droidfish/DroidFish/jni/stockfish/position.cpp

1786 lines
53 KiB
C++
Raw Normal View History

2011-11-12 20:44:06 +01:00
/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
2011-11-12 20:44:06 +01:00
Stockfish 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.
Stockfish 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/>.
*/
#include <cassert>
#include <cstring>
#include <fstream>
#include <iostream>
#include <sstream>
#include <algorithm>
2011-11-12 20:44:06 +01:00
#include "bitcount.h"
#include "movegen.h"
#include "position.h"
#include "psqtab.h"
#include "rkiss.h"
#include "thread.h"
#include "tt.h"
using std::string;
using std::cout;
using std::endl;
Key Position::zobrist[2][8][64];
Key Position::zobEp[64];
Key Position::zobCastle[16];
Key Position::zobSideToMove;
Key Position::zobExclusion;
Score Position::pieceSquareTable[16][64];
2011-11-12 20:44:06 +01:00
// Material values arrays, indexed by Piece
const Value PieceValueMidgame[17] = {
2011-11-12 20:44:06 +01:00
VALUE_ZERO,
PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
RookValueMidgame, QueenValueMidgame,
VALUE_ZERO, VALUE_ZERO, VALUE_ZERO,
2011-11-12 20:44:06 +01:00
PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
RookValueMidgame, QueenValueMidgame
};
const Value PieceValueEndgame[17] = {
2011-11-12 20:44:06 +01:00
VALUE_ZERO,
PawnValueEndgame, KnightValueEndgame, BishopValueEndgame,
RookValueEndgame, QueenValueEndgame,
VALUE_ZERO, VALUE_ZERO, VALUE_ZERO,
2011-11-12 20:44:06 +01:00
PawnValueEndgame, KnightValueEndgame, BishopValueEndgame,
RookValueEndgame, QueenValueEndgame
};
namespace {
// Bonus for having the side to move (modified by Joona Kiiski)
const Score TempoValue = make_score(48, 22);
// To convert a Piece to and from a FEN char
const string PieceToChar(" PNBRQK pnbrqk .");
2011-11-12 20:44:06 +01:00
}
/// CheckInfo c'tor
CheckInfo::CheckInfo(const Position& pos) {
Color them = ~pos.side_to_move();
ksq = pos.king_square(them);
2011-11-12 20:44:06 +01:00
pinned = pos.pinned_pieces();
dcCandidates = pos.discovered_check_candidates();
2011-11-12 20:44:06 +01:00
checkSq[PAWN] = pos.attacks_from<PAWN>(ksq, them);
2011-11-12 20:44:06 +01:00
checkSq[KNIGHT] = pos.attacks_from<KNIGHT>(ksq);
checkSq[BISHOP] = pos.attacks_from<BISHOP>(ksq);
checkSq[ROOK] = pos.attacks_from<ROOK>(ksq);
checkSq[QUEEN] = checkSq[BISHOP] | checkSq[ROOK];
checkSq[KING] = 0;
2011-11-12 20:44:06 +01:00
}
/// Position c'tors. Here we always create a copy of the original position
/// or the FEN string, we want the new born Position object do not depend
/// on any external data so we detach state pointer from the source one.
void Position::copy(const Position& pos, int th) {
2011-11-12 20:44:06 +01:00
memcpy(this, &pos, sizeof(Position));
startState = *st;
st = &startState;
2011-11-12 20:44:06 +01:00
threadID = th;
nodes = 0;
assert(pos_is_ok());
2011-11-12 20:44:06 +01:00
}
Position::Position(const string& fen, bool isChess960, int th) {
from_fen(fen, isChess960);
threadID = th;
}
/// 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 string& fenStr, bool isChess960) {
2011-11-12 20:44:06 +01:00
/*
A FEN string defines a particular position using only the ASCII character set.
A FEN string contains six fields separated by a space. The fields are:
2011-11-12 20:44:06 +01:00
1) Piece placement (from white's perspective). Each rank is described, starting
with rank 8 and ending with rank 1; within each rank, the contents of each
square are described from file A through file H. Following the Standard
Algebraic Notation (SAN), each piece is identified by a single letter taken
from the standard English names. White pieces are designated using upper-case
letters ("PNBRQK") while Black take lowercase ("pnbrqk"). Blank squares are
noted using digits 1 through 8 (the number of blank squares), and "/"
separates ranks.
2011-11-12 20:44:06 +01:00
2) Active color. "w" means white moves next, "b" means black.
3) Castling availability. If neither side can castle, this is "-". Otherwise,
this has one or more letters: "K" (White can castle kingside), "Q" (White
can castle queenside), "k" (Black can castle kingside), and/or "q" (Black
can castle queenside).
2011-11-12 20:44:06 +01:00
4) En passant target square (in algebraic notation). If there's no en passant
target square, this is "-". If a pawn has just made a 2-square move, this
is the position "behind" the pawn. This is recorded regardless of whether
there is a pawn in position to make an en passant capture.
2011-11-12 20:44:06 +01:00
5) Halfmove clock. This is the number of halfmoves since the last pawn advance
or capture. This is used to determine if a draw can be claimed under the
fifty-move rule.
2011-11-12 20:44:06 +01:00
6) Fullmove number. The number of the full move. It starts at 1, and is
incremented after Black's move.
