos, Bitboard target,
Bitboard dc, Square ksq, MoveStack* mlist);
inline Bitboard next_row_white(Bitboard b) { return b << 8; }
inline Bitboard next_row_black(Bitboard b) { return b >> 8; }
struct PawnOffsets {
Bitboard Rank3BB;
Bitboard Rank8BB;
SquareDelta DELTA_N;
Color them;
Bitboard (*next_row_fn)(Bitboard b);
};
const PawnOffsets WhitePawnOffsets = { Rank3BB, Rank8BB, DELTA_N, BLACK, &next_row_white };
const PawnOffsets BlackPawnOffsets = { Rank6BB, Rank1BB, DELTA_S, WHITE, &next_row_black };
int generate_pawn_checks(const PawnOffsets& ofs, const Position& pos, Bitboard dc,
Square ksq, MoveStack* mlist);
}
@ -107,146 +124,45 @@ int generate_checks(const Position& pos, MoveStack* mlist, Bitboard dc) {
assert(pos.is_ok());
assert(!pos.is_check());
Color us, them;
Square ksq, from, to;
Bitboard empty, b1, b2, b3;
Color us = pos.side_to_move();
Square ksq = pos.king_square(opposite_color(us));
int n = 0;
us = pos.side_to_move();
them = opposite_color(us);
ksq = pos.king_square(them);
assert(pos.piece_on(ksq) == king_of_color(them));
assert(pos.piece_on(ksq) == king_of_color(opposite_color(us)));
dc = pos.discovered_check_candidates(us);
empty = pos.empty_squares();
// Pawn moves. This is somewhat messy, and we use separate code for white
// and black, because we can't shift by negative numbers in C/C++. :-(
// Pawn moves
if (us == WHITE)
{
// Pawn moves which give discovered check. This is possible only if the
// pawn is not on the same file as the enemy king, because we don't
// generate captures.
n += generate_pawn_checks(WhitePawnOffsets, pos, dc, ksq, mlist);
else
n += generate_pawn_checks(BlackPawnOffsets, pos, dc, ksq, mlist);
// Find all friendly pawns not on the enemy king's file
b1 = pos.pawns(us) & ~file_bb(ksq);
// Pieces moves
Bitboard b = pos.knights(us);
if (b)
n += generate_piece_checks(KNIGHT, pos, b, dc, ksq, mlist);
// Discovered checks, single pawn pushes
b2 = b3 = ((b1 & dc) << 8) & ~Rank8BB & empty;
while (b3)
{
to = pop_1st_bit(&b3);
mlist[n++].move = make_move(to - DELTA_N, to);
}
b = pos.bishops(us);
if (b)
n += generate_piece_checks(BISHOP, pos, b, dc, ksq, mlist);
// Discovered checks, double pawn pushes
b3 = ((b2 & Rank3BB) << 8) & empty;
while (b3)
{
to = pop_1st_bit(&b3);
mlist[n++].move = make_move(to - DELTA_N - DELTA_N, to);
}
b = pos.rooks(us);
if (b)
n += generate_piece_checks(ROOK, pos, b, dc, ksq, mlist);
// Direct checks. These are possible only for pawns on neighboring files
// of the enemy king
b1 &= (~dc & neighboring_files_bb(ksq)); // FIXME why ~dc ??
// Direct checks, single pawn pushes
b2 = (b1 << 8) & empty;
b3 = b2 & pos.pawn_attacks(BLACK, ksq);
while (b3)
{
to = pop_1st_bit(&b3);
mlist[n++].move = make_move(to - DELTA_N, to);
}
// Direct checks, double pawn pushes
b3 = ((b2 & Rank3BB) << 8) & empty & pos.pawn_attacks(BLACK, ksq);
while (b3)
{
to = pop_1st_bit(&b3);
mlist[n++].move = make_move(to - DELTA_N - DELTA_N, to);
}
}
else { // (us == BLACK)
// Pawn moves which give discovered check. This is possible only if the
// pawn is not on the same file as the enemy king, because we don't
// generate captures.
