std::list<std::shared_ptr<Food>> Collision_detector::get_fo_coll(std::shared_ptr<Ant> p_ant)
{
//We get first the square where the ant is
//Ant ant = *p_ant ;
//Position pos = ant._pos;
std::tuple<int,int> square = get_in_which_square ((*p_ant)._pos,_sub_size_olf);
//Then we look in the squares arround its to search for collisions
int x,z,i ;
std::tie (x,z) = square;
std::list<std::shared_ptr<Food>> res;
for (i=0; i<9; i++)
{
std::tuple<int,int> sq (x+ i%3-1,z+ i/3-1) ;
if (_map_food_for_ant.count(sq) == 1)
{
for (std::list<std::shared_ptr<Food>>::iterator it= (_map_food_for_ant.at(sq)).begin(); it != (_map_food_for_ant.at(sq)).end(); ++it)
{
double r = (*(*it)).get_size() + (*p_ant).get_size();
if ((square_distance ((*p_ant)._pos, (*(*it))._pos) < r*r) && (*(*it)).is_alive())
res.push_back(*it);
}
}
}
return res ;
}
bool LineChart::on_chart(const QPoint& mouse_position, size_t& point_index) const
{
const double MinDistance = 8.0;
const Vector2d mp(mouse_position.x(), mouse_position.y());
double closest_square_distance = numeric_limits<double>::max();
size_t closest_index = 0;
for (size_t i = 0; i < m_points.size(); ++i)
{
const Vector2d p = convert_to_frame(m_points[i]);
const double d = square_distance(mp, p);
if (closest_square_distance > d)
{
closest_square_distance = d;
closest_index = i;
}
}
if (closest_square_distance < MinDistance * MinDistance)
{
point_index = closest_index;
return true;
}
return false;
}
Value EvaluationFunction<KBNK>::apply(const Position& pos) const {
assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO);
assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame + BishopValueMidgame);
assert(pos.piece_count(strongerSide, BISHOP) == 1);
assert(pos.piece_count(strongerSide, KNIGHT) == 1);
assert(pos.piece_count(strongerSide, PAWN) == 0);
Square winnerKSq = pos.king_square(strongerSide);
Square loserKSq = pos.king_square(weakerSide);
Square bishopSquare = pos.piece_list(strongerSide, BISHOP, 0);
// kbnk_mate_table() tries to drive toward corners A1 or H8,
// if we have a bishop that cannot reach the above squares we
// mirror the kings so to drive enemy toward corners A8 or H1.
if (!same_color_squares(bishopSquare, SQ_A1))
{
winnerKSq = flop_square(winnerKSq);
loserKSq = flop_square(loserKSq);
}
Value result = VALUE_KNOWN_WIN
+ distance_bonus(square_distance(winnerKSq, loserKSq))
+ kbnk_mate_table(loserKSq);
return strongerSide == pos.side_to_move() ? result : -result;
}
ScaleFactor ScalingFunction<KNPK>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame);
assert(pos.piece_count(strongerSide, KNIGHT) == 1);
assert(pos.piece_count(strongerSide, PAWN) == 1);
assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
assert(pos.piece_count(weakerSide, PAWN) == 0);
Square pawnSq = pos.piece_list(strongerSide, PAWN, 0);
Square weakerKingSq = pos.king_square(weakerSide);
if ( pawnSq == relative_square(strongerSide, SQ_A7)
&& square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1)
return SCALE_FACTOR_ZERO;
if ( pawnSq == relative_square(strongerSide, SQ_H7)
&& square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1)
return SCALE_FACTOR_ZERO;
return SCALE_FACTOR_NONE;
}
void init_direction_table() {
SquareDelta deltas[8] = {
DELTA_E, DELTA_W, DELTA_N, DELTA_S, DELTA_NE, DELTA_SW, DELTA_NW, DELTA_SE
};
for(Square s1 = SQ_A1; s1 <= SQ_H8; s1++)
for(Square s2 = SQ_A1; s2 <= SQ_H8; s2++) {
DirectionTable[s1][s2] = uint8_t(DIR_NONE);
SignedDirectionTable[s1][s2] = uint8_t(SIGNED_DIR_NONE);
if(s1 == s2) continue;
for(SignedDirection d = SIGNED_DIR_E; d <= SIGNED_DIR_SE; d++) {
SquareDelta delta = deltas[d];
Square s3, s4;
for(s4 = s1 + delta, s3 = s1;
square_distance(s4, s3) == 1 && s4 != s2 && square_is_ok(s4);
s3 = s4, s4 += delta);
if(s4 == s2 && square_distance(s4, s3) == 1) {