2011-11-12 20:44:06 +01:00
*/
char col, row, token;
size_t p;
2011-11-12 20:44:06 +01:00
Square sq = SQ_A8;
std::istringstream fen(fenStr);
2011-11-12 20:44:06 +01:00
clear();
fen >> std::noskipws;
2011-11-12 20:44:06 +01:00
// 1. Piece placement
while ((fen >> token) && !isspace(token))
2011-11-12 20:44:06 +01:00
{
if (isdigit(token))
sq += Square(token - '0'); // Advance the given number of files
else if (token == '/')
sq = make_square(FILE_A, rank_of(sq) - Rank(2));
else if ((p = PieceToChar.find(token)) != string::npos)
2011-11-12 20:44:06 +01:00
{
put_piece(Piece(p), sq);
2011-11-12 20:44:06 +01:00
sq++;
}
}
// 2. Active color
fen >> token;
2011-11-12 20:44:06 +01:00
sideToMove = (token == 'w' ? WHITE : BLACK);
fen >> token;
// 3. Castling availability. Compatible with 3 standards: Normal FEN standard,
// Shredder-FEN that uses the letters of the columns on which the rooks began
// the game instead of KQkq and also X-FEN standard that, in case of Chess960,
// if an inner rook is associated with the castling right, the castling tag is
// replaced by the file letter of the involved rook, as for the Shredder-FEN.
while ((fen >> token) && !isspace(token))
{
Square rsq;
Color c = islower(token) ? BLACK : WHITE;
2011-11-12 20:44:06 +01:00
token = char(toupper(token));
2011-11-12 20:44:06 +01:00
if (token == 'K')
for (rsq = relative_square(c, SQ_H1); type_of(piece_on(rsq)) != ROOK; rsq--) {}
2011-11-12 20:44:06 +01:00
else if (token == 'Q')
for (rsq = relative_square(c, SQ_A1); type_of(piece_on(rsq)) != ROOK; rsq++) {}
2011-11-12 20:44:06 +01:00
else if (token >= 'A' && token <= 'H')
rsq = make_square(File(token - 'A'), relative_rank(c, RANK_1));
else
continue;
set_castle_right(c, rsq);
2011-11-12 20:44:06 +01:00
}
// 4. En passant square. Ignore if no pawn capture is possible
if ( ((fen >> col) && (col >= 'a' && col <= 'h'))
&& ((fen >> row) && (row == '3' || row == '6')))
{
st->epSquare = make_square(File(col - 'a'), Rank(row - '1'));
2011-11-12 20:44:06 +01:00
if (!(attackers_to(st->epSquare) & pieces(PAWN, sideToMove)))
st->epSquare = SQ_NONE;
}
2011-11-12 20:44:06 +01:00
// 5-6. Halfmove clock and fullmove number
fen >> std::skipws >> st->rule50 >> startPosPly;
2011-11-12 20:44:06 +01:00
// Convert from fullmove starting from 1 to ply starting from 0,
// handle also common incorrect FEN with fullmove = 0.
startPosPly = std::max(2 * (startPosPly - 1), 0) + int(sideToMove == BLACK);
2011-11-12 20:44:06 +01:00
st->key = compute_key();
st->pawnKey = compute_pawn_key();
st->materialKey = compute_material_key();
st->value = compute_value();
st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
st->npMaterial[BLACK] = compute_non_pawn_material(BLACK);
st->checkersBB = attackers_to(king_square(sideToMove)) & pieces(~sideToMove);
chess960 = isChess960;
2011-11-12 20:44:06 +01:00
assert(pos_is_ok());
2011-11-12 20:44:06 +01:00
}
/// Position::set_castle_right() is an helper function used to set castling
/// rights given the corresponding color and the rook starting square.
2011-11-12 20:44:06 +01:00
void Position::set_castle_right(Color c, Square rsq) {
int f = (rsq < king_square(c) ? WHITE_OOO : WHITE_OO) << c;
st->castleRights |= f;
castleRightsMask[king_square(c)] ^= f;
castleRightsMask[rsq] ^= f;
castleRookSquare[f] = rsq;
2011-11-12 20:44:06 +01:00
}
/// Position::to_fen() returns a FEN representation of the position. In case
/// of Chess960 the Shredder-FEN notation is used. Mainly a debugging function.
const string Position::to_fen() const {
std::ostringstream fen;
2011-11-12 20:44:06 +01:00
Square sq;
int emptyCnt;
2011-11-12 20:44:06 +01:00
for (Rank rank = RANK_8; rank >= RANK_1; rank--)
2011-11-12 20:44:06 +01:00
{
emptyCnt = 0;
2011-11-12 20:44:06 +01:00
for (File file = FILE_A; file <= FILE_H; file++)
{
sq = make_square(file, rank);
if (square_is_empty(sq))
emptyCnt++;
else
2011-11-12 20:44:06 +01:00
{
if (emptyCnt > 0)
2011-11-12 20:44:06 +01:00
{
fen << emptyCnt;
emptyCnt = 0;
2011-11-12 20:44:06 +01:00
}
fen << PieceToChar[piece_on(sq)];
}
2011-11-12 20:44:06 +01:00
}
if (emptyCnt > 0)
fen << emptyCnt;
if (rank > RANK_1)
fen << '/';
2011-11-12 20:44:06 +01:00
}
fen << (sideToMove == WHITE ? " w " : " b ");
2011-11-12 20:44:06 +01:00
if (can_castle(WHITE_OO))
fen << (chess960 ? char(toupper(file_to_char(file_of(castle_rook_square(WHITE_OO))))) : 'K');
2011-11-12 20:44:06 +01:00
if (can_castle(WHITE_OOO))
fen << (chess960 ? char(toupper(file_to_char(file_of(castle_rook_square(WHITE_OOO))))) : 'Q');
2011-11-12 20:44:06 +01:00
if (can_castle(BLACK_OO))
fen << (chess960 ? file_to_char(file_of(castle_rook_square(BLACK_OO))) : 'k');
2011-11-12 20:44:06 +01:00
if (can_castle(BLACK_OOO))
fen << (chess960 ? file_to_char(file_of(castle_rook_square(BLACK_OOO))) : 'q');
2011-11-12 20:44:06 +01:00
if (st->castleRights == CASTLES_NONE)
fen << '-';
fen << (ep_square() == SQ_NONE ? " - " : " " + square_to_string(ep_square()) + " ")
<< st->rule50 << " " << 1 + (startPosPly - int(sideToMove == BLACK)) / 2;
return fen.str();
2011-11-12 20:44:06 +01:00
}
/// Position::print() prints an ASCII representation of the position to
/// the standard output. If a move is given then also the san is printed.