// Find all friendly pawns not on the enemy king's file:
b1 = pos.pawns(us) & ~file_bb(ksq);
// Discovered checks, single pawn pushes
b2 = b3 = ((b1 & dc) >> 8) & ~Rank1BB & empty;
while (b3)
{
to = pop_1st_bit(&b3);
mlist[n++].move = make_move(to - DELTA_S, to);
}
// Discovered checks, double pawn pushes
b3 = ((b2 & Rank6BB) >> 8) & empty;
while (b3)
{
to = pop_1st_bit(&b3);
mlist[n++].move = make_move(to - DELTA_S - DELTA_S, to);
}
// Direct checks. These are possible only for pawns on neighboring files
// of the enemy king
b1 &= (~dc & neighboring_files_bb(ksq));
// Direct checks, single pawn pushes:
b2 = (b1 >> 8) & empty;
b3 = b2 & pos.pawn_attacks(WHITE, ksq);
while (b3)
{
to = pop_1st_bit(&b3);
mlist[n++].move = make_move(to - DELTA_S, to);
}
// Direct checks, double pawn pushes
b3 = ((b2 & Rank6BB) >> 8) & empty & pos.pawn_attacks(WHITE, ksq);
while (b3)
{
to = pop_1st_bit(&b3);
mlist[n++].move = make_move(to - DELTA_S - DELTA_S, to);
}
}
// Knight moves
b1 = pos.knights(us);
if (b1)
n += generate_piece_checks(KNIGHT, pos, b1, dc, ksq, mlist);
// Bishop moves
b1 = pos.bishops(us);
if (b1)
n += generate_piece_checks(BISHOP, pos, b1, dc, ksq, mlist);
// Rook moves
b1 = pos.rooks(us);
if (b1)
n += generate_piece_checks(ROOK, pos, b1, dc, ksq, mlist);
// Queen moves
b1 = pos.queens(us);
if (b1)
n += generate_piece_checks(QUEEN, pos, b1, dc, ksq, mlist);
b = pos.queens(us);
if (b)
n += generate_piece_checks(QUEEN, pos, b, dc, ksq, mlist);
// King moves
from = pos.king_square(us);
Square from = pos.king_square(us);
if (bit_is_set(dc, from))
{
b1 = pos.king_attacks(from) & empty & ~QueenPseudoAttacks[ksq];
while (b1)
b = pos.king_attacks(from) & pos.empty_squares() & ~QueenPseudoAttacks[ksq];
while (b)
{
to = pop_1st_bit(&b1);
Square to = pop_1st_bit(&b);
mlist[n++].move = make_move(from, to);
}
}
@ -1068,4 +984,55 @@ namespace {
}
return n;
}
int generate_pawn_checks(const PawnOffsets& ofs, const Position& pos, Bitboard dc, Square ksq, MoveStack* mlist)
{
// Pawn moves which give discovered check. This is possible only if the
// pawn is not on the same file as the enemy king, because we don't
// generate captures.
int n = 0;
Bitboard empty = pos.empty_squares();
// Find all friendly pawns not on the enemy king's file
Bitboard b1 = pos.pawns(pos.side_to_move()) & ~file_bb(ksq), b2, b3;
// Discovered checks, single pawn pushes
b2 = b3 = (ofs.next_row_fn)(b1 & dc) & ~ofs.Rank8BB & empty;
while (b3)
{
Square to = pop_1st_bit(&b3);
mlist[n++].move = make_move(to - ofs.DELTA_N, to);
}
// Discovered checks, double pawn pushes
b3 = (ofs.next_row_fn)(b2 & ofs.Rank3BB) & empty;
while (b3)
{
Square to = pop_1st_bit(&b3);
mlist[n++].move = make_move(to - ofs.DELTA_N - ofs.DELTA_N, to);
}
// Direct checks. These are possible only for pawns on neighboring files
// of the enemy king
b1 &= (~dc & neighboring_files_bb(ksq)); // FIXME why ~dc ??
// Direct checks, single pawn pushes
b2 = (ofs.next_row_fn)(b1) & empty;
b3 = b2 & pos.pawn_attacks(ofs.them, ksq);
while (b3)
{
Square to = pop_1st_bit(&b3);
mlist[n++].move = make_move(to - ofs.DELTA_N, to);
}
// Direct checks, double pawn pushes
b3 = (ofs.next_row_fn)(b2 & ofs.Rank3BB) & empty & pos.pawn_attacks(ofs.them, ksq);
while (b3)
{
Square to = pop_1st_bit(&b3);
mlist[n++].move = make_move(to - ofs.DELTA_N - ofs.DELTA_N, to);
}
return n;
}
}