SignedDirectionTable[s1][s2] = uint8_t(d);
DirectionTable[s1][s2] = uint8_t(d/2);
break;
}
}
}
}
ScaleFactor ScalingFunction<KBPKB>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
assert(pos.piece_count(strongerSide, BISHOP) == 1);
assert(pos.piece_count(strongerSide, PAWN) == 1);
assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame);
assert(pos.piece_count(weakerSide, BISHOP) == 1);
assert(pos.piece_count(weakerSide, PAWN) == 0);
Square pawnSq = pos.piece_list(strongerSide, PAWN, 0);
Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP, 0);
Square weakerBishopSq = pos.piece_list(weakerSide, BISHOP, 0);
Square weakerKingSq = pos.king_square(weakerSide);
// Case 1: Defending king blocks the pawn, and cannot be driven away
if ( square_file(weakerKingSq) == square_file(pawnSq)
&& relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
&& ( !same_color_squares(weakerKingSq, strongerBishopSq)
|| relative_rank(strongerSide, weakerKingSq) <= RANK_6))
return SCALE_FACTOR_ZERO;
// Case 2: Opposite colored bishops
if (!same_color_squares(strongerBishopSq, weakerBishopSq))
{
// We assume that the position is drawn in the following three situations:
//
// a. The pawn is on rank 5 or further back.
// b. The defending king is somewhere in the pawn's path.
// c. The defending bishop attacks some square along the pawn's path,
// and is at least three squares away from the pawn.
//
// These rules are probably not perfect, but in practice they work
// reasonably well.
if (relative_rank(strongerSide, pawnSq) <= RANK_5)
return SCALE_FACTOR_ZERO;
else
{
Bitboard path = squares_in_front_of(strongerSide, pawnSq);
if (path & pos.pieces(KING, weakerSide))
return SCALE_FACTOR_ZERO;
if ( (pos.attacks_from<BISHOP>(weakerBishopSq) & path)
&& square_distance(weakerBishopSq, pawnSq) >= 3)
return SCALE_FACTOR_ZERO;
}
}
return SCALE_FACTOR_NONE;
}
Value EvaluationFunction<KBBKN>::apply(const Position& pos) const {
assert(pos.piece_count(strongerSide, BISHOP) == 2);
assert(pos.non_pawn_material(strongerSide) == 2*BishopValueMidgame);
assert(pos.piece_count(weakerSide, KNIGHT) == 1);
assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame);
assert(pos.pieces(PAWN) == EmptyBoardBB);
Value result = BishopValueEndgame;
Square wksq = pos.king_square(strongerSide);
Square bksq = pos.king_square(weakerSide);
Square nsq = pos.piece_list(weakerSide, KNIGHT, 0);
// Bonus for attacking king close to defending king
result += distance_bonus(square_distance(wksq, bksq));
// Bonus for driving the defending king and knight apart
result += Value(square_distance(bksq, nsq) * 32);
// Bonus for restricting the knight's mobility
result += Value((8 - count_1s<CNT32_MAX15>(pos.attacks_from<KNIGHT>(nsq))) * 8);
return strongerSide == pos.side_to_move() ? result : -result;
}
ScaleFactor ScalingFunction<KBPsK>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
assert(pos.piece_count(strongerSide, BISHOP) == 1);
assert(pos.piece_count(strongerSide, PAWN) >= 1);
// No assertions about the material of weakerSide, because we want draws to
// be detected even when the weaker side has some pawns.
Bitboard pawns = pos.pieces(PAWN, strongerSide);
File pawnFile = square_file(pos.piece_list(strongerSide, PAWN, 0));
// All pawns are on a single rook file ?
if ( (pawnFile == FILE_A || pawnFile == FILE_H)
&& (pawns & ~file_bb(pawnFile)) == EmptyBoardBB)
{
Square bishopSq = pos.piece_list(strongerSide, BISHOP, 0);
Square queeningSq = relative_square(strongerSide, make_square(pawnFile, RANK_8));
Square kingSq = pos.king_square(weakerSide);
if ( !same_color_squares(queeningSq, bishopSq)
&& file_distance(square_file(kingSq), pawnFile) <= 1)
{
// The bishop has the wrong color, and the defending king is on the
// file of the pawn(s) or the neighboring file. Find the rank of the
// frontmost pawn.
