ScaleFactor ScalingFunction<KPsK>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
assert(pos.piece_count(strongerSide, PAWN) >= 2);
assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
assert(pos.piece_count(weakerSide, PAWN) == 0);
Square ksq = pos.king_square(weakerSide);
Bitboard pawns = pos.pieces(PAWN, strongerSide);
// Are all pawns on the 'a' file?
if ((pawns & ~FileABB) == EmptyBoardBB)
{
// Does the defending king block the pawns?
if ( square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1
|| ( square_file(ksq) == FILE_A
&& (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB))
return SCALE_FACTOR_ZERO;
}
// Are all pawns on the 'h' file?
else if ((pawns & ~FileHBB) == EmptyBoardBB)
{
// Does the defending king block the pawns?
if ( square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1
|| ( square_file(ksq) == FILE_H
&& (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB))
return SCALE_FACTOR_ZERO;
}
return SCALE_FACTOR_NONE;
}
static int ambiguity(int move, const board_t * board) {
int from, to, piece;
list_t list[1];
int i, n, m;
// init
from = move_from(move);
to = move_to(move);
piece = move_piece(move,board);
gen_legal_moves(list,board);
// no ambiguity?
n = 0;
for (i = 0; i < list_size(list); i++) {
m = list_move(list,i);
if (move_piece(m,board) == piece && move_to(m) == to) {
n++;
}
}
if (n == 1) return AMBIGUITY_NONE;
// file ambiguity?
n = 0;
for (i = 0; i < list_size(list); i++) {
m = list_move(list,i);
if (move_piece(m,board) == piece && move_to(m) == to) {
if (square_file(move_from(m)) == square_file(from)) n++;
}
}
if (n == 1) return AMBIGUITY_FILE;
// rank ambiguity?
n = 0;
for (i = 0; i < list_size(list); i++) {
m = list_move(list,i);
if (move_piece(m,board) == piece && move_to(m) == to) {
if (square_rank(move_from(m)) == square_rank(from)) n++;
}
}
if (n == 1) return AMBIGUITY_RANK;
// square ambiguity
return AMBIGUITY_SQUARE;
}
Value EvaluationFunction<KRKP>::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) == 0);
assert(pos.piece_count(weakerSide, PAWN) == 1);
Square wksq, wrsq, bksq, bpsq;
int tempo = (pos.side_to_move() == strongerSide);
wksq = pos.king_square(strongerSide);
wrsq = pos.piece_list(strongerSide, ROOK, 0);
bksq = pos.king_square(weakerSide);
bpsq = pos.piece_list(weakerSide, PAWN, 0);
if (strongerSide == BLACK)
{
wksq = flip_square(wksq);
wrsq = flip_square(wrsq);
bksq = flip_square(bksq);
bpsq = flip_square(bpsq);
}
Square queeningSq = make_square(square_file(bpsq), RANK_1);
Value result;
// If the stronger side's king is in front of the pawn, it's a win
if (wksq < bpsq && square_file(wksq) == square_file(bpsq))
result = RookValueEndgame - Value(square_distance(wksq, bpsq));
// If the weaker side's king is too far from the pawn and the rook,
// it's a win
else if ( square_distance(bksq, bpsq) - (tempo ^ 1) >= 3
&& square_distance(bksq, wrsq) >= 3)
result = RookValueEndgame - Value(square_distance(wksq, bpsq));
// If the pawn is far advanced and supported by the defending king,
// the position is drawish
else if ( square_rank(bksq) <= RANK_3
&& square_distance(bksq, bpsq) == 1
&& square_rank(wksq) >= RANK_4
&& square_distance(wksq, bpsq) - tempo > 2)
result = Value(80 - square_distance(wksq, bpsq) * 8);
else
result = Value(200)
- Value(square_distance(wksq, bpsq + DELTA_S) * 8)
+ Value(square_distance(bksq, bpsq + DELTA_S) * 8)
+ Value(square_distance(bpsq, queeningSq) * 8);
return strongerSide == pos.side_to_move() ? result : -result;
}
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;
}
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;
}
ScaleFactor ScalingFunction<KPKP>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
assert(pos.piece_count(WHITE, PAWN) == 1);
assert(pos.piece_count(BLACK, PAWN) == 1);
Square wksq, bksq, wpsq;
Color stm;
if (strongerSide == WHITE)
{
wksq = pos.king_square(WHITE);
bksq = pos.king_square(BLACK);
wpsq = pos.piece_list(WHITE, PAWN, 0);
stm = pos.side_to_move();
}
else
{
wksq = flip_square(pos.king_square(BLACK));
bksq = flip_square(pos.king_square(WHITE));
wpsq = flip_square(pos.piece_list(BLACK, PAWN, 0));
stm = opposite_color(pos.side_to_move());
}
if (square_file(wpsq) >= FILE_E)
{
wksq = flop_square(wksq);
bksq = flop_square(bksq);
wpsq = flop_square(wpsq);
}
// If the pawn has advanced to the fifth rank or further, and is not a
// rook pawn, it's too dangerous to assume that it's at least a draw.
