/*
* Generate all moves that evade check in the given position. This is purely
* legal move generation; no pseudo-legal moves.
*/
int generate_evasions(const position_t* pos, move_t* moves)
{
assert(pos->is_check && pos->board[pos->check_square]);
move_t* moves_head = moves;
color_t side = pos->side_to_move, other_side = side^1;
square_t king_sq = pos->pieces[side][0];
square_t check_sq = pos->check_square;
piece_t king = create_piece(side, KING);
piece_t checker = pos->board[check_sq];
// Generate king moves.
// Don't let the king mask its possible destination squares in calls
// to is_square_attacked.
square_t from = king_sq, to = INVALID_SQUARE;
((position_t*)pos)->board[king_sq] = EMPTY;
for (const direction_t* delta = piece_deltas[king]; *delta; ++delta) {
to = from + *delta;
piece_t capture = pos->board[to];
if (capture != EMPTY && !can_capture(king, capture)) continue;
if (is_square_attacked((position_t*)pos,to,other_side)) continue;
((position_t*)pos)->board[king_sq] = king;
moves = add_move(pos, create_move(from, to, king, capture), moves);
((position_t*)pos)->board[king_sq] = EMPTY;
}
((position_t*)pos)->board[king_sq] = king;
// If there are multiple checkers, only king moves are possible.
if (pos->is_check > 1) {
*moves = 0;
return moves-moves_head;
}
// First, the most common case: a check that can be evaded via an
// en passant capture. Note that if we're in check and an en passant
// capture is available, the only way the en passant capture would evade
// the check is if it's the newly moved pawn that's checking us.
direction_t pin_dir;
if (pos->ep_square != EMPTY &&
check_sq+pawn_push[side] == pos->ep_square &&
pos->board[pos->ep_square] == EMPTY) {
piece_t our_pawn = create_piece(side, PAWN);
to = pos->ep_square;
for (int i=0; i<2; ++i) {
from = to-piece_deltas[our_pawn][i];
if (pos->board[from] && pos->board[from] == our_pawn) {
pin_dir = pin_direction(pos, from, king_sq);
if (pin_dir) continue;
moves = add_move(pos,
create_move_enpassant(from, to, our_pawn, checker),
moves);
}
}
}
// Generate captures of the checker.
for (int i = 0; i < pos->num_pawns[side]; ++i) {
from = pos->pawns[side][i];
piece_t piece = create_piece(side, PAWN);
pin_dir = pin_direction(pos, from, king_sq);
if (pin_dir) continue;
if (!possible_attack(from, check_sq, piece)) continue;
if (relative_rank[side][square_rank(from)] == RANK_7) {
// Capture and promote.
for (piece_t promoted=QUEEN; promoted > PAWN; --promoted) {
moves = add_move(pos,
create_move_promote(from, check_sq, piece,
checker, promoted),
moves);
}
} else {
moves = add_move(pos,
create_move(from, check_sq, piece, checker),
moves);
}
}
for (int i = 1; i < pos->num_pieces[side]; ++i) {
from = pos->pieces[side][i];
piece_t piece = pos->board[from];
pin_dir = pin_direction(pos, from, king_sq);
if (pin_dir) continue;
if (!possible_attack(from, check_sq, piece)) continue;
if (piece_slide_type(piece) == NONE) {
moves = add_move(pos,
create_move(from, check_sq, piece, checker),
moves);
} else {
// A sliding piece, keep going until we hit something.
direction_t check_dir = direction(from, check_sq);
for (to=from+check_dir; pos->board[to] == EMPTY; to+=check_dir) {}
if (to == check_sq) {
moves = add_move(pos,
create_move(from, to, piece, checker),
moves);
continue;
}
}
}
if (piece_slide_type(checker) == NONE) {
*moves = 0;
return moves-moves_head;
}
// A slider is doing the checking; generate blocking moves.
direction_t block_dir = direction(check_sq, king_sq);
for (int i = 0; i < pos->num_pawns[side]; ++i) {
from = pos->pawns[side][i];
piece_t piece = create_piece(side, PAWN);
direction_t k_dir;
pin_dir = pin_direction(pos, from, king_sq);
if (pin_dir) continue;
to = from + pawn_push[side];
if (pos->board[to] != EMPTY) continue;
rank_t rank = relative_rank[side][square_rank(from)];
k_dir = direction(to, king_sq);
if (k_dir == block_dir &&
((king_sq < to && check_sq > to) ||
(king_sq > to && check_sq < to))) {
if (rank == RANK_7) {
// Block and promote.
