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stockfish/src/position.cpp

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/*
Glaurung, a UCI chess playing engine.
Copyright (C) 2004-2008 Tord Romstad
Glaurung is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Glaurung is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
////
//// Includes
////
#include <cassert>
#include <cstdio>
#include <iostream>
#include <fstream>
#include "mersenne.h"
#include "movegen.h"
#include "movepick.h"
#include "position.h"
#include "psqtab.h"
#include "ucioption.h"
////
//// Variables
////
int Position::castleRightsMask[64];
Key Position::zobrist[2][8][64];
Key Position::zobEp[64];
Key Position::zobCastle[16];
Key Position::zobMaterial[2][8][16];
Key Position::zobSideToMove;
Value Position::MgPieceSquareTable[16][64];
Value Position::EgPieceSquareTable[16][64];
////
//// Functions
////
/// Constructors
Position::Position() { } // Do we really need this one?
Position::Position(const Position &pos) {
this->copy(pos);
}
Position::Position(const std::string &fen) {
this->from_fen(fen);
}
/// Position::from_fen() initializes the position object with the given FEN
/// string. This function is not very robust - make sure that input FENs are
/// correct (this is assumed to be the responsibility of the GUI).
void Position::from_fen(const std::string &fen) {
File file;
Rank rank;
int i;
this->clear();
// Board
rank = RANK_8;
file = FILE_A;
for(i = 0; fen[i] != ' '; i++) {
if(isdigit(fen[i]))
// Skip the given number of files
file += (fen[i] - '1' + 1);
else {
Square square = make_square(file, rank);
switch(fen[i]) {
case 'K': this->put_piece(WK, square); file++; break;
case 'Q': this->put_piece(WQ, square); file++; break;
case 'R': this->put_piece(WR, square); file++; break;
case 'B': this->put_piece(WB, square); file++; break;
case 'N': this->put_piece(WN, square); file++; break;
case 'P': this->put_piece(WP, square); file++; break;
case 'k': this->put_piece(BK, square); file++; break;
case 'q': this->put_piece(BQ, square); file++; break;
case 'r': this->put_piece(BR, square); file++; break;
case 'b': this->put_piece(BB, square); file++; break;
case 'n': this->put_piece(BN, square); file++; break;
case 'p': this->put_piece(BP, square); file++; break;
case '/': file = FILE_A; rank--; break;
case ' ': break;
default:
std::cout << "Error in FEN at character " << i << std::endl;
return;
}
}
}
// Side to move
i++;
if(fen[i] == 'w')
sideToMove = WHITE;
else if(fen[i] == 'b')
sideToMove = BLACK;
else {
std::cout << "Error in FEN at character " << i << std::endl;
return;
}
// Castling rights:
i++;
if(fen[i] != ' ') {
std::cout << "Error in FEN at character " << i << std::endl;
return;
}
i++;
while(strchr("KQkqabcdefghABCDEFGH-", fen[i])) {
if(fen[i] == '-') {
i++; break;
}
else if(fen[i] == 'K') this->allow_oo(WHITE);
else if(fen[i] == 'Q') this->allow_ooo(WHITE);
else if(fen[i] == 'k') this->allow_oo(BLACK);
else if(fen[i] == 'q') this->allow_ooo(BLACK);
else if(fen[i] >= 'A' && fen[i] <= 'H') {
File rookFile, kingFile = FILE_NONE;
for(Square square = SQ_B1; square <= SQ_G1; square++)
if(this->piece_on(square) == WK)
kingFile = square_file(square);
if(kingFile == FILE_NONE) {
std::cout << "Error in FEN at character " << i << std::endl;
return;
}
initialKFile = kingFile;
rookFile = File(fen[i] - 'A') + FILE_A;
if(rookFile < initialKFile) {
this->allow_ooo(WHITE);
initialQRFile = rookFile;
}
else {
this->allow_oo(WHITE);
initialKRFile = rookFile;
}
}
else if(fen[i] >= 'a' && fen[i] <= 'h') {
File rookFile, kingFile = FILE_NONE;
for(Square square = SQ_B8; square <= SQ_G8; square++)
if(this->piece_on(square) == BK)
kingFile = square_file(square);
if(kingFile == FILE_NONE) {
std::cout << "Error in FEN at character " << i << std::endl;
return;
}
initialKFile = kingFile;
rookFile = File(fen[i] - 'a') + FILE_A;
if(rookFile < initialKFile) {
this->allow_ooo(BLACK);
initialQRFile = rookFile;
}
else {
this->allow_oo(BLACK);
initialKRFile = rookFile;
}
}
else {
std::cout << "Error in FEN at character " << i << std::endl;
return;
}
i++;
}
while(fen[i] == ' ')
i++;
// En passant square
if(i < int(fen.length()) - 2)
if(fen[i] >= 'a' && fen[i] <= 'h' && (fen[i+1] == '3' || fen[i+1] == '6'))
epSquare = square_from_string(fen.substr(i, 2));
// Various initialisation
for(Square sq = SQ_A1; sq <= SQ_H8; sq++)
castleRightsMask[sq] = ALL_CASTLES;
castleRightsMask[make_square(initialKFile, RANK_1)] ^=
(WHITE_OO|WHITE_OOO);
castleRightsMask[make_square(initialKFile, RANK_8)] ^=
(BLACK_OO|BLACK_OOO);
castleRightsMask[make_square(initialKRFile, RANK_1)] ^= WHITE_OO;
castleRightsMask[make_square(initialKRFile, RANK_8)] ^= BLACK_OO;
castleRightsMask[make_square(initialQRFile, RANK_1)] ^= WHITE_OOO;
castleRightsMask[make_square(initialQRFile, RANK_8)] ^= BLACK_OOO;
this->find_checkers();
key = this->compute_key();
pawnKey = this->compute_pawn_key();
materialKey = this->compute_material_key();
mgValue = this->compute_mg_value();
egValue = this->compute_eg_value();
npMaterial[WHITE] = this->compute_non_pawn_material(WHITE);
npMaterial[BLACK] = this->compute_non_pawn_material(BLACK);
}
/// Position::to_fen() converts the position object to a FEN string. This is
/// probably only useful for debugging.
const std::string Position::to_fen() const {
char pieceLetters[] = " PNBRQK pnbrqk";
std::string result;
int skip;
for(Rank rank = RANK_8; rank >= RANK_1; rank--) {
skip = 0;
for(File file = FILE_A; file <= FILE_H; file++) {
Square square = make_square(file, rank);
if(this->square_is_occupied(square)) {
if(skip > 0) result += (char)skip + '0';
result += pieceLetters[this->piece_on(square)];
skip = 0;
}
else skip++;
}
if(skip > 0) result += (char)skip + '0';
result += (rank > RANK_1)? '/' : ' ';
}
result += (sideToMove == WHITE)? 'w' : 'b';
result += ' ';
if(castleRights == NO_CASTLES) result += '-';
else {
if(this->can_castle_kingside(WHITE)) result += 'K';
if(this->can_castle_queenside(WHITE)) result += 'Q';
if(this->can_castle_kingside(BLACK)) result += 'k';
if(this->can_castle_queenside(BLACK)) result += 'q';
}
result += ' ';
if(this->ep_square() == SQ_NONE) result += '-';
else result += square_to_string(this->ep_square());
return result;
}
/// Position::print() prints an ASCII representation of the position to
/// the standard output.
void Position::print() const {
char pieceStrings[][8] =
{"| ? ", "| P ", "| N ", "| B ", "| R ", "| Q ", "| K ", "| ? ",
"| ? ", "|=P=", "|=N=", "|=B=", "|=R=", "|=Q=", "|=K="
};
for(Rank rank = RANK_8; rank >= RANK_1; rank--) {
std::cout << "+---+---+---+---+---+---+---+---+\n";
for(File file = FILE_A; file <= FILE_H; file++) {
Square sq = make_square(file, rank);
Piece piece = this->piece_on(sq);
if(piece == EMPTY)
std::cout << ((square_color(sq) == WHITE)? "| " : "| . ");
else
std::cout << pieceStrings[piece];
}
std::cout << "|\n";
}
std::cout << "+---+---+---+---+---+---+---+---+\n";
std::cout << this->to_fen() << std::endl;
std::cout << key << std::endl;
}
/// Position::copy() creates a copy of the input position.
void Position::copy(const Position &pos) {
memcpy(this, &pos, sizeof(Position));
}
/// Position:pinned_pieces() returns a bitboard of all pinned (against the
/// king) pieces for the given color.