if ( square_rank(wpsq) >= RANK_5
&& square_file(wpsq) != FILE_A)
return SCALE_FACTOR_NONE;
// Probe the KPK bitbase with the weakest side's pawn removed. If it's a
// draw, it's probably at least a draw even with the pawn.
return probe_kpk(wksq, wpsq, bksq, stm) ? SCALE_FACTOR_NONE : SCALE_FACTOR_ZERO;
}
ScaleFactor ScalingFunction<KBPKN>::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) == KnightValueMidgame);
assert(pos.piece_count(weakerSide, KNIGHT) == 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 weakerKingSq = pos.king_square(weakerSide);
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;
return SCALE_FACTOR_NONE;
}
Value EvaluationFunction<KPK>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
assert(pos.piece_count(strongerSide, PAWN) == 1);
assert(pos.piece_count(weakerSide, PAWN) == 0);
Square wksq, bksq, wpsq;
Color stm;
if (strongerSide == WHITE)
{
wksq = pos.king_square(WHITE);
bksq = pos.king_square(BLACK);
wpsq = pos.piece_list(WHITE, PAWN, 0);
stm = pos.side_to_move();
}
else
{
wksq = flip_square(pos.king_square(BLACK));
bksq = flip_square(pos.king_square(WHITE));
wpsq = flip_square(pos.piece_list(BLACK, PAWN, 0));
stm = opposite_color(pos.side_to_move());
}
if (square_file(wpsq) >= FILE_E)
{
wksq = flop_square(wksq);
bksq = flop_square(bksq);
wpsq = flop_square(wpsq);
}
if (!probe_kpk(wksq, wpsq, bksq, stm))
return VALUE_DRAW;
Value result = VALUE_KNOWN_WIN
+ PawnValueEndgame
+ Value(square_rank(wpsq));
return strongerSide == pos.side_to_move() ? result : -result;
}
const std::string move_to_san(Position &pos, Move m) {
std::string str;
assert(pos.is_ok());
assert(move_is_ok(m));
Square from, to;
Piece pc;
from = move_from(m);
to = move_to(m);
pc = pos.piece_on(move_from(m));
if(m == MOVE_NONE) {
str = "(none)";
return str;
}
else if(m == MOVE_NULL) {
str = "(null)";
return str;
}
else if(move_is_long_castle(m)
|| (int(to - from) == -2 && type_of_piece(pc) == KING))
str = "O-O-O";
else if(move_is_short_castle(m)
|| (int(to - from) == 2 && type_of_piece(pc) == KING))
str = "O-O";
else {
str = "";
if(type_of_piece(pc) == PAWN) {
if(pos.move_is_capture(m))
str += file_to_char(square_file(move_from(m)));
}
else {
str += piece_type_to_char(type_of_piece(pc), true);
Ambiguity amb = move_ambiguity(pos, m);
switch(amb) {
case AMBIGUITY_NONE:
break;
case AMBIGUITY_FILE:
str += file_to_char(square_file(from));
break;
case AMBIGUITY_RANK:
str += rank_to_char(square_rank(from));
break;
case AMBIGUITY_BOTH:
str += square_to_string(from);
break;
default:
assert(false);
}
}
if(pos.move_is_capture(m))
str += "x";
str += square_to_string(move_to(m));
if(move_promotion(m)) {
str += "=";
str += piece_type_to_char(move_promotion(m), true);
}
}
// Is the move check? We don't use pos.move_is_check(m) here, because
// Position::move_is_check doesn't detect all checks (not castling moves,
// promotions and en passant captures).