void Position::print(Move move) const {
const char* dottedLine = "\n+---+---+---+---+---+---+---+---+\n";
if (move)
{
Position p(*this, thread());
cout << "\nMove is: " << (sideToMove == BLACK ? ".." : "") << move_to_san(p, move);
2011-11-12 20:44:06 +01:00
}
for (Rank rank = RANK_8; rank >= RANK_1; rank--)
{
cout << dottedLine << '|';
for (File file = FILE_A; file <= FILE_H; file++)
{
Square sq = make_square(file, rank);
Piece piece = piece_on(sq);
char c = (color_of(piece) == BLACK ? '=' : ' ');
2011-11-12 20:44:06 +01:00
if (piece == NO_PIECE && !opposite_colors(sq, SQ_A1))
piece++; // Index the dot
2011-11-12 20:44:06 +01:00
cout << c << PieceToChar[piece] << c << '|';
2011-11-12 20:44:06 +01:00
}
}
cout << dottedLine << "Fen is: " << to_fen() << "\nKey is: " << st->key << endl;
}
/// Position:hidden_checkers<>() returns a bitboard of all pinned (against the
/// king) pieces for the given color. Or, when template parameter FindPinned is
/// false, the function return the pieces of the given color candidate for a
/// discovery check against the enemy king.
2011-11-12 20:44:06 +01:00
template<bool FindPinned>
Bitboard Position::hidden_checkers() const {
2011-11-12 20:44:06 +01:00
// Pinned pieces protect our king, dicovery checks attack the enemy king
Bitboard b, result = 0;
Bitboard pinners = pieces(FindPinned ? ~sideToMove : sideToMove);
Square ksq = king_square(FindPinned ? sideToMove : ~sideToMove);
2011-11-12 20:44:06 +01:00
// Pinners are sliders, that give check when candidate pinned is removed
pinners &= (pieces(ROOK, QUEEN) & PseudoAttacks[ROOK][ksq])
| (pieces(BISHOP, QUEEN) & PseudoAttacks[BISHOP][ksq]);
2011-11-12 20:44:06 +01:00
while (pinners)
{
b = squares_between(ksq, pop_1st_bit(&pinners)) & occupied_squares();
2011-11-12 20:44:06 +01:00
// Only one bit set and is an our piece?
if (b && !(b & (b - 1)) && (b & pieces(sideToMove)))
2011-11-12 20:44:06 +01:00
result |= b;
}
return result;
}
// Explicit template instantiations
template Bitboard Position::hidden_checkers<true>() const;
template Bitboard Position::hidden_checkers<false>() const;
2011-11-12 20:44:06 +01:00
/// Position::attackers_to() computes a bitboard of all pieces which attack a
/// given square. Slider attacks use occ bitboard as occupancy.
2011-11-12 20:44:06 +01:00
Bitboard Position::attackers_to(Square s, Bitboard occ) const {
2011-11-12 20:44:06 +01:00
return (attacks_from<PAWN>(s, BLACK) & pieces(PAWN, WHITE))
| (attacks_from<PAWN>(s, WHITE) & pieces(PAWN, BLACK))
| (attacks_from<KNIGHT>(s) & pieces(KNIGHT))
| (rook_attacks_bb(s, occ) & pieces(ROOK, QUEEN))
| (bishop_attacks_bb(s, occ) & pieces(BISHOP, QUEEN))
2011-11-12 20:44:06 +01:00
| (attacks_from<KING>(s) & pieces(KING));
}
/// Position::attacks_from() computes a bitboard of all attacks of a given piece
/// put in a given square. Slider attacks use occ bitboard as occupancy.
2011-11-12 20:44:06 +01:00
Bitboard Position::attacks_from(Piece p, Square s, Bitboard occ) {
assert(square_is_ok(s));
switch (type_of(p))
2011-11-12 20:44:06 +01:00
{
case BISHOP: return bishop_attacks_bb(s, occ);
case ROOK : return rook_attacks_bb(s, occ);
case QUEEN : return bishop_attacks_bb(s, occ) | rook_attacks_bb(s, occ);
default : return StepAttacksBB[p][s];
2011-11-12 20:44:06 +01:00
}
}
/// Position::move_attacks_square() tests whether a move from the current
/// position attacks a given square.
bool Position::move_attacks_square(Move m, Square s) const {
assert(is_ok(m));
2011-11-12 20:44:06 +01:00
assert(square_is_ok(s));
Bitboard occ, xray;
Square from = from_sq(m);
Square to = to_sq(m);
Piece piece = piece_on(from);
2011-11-12 20:44:06 +01:00
assert(!square_is_empty(from));
2011-11-12 20:44:06 +01:00
// Update occupancy as if the piece is moving
2011-11-12 20:44:06 +01:00
occ = occupied_squares();
do_move_bb(&occ, make_move_bb(from, to));
2011-11-12 20:44:06 +01:00
// The piece moved in 'to' attacks the square 's' ?
if (bit_is_set(attacks_from(piece, to, occ), s))
return true;
2011-11-12 20:44:06 +01:00
// Scan for possible X-ray attackers behind the moved piece
xray = (rook_attacks_bb(s, occ) & pieces(ROOK, QUEEN, color_of(piece)))
|(bishop_attacks_bb(s, occ) & pieces(BISHOP, QUEEN, color_of(piece)));
2011-11-12 20:44:06 +01:00
// Verify attackers are triggered by our move and not already existing
return xray && (xray ^ (xray & attacks_from<QUEEN>(s)));
2011-11-12 20:44:06 +01:00
}
/// Position::pl_move_is_legal() tests whether a pseudo-legal move is legal
bool Position::pl_move_is_legal(Move m, Bitboard pinned) const {
assert(is_ok(m));
assert(pinned == pinned_pieces());
2011-11-12 20:44:06 +01:00
Color us = sideToMove;
Square from = from_sq(m);
2011-11-12 20:44:06 +01:00
assert(color_of(piece_on(from)) == us);
assert(piece_on(king_square(us)) == make_piece(us, KING));
// 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 (is_enpassant(m))
2011-11-12 20:44:06 +01:00
{
Color them = ~us;
Square to = to_sq(m);
Square capsq = to + pawn_push(them);
2011-11-12 20:44:06 +01:00
Square ksq = king_square(us);
Bitboard b = occupied_squares();
assert(to == ep_square());
assert(piece_on(from) == make_piece(us, PAWN));
assert(piece_on(capsq) == make_piece(them, PAWN));
assert(piece_on(to) == NO_PIECE);
2011-11-12 20:44:06 +01:00
clear_bit(&b, from);
clear_bit(&b, capsq);
set_bit(&b, to);
return !(rook_attacks_bb(ksq, b) & pieces(ROOK, QUEEN, them))
&& !(bishop_attacks_bb(ksq, b) & pieces(BISHOP, QUEEN, them));
}
// If the moving piece is a king, check whether the destination
// square is attacked by the opponent. Castling moves are checked
// for legality during move generation.