Rank rank;
if (strongerSide == WHITE)
{
for (rank = RANK_7; (rank_bb(rank) & pawns) == EmptyBoardBB; rank--) {}
assert(rank >= RANK_2 && rank <= RANK_7);
}
else
{
for (rank = RANK_2; (rank_bb(rank) & pawns) == EmptyBoardBB; rank++) {}
rank = Rank(rank ^ 7); // HACK to get the relative rank
assert(rank >= RANK_2 && rank <= RANK_7);
}
// If the defending king has distance 1 to the promotion square or
// is placed somewhere in front of the pawn, it's a draw.
if ( square_distance(kingSq, queeningSq) <= 1
|| relative_rank(strongerSide, kingSq) >= rank)
return SCALE_FACTOR_ZERO;
}
}
return SCALE_FACTOR_NONE;
}
Value EvaluationFunction<KQKR>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 0);
assert(pos.non_pawn_material(weakerSide) == RookValueMidgame);
assert(pos.piece_count(weakerSide, PAWN) == 0);
Square winnerKSq = pos.king_square(strongerSide);
Square loserKSq = pos.king_square(weakerSide);
Value result = QueenValueEndgame
- RookValueEndgame
+ mate_table(loserKSq)
+ distance_bonus(square_distance(winnerKSq, loserKSq));
return strongerSide == pos.side_to_move() ? result : -result;
}
Value EvaluationFunction<KRKN>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 0);
assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame);
assert(pos.piece_count(weakerSide, PAWN) == 0);
assert(pos.piece_count(weakerSide, KNIGHT) == 1);
Square defendingKSq = pos.king_square(weakerSide);
Square nSq = pos.piece_list(weakerSide, KNIGHT, 0);
int d = square_distance(defendingKSq, nSq);
Value result = Value(10)
+ mate_table(defendingKSq)
+ krkn_king_knight_distance_penalty(d);
return strongerSide == pos.side_to_move() ? result : -result;
}
Value EvaluationFunction<KXK>::apply(const Position& pos) const {
assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO);
Square winnerKSq = pos.king_square(strongerSide);
Square loserKSq = pos.king_square(weakerSide);
Value result = pos.non_pawn_material(strongerSide)
+ pos.piece_count(strongerSide, PAWN) * PawnValueEndgame
+ mate_table(loserKSq)
+ distance_bonus(square_distance(winnerKSq, loserKSq));
if ( pos.piece_count(strongerSide, QUEEN)
|| pos.piece_count(strongerSide, ROOK)
|| pos.piece_count(strongerSide, BISHOP) > 1)
// TODO: check for two equal-colored bishops!
result += VALUE_KNOWN_WIN;
return strongerSide == pos.side_to_move() ? result : -result;
}
bool closer(point viewer, point const & a, point const & b) {
return square_distance(a, viewer) < square_distance(b, viewer);
}
point closest_from_two(point viewer, point const & a, point const & b) {
return ((square_distance(a, viewer) < square_distance(b, viewer)) ? a : b);
}
inline void calc_piece_value(struct t_board *board, struct t_chess_eval *eval) {
t_chess_color color, opponent;
t_chess_square square;
t_chess_piece piece;
t_chess_piece piece_type;
t_bitboard b;
t_bitboard attack_squares;
t_bitboard moves;
int move_count;
struct t_pawn_hash_record *pawn_record = eval->pawn_evaluation;
for (color = WHITE; color <= BLACK; color++) {
t_chess_value middlegame = 0;
t_chess_value endgame = 0;
opponent = OPPONENT(color);
//=========================================================
//-- Rooks first
//=========================================================
piece = PIECEINDEX(color, ROOK);
eval->attacklist[piece] = 0;
b = board->piecelist[piece];
//-- Remove Rook and Queens (so we can easily evaluate rams)
t_bitboard _all_pieces = board->all_pieces ^ board->pieces[color][QUEEN] ^ b;
t_bitboard _not_occupied = ~(board->occupied[color] & _all_pieces);
//-- Rooks on the 7th
if ((b & rank_mask[color][6]) && (board->pieces[opponent][KING] & rank_mask[color][7])) {
middlegame += MG_ROOK_ON_7TH;
endgame += MG_ROOK_ON_7TH;
}
//-- Rooks on Open file
if (b & pawn_record->open_file) {
middlegame += popcount(b & pawn_record->open_file) * pawn_record->pawn_count[color] * MG_ROOK_ON_OPEN_FILE;
}
//-- Rooks on Semi-Open file
if (b & pawn_record->semi_open_file[color]) {
middlegame += popcount(b & pawn_record->semi_open_file[color]) * pawn_record->pawn_count[color] * MG_ROOK_ON_SEMI_OPEN_FILE;
}
//-- Loop around for all pieces
while (b) {
//-- Find the square it resides