UndoInfo u;
pos.do_move(m, u);
if(pos.is_check())
str += pos.is_mate()? "#" : "+";
pos.undo_move(m, u);
return str;
}
Move move_from_san(Position &pos, const std::string &movestr) {
assert(pos.is_ok());
MovePicker mp = MovePicker(pos, false, MOVE_NONE, MOVE_NONE, MOVE_NONE,
MOVE_NONE, OnePly);
// Castling moves
if(movestr == "O-O-O") {
Move m;
while((m = mp.get_next_move()) != MOVE_NONE)
if(move_is_long_castle(m) && pos.move_is_legal(m))
return m;
return MOVE_NONE;
}
else if(movestr == "O-O") {
Move m;
while((m = mp.get_next_move()) != MOVE_NONE)
if(move_is_short_castle(m) && pos.move_is_legal(m))
return m;
return MOVE_NONE;
}
// Normal moves
const char *cstr = movestr.c_str();
const char *c;
char *cc;
char str[10];
int i;
// Initialize str[] by making a copy of movestr with the characters
// 'x', '=', '+' and '#' removed.
cc = str;
for(i=0, c=cstr; i<10 && *c!='\0' && *c!='\n' && *c!=' '; i++, c++)
if(!strchr("x=+#", *c)) {
*cc = strchr("nrq", *c)? toupper(*c) : *c;
cc++;
}
*cc = '\0';
int left = 0, right = strlen(str) - 1;
PieceType pt = NO_PIECE_TYPE, promotion;
Square to;
File fromFile = FILE_NONE;
Rank fromRank = RANK_NONE;
// Promotion?
if(strchr("BNRQ", str[right])) {
promotion = piece_type_from_char(str[right]);
right--;
}
else
promotion = NO_PIECE_TYPE;
// Find the moving piece:
if(left < right) {
if(strchr("BNRQK", str[left])) {
pt = piece_type_from_char(str[left]);
left++;
}
else
pt = PAWN;
}
// Find the to square:
if(left < right) {
if(str[right] < '1' || str[right] > '8' ||
str[right-1] < 'a' || str[right-1] > 'h')
return MOVE_NONE;
to = make_square(file_from_char(str[right-1]), rank_from_char(str[right]));
right -= 2;
}
else
return MOVE_NONE;
// Find the file and/or rank of the from square:
if(left <= right) {
if(strchr("abcdefgh", str[left])) {
fromFile = file_from_char(str[left]);
left++;
}
if(strchr("12345678", str[left]))
fromRank = rank_from_char(str[left]);
}
// Look for a matching move:
Move m, move = MOVE_NONE;
int matches = 0;
while((m = mp.get_next_move()) != MOVE_NONE) {
bool match = true;
if(pos.type_of_piece_on(move_from(m)) != pt)
match = false;
else if(move_to(m) != to)
match = false;
else if(move_promotion(m) != promotion)
match = false;
else if(fromFile != FILE_NONE && fromFile != square_file(move_from(m)))
match = false;
else if(fromRank != RANK_NONE && fromRank != square_rank(move_from(m)))
match = false;
if(match) {
move = m;
matches++;
}
}
if(matches == 1)
return move;
else
return MOVE_NONE;
}
void move_do(board_t * board, int move) {
int me, opp;
int from, to;
int piece, pos, capture;
int old_flags, new_flags;
int sq, ep_square;
int pawn;
ASSERT(board_is_ok(board));
ASSERT(move_is_ok(move));
ASSERT(move_is_pseudo(move,board));
// init
me = board->turn;
opp = colour_opp(me);
from = move_from(move);
to = move_to(move);
piece = board->square[from];
ASSERT(colour_equal(piece,me));
pos = board->pos[from];
ASSERT(pos>=0);
// update turn
board->turn = opp;
board->key ^= random_64(RandomTurn);
// update castling rights
old_flags = board_flags(board);
if (piece_is_king(piece)) {
board->castle[me][SideH] = SquareNone;
board->castle[me][SideA] = SquareNone;
}
if (board->castle[me][SideH] == from) board->castle[me][SideH] = SquareNone;