if (type_of(piece_on(from)) == KING)
return is_castle(m) || !(attackers_to(to_sq(m)) & pieces(~us));
2011-11-12 20:44:06 +01:00
// 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.
return !pinned
|| !bit_is_set(pinned, from)
|| squares_aligned(from, to_sq(m), king_square(us));
2011-11-12 20:44:06 +01:00
}
/// Position::move_is_legal() takes a random move and tests whether the move
/// is legal. This version is not very fast and should be used only in non
/// time-critical paths.
2011-11-12 20:44:06 +01:00
bool Position::move_is_legal(const Move m) const {
for (MoveList<MV_LEGAL> ml(*this); !ml.end(); ++ml)
if (ml.move() == m)
return true;
2011-11-12 20:44:06 +01:00
return false;
}
/// Position::is_pseudo_legal() takes a random move and tests whether the move
/// is pseudo legal. It is used to validate moves from TT that can be corrupted
/// due to SMP concurrent access or hash position key aliasing.
2011-11-12 20:44:06 +01:00
bool Position::is_pseudo_legal(const Move m) const {
2011-11-12 20:44:06 +01:00
Color us = sideToMove;
Color them = ~sideToMove;
Square from = from_sq(m);
Square to = to_sq(m);
2011-11-12 20:44:06 +01:00
Piece pc = piece_on(from);
// Use a slower but simpler function for uncommon cases
if (is_special(m))
2011-11-12 20:44:06 +01:00
return move_is_legal(m);
// Is not a promotion, so promotion piece must be empty
if (promotion_piece_type(m) - 2 != NO_PIECE_TYPE)
return false;
2011-11-12 20:44:06 +01:00
// If the from square is not occupied by a piece belonging to the side to
// move, the move is obviously not legal.
if (pc == NO_PIECE || color_of(pc) != us)
2011-11-12 20:44:06 +01:00
return false;
// The destination square cannot be occupied by a friendly piece
if (color_of(piece_on(to)) == us)
2011-11-12 20:44:06 +01:00
return false;
// Handle the special case of a pawn move
if (type_of(pc) == PAWN)
2011-11-12 20:44:06 +01:00
{
// Move direction must be compatible with pawn color
int direction = to - from;
if ((us == WHITE) != (direction > 0))
return false;
// We have already handled promotion moves, so destination
// cannot be on the 8/1th rank.
if (rank_of(to) == RANK_8 || rank_of(to) == RANK_1)
2011-11-12 20:44:06 +01:00
return false;
// Proceed according to the square delta between the origin and
// destination squares.
switch (direction)
{
case DELTA_NW:
case DELTA_NE:
case DELTA_SW:
case DELTA_SE:
// Capture. The destination square must be occupied by an enemy
// piece (en passant captures was handled earlier).
if (color_of(piece_on(to)) != them)
return false;
// From and to files must be one file apart, avoids a7h5
if (abs(file_of(from) - file_of(to)) != 1)
return false;
break;
2011-11-12 20:44:06 +01:00
case DELTA_N:
case DELTA_S:
// Pawn push. The destination square must be empty.
if (!square_is_empty(to))
return false;
break;
2011-11-12 20:44:06 +01:00
case DELTA_NN:
// Double white pawn push. The destination square must be on the fourth
// rank, and both the destination square and the square between the
// source and destination squares must be empty.
if ( rank_of(to) != RANK_4
2011-11-12 20:44:06 +01:00
|| !square_is_empty(to)
|| !square_is_empty(from + DELTA_N))
return false;
break;
2011-11-12 20:44:06 +01:00
case DELTA_SS:
// Double black pawn push. The destination square must be on the fifth
// rank, and both the destination square and the square between the
// source and destination squares must be empty.
if ( rank_of(to) != RANK_5
|| !square_is_empty(to)
|| !square_is_empty(from + DELTA_S))
return false;
break;
2011-11-12 20:44:06 +01:00
default:
return false;
}
}
else if (!bit_is_set(attacks_from(pc, from), to))
return false;
// Evasions generator already takes care to avoid some kind of illegal moves
// and pl_move_is_legal() relies on this. So we have to take care that the
// same kind of moves are filtered out here.
if (in_check())
{
// In case of king moves under check we have to remove king so to catch
// as invalid moves like b1a1 when opposite queen is on c1.
if (type_of(piece_on(from)) == KING)
{
Bitboard b = occupied_squares();
clear_bit(&b, from);
if (attackers_to(to_sq(m), b) & pieces(~us))
return false;
}
else
{
Bitboard target = checkers();
Square checksq = pop_1st_bit(&target);
2011-11-12 20:44:06 +01:00
if (target) // double check ? In this case a king move is required
return false;
2011-11-12 20:44:06 +01:00
// Our move must be a blocking evasion or a capture of the checking piece
target = squares_between(checksq, king_square(us)) | checkers();
if (!bit_is_set(target, to_sq(m)))
return false;
}
}
2011-11-12 20:44:06 +01:00
return true;
2011-11-12 20:44:06 +01:00
}
/// Position::move_gives_check() tests whether a pseudo-legal move gives a check
2011-11-12 20:44:06 +01:00
bool Position::move_gives_check(Move m, const CheckInfo& ci) const {
assert(is_ok(m));
assert(ci.dcCandidates == discovered_check_candidates());
assert(color_of(piece_moved(m)) == sideToMove);
2011-11-12 20:44:06 +01:00
Square from = from_sq(m);
Square to = to_sq(m);
PieceType pt = type_of(piece_on(from));
2011-11-12 20:44:06 +01:00
// Direct check ?