Bitboard Position::pinned_pieces(Color c) const {
Bitboard b1, b2, pinned, pinners, sliders;
Square ksq = this->king_square(c), s;
Color them = opposite_color(c);
pinned = EmptyBoardBB;
b1 = this->occupied_squares();
sliders = this->rooks_and_queens(them) & ~this->checkers();
if(sliders & RookPseudoAttacks[ksq]) {
b2 = this->rook_attacks(ksq) & this->pieces_of_color(c);
pinners = rook_attacks_bb(ksq, b1 ^ b2) & sliders;
while(pinners) {
s = pop_1st_bit(&pinners);
pinned |= (squares_between(s, ksq) & b2);
}
}
sliders = this->bishops_and_queens(them) & ~this->checkers();
if(sliders & BishopPseudoAttacks[ksq]) {
b2 = this->bishop_attacks(ksq) & this->pieces_of_color(c);
pinners = bishop_attacks_bb(ksq, b1 ^ b2) & sliders;
while(pinners) {
s = pop_1st_bit(&pinners);
pinned |= (squares_between(s, ksq) & b2);
}
}
return pinned;
}
/// Position:discovered_check_candidates() returns a bitboard containing all
/// pieces for the given side which are candidates for giving a discovered
/// check. The code is almost the same as the function for finding pinned
/// pieces.
Bitboard Position::discovered_check_candidates(Color c) const {
Bitboard b1, b2, dc, checkers, sliders;
Square ksq = this->king_square(opposite_color(c)), s;
dc = EmptyBoardBB;
b1 = this->occupied_squares();
sliders = this->rooks_and_queens(c);
if(sliders & RookPseudoAttacks[ksq]) {
b2 = this->rook_attacks(ksq) & this->pieces_of_color(c);
checkers = rook_attacks_bb(ksq, b1 ^ b2) & sliders;
while(checkers) {
s = pop_1st_bit(&checkers);
dc |= (squares_between(s, ksq) & b2);
}
}
sliders = this->bishops_and_queens(c);
if(sliders & BishopPseudoAttacks[ksq]) {
b2 = this->bishop_attacks(ksq) & this->pieces_of_color(c);
checkers = bishop_attacks_bb(ksq, b1 ^ b2) & sliders;
while(checkers) {
s = pop_1st_bit(&checkers);
dc |= (squares_between(s, ksq) & b2);
}
}
return dc;
}
/// Position::square_is_attacked() checks whether the given side attacks the
/// given square.
bool Position::square_is_attacked(Square s, Color c) const {
return
(this->pawn_attacks(opposite_color(c), s) & this->pawns(c)) ||
(this->knight_attacks(s) & this->knights(c)) ||
(this->king_attacks(s) & this->kings(c)) ||
(this->rook_attacks(s) & this->rooks_and_queens(c)) ||
(this->bishop_attacks(s) & this->bishops_and_queens(c));
}
/// Position::attacks_to() computes a bitboard containing all pieces which
/// attacks a given square. There are two versions of this function: One
/// which finds attackers of both colors, and one which only finds the
/// attackers for one side.
Bitboard Position::attacks_to(Square s) const {
return
(this->black_pawn_attacks(s) & this->pawns(WHITE)) |
(this->white_pawn_attacks(s) & this->pawns(BLACK)) |
(this->knight_attacks(s) & this->pieces_of_type(KNIGHT)) |
(this->rook_attacks(s) & this->rooks_and_queens()) |
(this->bishop_attacks(s) & this->bishops_and_queens()) |
(this->king_attacks(s) & this->pieces_of_type(KING));
}
Bitboard Position::attacks_to(Square s, Color c) const {
return this->attacks_to(s) & this->pieces_of_color(c);
}
/// Position::piece_attacks_square() tests whether the piece on square f
/// attacks square t.
bool Position::piece_attacks_square(Square f, Square t) const {
assert(square_is_ok(f));
assert(square_is_ok(t));
switch(this->piece_on(f)) {
case WP: return this->white_pawn_attacks_square(f, t);
case BP: return this->black_pawn_attacks_square(f, t);
case WN: case BN: return this->knight_attacks_square(f, t);
case WB: case BB: return this->bishop_attacks_square(f, t);
case WR: case BR: return this->rook_attacks_square(f, t);
case WQ: case BQ: return this->queen_attacks_square(f, t);
case WK: case BK: return this->king_attacks_square(f, t);
default: return false;
}
return false;
}
/// Position::find_checkers() computes the checkersBB bitboard, which
/// contains a nonzero bit for each checking piece (0, 1 or 2). It
/// currently works by calling Position::attacks_to, which is probably
/// inefficient. Consider rewriting this function to use the last move
/// played, like in non-bitboard versions of Glaurung.
void Position::find_checkers() {
checkersBB = attacks_to(this->king_square(this->side_to_move()),
opposite_color(this->side_to_move()));
}
/// Position::move_is_legal() tests whether a pseudo-legal move is legal.
/// There are two versions of this function: One which takes only a
/// move as input, and one which takes a move and a bitboard of pinned
/// pieces. The latter function is faster, and should always be preferred
/// when a pinned piece bitboard has already been computed.
bool Position::move_is_legal(Move m) const {
return this->move_is_legal(m, this->pinned_pieces(this->side_to_move()));
}
bool Position::move_is_legal(Move m, Bitboard pinned) const {
Color us, them;
Square ksq, from;
assert(this->is_ok());
assert(move_is_ok(m));
assert(pinned == this->pinned_pieces(this->side_to_move()));
// If we're in check, all pseudo-legal moves are legal, because our
// check evasion generator only generates true legal moves.
if(this->is_check()) return true;
// Castling moves are checked for legality during move generation.
if(move_is_castle(m)) return true;
us = this->side_to_move();
them = opposite_color(us);
from = move_from(m);
ksq = this->king_square(us);
assert(this->color_of_piece_on(from) == us);
assert(this->piece_on(ksq) == king_of_color(us));
// En passant captures are a tricky special case. Because they are
// rather uncommon, we do it simply by testing whether the king is attacked
// after the move is made:
if(move_is_ep(m)) {
Square to = move_to(m);
Square capsq = make_square(square_file(to), square_rank(from));
Bitboard b = this->occupied_squares();
assert(to == this->ep_square());
assert(this->piece_on(from) == pawn_of_color(us));
assert(this->piece_on(capsq) == pawn_of_color(them));
assert(this->piece_on(to) == EMPTY);
clear_bit(&b, from); clear_bit(&b, capsq); set_bit(&b, to);
return
(!(rook_attacks_bb(ksq, b) & this->rooks_and_queens(them)) &&
!(bishop_attacks_bb(ksq, b) & this->bishops_and_queens(them)));
}
// If the moving piece is a king, check whether the destination
// square is attacked by the opponent.
if(from == ksq) return !(this->square_is_attacked(move_to(m), them));
// A non-king move is legal if and only if it is not pinned or it
// is moving along the ray towards or away from the king.
if(!bit_is_set(pinned, from)) return true;
if(direction_between_squares(from, ksq) ==
direction_between_squares(move_to(m), ksq))
return true;
return false;
}
/// Position::move_is_check() tests whether a pseudo-legal move is a check.
/// There are two versions of this function: One which takes only a move as
/// input, and one which takes a move and a bitboard of discovered check
/// candidates. The latter function is faster, and should always be preferred
/// when a discovered check candidates bitboard has already been computed.
bool Position::move_is_check(Move m) const {
Bitboard dc = this->discovered_check_candidates(this->side_to_move());
return this->move_is_check(m, dc);
}
bool Position::move_is_check(Move m, Bitboard dcCandidates) const {
Color us, them;
Square ksq, from, to;
assert(this->is_ok());
assert(move_is_ok(m));
assert(dcCandidates ==
this->discovered_check_candidates(this->side_to_move()));
us = this->side_to_move();
them = opposite_color(us);
from = move_from(m);
to = move_to(m);
ksq = this->king_square(them);
assert(this->color_of_piece_on(from) == us);
assert(this->piece_on(ksq) == king_of_color(them));
// Proceed according to the type of the moving piece:
switch(this->type_of_piece_on(from)) {
case PAWN:
// Normal check?
if(bit_is_set(this->pawn_attacks(them, ksq), to))
return true;
// Discovered check?
else if(bit_is_set(dcCandidates, from) &&
direction_between_squares(from, ksq) !=
direction_between_squares(to, ksq))
return true;
// Promotion with check?
else if(move_promotion(m)) {
Bitboard b = this->occupied_squares();
clear_bit(&b, from);
switch(move_promotion(m)) {
case KNIGHT:
return this->knight_attacks_square(to, ksq);
case BISHOP:
return bit_is_set(bishop_attacks_bb(to, b), ksq);
case ROOK:
return bit_is_set(rook_attacks_bb(to, b), ksq);
case QUEEN:
return bit_is_set(queen_attacks_bb(to, b), ksq);
default:
assert(false);
}
}
// En passant capture with check? We have already handled the case
// of direct checks and ordinary discovered check, the only case we
// need to handle is the unusual case of a discovered check through the
// captured pawn.
else if(move_is_ep(m)) {
Square capsq = make_square(square_file(to), square_rank(from));
Bitboard b = this->occupied_squares();
clear_bit(&b, from); clear_bit(&b, capsq); set_bit(&b, to);
return
((rook_attacks_bb(ksq, b) & this->rooks_and_queens(us)) ||
(bishop_attacks_bb(ksq, b) & this->bishops_and_queens(us)));
}
return false;
case KNIGHT:
// Discovered check?