if (board->castle[me][SideA] == from) board->castle[me][SideA] = SquareNone;
if (board->castle[opp][SideH] == to) board->castle[opp][SideH] = SquareNone;
if (board->castle[opp][SideA] == to) board->castle[opp][SideA] = SquareNone;
new_flags = board_flags(board);
board->key ^= hash_castle_key(new_flags^old_flags); // HACK
// update en-passant square
ep_square = sq = board->ep_square;
if (sq != SquareNone) {
board->key ^= random_64(RandomEnPassant+square_file(sq));
board->ep_square = SquareNone;
}
if (piece_is_pawn(piece) && abs(to-from) == 32) {
pawn = piece_make_pawn(opp);
if (board->square[to-1] == pawn || board->square[to+1] == pawn) {
board->ep_square = sq = (from + to) / 2;
board->key ^= random_64(RandomEnPassant+square_file(sq));
}
}
// update ply number (captures are handled later)
board->ply_nb++;
if (piece_is_pawn(piece)) board->ply_nb = 0; // conversion
// update move number
if (me == Black) board->move_nb++;
// castle
if (colour_equal(board->square[to],me)) {
int rank;
int king_from, king_to;
int rook_from, rook_to;
int rook;
rank = colour_is_white(me) ? Rank1 : Rank8;
king_from = from;
rook_from = to;
if (to > from) { // h side
king_to = square_make(FileG,rank);
rook_to = square_make(FileF,rank);
} else { // a side
king_to = square_make(FileC,rank);
rook_to = square_make(FileD,rank);
}
// remove the rook
pos = board->pos[rook_from];
ASSERT(pos>=0);
rook = Rook64 | me; // HACK
square_clear(board,rook_from,rook);
// move the king
square_move(board,king_from,king_to,piece);
// put the rook back
square_set(board,rook_to,rook,pos);
ASSERT(board->key==hash_key(board));
return;
}
// remove the captured piece
if (piece_is_pawn(piece) && to == ep_square) {
// en-passant capture
sq = square_ep_dual(to);
capture = board->square[sq];
ASSERT(capture==piece_make_pawn(opp));
square_clear(board,sq,capture);
board->ply_nb = 0; // conversion
} else {
capture = board->square[to];
if (capture != Empty) {
// normal capture
ASSERT(colour_equal(capture,opp));
ASSERT(!piece_is_king(capture));
square_clear(board,to,capture);
board->ply_nb = 0; // conversion
}
}
// move the piece
if (move_is_promote(move)) {
// promote
square_clear(board,from,piece);
piece = move_promote_hack(move) | me; // HACK
square_set(board,to,piece,pos);
} else {
// normal move
square_move(board,from,to,piece);
}
ASSERT(board->key==hash_key(board));
}
bool board_to_fen(const board_t * board, char string[], int size) {
int pos;
int file, rank;
int sq, piece;
int c;
int len;
int old_pos;
ASSERT(board_is_ok(board));
ASSERT(string!=NULL);
ASSERT(size>=92);
// init
if (size < 92) return false;
pos = 0;
// piece placement
for (rank = 7; rank >= 0; rank--) {
for (file = 0; file < 8;) {
sq = square_make(file,rank);
piece = board->square[sq];
ASSERT(piece==Empty||piece_is_ok(piece));
if (piece == Empty) {
len = 0;
for (; file < 8 && board->square[square_make(file,rank)] == Empty; file++) {
len++;
}
ASSERT(len>=1&&len<=8);
c = '0' + len;
} else {
c = piece_to_char(piece);
file++;
}
string[pos++] = c;
}
string[pos++] = '/';
}
string[pos-1] = ' '; // HACK: remove the last '/'
// active colour
string[pos++] = (colour_is_white(board->turn)) ? 'w' : 'b';
string[pos++] = ' ';
// castling
old_pos = pos;
if (option_get_bool("Chess960")) {
// FEN-960