if (bit_is_set(ci.checkSq[pt], to))
return true;
// Discovery check ?
if (ci.dcCandidates && bit_is_set(ci.dcCandidates, from))
{
// For pawn and king moves we need to verify also direction
if ( (pt != PAWN && pt != KING)
|| !squares_aligned(from, to, king_square(~sideToMove)))
2011-11-12 20:44:06 +01:00
return true;
}
// Can we skip the ugly special cases ?
if (!is_special(m))
2011-11-12 20:44:06 +01:00
return false;
Color us = sideToMove;
2011-11-12 20:44:06 +01:00
Bitboard b = occupied_squares();
Square ksq = king_square(~us);
2011-11-12 20:44:06 +01:00
// Promotion with check ?
if (is_promotion(m))
2011-11-12 20:44:06 +01:00
{
clear_bit(&b, from);
return bit_is_set(attacks_from(Piece(promotion_piece_type(m)), to, b), ksq);
2011-11-12 20:44:06 +01:00
}
// 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.
if (is_enpassant(m))
2011-11-12 20:44:06 +01:00
{
Square capsq = make_square(file_of(to), rank_of(from));
2011-11-12 20:44:06 +01:00
clear_bit(&b, from);
clear_bit(&b, capsq);
set_bit(&b, to);
return (rook_attacks_bb(ksq, b) & pieces(ROOK, QUEEN, us))
||(bishop_attacks_bb(ksq, b) & pieces(BISHOP, QUEEN, us));
2011-11-12 20:44:06 +01:00
}
// Castling with check ?
if (is_castle(m))
2011-11-12 20:44:06 +01:00
{
Square kfrom, kto, rfrom, rto;
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);
2011-11-12 20:44:06 +01:00
}
return false;
}
/// Position::do_move() makes a move, and saves all information necessary
/// to a StateInfo object. The move is assumed to be legal. Pseudo-legal
/// moves should be filtered out before this function is called.
void Position::do_move(Move m, StateInfo& newSt) {
CheckInfo ci(*this);
do_move(m, newSt, ci, move_gives_check(m, ci));
}
void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveIsCheck) {
assert(is_ok(m));
2011-11-12 20:44:06 +01:00
assert(&newSt != st);
nodes++;
Key k = st->key;
2011-11-12 20:44:06 +01:00
// Copy some fields of old state to our new StateInfo object except the ones
// which are recalculated from scratch anyway, then switch our state pointer
// to point to the new, ready to be updated, state.
2011-11-12 20:44:06 +01:00
struct ReducedStateInfo {
Key pawnKey, materialKey;
Value npMaterial[2];
int castleRights, rule50, pliesFromNull;
Score value;
Square epSquare;
2011-11-12 20:44:06 +01:00
};
memcpy(&newSt, st, sizeof(ReducedStateInfo));
newSt.previous = st;
st = &newSt;
// Update side to move
k ^= zobSideToMove;
2011-11-12 20:44:06 +01:00
// Increment the 50 moves rule draw counter. Resetting it to zero in the
// case of non-reversible moves is taken care of later.
st->rule50++;
st->pliesFromNull++;
if (is_castle(m))
2011-11-12 20:44:06 +01:00
{
st->key = k;
do_castle_move<true>(m);
2011-11-12 20:44:06 +01:00
return;
}
Color us = sideToMove;
Color them = ~us;
Square from = from_sq(m);
Square to = to_sq(m);
2011-11-12 20:44:06 +01:00
Piece piece = piece_on(from);
PieceType pt = type_of(piece);
PieceType capture = is_enpassant(m) ? PAWN : type_of(piece_on(to));
2011-11-12 20:44:06 +01:00
assert(color_of(piece) == us);
assert(color_of(piece_on(to)) != us);
assert(capture != KING);
2011-11-12 20:44:06 +01:00
if (capture)
{
Square capsq = to;
// If the captured piece is a pawn, update pawn hash key, otherwise
// update non-pawn material.
if (capture == PAWN)
{
if (is_enpassant(m))
{
capsq += pawn_push(them);
assert(pt == PAWN);
assert(to == st->epSquare);
assert(relative_rank(us, to) == RANK_6);
assert(piece_on(to) == NO_PIECE);
assert(piece_on(capsq) == make_piece(them, PAWN));
board[capsq] = NO_PIECE;
}
st->pawnKey ^= zobrist[them][PAWN][capsq];
}
else
st->npMaterial[them] -= PieceValueMidgame[capture];
// Remove the captured piece
clear_bit(&byColorBB[them], capsq);
clear_bit(&byTypeBB[capture], capsq);
clear_bit(&occupied, capsq);
// Update piece list, move the last piece at index[capsq] position and
// shrink the list.
//
// WARNING: This is a not revresible operation. When we will reinsert the
// captured piece in undo_move() we will put it at the end of the list and
// not in its original place, it means index[] and pieceList[] are not
// guaranteed to be invariant to a do_move() + undo_move() sequence.