if(bit_is_set(dcCandidates, from))
return true;
// Normal check?
else
return bit_is_set(this->knight_attacks(ksq), to);
case BISHOP:
// Discovered check?
if(bit_is_set(dcCandidates, from))
return true;
// Normal check?
else
return bit_is_set(this->bishop_attacks(ksq), to);
case ROOK:
// Discovered check?
if(bit_is_set(dcCandidates, from))
return true;
// Normal check?
else
return bit_is_set(this->rook_attacks(ksq), to);
case QUEEN:
// Discovered checks are impossible!
assert(!bit_is_set(dcCandidates, from));
// Normal check?
return bit_is_set(this->queen_attacks(ksq), to);
case KING:
// Discovered check?
if(bit_is_set(dcCandidates, from) &&
direction_between_squares(from, ksq) !=
direction_between_squares(to, ksq))
return true;
// Castling with check?
if(move_is_castle(m)) {
Square kfrom, kto, rfrom, rto;
Bitboard b = this->occupied_squares();
kfrom = from;
rfrom = to;
if(rfrom > kfrom) {
kto = relative_square(us, SQ_G1);
rto = relative_square(us, SQ_F1);
}
else {
kto = relative_square(us, SQ_C1);
rto = relative_square(us, SQ_D1);
}
clear_bit(&b, kfrom); clear_bit(&b, rfrom);
set_bit(&b, rto); set_bit(&b, kto);
return bit_is_set(rook_attacks_bb(rto, b), ksq);
}
return false;
default:
assert(false);
return false;
}
assert(false);
return false;
}
/// Position::move_is_capture() tests whether a move from the current
/// position is a capture.
bool Position::move_is_capture(Move m) const {
return
this->color_of_piece_on(move_to(m)) == opposite_color(this->side_to_move())
|| move_is_ep(m);
}
/// Position::move_attacks_square() tests whether a move from the current
/// position attacks a given square. Only attacks by the moving piece are
/// considered; the function does not handle X-ray attacks.
bool Position::move_attacks_square(Move m, Square s) const {
assert(move_is_ok(m));
assert(square_is_ok(s));
Square f = move_from(m), t = move_to(m);
assert(this->square_is_occupied(f));
switch(this->piece_on(f)) {
case WP: return this->white_pawn_attacks_square(t, s);
case BP: return this->black_pawn_attacks_square(t, s);
case WN: case BN: return this->knight_attacks_square(t, s);
case WB: case BB: return this->bishop_attacks_square(t, s);
case WR: case BR: return this->rook_attacks_square(t, s);
case WQ: case BQ: return this->queen_attacks_square(t, s);
case WK: case BK: return this->king_attacks_square(t, s);
default: assert(false);
}
return false;
}
/// Position::backup() is called when making a move. All information
/// necessary to restore the position when the move is later unmade
/// is saved to an UndoInfo object. The function Position::restore
/// does the reverse operation: When one does a backup followed by
/// a restore with the same UndoInfo object, the position is restored
/// to the state before backup was called.
void Position::backup(UndoInfo &u) const {
u.castleRights = castleRights;
u.epSquare = epSquare;
u.checkersBB = checkersBB;
u.key = key;
u.pawnKey = pawnKey;
u.materialKey = materialKey;
u.rule50 = rule50;
u.lastMove = lastMove;
u.capture = NO_PIECE_TYPE;
u.mgValue = mgValue;
u.egValue = egValue;
}
/// Position::restore() is called when unmaking a move. It copies back
/// the information backed up during a previous call to Position::backup.
void Position::restore(const UndoInfo &u) {
castleRights = u.castleRights;
epSquare = u.epSquare;
checkersBB = u.checkersBB;
key = u.key;
pawnKey = u.pawnKey;
materialKey = u.materialKey;
rule50 = u.rule50;
lastMove = u.lastMove;
mgValue = u.mgValue;
egValue = u.egValue;
}
/// Position::do_move() makes a move, and backs up all information necessary
/// to undo the move to an UndoInfo object. The move is assumed to be legal.
/// Pseudo-legal moves should be filtered out before this function is called.
/// There are two versions of this function, one which takes only the move and
/// the UndoInfo as input, and one which takes a third parameter, a bitboard of
/// discovered check candidates. The second version is faster, because knowing
/// the discovered check candidates makes it easier to update the checkersBB
/// member variable in the position object.
void Position::do_move(Move m, UndoInfo &u) {
this->do_move(m, u, this->discovered_check_candidates(this->side_to_move()));
}
void Position::do_move(Move m, UndoInfo &u, Bitboard dcCandidates) {
assert(this->is_ok());
assert(move_is_ok(m));
// Back up the necessary information to our UndoInfo object (except the
// captured piece, which is taken care of later:
this->backup(u);
// Save the current key to the history[] array, in order to be able to
// detect repetition draws:
history[gamePly] = key;
// Increment the 50 moves rule draw counter. Resetting it to zero in the
// case of non-reversible moves is taken care of later.
rule50++;
if(move_is_castle(m))
this->do_castle_move(m);
else if(move_promotion(m))
this->do_promotion_move(m, u);
else if(move_is_ep(m))
this->do_ep_move(m);
else {
Color us, them;
Square from, to;
PieceType piece, capture;
us = this->side_to_move();
them = opposite_color(us);
from = move_from(m);
to = move_to(m);
assert(this->color_of_piece_on(from) == us);
assert(this->color_of_piece_on(to) == them || this->piece_on(to) == EMPTY);
piece = this->type_of_piece_on(from);
capture = this->type_of_piece_on(to);
if(capture) {
assert(capture != KING);
// Remove captured piece:
clear_bit(&(byColorBB[them]), to);
clear_bit(&(byTypeBB[capture]), to);
// Update hash key:
key ^= zobrist[them][capture][to];
// If the captured piece was a pawn, update pawn hash key:
if(capture == PAWN)
pawnKey ^= zobrist[them][PAWN][to];
// Update incremental scores:
mgValue -= this->mg_pst(them, capture, to);
egValue -= this->eg_pst(them, capture, to);
// Update material:
if(capture != PAWN)
npMaterial[them] -= piece_value_midgame(capture);
// Update material hash key:
materialKey ^= zobMaterial[them][capture][pieceCount[them][capture]];
// Update piece count:
pieceCount[them][capture]--;
// Update piece list:
pieceList[them][capture][index[to]] =
pieceList[them][capture][pieceCount[them][capture]];
index[pieceList[them][capture][index[to]]] = index[to];
// Remember the captured piece, in order to be able to undo the move
// correctly:
u.capture = capture;
// Reset rule 50 counter:
rule50 = 0;
}
// Move the piece:
clear_bit(&(byColorBB[us]), from);
clear_bit(&(byTypeBB[piece]), from);
clear_bit(&(byTypeBB[0]), from); // HACK: byTypeBB[0] == occupied squares
set_bit(&(byColorBB[us]), to);
set_bit(&(byTypeBB[piece]), to);
set_bit(&(byTypeBB[0]), to); // HACK: byTypeBB[0] == occupied squares
board[to] = board[from];
board[from] = EMPTY;
// Update hash key:
key ^= zobrist[us][piece][from] ^ zobrist[us][piece][to];
// Update incremental scores:
mgValue -= this->mg_pst(us, piece, from);
mgValue += this->mg_pst(us, piece, to);
egValue -= this->eg_pst(us, piece, from);
egValue += this->eg_pst(us, piece, to);
// If the moving piece was a king, update the king square:
if(piece == KING)
kingSquare[us] = to;
// If the move was a double pawn push, set the en passant square.
// This code is a bit ugly right now, and should be cleaned up later.