if (board->castle[White][SideH] != SquareNone) {
string[pos++] = toupper(file_to_char(square_file(board->castle[White][SideH])));
}
if (board->castle[White][SideA] != SquareNone) {
string[pos++] = toupper(file_to_char(square_file(board->castle[White][SideA])));
}
if (board->castle[Black][SideH] != SquareNone) {
string[pos++] = tolower(file_to_char(square_file(board->castle[Black][SideH])));
}
if (board->castle[Black][SideA] != SquareNone) {
string[pos++] = tolower(file_to_char(square_file(board->castle[Black][SideA])));
}
} else {
// FEN
if (board->castle[White][SideH] != SquareNone) string[pos++] = 'K';
if (board->castle[White][SideA] != SquareNone) string[pos++] = 'Q';
if (board->castle[Black][SideH] != SquareNone) string[pos++] = 'k';
if (board->castle[Black][SideA] != SquareNone) string[pos++] = 'q';
}
if (pos == old_pos) string[pos++] = '-';
string[pos++] = ' ';
// en-passant
if (board->ep_square == SquareNone) {
string[pos++] = '-';
} else {
if (!square_to_string(board->ep_square,&string[pos],3)) return false;
pos += 2;
}
string[pos++] = ' ';
// halfmove clock and fullmove number
sprintf(&string[pos],"%d %d",board->ply_nb,board->move_nb+1);
return true;
}
ScaleFactor ScalingFunction<KBPPKB>::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) == 2);
assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame);
assert(pos.piece_count(weakerSide, BISHOP) == 1);
assert(pos.piece_count(weakerSide, PAWN) == 0);
Square wbsq = pos.piece_list(strongerSide, BISHOP, 0);
Square bbsq = pos.piece_list(weakerSide, BISHOP, 0);
if (same_color_squares(wbsq, bbsq))
// Not opposite-colored bishops, no scaling
return SCALE_FACTOR_NONE;
Square ksq = pos.king_square(weakerSide);
Square psq1 = pos.piece_list(strongerSide, PAWN, 0);
Square psq2 = pos.piece_list(strongerSide, PAWN, 1);
Rank r1 = square_rank(psq1);
Rank r2 = square_rank(psq2);
Square blockSq1, blockSq2;
if (relative_rank(strongerSide, psq1) > relative_rank(strongerSide, psq2))
{
blockSq1 = psq1 + pawn_push(strongerSide);
blockSq2 = make_square(square_file(psq2), square_rank(psq1));
}
else
{
blockSq1 = psq2 + pawn_push(strongerSide);
blockSq2 = make_square(square_file(psq1), square_rank(psq2));
}
switch (file_distance(psq1, psq2))
{
case 0:
// Both pawns are on the same file. Easy draw if defender firmly controls
// some square in the frontmost pawn's path.
if ( square_file(ksq) == square_file(blockSq1)
&& relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1)
&& !same_color_squares(ksq, wbsq))
return SCALE_FACTOR_ZERO;
else
return SCALE_FACTOR_NONE;
case 1:
// Pawns on neighboring files. Draw if defender firmly controls the square
// in front of the frontmost pawn's path, and the square diagonally behind
// this square on the file of the other pawn.
if ( ksq == blockSq1
&& !same_color_squares(ksq, wbsq)
&& ( bbsq == blockSq2
|| (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(BISHOP, weakerSide))
|| rank_distance(r1, r2) >= 2))
return SCALE_FACTOR_ZERO;
else if ( ksq == blockSq2
&& !same_color_squares(ksq, wbsq)
&& ( bbsq == blockSq1
|| (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(BISHOP, weakerSide))))
return SCALE_FACTOR_ZERO;
else
return SCALE_FACTOR_NONE;
default:
// The pawns are not on the same file or adjacent files. No scaling.