Square lastSquare = pieceList[them][capture][--pieceCount[them][capture]];
index[lastSquare] = index[capsq];
pieceList[them][capture][index[lastSquare]] = lastSquare;
pieceList[them][capture][pieceCount[them][capture]] = SQ_NONE;
// Update hash keys
k ^= zobrist[them][capture][capsq];
st->materialKey ^= zobrist[them][capture][pieceCount[them][capture]];
// Update incremental scores
st->value -= pst(make_piece(them, capture), capsq);
// Reset rule 50 counter
st->rule50 = 0;
}
2011-11-12 20:44:06 +01:00
// Update hash key
k ^= zobrist[us][pt][from] ^ zobrist[us][pt][to];
2011-11-12 20:44:06 +01:00
// Reset en passant square
if (st->epSquare != SQ_NONE)
{
k ^= zobEp[st->epSquare];
2011-11-12 20:44:06 +01:00
st->epSquare = SQ_NONE;
}
// Update castle rights if needed
if ( st->castleRights != CASTLES_NONE
&& (castleRightsMask[from] & castleRightsMask[to]) != ALL_CASTLES)
2011-11-12 20:44:06 +01:00
{
k ^= zobCastle[st->castleRights];
st->castleRights &= castleRightsMask[from] & castleRightsMask[to];
k ^= zobCastle[st->castleRights];
2011-11-12 20:44:06 +01:00
}
// Prefetch TT access as soon as we know key is updated
prefetch((char*)TT.first_entry(k));
2011-11-12 20:44:06 +01:00
// Move the piece
Bitboard move_bb = make_move_bb(from, to);
do_move_bb(&byColorBB[us], move_bb);
do_move_bb(&byTypeBB[pt], move_bb);
do_move_bb(&occupied, move_bb);
2011-11-12 20:44:06 +01:00
board[to] = board[from];
board[from] = NO_PIECE;
2011-11-12 20:44:06 +01:00
// Update piece lists, index[from] is not updated and becomes stale. This
// works as long as index[] is accessed just by known occupied squares.
2011-11-12 20:44:06 +01:00
index[to] = index[from];
pieceList[us][pt][index[to]] = to;
// If the moving piece is a pawn do some special extra work
2011-11-12 20:44:06 +01:00
if (pt == PAWN)
{
// Set en-passant square, only if moved pawn can be captured
if ( (to ^ from) == 16
&& (attacks_from<PAWN>(from + pawn_push(us), us) & pieces(PAWN, them)))
2011-11-12 20:44:06 +01:00
{
st->epSquare = Square((from + to) / 2);
k ^= zobEp[st->epSquare];
2011-11-12 20:44:06 +01:00
}
if (is_promotion(m))
2011-11-12 20:44:06 +01:00
{
PieceType promotion = promotion_piece_type(m);
2011-11-12 20:44:06 +01:00
assert(relative_rank(us, to) == RANK_8);
2011-11-12 20:44:06 +01:00
assert(promotion >= KNIGHT && promotion <= QUEEN);
// Replace the pawn with the promoted piece
clear_bit(&byTypeBB[PAWN], to);
set_bit(&byTypeBB[promotion], to);
2011-11-12 20:44:06 +01:00
board[to] = make_piece(us, promotion);
// Update piece lists, move the last pawn at index[to] position
// and shrink the list. Add a new promotion piece to the list.
Square lastSquare = pieceList[us][PAWN][--pieceCount[us][PAWN]];
index[lastSquare] = index[to];
pieceList[us][PAWN][index[lastSquare]] = lastSquare;
2011-11-12 20:44:06 +01:00
pieceList[us][PAWN][pieceCount[us][PAWN]] = SQ_NONE;
index[to] = pieceCount[us][promotion];
2011-11-12 20:44:06 +01:00
pieceList[us][promotion][index[to]] = to;
// Update hash keys
k ^= zobrist[us][PAWN][to] ^ zobrist[us][promotion][to];
2011-11-12 20:44:06 +01:00
st->pawnKey ^= zobrist[us][PAWN][to];
st->materialKey ^= zobrist[us][promotion][pieceCount[us][promotion]++]
^ zobrist[us][PAWN][pieceCount[us][PAWN]];
2011-11-12 20:44:06 +01:00
// Update incremental score
st->value += pst(make_piece(us, promotion), to)
- pst(make_piece(us, PAWN), to);
2011-11-12 20:44:06 +01:00
// Update material
st->npMaterial[us] += PieceValueMidgame[promotion];
}
// Update pawn hash key
st->pawnKey ^= zobrist[us][PAWN][from] ^ zobrist[us][PAWN][to];
// Reset rule 50 draw counter
st->rule50 = 0;
2011-11-12 20:44:06 +01:00
}
// Prefetch pawn and material hash tables
Threads[threadID].pawnTable.prefetch(st->pawnKey);
Threads[threadID].materialTable.prefetch(st->materialKey);
// Update incremental scores
st->value += pst_delta(piece, from, to);
// Set capture piece
st->capturedType = capture;
// Update the key with the final value
st->key = k;
2011-11-12 20:44:06 +01:00
// Update checkers bitboard, piece must be already moved
st->checkersBB = 0;
2011-11-12 20:44:06 +01:00
if (moveIsCheck)
{
if (is_special(m))
st->checkersBB = attackers_to(king_square(them)) & pieces(us);
2011-11-12 20:44:06 +01:00
else
{
// Direct checks
if (bit_is_set(ci.checkSq[pt], to))
st->checkersBB = SetMaskBB[to];
// Discovery checks
if (ci.dcCandidates && bit_is_set(ci.dcCandidates, from))
{
if (pt != ROOK)
st->checkersBB |= attacks_from<ROOK>(king_square(them)) & pieces(ROOK, QUEEN, us);
2011-11-12 20:44:06 +01:00
if (pt != BISHOP)
st->checkersBB |= attacks_from<BISHOP>(king_square(them)) & pieces(BISHOP, QUEEN, us);
2011-11-12 20:44:06 +01:00
}
}
}
// Finish
sideToMove = ~sideToMove;
2011-11-12 20:44:06 +01:00
st->value += (sideToMove == WHITE ? TempoValue : -TempoValue);
assert(pos_is_ok());
2011-11-12 20:44:06 +01:00
}
/// 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.