for (piece_t promoted=QUEEN; promoted > PAWN; --promoted) {
moves = add_move(pos,
create_move_promote(from, to, piece, EMPTY, promoted),
moves);
}
} else {
moves = add_move(pos,
create_move(from, to, piece, EMPTY),
moves);
}
}
if (rank != RANK_2) continue;
to += pawn_push[side];
if (pos->board[to]) continue;
k_dir = direction(to, king_sq);
if (k_dir == block_dir &&
((king_sq < to && check_sq > to) ||
(king_sq > to && check_sq < to))) {
moves = add_move(pos,
create_move(from, to, piece, EMPTY),
moves);
}
}
for (int i=1; i<pos->num_pieces[side]; ++i) {
from = pos->pieces[side][i];
piece_t piece = pos->board[from];
direction_t k_dir;
pin_dir = pin_direction(pos, from, king_sq);
if (pin_dir) continue;
if (piece_is_type(piece, KNIGHT)) {
for (const direction_t* delta=piece_deltas[piece];
*delta; ++delta) {
to = from + *delta;
if (pos->board[to] != EMPTY) continue;
k_dir = direction(to, king_sq);
if (k_dir == block_dir &&
((king_sq < to && check_sq > to) ||
(king_sq > to && check_sq < to))) {
moves = add_move(pos,
create_move(from, to, piece, EMPTY),
moves);
}
}
} else {
for (const direction_t* delta=piece_deltas[piece];
*delta; ++delta) {
for (to = from+*delta; pos->board[to] == EMPTY; to+=*delta) {
k_dir = direction(to, king_sq);
if (k_dir == block_dir &&
((king_sq < to && check_sq > to) ||
(king_sq > to && check_sq < to))) {
moves = add_move(pos,
create_move(from, to, piece, EMPTY),
moves);
break;
}
}
}
}
}
*moves = 0;
return moves-moves_head;
}
BOOL test_genmove() {
BOOL ok = TRUE;
struct t_move_list moves[1];
set_fen(position, "r5r1/n1q1pP1k/3pPppp/P1pP4/2P4N/R1B5/2Q3PP/7K w - -");
assert(integrity(position));
assert(is_square_attacked(position, E4, WHITE));
assert(!is_square_attacked(position, A7, WHITE));
assert(!is_square_attacked(position, F4, BLACK));
assert(is_square_attacked(position, D8, BLACK));
generate_moves(position, moves);
ok = ok && (moves->count == 42);
flip_board(position);
generate_moves(position, moves);
//write_move_list(moves, "movelist.txt");
ok = ok && (moves->count == 42);
set_fen(position, "1r2k2r/p1ppqpb1/b3pnp1/3PN3/1pn1P3/2N2Q1p/PPPBBPPP/R4K1R w - -");
assert(integrity(position));
generate_moves(position, moves);
assert(move_list_integrity(position, moves));
ok = ok && (moves->count == 44);
set_fen(position, "4q3/3P1P2/b4N2/8/3Q2Bb/2p3B1/1k4N1/4K1Nr w - -");
assert(integrity(position));
generate_evade_check(position, moves);
ok = ok && (moves->count == 18);
flip_board(position);
generate_evade_check(position, moves);
ok = ok && (moves->count == 18);
set_fen(position, "1r2k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R4K1R w --k- -");
assert(integrity(position));
generate_moves(position, moves);
//write_move_list(moves, "movelist.txt");
assert(move_list_integrity(position, moves));
ok = ok && (moves->count == 46);
flip_board(position);
generate_moves(position, moves);
ok = ok && (moves->count == 46);
// Chess960 Examples
set_fen(position, "Rr4kr/8/8/8/8/8/PPPP4/R1K5 w Ahb -");
assert(integrity(position));
generate_moves(position, moves);
assert(move_list_integrity(position, moves));
ok = ok && (moves->count == 18);
flip_board(position);
generate_moves(position, moves);
ok = ok && (moves->count == 18);
set_fen(position, "1r1kbb1r/1pp2ppp/3npn2/3pN3/1Q3P2/4PN2/2PP2PP/qR1KBB1R w HBhb -");
assert(integrity(position));
generate_legal_moves(position, moves);
assert(move_list_integrity(position, moves));
ok = ok && (moves->count == 48);
set_fen(position, "rkrbqnb1/pp2p2p/3p1pp1/2p1nP2/2P1P3/3P2N1/PP4PP/RKRBQNB1 w CAca -");
assert(integrity(position));
generate_legal_moves(position, moves);
write_move_list(moves, "movelist.txt");
assert(move_list_integrity(position, moves));
ok = ok && (moves->count == 34);
flip_board(position);
generate_legal_moves(position, moves);
ok = ok && (moves->count == 34);
return ok;
}
/*
* Generate pseudo-legal moves which are neither captures nor promotions.