// FIXME
if(epSquare != SQ_NONE) {
key ^= zobEp[epSquare];
epSquare = SQ_NONE;
}
if(piece == PAWN) {
if(abs(int(to) - int(from)) == 16) {
if((us == WHITE && (this->white_pawn_attacks(from + DELTA_N) &
this->pawns(BLACK))) ||
(us == BLACK && (this->black_pawn_attacks(from + DELTA_S) &
this->pawns(WHITE)))) {
epSquare = Square((int(from) + int(to)) / 2);
key ^= zobEp[epSquare];
}
}
// Reset rule 50 draw counter.
rule50 = 0;
// Update pawn hash key:
pawnKey ^= zobrist[us][PAWN][from] ^ zobrist[us][PAWN][to];
}
// Update piece lists:
pieceList[us][piece][index[from]] = to;
index[to] = index[from];
// Update castle rights:
key ^= zobCastle[castleRights];
castleRights &= castleRightsMask[from];
castleRights &= castleRightsMask[to];
key ^= zobCastle[castleRights];
// Update checkers bitboard:
checkersBB = EmptyBoardBB;
Square ksq = this->king_square(them);
switch(piece) {
case PAWN:
if(bit_is_set(this->pawn_attacks(them, ksq), to))
set_bit(&checkersBB, to);
if(bit_is_set(dcCandidates, from))
checkersBB |=
((this->rook_attacks(ksq) & this->rooks_and_queens(us)) |
(this->bishop_attacks(ksq) & this->bishops_and_queens(us)));
break;
case KNIGHT:
if(bit_is_set(this->knight_attacks(ksq), to))
set_bit(&checkersBB, to);
if(bit_is_set(dcCandidates, from))
checkersBB |=
((this->rook_attacks(ksq) & this->rooks_and_queens(us)) |
(this->bishop_attacks(ksq) & this->bishops_and_queens(us)));
break;
case BISHOP:
if(bit_is_set(this->bishop_attacks(ksq), to))
set_bit(&checkersBB, to);
if(bit_is_set(dcCandidates, from))
checkersBB |=
(this->rook_attacks(ksq) & this->rooks_and_queens(us));
break;
case ROOK:
if(bit_is_set(this->rook_attacks(ksq), to))
set_bit(&checkersBB, to);
if(bit_is_set(dcCandidates, from))
checkersBB |=
(this->bishop_attacks(ksq) & this->bishops_and_queens(us));
break;
case QUEEN:
if(bit_is_set(this->queen_attacks(ksq), to))
set_bit(&checkersBB, to);
break;
case KING:
if(bit_is_set(dcCandidates, from))
checkersBB |=
((this->rook_attacks(ksq) & this->rooks_and_queens(us)) |
(this->bishop_attacks(ksq) & this->bishops_and_queens(us)));
break;
default:
assert(false);
break;
}
}
// Finish
key ^= zobSideToMove;
sideToMove = opposite_color(sideToMove);
gamePly++;
mgValue += (sideToMove == WHITE)? TempoValueMidgame : -TempoValueMidgame;
egValue += (sideToMove == WHITE)? TempoValueEndgame : -TempoValueEndgame;
assert(this->is_ok());
}
/// Position::do_castle_move() is a private method used to make a castling
/// move. It is called from the main Position::do_move function. Note that
/// castling moves are encoded as "king captures friendly rook" moves, for
/// instance white short castling in a non-Chess960 game is encoded as e1h1.
void Position::do_castle_move(Move m) {
Color us, them;
Square kfrom, kto, rfrom, rto;
assert(this->is_ok());
assert(move_is_ok(m));
assert(move_is_castle(m));
us = this->side_to_move();
them = opposite_color(us);
// Find source squares for king and rook:
kfrom = move_from(m);
rfrom = move_to(m); // HACK: See comment at beginning of function.
assert(this->piece_on(kfrom) == king_of_color(us));
assert(this->piece_on(rfrom) == rook_of_color(us));
// Find destination squares for king and rook:
if(rfrom > kfrom) { // O-O
kto = relative_square(us, SQ_G1);
rto = relative_square(us, SQ_F1);
}
else { // O-O-O
kto = relative_square(us, SQ_C1);
rto = relative_square(us, SQ_D1);
}
// Remove pieces from source squares:
clear_bit(&(byColorBB[us]), kfrom);
clear_bit(&(byTypeBB[KING]), kfrom);
clear_bit(&(byTypeBB[0]), kfrom); // HACK: byTypeBB[0] == occupied squares
clear_bit(&(byColorBB[us]), rfrom);
clear_bit(&(byTypeBB[ROOK]), rfrom);
clear_bit(&(byTypeBB[0]), rfrom); // HACK: byTypeBB[0] == occupied squares
// Put pieces on destination squares:
set_bit(&(byColorBB[us]), kto);
set_bit(&(byTypeBB[KING]), kto);
set_bit(&(byTypeBB[0]), kto); // HACK: byTypeBB[0] == occupied squares
set_bit(&(byColorBB[us]), rto);
set_bit(&(byTypeBB[ROOK]), rto);
set_bit(&(byTypeBB[0]), rto); // HACK: byTypeBB[0] == occupied squares
// Update board array:
board[kfrom] = board[rfrom] = EMPTY;
board[kto] = king_of_color(us);
board[rto] = rook_of_color(us);
// Update king square:
kingSquare[us] = kto;
// Update piece lists:
pieceList[us][KING][index[kfrom]] = kto;
pieceList[us][ROOK][index[rfrom]] = rto;
int tmp = index[rfrom];
index[kto] = index[kfrom];
index[rto] = tmp;
// Update incremental scores:
mgValue -= this->mg_pst(us, KING, kfrom);
mgValue += this->mg_pst(us, KING, kto);
egValue -= this->eg_pst(us, KING, kfrom);
egValue += this->eg_pst(us, KING, kto);
mgValue -= this->mg_pst(us, ROOK, rfrom);
mgValue += this->mg_pst(us, ROOK, rto);
egValue -= this->eg_pst(us, ROOK, rfrom);
egValue += this->eg_pst(us, ROOK, rto);
// Update hash key:
key ^= zobrist[us][KING][kfrom] ^ zobrist[us][KING][kto];
key ^= zobrist[us][ROOK][rfrom] ^ zobrist[us][ROOK][rto];
// Clear en passant square:
if(epSquare != SQ_NONE) {
key ^= zobEp[epSquare];
epSquare = SQ_NONE;
}
// Update castling rights:
key ^= zobCastle[castleRights];
castleRights &= castleRightsMask[kfrom];
key ^= zobCastle[castleRights];
// Reset rule 50 counter:
rule50 = 0;
// Update checkers BB:
checkersBB = attacks_to(this->king_square(them), us);
}
/// Position::do_promotion_move() is a private method used to make a promotion
/// move. It is called from the main Position::do_move function. The
/// UndoInfo object, which has been initialized in Position::do_move, is
/// used to store the captured piece (if any).
void Position::do_promotion_move(Move m, UndoInfo &u) {
Color us, them;
Square from, to;
PieceType capture, promotion;
assert(this->is_ok());
assert(move_is_ok(m));
assert(move_promotion(m));
us = this->side_to_move();
them = opposite_color(us);
from = move_from(m);
to = move_to(m);
assert(pawn_rank(us, to) == RANK_8);
assert(this->piece_on(from) == pawn_of_color(us));
assert(this->color_of_piece_on(to) == them || this->square_is_empty(to));
capture = this->type_of_piece_on(to);
if(capture) {
assert(capture != KING);
// Remove captured piece:
clear_bit(&(byColorBB[them]), to);
clear_bit(&(byTypeBB[capture]), to);
// Update hash key:
key ^= zobrist[them][capture][to];
// Update incremental scores:
mgValue -= this->mg_pst(them, capture, to);
egValue -= this->eg_pst(them, capture, to);
// Update material. Because our move is a promotion, we know that the
// captured piece is not a pawn.
assert(capture != PAWN);
npMaterial[them] -= piece_value_midgame(capture);
// Update material hash key:
materialKey ^= zobMaterial[them][capture][pieceCount[them][capture]];
// Update piece count:
pieceCount[them][capture]--;
// Update piece list:
pieceList[them][capture][index[to]] =
pieceList[them][capture][pieceCount[them][capture]];
index[pieceList[them][capture][index[to]]] = index[to];
// Remember the captured piece, in order to be able to undo the move
// correctly:
u.capture = capture;
}
// Remove pawn:
clear_bit(&(byColorBB[us]), from);
clear_bit(&(byTypeBB[PAWN]), from);
clear_bit(&(byTypeBB[0]), from); // HACK: byTypeBB[0] == occupied squares
board[from] = EMPTY;
// Insert promoted piece:
promotion = move_promotion(m);
assert(promotion >= KNIGHT && promotion <= QUEEN);
set_bit(&(byColorBB[us]), to);
set_bit(&(byTypeBB[promotion]), to);
set_bit(&(byTypeBB[0]), to); // HACK: byTypeBB[0] == occupied squares
board[to] = piece_of_color_and_type(us, promotion);
// Update hash key:
key ^= zobrist[us][PAWN][from] ^ zobrist[us][promotion][to];
// Update pawn hash key:
pawnKey ^= zobrist[us][PAWN][from];
// Update material key:
materialKey ^= zobMaterial[us][PAWN][pieceCount[us][PAWN]];
materialKey ^= zobMaterial[us][promotion][pieceCount[us][promotion]+1];
// Update piece counts:
pieceCount[us][PAWN]--;
pieceCount[us][promotion]++;
// Update piece lists:
pieceList[us][PAWN][index[from]] =
pieceList[us][PAWN][pieceCount[us][PAWN]];
index[pieceList[us][PAWN][index[from]]] = index[from];
pieceList[us][promotion][pieceCount[us][promotion] - 1] = to;
index[to] = pieceCount[us][promotion] - 1;
// Update incremental scores:
mgValue -= this->mg_pst(us, PAWN, from);
mgValue += this->mg_pst(us, promotion, to);
egValue -= this->eg_pst(us, PAWN, from);
egValue += this->eg_pst(us, promotion, to);
// Update material:
npMaterial[us] += piece_value_midgame(promotion);
// Clear the en passant square:
if(epSquare != SQ_NONE) {
key ^= zobEp[epSquare];
epSquare = SQ_NONE;
}
// Update castle rights:
key ^= zobCastle[castleRights];
castleRights &= castleRightsMask[to];
key ^= zobCastle[castleRights];
// Reset rule 50 counter:
rule50 = 0;
// Update checkers BB:
checkersBB = attacks_to(this->king_square(them), us);
}
/// Position::do_ep_move() is a private method used to make an en passant
/// capture. It is called from the main Position::do_move function. Because
/// the captured piece is always a pawn, we don't need to pass an UndoInfo
/// object in which to store the captured piece.