square = bitscan_reset(&b);
//-- Generate moves
moves = rook_magic_moves[square][((rook_magic[square].mask & _all_pieces) * rook_magic[square].magic) >> 52];
eval->attacks[color][ROOK] |= moves;
moves &= _not_occupied;
//-- Mobility (along ranks)
move_count = popcount(moves & square_rank_mask[square]);
middlegame += horizontal_rook_mobility[MIDDLEGAME][move_count];
endgame += horizontal_rook_mobility[ENDGAME][move_count];
//-- Mobility (along files)
move_count = popcount(moves & square_column_mask[square]);
middlegame += vertical_rook_mobility[MIDDLEGAME][move_count];
endgame += vertical_rook_mobility[ENDGAME][move_count];
//-- King safety
if (attack_squares = (moves & eval->king_zone[opponent])) {
eval->king_attack_count[opponent]++;
eval->king_attack_pressure[opponent] += popcount(attack_squares) * 40;
}
assert(eval->king_zone[opponent] != 0);
// piece-square tables
middlegame += piece_square_table[piece][MIDDLEGAME][square];
endgame += piece_square_table[piece][ENDGAME][square];
}
//=========================================================
//-- Queens
//=========================================================
piece = PIECEINDEX(color, QUEEN);
eval->attacklist[piece] = 0;
b = board->piecelist[piece];
_all_pieces ^= board->pieces[color][BISHOP];
_not_occupied = ~(board->occupied[color] & _all_pieces);
while (b) {
//-- Find the square it resides
square = bitscan_reset(&b);
//-- Rook-like Moves
t_bitboard rook_moves = rook_magic_moves[square][((rook_magic[square].mask & _all_pieces) * rook_magic[square].magic) >> 52];
eval->attacklist[piece] |= rook_moves;
rook_moves &= _not_occupied;
//-- Bishop-like moves
t_bitboard bishop_moves = bishop_magic_moves[square][((bishop_magic[square].mask & _all_pieces) * bishop_magic[square].magic) >> 55];
eval->attacklist[piece] |= bishop_moves;
bishop_moves &= _not_occupied;
//-- Mobility
move_count = popcount((rook_moves & square_column_mask[square]) | bishop_moves);
middlegame += move_count;
//-- King safety
if (attack_squares = ((rook_moves | bishop_moves) & eval->king_zone[opponent])) {
eval->king_attack_count[opponent]++;
eval->king_attack_pressure[opponent] += 80 * popcount(attack_squares);
}
//-- piece-square tables
middlegame += piece_square_table[piece][MIDDLEGAME][square];
endgame += piece_square_table[piece][ENDGAME][square];
}
//-- Interaction of double pawns & major pieces
if (pawn_record->double_pawns[color]) {
int double_pawn_count = popcount(pawn_record->double_pawns[color]);
int major_piece_count = popcount(board->pieces[color][ROOK] | board->pieces[color][QUEEN]);
switch (major_piece_count) {
case 0:
break;
case 1:
middlegame += (double_pawn_count * 12) - pawn_record->semi_open_double_pawns[color] * 30;
endgame += (double_pawn_count * 12) - pawn_record->semi_open_double_pawns[color] * 25;
break;
case 2:
middlegame += (double_pawn_count * 24) - pawn_record->semi_open_double_pawns[color] * 35;
endgame += (double_pawn_count * 24) - pawn_record->semi_open_double_pawns[color] * 30;
break;
case 3:
middlegame += (double_pawn_count * 30) - pawn_record->semi_open_double_pawns[color] * 40;
endgame += (double_pawn_count * 30) - pawn_record->semi_open_double_pawns[color] * 35;
break;
case 4:
middlegame += (double_pawn_count * 30) - pawn_record->semi_open_double_pawns[color] * 40;
endgame += (double_pawn_count * 30) - pawn_record->semi_open_double_pawns[color] * 35;
break;
case 5:
middlegame += (double_pawn_count * 30) - pawn_record->semi_open_double_pawns[color] * 40;
endgame += (double_pawn_count * 30) - pawn_record->semi_open_double_pawns[color] * 35;
break;
}
}
//=========================================================
//-- Bishops
//=========================================================
piece = PIECEINDEX(color, BISHOP);
eval->attacklist[piece] = 0;
b = board->piecelist[piece];
//-- Bishop pair bonus
if (b & (b - 1)) {
middlegame += MG_BISHOP_PAIR;
endgame += EG_BISHOP_PAIR;
}
//-- Remove Own Pieces (leave pawns)
_all_pieces = board->all_pieces ^ board->pieces[color][KNIGHT] ^ board->pieces[color][QUEEN];
_not_occupied = ~(board->occupied[color] & _all_pieces);
while (b) {