return SCALE_FACTOR_NONE;
}
}
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;
}
bool move_to_san(int move, const board_t * board, char string[], int size) {
int from, to, piece;
char tmp_string[256];
ASSERT(move_is_ok(move));
ASSERT(board_is_ok(board));
ASSERT(string!=NULL);
ASSERT(size>=8);
ASSERT(move_is_legal(move,board));
if (size < 8) return false;
// init
from = move_from(move);
to = move_to(move);
string[0] = '\0';
// castle
if (move_is_castle(move,board)) {
if (to > from) {
strcat(string,"O-O");
} else {
strcat(string,"O-O-O");
}
goto check;
}
// from
piece = board->square[from];
if (piece_is_pawn(piece)) {
// pawn
if (move_is_capture(move,board)) {
sprintf(tmp_string,"%c",file_to_char(square_file(from)));
strcat(string,tmp_string);
}
} else {
// piece
sprintf(tmp_string,"%c",toupper(piece_to_char(piece)));
strcat(string,tmp_string);
// ambiguity
switch (ambiguity(move,board)) {
case AMBIGUITY_NONE:
break;
case AMBIGUITY_FILE:
sprintf(tmp_string,"%c",file_to_char(square_file(from)));
strcat(string,tmp_string);
break;
case AMBIGUITY_RANK:
sprintf(tmp_string,"%c",rank_to_char(square_rank(from)));
strcat(string,tmp_string);
break;
case AMBIGUITY_SQUARE:
if (!square_to_string(from,tmp_string,256)) return false;
strcat(string,tmp_string);
break;
default:
ASSERT(false);
break;
}
}
// capture
if (move_is_capture(move,board)) strcat(string,"x");
// to
if (!square_to_string(to,tmp_string,256)) return false;
strcat(string,tmp_string);
// promote
if (move_is_promote(move)) {
sprintf(tmp_string,"=%c",toupper(piece_to_char(move_promote(move,board))));
strcat(string,tmp_string);
}
// check
check:
if (move_is_mate(move,board)) {
strcat(string,"#");
} else if (move_is_check(move,board)) {
strcat(string,"+");
}
return true;
}
static int move_from_lan(const char string[], const board_t * board) {
int len;
int move;
int promote;
char s[256];
int from, to;
int colour;
int inc;
int piece_char;
int n;
const uint8 * ptr;
int piece;
int side;
ASSERT(string!=NULL);
ASSERT(board_is_ok(board));
// init
len = strlen(string);
if (len != 7) return MoveNone;
move = MoveNone;
colour = board->turn;
// promote
promote = 0;
switch (string[6]) {
case '?': // not a promotion
break;
case 'N':
promote = MovePromoteKnight;
break;
case 'B':
promote = MovePromoteBishop;
break;
case 'R':
promote = MovePromoteRook;
break;
case 'Q':
promote = MovePromoteQueen;
break;
default:
return MoveNone;
break;
}
// to square
s[0] = string[4];
s[1] = string[5];
s[2] = '\0';
to = square_from_string(s);
if (to == SquareNone) return MoveNone;
// known from square?
if (string[1] != '?' && string[2] != '?') {
// from square
s[0] = string[1];
s[1] = string[2];
s[2] = '\0';
from = square_from_string(s);
if (from == SquareNone) return MoveNone;
// convert "king slide" castling to KxR
if (piece_is_king(board->square[from])
&& square_rank(to) == square_rank(from)
&& abs(to-from) > 1) {
side = (to > from) ? SideH : SideA;
to = board->castle[colour][side];
if (to == SquareNone) return MoveNone;
}
// move
move = move_make(from,to) | promote;
return move;
}
// pawn non-capture?
if (string[0] == '?' && string[1] == '?') {
if (board->square[to] != Empty) return MoveNone; // useful?
inc = (colour_is_white(colour)) ? +16 : -16;
from = to - inc;
if (board->square[from] == Empty && square_side_rank(to,colour) == Rank4) {
from -= inc;
}
if (board->square[from] != piece_make_pawn(colour)) { // useful?
return MoveNone;
}
// move
move = move_make(from,to) | promote;
return move;
}
// pawn capture?
piece_char = string[0];
if (piece_char == '?' && string[1] != '?') {
piece_char = 'P';
}
// attack loop
n = 0;
for (ptr = board->list[colour]; (from=*ptr) != SquareNone; ptr++) {
piece = board->square[from];
if (toupper(piece_to_char(piece)) == piece_char) {
if (piece_attack(board,piece,from,to)) {
if (true
&& (string[1] == '?' || file_to_char(square_file(from)) == string[1])
&& (string[2] == '?' || rank_to_char(square_rank(from)) == string[2])) {
if (!is_pinned(board,from,to,colour)) {
move = move_make(from,to) | promote;
n++;
}
}
}
}
}
if (n != 1) move = MoveNone;
return move;
}