void Position::do_ep_move(Move m) {
Color us, them;
Square from, to, capsq;
assert(this->is_ok());
assert(move_is_ok(m));
assert(move_is_ep(m));
us = this->side_to_move();
them = opposite_color(us);
// Find from, to and capture squares:
from = move_from(m);
to = move_to(m);
capsq = (us == WHITE)? (to - DELTA_N) : (to - DELTA_S);
assert(to == epSquare);
assert(pawn_rank(us, to) == RANK_6);
assert(this->piece_on(to) == EMPTY);
assert(this->piece_on(from) == pawn_of_color(us));
assert(this->piece_on(capsq) == pawn_of_color(them));
// Remove captured piece:
clear_bit(&(byColorBB[them]), capsq);
clear_bit(&(byTypeBB[PAWN]), capsq);
clear_bit(&(byTypeBB[0]), capsq); // HACK: byTypeBB[0] == occupied squares
board[capsq] = EMPTY;
// Remove moving piece from source square:
clear_bit(&(byColorBB[us]), from);
clear_bit(&(byTypeBB[PAWN]), from);
clear_bit(&(byTypeBB[0]), from); // HACK: byTypeBB[0] == occupied squares
// Put moving piece on destination square:
set_bit(&(byColorBB[us]), to);
set_bit(&(byTypeBB[PAWN]), to);
set_bit(&(byTypeBB[0]), to); // HACK: byTypeBB[0] == occupied squares
board[to] = board[from];
board[from] = EMPTY;
// Update material hash key:
materialKey ^= zobMaterial[them][PAWN][pieceCount[them][PAWN]];
// Update piece count:
pieceCount[them][PAWN]--;
// Update piece list:
pieceList[us][PAWN][index[from]] = to;
index[to] = index[from];
pieceList[them][PAWN][index[capsq]] =
pieceList[them][PAWN][pieceCount[them][PAWN]];
index[pieceList[them][PAWN][index[capsq]]] = index[capsq];
// Update hash key:
key ^= zobrist[us][PAWN][from] ^ zobrist[us][PAWN][to];
key ^= zobrist[them][PAWN][capsq];
key ^= zobEp[epSquare];
// Update pawn hash key:
pawnKey ^= zobrist[us][PAWN][from] ^ zobrist[us][PAWN][to];
pawnKey ^= zobrist[them][PAWN][capsq];
// Update incremental scores:
mgValue -= this->mg_pst(them, PAWN, capsq);
mgValue -= this->mg_pst(us, PAWN, from);
mgValue += this->mg_pst(us, PAWN, to);
egValue -= this->eg_pst(them, PAWN, capsq);
egValue -= this->eg_pst(us, PAWN, from);
egValue += this->eg_pst(us, PAWN, to);
// Reset en passant square:
epSquare = SQ_NONE;
// Reset rule 50 counter:
rule50 = 0;
// Update checkers BB:
checkersBB = attacks_to(this->king_square(them), us);
}
/// Position::undo_move() unmakes a move. When it returns, the position should
/// be restored to exactly the same state as before the move was made. It is
/// important that Position::undo_move is called with the same move and UndoInfo
/// object as the earlier call to Position::do_move.
void Position::undo_move(Move m, const UndoInfo &u) {
assert(this->is_ok());
assert(move_is_ok(m));
gamePly--;
sideToMove = opposite_color(sideToMove);
// Restore information from our UndoInfo object (except the captured piece,
// which is taken care of later):
this->restore(u);
if(move_is_castle(m))
this->undo_castle_move(m);
else if(move_promotion(m))
this->undo_promotion_move(m, u);
else if(move_is_ep(m))
this->undo_ep_move(m);
else {
Color us, them;
Square from, to;
PieceType piece, capture;
us = this->side_to_move();
them = opposite_color(us);
from = move_from(m);
to = move_to(m);
assert(this->piece_on(from) == EMPTY);
assert(color_of_piece_on(to) == us);
// Put the piece back at the source square:
piece = this->type_of_piece_on(to);
set_bit(&(byColorBB[us]), from);
set_bit(&(byTypeBB[piece]), from);
set_bit(&(byTypeBB[0]), from); // HACK: byTypeBB[0] == occupied squares
board[from] = piece_of_color_and_type(us, piece);
// Clear the destination square
clear_bit(&(byColorBB[us]), to);
clear_bit(&(byTypeBB[piece]), to);
clear_bit(&(byTypeBB[0]), to); // HACK: byTypeBB[0] == occupied squares
// If the moving piece was a king, update the king square:
if(piece == KING)
kingSquare[us] = from;
// Update piece list:
pieceList[us][piece][index[to]] = from;
index[from] = index[to];
capture = u.capture;
if(capture) {
assert(capture != KING);
// Replace the captured piece:
set_bit(&(byColorBB[them]), to);
set_bit(&(byTypeBB[capture]), to);
set_bit(&(byTypeBB[0]), to);
board[to] = piece_of_color_and_type(them, capture);
// Update material:
if(capture != PAWN)
npMaterial[them] += piece_value_midgame(capture);
// Update piece list:
pieceList[them][capture][pieceCount[them][capture]] = to;
index[to] = pieceCount[them][capture];
// Update piece count:
pieceCount[them][capture]++;
}
else
board[to] = EMPTY;
}
assert(this->is_ok());
}
/// Position::undo_castle_move() is a private method used to unmake a castling
/// move. It is called from the main Position::undo_move function. Note that
/// castling moves are encoded as "king captures friendly rook" moves, for
/// instance white short castling in a non-Chess960 game is encoded as e1h1.
void Position::undo_castle_move(Move m) {
Color us, them;
Square kfrom, kto, rfrom, rto;
assert(move_is_ok(m));
assert(move_is_castle(m));
// When we have arrived here, some work has already been done by
// Position::undo_move. In particular, the side to move has been switched,
// so the code below is correct.
us = this->side_to_move();
them = opposite_color(us);
// Find source squares for king and rook:
kfrom = move_from(m);
rfrom = move_to(m); // HACK: See comment at beginning of function.
// Find destination squares for king and rook:
if(rfrom > kfrom) { // O-O
kto = relative_square(us, SQ_G1);
rto = relative_square(us, SQ_F1);
}
else { // O-O-O
kto = relative_square(us, SQ_C1);
rto = relative_square(us, SQ_D1);
}
assert(this->piece_on(kto) == king_of_color(us));
assert(this->piece_on(rto) == rook_of_color(us));
// Remove pieces from destination squares:
clear_bit(&(byColorBB[us]), kto);
clear_bit(&(byTypeBB[KING]), kto);
clear_bit(&(byTypeBB[0]), kto); // HACK: byTypeBB[0] == occupied squares
clear_bit(&(byColorBB[us]), rto);
clear_bit(&(byTypeBB[ROOK]), rto);
clear_bit(&(byTypeBB[0]), rto); // HACK: byTypeBB[0] == occupied squares
// Put pieces on source squares:
set_bit(&(byColorBB[us]), kfrom);
set_bit(&(byTypeBB[KING]), kfrom);
set_bit(&(byTypeBB[0]), kfrom); // HACK: byTypeBB[0] == occupied squares
set_bit(&(byColorBB[us]), rfrom);
set_bit(&(byTypeBB[ROOK]), rfrom);
set_bit(&(byTypeBB[0]), rfrom); // HACK: byTypeBB[0] == occupied squares
// Update board:
board[rto] = board[kto] = EMPTY;
board[rfrom] = rook_of_color(us);
board[kfrom] = king_of_color(us);
// Update king square:
kingSquare[us] = kfrom;
// Update piece lists:
pieceList[us][KING][index[kto]] = kfrom;
pieceList[us][ROOK][index[rto]] = rfrom;
int tmp = index[rto]; // Necessary because we may have rto == kfrom in FRC.
index[kfrom] = index[kto];
index[rfrom] = tmp;
}
/// Position::undo_promotion_move() is a private method used to unmake a
/// promotion move. It is called from the main Position::do_move
/// function. The UndoInfo object, which has been initialized in
/// Position::do_move, is used to put back the captured piece (if any).