//-- Find the square it resides
square = bitscan_reset(&b);
//-- Generate moves
moves = bishop_magic_moves[square][((bishop_magic[square].mask & _all_pieces) * bishop_magic[square].magic) >> 55];
eval->attacklist[piece] |= moves;
moves &= _not_occupied;
//-- Mobility
move_count = popcount(moves);
middlegame += bishop_mobility[MIDDLEGAME][move_count];
endgame += bishop_mobility[ENDGAME][move_count];
//-- Trapped
//middlegame -= trapped_bishop[MIDDLEGAME][move_count];
//endgame -= trapped_bishop[ENDGAME][move_count];
//-- King safety
if (attack_squares = (moves & eval->king_zone[opponent])) {
eval->king_attack_count[opponent]++;
eval->king_attack_pressure[opponent] += 20 * popcount(attack_squares);
}
// piece-square tables
middlegame += piece_square_table[piece][MIDDLEGAME][square];
endgame += piece_square_table[piece][ENDGAME][square];
}
//=========================================================
//-- Knights
//=========================================================
piece = PIECEINDEX(color, KNIGHT);
eval->attacklist[piece] = 0;
b = board->piecelist[piece];
_not_occupied = ~board->occupied[color] & ~eval->attacks[opponent][PAWN];
//-- Outposts
t_bitboard knight_outpost = b & pawn_record->potential_outpost[color];
while (knight_outpost) {
square = bitscan_reset(&knight_outpost);
t_chess_color square_color = SQUARECOLOR(square);
//-- Can it be taken by a minor piece?
if ((board->pieces[opponent][KNIGHT] == 0) && ((board->pieces[opponent][BISHOP] & color_square_mask[square_color]) == 0)) {
middlegame += 25 - square_distance(square, board->king_square[opponent]);
endgame += 10;
}
else {
middlegame += 15 - square_distance(square, board->king_square[opponent]);
endgame += 8;
}
}
while (b) {
//-- Find the square it resides
square = bitscan_reset(&b);
//-- Opponents King Tropism
middlegame -= square_distance(square, board->king_square[opponent]) * 2;
//-- Generate moves
moves = knight_mask[square];
eval->attacklist[piece] |= moves;
//-- Connected to another knight
if (moves & board->piecelist[piece]) {
middlegame += MG_CONNECTED_KNIGHTS;
endgame += EG_CONNECTED_KNIGHTS;
}
//-- King safety
if (attack_squares = (moves & eval->king_zone[opponent])) {
eval->king_attack_count[opponent]++;
eval->king_attack_pressure[opponent] += 20 * popcount(attack_squares);
}
//-- Mobility (not including any squares attacked by enemy pawns)
moves &= _not_occupied;
move_count = popcount(moves);
middlegame += knight_mobility[MIDDLEGAME][move_count];
endgame += knight_mobility[ENDGAME][move_count];
// piece-square tables
middlegame += piece_square_table[piece][MIDDLEGAME][square];
endgame += piece_square_table[piece][ENDGAME][square];
}
//=========================================================
//-- King Attacks
//=========================================================
piece = PIECEINDEX(color, KING);
eval->attacklist[piece] = king_mask[board->king_square[color]];
//=========================================================
//-- Blocked Central Pawns
//=========================================================
if (b = (central_kq_pawns[color] & board->pieces[color][PAWN])){
b = ((b << 8) >> (color * 16)) & board->all_pieces;
middlegame += -10 * popcount(b);
}
//-- Add to board scores
eval->middlegame += middlegame * (1 - color * 2);
eval->endgame += endgame * (1 - color * 2);
//-- Create combined attacks
eval->attacks[color][BLANK] = eval->attacks[color][PAWN] | eval->attacks[color][ROOK] | eval->attacks[color][BISHOP] | eval->attacks[color][KNIGHT] | eval->attacks[color][QUEEN] | eval->attacks[color][KING];
}
ScaleFactor ScalingFunction<KRPKR>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 1);
assert(pos.non_pawn_material(weakerSide) == RookValueMidgame);
assert(pos.piece_count(weakerSide, PAWN) == 0);
Square wksq = pos.king_square(strongerSide);
Square wrsq = pos.piece_list(strongerSide, ROOK, 0);
Square wpsq = pos.piece_list(strongerSide, PAWN, 0);
Square bksq = pos.king_square(weakerSide);
Square brsq = pos.piece_list(weakerSide, ROOK, 0);
// Orient the board in such a way that the stronger side is white, and the
// pawn is on the left half of the board.