void Position::undo_move(Move m) {
assert(is_ok(m));
2011-11-12 20:44:06 +01:00
sideToMove = ~sideToMove;
2011-11-12 20:44:06 +01:00
if (is_castle(m))
2011-11-12 20:44:06 +01:00
{
do_castle_move<false>(m);
2011-11-12 20:44:06 +01:00
return;
}
Color us = sideToMove;
Color them = ~us;
Square from = from_sq(m);
Square to = to_sq(m);
Piece piece = piece_on(to);
PieceType pt = type_of(piece);
PieceType capture = st->capturedType;
2011-11-12 20:44:06 +01:00
assert(square_is_empty(from));
assert(color_of(piece) == us);
assert(capture != KING);
2011-11-12 20:44:06 +01:00
if (is_promotion(m))
2011-11-12 20:44:06 +01:00
{
PieceType promotion = promotion_piece_type(m);
2011-11-12 20:44:06 +01:00
assert(promotion == pt);
assert(relative_rank(us, to) == RANK_8);
2011-11-12 20:44:06 +01:00
assert(promotion >= KNIGHT && promotion <= QUEEN);
// Replace the promoted piece with the pawn
clear_bit(&byTypeBB[promotion], to);
set_bit(&byTypeBB[PAWN], to);
board[to] = make_piece(us, PAWN);
2011-11-12 20:44:06 +01:00
// Update piece lists, move the last promoted piece at index[to] position
// and shrink the list. Add a new pawn to the list.
Square lastSquare = pieceList[us][promotion][--pieceCount[us][promotion]];
index[lastSquare] = index[to];
pieceList[us][promotion][index[lastSquare]] = lastSquare;
2011-11-12 20:44:06 +01:00
pieceList[us][promotion][pieceCount[us][promotion]] = SQ_NONE;
index[to] = pieceCount[us][PAWN]++;
2011-11-12 20:44:06 +01:00
pieceList[us][PAWN][index[to]] = to;
pt = PAWN;
2011-11-12 20:44:06 +01:00
}
// Put the piece back at the source square
Bitboard move_bb = make_move_bb(to, from);
do_move_bb(&byColorBB[us], move_bb);
do_move_bb(&byTypeBB[pt], move_bb);
do_move_bb(&occupied, move_bb);
2011-11-12 20:44:06 +01:00
board[from] = board[to];
board[to] = NO_PIECE;
2011-11-12 20:44:06 +01:00
// Update piece lists, index[to] is not updated and becomes stale. This
// works as long as index[] is accessed just by known occupied squares.
2011-11-12 20:44:06 +01:00
index[from] = index[to];
pieceList[us][pt][index[from]] = from;
if (capture)
2011-11-12 20:44:06 +01:00
{
Square capsq = to;
if (is_enpassant(m))
{
capsq -= pawn_push(us);
2011-11-12 20:44:06 +01:00
assert(pt == PAWN);
assert(to == st->previous->epSquare);
assert(relative_rank(us, to) == RANK_6);
assert(piece_on(capsq) == NO_PIECE);
}
2011-11-12 20:44:06 +01:00
// Restore the captured piece
set_bit(&byColorBB[them], capsq);
set_bit(&byTypeBB[capture], capsq);
set_bit(&occupied, capsq);
2011-11-12 20:44:06 +01:00
board[capsq] = make_piece(them, capture);
2011-11-12 20:44:06 +01:00
// Update piece list, add a new captured piece in capsq square
index[capsq] = pieceCount[them][capture]++;
pieceList[them][capture][index[capsq]] = capsq;
2011-11-12 20:44:06 +01:00
}
// Finally point our state pointer back to the previous state
st = st->previous;
assert(pos_is_ok());
2011-11-12 20:44:06 +01:00
}
/// Position::do_castle_move() is a private method used to do/undo a castling
/// move. 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.
template<bool Do>
void Position::do_castle_move(Move m) {
2011-11-12 20:44:06 +01:00
assert(is_ok(m));
assert(is_castle(m));
2011-11-12 20:44:06 +01:00
Square kto, kfrom, rfrom, rto, kAfter, rAfter;
2011-11-12 20:44:06 +01:00
Color us = sideToMove;
Square kBefore = from_sq(m);
Square rBefore = to_sq(m);
2011-11-12 20:44:06 +01:00
// Find after-castle squares for king and rook
if (rBefore > kBefore) // O-O
2011-11-12 20:44:06 +01:00
{
kAfter = relative_square(us, SQ_G1);
rAfter = relative_square(us, SQ_F1);
2011-11-12 20:44:06 +01:00
}
else // O-O-O
{
kAfter = relative_square(us, SQ_C1);
rAfter = relative_square(us, SQ_D1);
}
kfrom = Do ? kBefore : kAfter;
rfrom = Do ? rBefore : rAfter;
2011-11-12 20:44:06 +01:00
kto = Do ? kAfter : kBefore;
rto = Do ? rAfter : rBefore;
assert(piece_on(kfrom) == make_piece(us, KING));
assert(piece_on(rfrom) == make_piece(us, ROOK));
// Remove pieces from source squares
clear_bit(&byColorBB[us], kfrom);
clear_bit(&byTypeBB[KING], kfrom);
clear_bit(&occupied, kfrom);
clear_bit(&byColorBB[us], rfrom);
clear_bit(&byTypeBB[ROOK], rfrom);
clear_bit(&occupied, rfrom);
// Put pieces on destination squares
set_bit(&byColorBB[us], kto);
set_bit(&byTypeBB[KING], kto);
set_bit(&occupied, kto);
set_bit(&byColorBB[us], rto);
set_bit(&byTypeBB[ROOK], rto);
set_bit(&occupied, rto);
2011-11-12 20:44:06 +01:00
// Update board
Piece king = make_piece(us, KING);
Piece rook = make_piece(us, ROOK);
board[kfrom] = board[rfrom] = NO_PIECE;
board[kto] = king;
board[rto] = rook;
2011-11-12 20:44:06 +01:00
// Update piece lists
pieceList[us][KING][index[kfrom]] = kto;
pieceList[us][ROOK][index[rfrom]] = rto;
int tmp = index[rfrom]; // In Chess960 could be kto == rfrom
index[kto] = index[kfrom];
index[rto] = tmp;
2011-11-12 20:44:06 +01:00
if (Do)
{
// Reset capture field
st->capturedType = NO_PIECE_TYPE;
2011-11-12 20:44:06 +01:00
// Update incremental scores
st->value += pst_delta(king, kfrom, kto);
st->value += pst_delta(rook, rfrom, rto);
// Update hash key
st->key ^= zobrist[us][KING][kfrom] ^ zobrist[us][KING][kto];
st->key ^= zobrist[us][ROOK][rfrom] ^ zobrist[us][ROOK][rto];
// Clear en passant square
if (st->epSquare != SQ_NONE)
{
st->key ^= zobEp[st->epSquare];
st->epSquare = SQ_NONE;
}
// Update castling rights
st->key ^= zobCastle[st->castleRights];
st->castleRights &= castleRightsMask[kfrom];
st->key ^= zobCastle[st->castleRights];
2011-11-12 20:44:06 +01:00
// Reset rule 50 counter
st->rule50 = 0;
// Update checkers BB
st->checkersBB = attackers_to(king_square(~us)) & pieces(us);
2011-11-12 20:44:06 +01:00
// Finish
sideToMove = ~sideToMove;
st->value += (sideToMove == WHITE ? TempoValue : -TempoValue);
}
else
// Undo: point our state pointer back to the previous state
st = st->previous;
2011-11-12 20:44:06 +01:00
assert(pos_is_ok());
}
/// Position::do_null_move() is used to do/undo a "null move": It flips the side
/// to move and updates the hash key without executing any move on the board.