void Position::undo_promotion_move(Move m, const UndoInfo &u) {
Color us, them;
Square from, to;
PieceType capture, promotion;
assert(move_is_ok(m));
assert(move_promotion(m));
// When we have arrived here, some work has already been done by
// Position::undo_move. In particular, the side to move has been switched,
// so the code below is correct.
us = this->side_to_move();
them = opposite_color(us);
from = move_from(m);
to = move_to(m);
assert(pawn_rank(us, to) == RANK_8);
assert(this->piece_on(from) == EMPTY);
// Remove promoted piece:
promotion = move_promotion(m);
assert(this->piece_on(to)==piece_of_color_and_type(us, promotion));
assert(promotion >= KNIGHT && promotion <= QUEEN);
clear_bit(&(byColorBB[us]), to);
clear_bit(&(byTypeBB[promotion]), to);
clear_bit(&(byTypeBB[0]), to); // HACK: byTypeBB[0] == occupied squares
// Insert pawn at source square:
set_bit(&(byColorBB[us]), from);
set_bit(&(byTypeBB[PAWN]), from);
set_bit(&(byTypeBB[0]), from); // HACK: byTypeBB[0] == occupied squares
board[from] = pawn_of_color(us);
// Update material:
npMaterial[us] -= piece_value_midgame(promotion);
// Update piece list:
pieceList[us][PAWN][pieceCount[us][PAWN]] = from;
index[from] = pieceCount[us][PAWN];
pieceList[us][promotion][index[to]] =
pieceList[us][promotion][pieceCount[us][promotion] - 1];
index[pieceList[us][promotion][index[to]]] = index[to];
// Update piece counts:
pieceCount[us][promotion]--;
pieceCount[us][PAWN]++;
capture = u.capture;
if(capture) {
assert(capture != KING);
// Insert captured piece:
set_bit(&(byColorBB[them]), to);
set_bit(&(byTypeBB[capture]), to);
set_bit(&(byTypeBB[0]), to); // HACK: byTypeBB[0] == occupied squares
board[to] = piece_of_color_and_type(them, capture);
// Update material. Because the move is a promotion move, we know
// that the captured piece cannot be a pawn.
assert(capture != PAWN);
npMaterial[them] += piece_value_midgame(capture);
// Update piece list:
pieceList[them][capture][pieceCount[them][capture]] = to;
index[to] = pieceCount[them][capture];
// Update piece count:
pieceCount[them][capture]++;
}
else
board[to] = EMPTY;
}
/// Position::undo_ep_move() is a private method used to unmake an en passant
/// capture. It is called from the main Position::undo_move function. Because
/// the captured piece is always a pawn, we don't need to pass an UndoInfo
/// object from which to retrieve the captured piece.
void Position::undo_ep_move(Move m) {
Color us, them;
Square from, to, capsq;
assert(move_is_ok(m));
assert(move_is_ep(m));
// When we have arrived here, some work has already been done by
// Position::undo_move. In particular, the side to move has been switched,
// so the code below is correct.
us = this->side_to_move();
them = opposite_color(us);
// Find from, to and captures squares:
from = move_from(m);
to = move_to(m);
capsq = (us == WHITE)? (to - DELTA_N) : (to - DELTA_S);
assert(to == this->ep_square());
assert(pawn_rank(us, to) == RANK_6);
assert(this->piece_on(to) == pawn_of_color(us));
assert(this->piece_on(from) == EMPTY);
assert(this->piece_on(capsq) == EMPTY);
// Replace captured piece:
set_bit(&(byColorBB[them]), capsq);
set_bit(&(byTypeBB[PAWN]), capsq);
set_bit(&(byTypeBB[0]), capsq);
board[capsq] = pawn_of_color(them);
// Remove moving piece from destination square:
clear_bit(&(byColorBB[us]), to);
clear_bit(&(byTypeBB[PAWN]), to);
clear_bit(&(byTypeBB[0]), to);
board[to] = EMPTY;
// Replace moving piece at source square:
set_bit(&(byColorBB[us]), from);
set_bit(&(byTypeBB[PAWN]), from);
set_bit(&(byTypeBB[0]), from);
board[from] = pawn_of_color(us);
// Update piece list:
pieceList[us][PAWN][index[to]] = from;
index[from] = index[to];
pieceList[them][PAWN][pieceCount[them][PAWN]] = capsq;
index[capsq] = pieceCount[them][PAWN];
// Update piece count:
pieceCount[them][PAWN]++;
}
/// Position::do_null_move makes() a "null move": It switches the side to move
/// and updates the hash key without executing any move on the board.
void Position::do_null_move(UndoInfo &u) {
assert(this->is_ok());
assert(!this->is_check());
// Back up the information necessary to undo the null move to the supplied
// UndoInfo object. In the case of a null move, the only thing we need to
// remember is the last move made and the en passant square.
u.lastMove = lastMove;
u.epSquare = epSquare;
// Save the current key to the history[] array, in order to be able to
// detect repetition draws:
history[gamePly] = key;
// Update the necessary information.
sideToMove = opposite_color(sideToMove);
if(epSquare != SQ_NONE)
key ^= zobEp[epSquare];
epSquare = SQ_NONE;
rule50++;
gamePly++;
key ^= zobSideToMove;
mgValue += (sideToMove == WHITE)? TempoValueMidgame : -TempoValueMidgame;
egValue += (sideToMove == WHITE)? TempoValueEndgame : -TempoValueEndgame;
assert(this->is_ok());
}
/// Position::undo_null_move() unmakes a "null move".
void Position::undo_null_move(const UndoInfo &u) {
assert(this->is_ok());
assert(!this->is_check());
// Restore information from the supplied UndoInfo object:
lastMove = u.lastMove;
epSquare = u.epSquare;
if(epSquare != SQ_NONE)
key ^= zobEp[epSquare];
// Update the necessary information.
sideToMove = opposite_color(sideToMove);
rule50--;
gamePly--;
key ^= zobSideToMove;
mgValue += (sideToMove == WHITE)? TempoValueMidgame : -TempoValueMidgame;
egValue += (sideToMove == WHITE)? TempoValueEndgame : -TempoValueEndgame;
assert(this->is_ok());
}
/// Position::see() is a static exchange evaluator: It tries to estimate the
/// material gain or loss resulting from a move. There are two versions of
/// this function: One which takes a move as input, and one which takes a
/// 'from' and a 'to' square. The function does not yet understand promotions
/// or en passant captures.
int Position::see(Square from, Square to) const {
// Approximate material values, with pawn = 1:
static const int seeValues[18] = {
0, 1, 3, 3, 5, 10, 100, 0, 0, 1, 3, 3, 5, 10, 100, 0, 0, 0
};
Color us, them;
Piece piece, capture;
Bitboard attackers, occ, b;
assert(square_is_ok(from));
assert(square_is_ok(to));
// Initialize colors:
us = this->color_of_piece_on(from);
them = opposite_color(us);
// Initialize pieces:
piece = this->piece_on(from);
capture = this->piece_on(to);
// Find all attackers to the destination square, with the moving piece
// removed, but possibly an X-ray attacker added behind it:
occ = this->occupied_squares();
clear_bit(&occ, from);
attackers =
(rook_attacks_bb(to, occ) & this->rooks_and_queens()) |
(bishop_attacks_bb(to, occ) & this->bishops_and_queens()) |
(this->knight_attacks(to) & this->knights()) |
(this->king_attacks(to) & this->kings()) |
(this->white_pawn_attacks(to) & this->pawns(BLACK)) |
(this->black_pawn_attacks(to) & this->pawns(WHITE));
attackers &= occ;
// If the opponent has no attackers, we are finished:
if((attackers & this->pieces_of_color(them)) == EmptyBoardBB)
return seeValues[capture];
// The destination square is defended, which makes things rather more
// difficult to compute. We proceed by building up a "swap list" containing
// the material gain or loss at each stop in a sequence of captures to the
// destianation square, where the sides alternately capture, and always
// capture with the least valuable piece. After each capture, we look for
// new X-ray attacks from behind the capturing piece.
int lastCapturingPieceValue = seeValues[piece];
int swapList[32], n = 1;
Color c = them;
PieceType pt;
swapList[0] = seeValues[capture];
do {
// Locate the least valuable attacker for the side to move. The loop
// below looks like it is potentially infinite, but it isn't. We know
// that the side to move still has at least one attacker left.