*/
int generate_pseudo_quiet_moves(const position_t* pos, move_t* moves)
{
move_t* moves_head = moves;
color_t side = pos->side_to_move;
piece_t piece;
square_t from;
// Castling. Castles are considered pseudo-legal if we have appropriate
// castling rights, the squares between king and rook are unoccupied,
// and the intermediate square is unattacked. Therefore checking for
// legality just requires seeing if we're in check afterwards.
// This is messy for Chess960, so it's separated into separate cases.
square_t my_king_home = king_home + side*A8;
if (!options.chess960) {
if (has_oo_rights(pos, side) &&
pos->board[my_king_home+1] == EMPTY &&
pos->board[my_king_home+2] == EMPTY &&
!is_square_attacked((position_t*)pos,my_king_home+1,side^1)) {
assert(pos->board[my_king_home] ==
create_piece(pos->side_to_move, KING));
moves = add_move(pos,
create_move_castle(my_king_home, my_king_home+2,
create_piece(side, KING)),
moves);
}
if (has_ooo_rights(pos, side) &&
pos->board[my_king_home-1] == EMPTY &&
pos->board[my_king_home-2] == EMPTY &&
pos->board[my_king_home-3] == EMPTY &&
!is_square_attacked((position_t*)pos,my_king_home-1,side^1)) {
assert(pos->board[my_king_home] ==
create_piece(pos->side_to_move, KING));
moves = add_move(pos,
create_move_castle(my_king_home, my_king_home-2,
create_piece(side, KING)),
moves);
}
} else {
if (has_oo_rights(pos, side)) {
square_t my_f1 = F1 + side*A8;
square_t my_g1 = G1 + side*A8;
square_t my_kr = king_rook_home + side*A8;
bool castle_ok = true;
// Check that rook is unimpeded.
for (square_t sq = MIN(my_kr, my_f1);
sq <= MAX(my_kr, my_f1); ++sq) {
if (sq != my_kr && sq != my_king_home &&
pos->board[sq] != EMPTY) {
castle_ok = false;
break;
}
}
// Check that the king is unimpeded and unattacked
if (castle_ok) {
for (square_t sq = MIN(my_king_home, my_g1);
sq <= my_g1; ++sq) {
if (sq != my_king_home && sq != my_kr &&
pos->board[sq] != EMPTY) {
castle_ok = false;
break;
}
if (sq != my_g1 &&
is_square_attacked((position_t*)pos, sq, side^1)) {
castle_ok = false;
break;
}
}
}
if (castle_ok) moves = add_move(pos,
create_move_castle(my_king_home, my_g1,
create_piece(side, KING)), moves);
}
if (has_ooo_rights(pos, side)) {
square_t my_d1 = D1 + side*A8;
square_t my_c1 = C1 + side*A8;
square_t my_qr = queen_rook_home + side*A8;
bool castle_ok = true;
// Check that rook is unimpeded.
for (square_t sq = MIN(my_qr, my_d1);
sq <= MAX(my_qr, my_d1); ++sq) {
if (sq != my_qr && sq != my_king_home &&
pos->board[sq] != EMPTY) {
castle_ok = false;
break;
}
}
// Check that the king is unimpeded and unattacked
if (castle_ok) {
for (square_t sq = MIN(my_king_home, my_c1);
sq <= MAX(my_king_home, my_c1); ++sq) {
if (sq != my_king_home && sq != my_qr &&
pos->board[sq] != EMPTY) {
castle_ok = false;
break;
}
if (sq != my_c1 &&
is_square_attacked((position_t*)pos, sq, side^1)) {
castle_ok = false;
break;
}
}
}
if (castle_ok) moves = add_move(pos,
create_move_castle(my_king_home, my_c1,
create_piece(side, KING)),
moves);
}
}
for (int i = 0; i < pos->num_pieces[side]; ++i) {
from = pos->pieces[side][i];
piece = pos->board[from];
assert(piece_color(piece) == side && piece_type(piece) != PAWN);
generate_piece_noncaptures(pos, from, piece, &moves);
}
piece = create_piece(side, PAWN);
for (int i=0; i<pos->num_pawns[side]; ++i) {
from = pos->pawns[side][i];
assert(pos->board[from] == piece);
generate_pawn_quiet_moves(pos, from, piece, &moves);
}
*moves = 0;
return (moves-moves_head);
}