if (strongerSide == BLACK)
{
wksq = flip_square(wksq);
wrsq = flip_square(wrsq);
wpsq = flip_square(wpsq);
bksq = flip_square(bksq);
brsq = flip_square(brsq);
}
if (square_file(wpsq) > FILE_D)
{
wksq = flop_square(wksq);
wrsq = flop_square(wrsq);
wpsq = flop_square(wpsq);
bksq = flop_square(bksq);
brsq = flop_square(brsq);
}
File f = square_file(wpsq);
Rank r = square_rank(wpsq);
Square queeningSq = make_square(f, RANK_8);
int tempo = (pos.side_to_move() == strongerSide);
// If the pawn is not too far advanced and the defending king defends the
// queening square, use the third-rank defence.
if ( r <= RANK_5
&& square_distance(bksq, queeningSq) <= 1
&& wksq <= SQ_H5
&& (square_rank(brsq) == RANK_6 || (r <= RANK_3 && square_rank(wrsq) != RANK_6)))
return SCALE_FACTOR_ZERO;
// The defending side saves a draw by checking from behind in case the pawn
// has advanced to the 6th rank with the king behind.
if ( r == RANK_6
&& square_distance(bksq, queeningSq) <= 1
&& square_rank(wksq) + tempo <= RANK_6
&& (square_rank(brsq) == RANK_1 || (!tempo && abs(square_file(brsq) - f) >= 3)))
return SCALE_FACTOR_ZERO;
if ( r >= RANK_6
&& bksq == queeningSq
&& square_rank(brsq) == RANK_1
&& (!tempo || square_distance(wksq, wpsq) >= 2))
return SCALE_FACTOR_ZERO;
// White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7
// and the black rook is behind the pawn.
if ( wpsq == SQ_A7
&& wrsq == SQ_A8
&& (bksq == SQ_H7 || bksq == SQ_G7)
&& square_file(brsq) == FILE_A
&& (square_rank(brsq) <= RANK_3 || square_file(wksq) >= FILE_D || square_rank(wksq) <= RANK_5))
return SCALE_FACTOR_ZERO;
// If the defending king blocks the pawn and the attacking king is too far
// away, it's a draw.
if ( r <= RANK_5
&& bksq == wpsq + DELTA_N
&& square_distance(wksq, wpsq) - tempo >= 2
&& square_distance(wksq, brsq) - tempo >= 2)
return SCALE_FACTOR_ZERO;
// Pawn on the 7th rank supported by the rook from behind usually wins if the
// attacking king is closer to the queening square than the defending king,
// and the defending king cannot gain tempi by threatening the attacking rook.
if ( r == RANK_7
&& f != FILE_A
&& square_file(wrsq) == f
&& wrsq != queeningSq
&& (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
&& (square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo))
return ScaleFactor(SCALE_FACTOR_MAX - 2 * square_distance(wksq, queeningSq));
// Similar to the above, but with the pawn further back
if ( f != FILE_A
&& square_file(wrsq) == f
&& wrsq < wpsq
&& (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
&& (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wpsq + DELTA_N) - 2 + tempo)
&& ( square_distance(bksq, wrsq) + tempo >= 3
|| ( square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo
&& (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wrsq) + tempo))))
return ScaleFactor( SCALE_FACTOR_MAX
- 8 * square_distance(wpsq, queeningSq)
- 2 * square_distance(wksq, queeningSq));
// If the pawn is not far advanced, and the defending king is somewhere in
// the pawn's path, it's probably a draw.
if (r <= RANK_4 && bksq > wpsq)
{
if (square_file(bksq) == square_file(wpsq))
return ScaleFactor(10);
if ( abs(square_file(bksq) - square_file(wpsq)) == 1
&& square_distance(wksq, bksq) > 2)
return ScaleFactor(24 - 2 * square_distance(wksq, bksq));
}
return SCALE_FACTOR_NONE;
}