for(pt = PAWN; !(attackers&this->pieces_of_color_and_type(c, pt)); pt++)
assert(pt < KING);
// Remove the attacker we just found from the 'attackers' bitboard,
// and scan for new X-ray attacks behind the attacker:
b = attackers & this->pieces_of_color_and_type(c, pt);
occ ^= (b & -b);
attackers |=
(rook_attacks_bb(to, occ) & this->rooks_and_queens()) |
(bishop_attacks_bb(to, occ) & this->bishops_and_queens());
attackers &= occ;
// Add the new entry to the swap list:
assert(n < 32);
swapList[n] = -swapList[n - 1] + lastCapturingPieceValue;
n++;
// Remember the value of the capturing piece, and change the side to move
// before beginning the next iteration:
lastCapturingPieceValue = seeValues[pt];
c = opposite_color(c);
// Stop after a king capture:
if(pt == KING && (attackers & this->pieces_of_color(c))) {
assert(n < 32);
swapList[n++] = 100;
break;
}
} while(attackers & this->pieces_of_color(c));
// Having built the swap list, we negamax through it to find the best
// achievable score from the point of view of the side to move:
while(--n) swapList[n-1] = Min(-swapList[n], swapList[n-1]);
return swapList[0];
}
int Position::see(Move m) const {
assert(move_is_ok(m));
return this->see(move_from(m), move_to(m));
}
/// Position::clear() erases the position object to a pristine state, with an
/// empty board, white to move, and no castling rights.
void Position::clear() {
int i, j;
for(i = 0; i < 64; i++) {
board[i] = EMPTY;
index[i] = 0;
}
for(i = 0; i < 2; i++)
byColorBB[i] = EmptyBoardBB;
for(i = 0; i < 7; i++) {
byTypeBB[i] = EmptyBoardBB;
pieceCount[0][i] = pieceCount[1][i] = 0;
for(j = 0; j < 8; j++)
pieceList[0][i][j] = pieceList[1][i][j] = SQ_NONE;
}
checkersBB = EmptyBoardBB;
lastMove = MOVE_NONE;
sideToMove = WHITE;
castleRights = NO_CASTLES;
initialKFile = FILE_E;
initialKRFile = FILE_H;
initialQRFile = FILE_A;
epSquare = SQ_NONE;
rule50 = 0;
gamePly = 0;
}
/// Position::reset_game_ply() simply sets gamePly to 0. It is used from the
/// UCI interface code, whenever a non-reversible move is made in a
/// 'position fen <fen> moves m1 m2 ...' command. This makes it possible
/// for the program to handle games of arbitrary length, as long as the GUI
/// handles draws by the 50 move rule correctly.
void Position::reset_game_ply() {
gamePly = 0;
}
/// Position::put_piece() puts a piece on the given square of the board,
/// updating the board array, bitboards, and piece counts.
void Position::put_piece(Piece p, Square s) {
Color c = color_of_piece(p);
PieceType pt = type_of_piece(p);
board[s] = p;
index[s] = pieceCount[c][pt];
pieceList[c][pt][index[s]] = s;
set_bit(&(byTypeBB[pt]), s);
set_bit(&(byColorBB[c]), s);
set_bit(&byTypeBB[0], s); // HACK: byTypeBB[0] contains all occupied squares.
pieceCount[c][pt]++;
if(pt == KING)
kingSquare[c] = s;
}
/// Position::allow_oo() gives the given side the right to castle kingside.
/// Used when setting castling rights during parsing of FEN strings.
void Position::allow_oo(Color c) {
castleRights |= (1 + int(c));
}
/// Position::allow_ooo() gives the given side the right to castle queenside.
/// Used when setting castling rights during parsing of FEN strings.
void Position::allow_ooo(Color c) {
castleRights |= (4 + 4*int(c));
}
/// Position::compute_key() computes the hash key of the position. The hash
/// key is usually updated incrementally as moves are made and unmade, the
/// compute_key() function is only used when a new position is set up, and
/// to verify the correctness of the hash key when running in debug mode.
Key Position::compute_key() const {
Key result = Key(0ULL);
for(Square s = SQ_A1; s <= SQ_H8; s++)
if(this->square_is_occupied(s))
result ^=
zobrist[this->color_of_piece_on(s)][this->type_of_piece_on(s)][s];
if(this->ep_square() != SQ_NONE)
result ^= zobEp[this->ep_square()];
result ^= zobCastle[castleRights];
if(this->side_to_move() == BLACK) result ^= zobSideToMove;
return result;
}
/// Position::compute_pawn_key() computes the hash key of the position. The
/// hash key is usually updated incrementally as moves are made and unmade,
/// the compute_pawn_key() function is only used when a new position is set
/// up, and to verify the correctness of the pawn hash key when running in
/// debug mode.
Key Position::compute_pawn_key() const {
Key result = Key(0ULL);
Bitboard b;
Square s;
for(Color c = WHITE; c <= BLACK; c++) {
b = this->pawns(c);
while(b) {
s = pop_1st_bit(&b);
result ^= zobrist[c][PAWN][s];
}
}
return result;
}
/// Position::compute_material_key() computes the hash key of the position.
/// The hash key is usually updated incrementally as moves are made and unmade,
/// the compute_material_key() function is only used when a new position is set
/// up, and to verify the correctness of the material hash key when running in
/// debug mode.
Key Position::compute_material_key() const {
Key result = Key(0ULL);
for(Color c = WHITE; c <= BLACK; c++)
for(PieceType pt = PAWN; pt <= QUEEN; pt++) {
int count = this->piece_count(c, pt);
for(int i = 0; i <= count; i++)
result ^= zobMaterial[c][pt][i];
}
return result;
}
/// Position::compute_mg_value() and Position::compute_eg_value() compute the
/// incremental scores for the middle game and the endgame. These functions
/// are used to initialize the incremental scores when a new position is set
/// up, and to verify that the scores are correctly updated by do_move
/// and undo_move when the program is running in debug mode.
Value Position::compute_mg_value() const {
Value result = Value(0);
Bitboard b;
Square s;
for(Color c = WHITE; c <= BLACK; c++)
for(PieceType pt = PAWN; pt <= KING; pt++) {
b = this->pieces_of_color_and_type(c, pt);
while(b) {
s = pop_1st_bit(&b);
assert(this->piece_on(s) == piece_of_color_and_type(c, pt));
result += this->mg_pst(c, pt, s);
}
}
result += (this->side_to_move() == WHITE)?
(TempoValueMidgame / 2) : -(TempoValueMidgame / 2);
return result;
}
Value Position::compute_eg_value() const {
Value result = Value(0);
Bitboard b;
Square s;
for(Color c = WHITE; c <= BLACK; c++)
for(PieceType pt = PAWN; pt <= KING; pt++) {
b = this->pieces_of_color_and_type(c, pt);
while(b) {
s = pop_1st_bit(&b);
assert(this->piece_on(s) == piece_of_color_and_type(c, pt));
result += this->eg_pst(c, pt, s);
}
}
result += (this->side_to_move() == WHITE)?
(TempoValueEndgame / 2) : -(TempoValueEndgame / 2);
return result;
}
/// Position::compute_non_pawn_material() computes the total non-pawn middle
/// game material score for the given side. Material scores are updated
/// incrementally during the search, this function is only used while
/// initializing a new Position object.
Value Position::compute_non_pawn_material(Color c) const {
Value result = Value(0);
Square s;
for(PieceType pt = KNIGHT; pt <= QUEEN; pt++) {
Bitboard b = this->pieces_of_color_and_type(c, pt);
while(b) {
s = pop_1st_bit(&b);
assert(this->piece_on(s) == piece_of_color_and_type(c, pt));
result += piece_value_midgame(pt);
}
}
return result;
}
/// Position::is_mate() returns true or false depending on whether the
/// side to move is checkmated. Note that this function is currently very
/// slow, and shouldn't be used frequently inside the search.
bool Position::is_mate() {
if(this->is_check()) {
MovePicker mp = MovePicker(*this, false, MOVE_NONE, MOVE_NONE, MOVE_NONE,
MOVE_NONE, Depth(0));
return mp.get_next_move() == MOVE_NONE;
}
else
return false;
}
/// Position::is_draw() tests whether the position is drawn by material,
/// repetition, or the 50 moves rule. It does not detect stalemates, this
/// must be done by the search.
bool Position::is_draw() const {
// Draw by material?
if(!this->pawns() &&
this->non_pawn_material(WHITE) + this->non_pawn_material(BLACK)
<= BishopValueMidgame)
return true;
// Draw by the 50 moves rule?
if(rule50 > 100 || (rule50 == 100 && !this->is_check()))
return true;
// Draw by repetition?
for(int i = 2; i < Min(gamePly, rule50); i += 2)
if(history[gamePly - i] == key)
return true;
return false;
}
/// Position::has_mate_threat() tests whether a given color has a mate in one
/// from the current position. This function is quite slow, but it doesn't
/// matter, because it is currently only called from PV nodes, which are rare.
bool Position::has_mate_threat(Color c) {
UndoInfo u1, u2;
Color stm = this->side_to_move();
// The following lines are useless and silly, but prevents gcc from
// emitting a stupid warning stating that u1.lastMove and u1.epSquare might
// be used uninitialized.
