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Final semplification of generate_evasions()

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Now it's readable!

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2008-10-19 09:33:33 +01:00
parent 4f18528a1c
commit 8e85aa3a65
1 changed files with 50 additions and 78 deletions
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128
src/movegen.cpp
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@ -43,16 +43,17 @@ namespace {
struct PawnOffsets {
Bitboard Rank3BB, Rank8BB;
Rank RANK_8;
SquareDelta DELTA_N, DELTA_NE, DELTA_NW;
Color us, them;
typedef Bitboard (*Shift_fn)(Bitboard b);
Shift_fn forward, forward_left, forward_right;
};
const PawnOffsets WhitePawnOffsets = { Rank3BB, Rank8BB, DELTA_N, DELTA_NE, DELTA_NW, WHITE, BLACK,
const PawnOffsets WhitePawnOffsets = { Rank3BB, Rank8BB, RANK_8, DELTA_N, DELTA_NE, DELTA_NW, WHITE, BLACK,
&forward_white, forward_left_white, forward_right_white };
const PawnOffsets BlackPawnOffsets = { Rank6BB, Rank1BB, DELTA_S, DELTA_SE, DELTA_SW, BLACK, WHITE,
const PawnOffsets BlackPawnOffsets = { Rank6BB, Rank1BB, RANK_1, DELTA_S, DELTA_SE, DELTA_SW, BLACK, WHITE,
&forward_black, &forward_left_black, &forward_right_black };
int generate_pawn_captures(const PawnOffsets&, const Position&, MoveStack*);
@ -62,6 +63,7 @@ namespace {
int generate_piece_moves(PieceType, const Position&, MoveStack*, Color, Bitboard);
int generate_castle_moves(const Position&, MoveStack*, Color);
int generate_piece_blocking_evasions(PieceType, const Position&, Bitboard, Bitboard, MoveStack*, int);
int generate_pawn_blocking_evasions(const PawnOffsets&, const Position&, Bitboard, Bitboard, MoveStack*, int);
}
@ -270,79 +272,11 @@ int generate_evasions(const Position& pos, MoveStack* mlist) {
assert((pos.occupied_squares() & blockSquares) == EmptyBoardBB);
// Pawn moves. Because a blocking evasion can never be a capture, we
// only generate pawn pushes. As so often, the code for pawns is a bit
// ugly, and uses separate clauses for white and black pawns. :-(
// only generate pawn pushes.
if (us == WHITE)
{
// Find non-pinned pawns
b1 = pos.pawns(WHITE) & not_pinned;
// Single pawn pushes. We don't have to AND with empty squares here,
// because the blocking squares will always be empty.
b2 = (b1 << 8) & blockSquares;
while(b2)
{
to = pop_1st_bit(&b2);
assert(pos.piece_on(to) == EMPTY);
if (square_rank(to) == RANK_8)
{
mlist[n++].move = make_promotion_move(to - DELTA_N, to, QUEEN);
mlist[n++].move = make_promotion_move(to - DELTA_N, to, ROOK);
mlist[n++].move = make_promotion_move(to - DELTA_N, to, BISHOP);
mlist[n++].move = make_promotion_move(to - DELTA_N, to, KNIGHT);
} else
mlist[n++].move = make_move(to - DELTA_N, to);
}
// Double pawn pushes
b2 = (((b1 << 8) & pos.empty_squares() & Rank3BB) << 8) & blockSquares;
while (b2)
{
to = pop_1st_bit(&b2);
assert(pos.piece_on(to) == EMPTY);
assert(square_rank(to) == RANK_4);
mlist[n++].move = make_move(to - DELTA_N - DELTA_N, to);
}
} else { // (us == BLACK)
// Find non-pinned pawns
b1 = pos.pawns(BLACK) & not_pinned;
// Single pawn pushes. We don't have to AND with empty squares here,
// because the blocking squares will always be empty.
b2 = (b1 >> 8) & blockSquares;
while (b2)
{
to = pop_1st_bit(&b2);
assert(pos.piece_on(to) == EMPTY);
if (square_rank(to) == RANK_1)
{
mlist[n++].move = make_promotion_move(to - DELTA_S, to, QUEEN);
mlist[n++].move = make_promotion_move(to - DELTA_S, to, ROOK);
mlist[n++].move = make_promotion_move(to - DELTA_S, to, BISHOP);
mlist[n++].move = make_promotion_move(to - DELTA_S, to, KNIGHT);
} else
mlist[n++].move = make_move(to - DELTA_S, to);
}
// Double pawn pushes
b2 = (((b1 >> 8) & pos.empty_squares() & Rank6BB) >> 8) & blockSquares;
while (b2)
{
to = pop_1st_bit(&b2);
assert(pos.piece_on(to) == EMPTY);
assert(square_rank(to) == RANK_5);
mlist[n++].move = make_move(to - DELTA_S - DELTA_S, to);
}
}
n = generate_pawn_blocking_evasions(WhitePawnOffsets, pos, not_pinned, blockSquares, mlist, n);
else
n = generate_pawn_blocking_evasions(BlackPawnOffsets, pos, not_pinned, blockSquares, mlist, n);
// Pieces moves
b1 = pos.knights(us) & not_pinned;
@ -352,13 +286,11 @@ int generate_evasions(const Position& pos, MoveStack* mlist) {
b1 = pos.bishops(us) & not_pinned;
if (b1)
n = generate_piece_blocking_evasions(BISHOP, pos, b1, blockSquares, mlist, n);
// Rook moves
b1 = pos.rooks(us) & not_pinned;
if (b1)
n = generate_piece_blocking_evasions(ROOK, pos, b1, blockSquares, mlist, n);
// Queen moves
b1 = pos.queens(us) & not_pinned;
if (b1)
n = generate_piece_blocking_evasions(QUEEN, pos, b1, blockSquares, mlist, n);
@ -927,4 +859,44 @@ namespace {
}
return n;
}
int generate_pawn_blocking_evasions(const PawnOffsets& ofs, const Position& pos, Bitboard not_pinned,
Bitboard blockSquares, MoveStack* mlist, int n) {
// Find non-pinned pawns
Bitboard b1 = pos.pawns(ofs.us) & not_pinned;
// Single pawn pushes. We don't have to AND with empty squares here,
// because the blocking squares will always be empty.
Bitboard b2 = (ofs.forward)(b1) & blockSquares;
while (b2)
{
Square to = pop_1st_bit(&b2);
assert(pos.piece_on(to) == EMPTY);
if (square_rank(to) == ofs.RANK_8)
{
mlist[n++].move = make_promotion_move(to - ofs.DELTA_N, to, QUEEN);
mlist[n++].move = make_promotion_move(to - ofs.DELTA_N, to, ROOK);
mlist[n++].move = make_promotion_move(to - ofs.DELTA_N, to, BISHOP);
mlist[n++].move = make_promotion_move(to - ofs.DELTA_N, to, KNIGHT);
} else
mlist[n++].move = make_move(to - ofs.DELTA_N, to);
}
// Double pawn pushes
b2 = (ofs.forward)((ofs.forward)(b1) & pos.empty_squares() & ofs.Rank3BB) & blockSquares;
while (b2)
{
Square to = pop_1st_bit(&b2);
assert(pos.piece_on(to) == EMPTY);
assert(ofs.us != WHITE || square_rank(to) == RANK_4);
assert(ofs.us != BLACK || square_rank(to) == RANK_5);
mlist[n++].move = make_move(to - ofs.DELTA_N - ofs.DELTA_N, to);
}
return n;
}
}