u1.lastMove = lastMove;
u1.epSquare = epSquare;
if(this->is_check())
return false;
// If the input color is not equal to the side to move, do a null move
if(c != stm) this->do_null_move(u1);
MoveStack mlist[120];
int count;
bool result = false;
// Generate legal moves
count = generate_legal_moves(*this, mlist);
// Loop through the moves, and see if one of them is mate.
for(int i = 0; i < count; i++) {
this->do_move(mlist[i].move, u2);
if(this->is_mate()) result = true;
this->undo_move(mlist[i].move, u2);
}
// Undo null move, if necessary
if(c != stm) this->undo_null_move(u1);
return result;
}
/// Position::init_zobrist() is a static member function which initializes the
/// various arrays used to compute hash keys.
void Position::init_zobrist() {
for(int i = 0; i < 2; i++)
for(int j = 0; j < 8; j++)
for(int k = 0; k < 64; k++)
zobrist[i][j][k] = Key(genrand_int64());
for(int i = 0; i < 64; i++)
zobEp[i] = Key(genrand_int64());
for(int i = 0; i < 16; i++)
zobCastle[i] = genrand_int64();
zobSideToMove = genrand_int64();
for(int i = 0; i < 2; i++)
for(int j = 0; j < 8; j++)
for(int k = 0; k < 16; k++)
zobMaterial[i][j][k] = (k > 0)? Key(genrand_int64()) : Key(0LL);
for(int i = 0; i < 16; i++)
zobMaterial[0][KING][i] = zobMaterial[1][KING][i] = Key(0ULL);
}
/// Position::init_piece_square_tables() initializes the piece square tables.
/// This is a two-step operation: First, the white halves of the tables are
/// copied from the MgPST[][] and EgPST[][] arrays, with a small random number
/// added to each entry if the "Randomness" UCI parameter is non-zero.
/// Second, the black halves of the tables are initialized by mirroring
/// and changing the sign of the corresponding white scores.
void Position::init_piece_square_tables() {
int r = get_option_value_int("Randomness"), i;
for(Square s = SQ_A1; s <= SQ_H8; s++) {
for(Piece p = WP; p <= WK; p++) {
i = (r == 0)? 0 : (genrand_int32() % (r*2) - r);
MgPieceSquareTable[p][s] = Value(MgPST[p][s] + i);
EgPieceSquareTable[p][s] = Value(EgPST[p][s] + i);
}
}
for(Square s = SQ_A1; s <= SQ_H8; s++)
for(Piece p = BP; p <= BK; p++) {
MgPieceSquareTable[p][s] = -MgPieceSquareTable[p-8][flip_square(s)];
EgPieceSquareTable[p][s] = -EgPieceSquareTable[p-8][flip_square(s)];
}
}
/// Position::flipped_copy() makes a copy of the input position, but with
/// the white and black sides reversed. This is only useful for debugging,
/// especially for finding evaluation symmetry bugs.
void Position::flipped_copy(const Position &pos) {
assert(pos.is_ok());
this->clear();
// Board
for(Square s = SQ_A1; s <= SQ_H8; s++)
if(!pos.square_is_empty(s))
this->put_piece(Piece(int(pos.piece_on(s)) ^ 8), flip_square(s));
// Side to move
sideToMove = opposite_color(pos.side_to_move());
// Castling rights
if(pos.can_castle_kingside(WHITE)) this->allow_oo(BLACK);
if(pos.can_castle_queenside(WHITE)) this->allow_ooo(BLACK);
if(pos.can_castle_kingside(BLACK)) this->allow_oo(WHITE);
if(pos.can_castle_queenside(BLACK)) this->allow_ooo(WHITE);
initialKFile = pos.initialKFile;
initialKRFile = pos.initialKRFile;
initialQRFile = pos.initialQRFile;
for(Square sq = SQ_A1; sq <= SQ_H8; sq++)
castleRightsMask[sq] = ALL_CASTLES;
castleRightsMask[make_square(initialKFile, RANK_1)] ^= (WHITE_OO|WHITE_OOO);
castleRightsMask[make_square(initialKFile, RANK_8)] ^= (BLACK_OO|BLACK_OOO);
castleRightsMask[make_square(initialKRFile, RANK_1)] ^= WHITE_OO;
castleRightsMask[make_square(initialKRFile, RANK_8)] ^= BLACK_OO;
castleRightsMask[make_square(initialQRFile, RANK_1)] ^= WHITE_OOO;
castleRightsMask[make_square(initialQRFile, RANK_8)] ^= BLACK_OOO;
// En passant square
if(pos.epSquare != SQ_NONE)
epSquare = flip_square(pos.epSquare);
// Checkers
this->find_checkers();
// Hash keys
key = this->compute_key();
pawnKey = this->compute_pawn_key();
materialKey = this->compute_material_key();
// Incremental scores
mgValue = this->compute_mg_value();
egValue = this->compute_eg_value();
// Material
npMaterial[WHITE] = this->compute_non_pawn_material(WHITE);
npMaterial[BLACK] = this->compute_non_pawn_material(BLACK);
assert(this->is_ok());
}
/// Position::is_ok() performs some consitency checks for the position object.
/// This is meant to be helpful when debugging.
bool Position::is_ok() const {
// What features of the position should be verified?
static const bool debugBitboards = false;
static const bool debugKingCount = false;
static const bool debugKingCapture = false;
static const bool debugCheckerCount = false;
static const bool debugKey = false;
static const bool debugMaterialKey = false;
static const bool debugPawnKey = false;
static const bool debugIncrementalEval = false;
static const bool debugNonPawnMaterial = false;
static const bool debugPieceCounts = false;
static const bool debugPieceList = false;
// Side to move OK?
if(!color_is_ok(this->side_to_move()))
return false;
// Are the king squares in the position correct?
if(this->piece_on(this->king_square(WHITE)) != WK)
return false;
if(this->piece_on(this->king_square(BLACK)) != BK)
return false;
// Castle files OK?
if(!file_is_ok(initialKRFile))
return false;
if(!file_is_ok(initialQRFile))
return false;
// Do both sides have exactly one king?
if(debugKingCount) {
int kingCount[2] = {0, 0};
for(Square s = SQ_A1; s <= SQ_H8; s++)
if(this->type_of_piece_on(s) == KING)
kingCount[this->color_of_piece_on(s)]++;
if(kingCount[0] != 1 || kingCount[1] != 1)
return false;
}
// Can the side to move capture the opponent's king?
if(debugKingCapture) {
Color us = this->side_to_move();
Color them = opposite_color(us);
Square ksq = this->king_square(them);
if(this->square_is_attacked(ksq, us))
return false;
}
// Is there more than 2 checkers?
if(debugCheckerCount && count_1s(checkersBB) > 2)
return false;
// Bitboards OK?
if(debugBitboards) {
// The intersection of the white and black pieces must be empty:
if((this->pieces_of_color(WHITE) & this->pieces_of_color(BLACK))
!= EmptyBoardBB)
return false;
// The union of the white and black pieces must be equal to all
// occupied squares:
if((this->pieces_of_color(WHITE) | this->pieces_of_color(BLACK))
!= this->occupied_squares())
return false;
// Separate piece type bitboards must have empty intersections:
for(PieceType p1 = PAWN; p1 <= KING; p1++)
for(PieceType p2 = PAWN; p2 <= KING; p2++)
if(p1 != p2 && (this->pieces_of_type(p1) & this->pieces_of_type(p2)))
return false;
}
// En passant square OK?
if(this->ep_square() != SQ_NONE) {
// The en passant square must be on rank 6, from the point of view of the
// side to move.
if(pawn_rank(this->side_to_move(), this->ep_square()) != RANK_6)
return false;
}
// Hash key OK?
if(debugKey && key != this->compute_key())
return false;
// Pawn hash key OK?
if(debugPawnKey && pawnKey != this->compute_pawn_key())
return false;
// Material hash key OK?
if(debugMaterialKey && materialKey != this->compute_material_key())
return false;
// Incremental eval OK?
if(debugIncrementalEval) {
if(mgValue != this->compute_mg_value())
return false;
if(egValue != this->compute_eg_value())
return false;
}
// Non-pawn material OK?
if(debugNonPawnMaterial) {
if(npMaterial[WHITE] != compute_non_pawn_material(WHITE))
return false;
if(npMaterial[BLACK] != compute_non_pawn_material(BLACK))
return false;
}
// Piece counts OK?
if(debugPieceCounts)
for(Color c = WHITE; c <= BLACK; c++)
for(PieceType pt = PAWN; pt <= KING; pt++)
if(pieceCount[c][pt] != count_1s(this->pieces_of_color_and_type(c, pt)))
return false;
if(debugPieceList) {
for(Color c = WHITE; c <= BLACK; c++)
for(PieceType pt = PAWN; pt <= KING; pt++)
for(int i = 0; i < pieceCount[c][pt]; i++) {
if(this->piece_on(this->piece_list(c, pt, i)) !=
piece_of_color_and_type(c, pt))
return false;
if(index[this->piece_list(c, pt, i)] != i)
return false;
}
}
return true;
}
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