template<bool Do>
2011-11-12 20:44:06 +01:00
void Position::do_null_move(StateInfo& backupSt) {
assert(!in_check());
// Back up the information necessary to undo the null move to the supplied
// StateInfo object. Note that differently from normal case here backupSt
// is actually used as a backup storage not as the new state. This reduces
// the number of fields to be copied.
StateInfo* src = Do ? st : &backupSt;
StateInfo* dst = Do ? &backupSt : st;
2011-11-12 20:44:06 +01:00
dst->key = src->key;
dst->epSquare = src->epSquare;
dst->value = src->value;
dst->rule50 = src->rule50;
dst->pliesFromNull = src->pliesFromNull;
2011-11-12 20:44:06 +01:00
sideToMove = ~sideToMove;
2011-11-12 20:44:06 +01:00
if (Do)
{
if (st->epSquare != SQ_NONE)
st->key ^= zobEp[st->epSquare];
2011-11-12 20:44:06 +01:00
st->key ^= zobSideToMove;
prefetch((char*)TT.first_entry(st->key));
2011-11-12 20:44:06 +01:00
st->epSquare = SQ_NONE;
st->rule50++;
st->pliesFromNull = 0;
st->value += (sideToMove == WHITE) ? TempoValue : -TempoValue;
}
2011-11-12 20:44:06 +01:00
assert(pos_is_ok());
2011-11-12 20:44:06 +01:00
}
// Explicit template instantiations
template void Position::do_null_move<false>(StateInfo& backupSt);
template void Position::do_null_move<true>(StateInfo& backupSt);
2011-11-12 20:44:06 +01:00
/// Position::see() is a static exchange evaluator: It tries to estimate the
/// material gain or loss resulting from a move. There are three versions of
/// this function: One which takes a destination square as input, one takes a
/// move, and one which takes a 'from' and a 'to' square. The function does
/// not yet understand promotions captures.
int Position::see_sign(Move m) const {
assert(is_ok(m));
2011-11-12 20:44:06 +01:00
Square from = from_sq(m);
Square to = to_sq(m);
2011-11-12 20:44:06 +01:00
// Early return if SEE cannot be negative because captured piece value
// is not less then capturing one. Note that king moves always return
// here because king midgame value is set to 0.
if (PieceValueMidgame[piece_on(to)] >= PieceValueMidgame[piece_on(from)])
2011-11-12 20:44:06 +01:00
return 1;
return see(m);
2011-11-12 20:44:06 +01:00
}
int Position::see(Move m) const {
2011-11-12 20:44:06 +01:00
Square from, to;
Bitboard occ, attackers, stmAttackers, b;
2011-11-12 20:44:06 +01:00
int swapList[32], slIndex = 1;
PieceType capturedType, pt;
Color stm;
assert(is_ok(m));
2011-11-12 20:44:06 +01:00
// As castle moves are implemented as capturing the rook, they have
// SEE == RookValueMidgame most of the times (unless the rook is under
// attack).
if (is_castle(m))
return 0;
2011-11-12 20:44:06 +01:00
from = from_sq(m);
to = to_sq(m);
capturedType = type_of(piece_on(to));
occ = occupied_squares();
2011-11-12 20:44:06 +01:00
// Handle en passant moves
if (is_enpassant(m))
2011-11-12 20:44:06 +01:00
{
Square capQq = to - pawn_push(sideToMove);
2011-11-12 20:44:06 +01:00
assert(!capturedType);
assert(type_of(piece_on(capQq)) == PAWN);
2011-11-12 20:44:06 +01:00
// Remove the captured pawn
clear_bit(&occ, capQq);
2011-11-12 20:44:06 +01:00
capturedType = PAWN;
}
// Find all attackers to the destination square, with the moving piece
// removed, but possibly an X-ray attacker added behind it.
clear_bit(&occ, from);
attackers = attackers_to(to, occ);
2011-11-12 20:44:06 +01:00
// If the opponent has no attackers we are finished
stm = ~color_of(piece_on(from));
stmAttackers = attackers & pieces(stm);
2011-11-12 20:44:06 +01:00
if (!stmAttackers)
return PieceValueMidgame[capturedType];
2011-11-12 20:44:06 +01:00
// 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
// destination 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.
swapList[0] = PieceValueMidgame[capturedType];
capturedType = type_of(piece_on(from));
2011-11-12 20:44:06 +01:00
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; !(stmAttackers & pieces(pt)); pt++)
assert(pt < KING);
// Remove the attacker we just found from the 'occupied' bitboard,
// and scan for new X-ray attacks behind the attacker.
b = stmAttackers & pieces(pt);
occ ^= (b & (~b + 1));
attackers |= (rook_attacks_bb(to, occ) & pieces(ROOK, QUEEN))
| (bishop_attacks_bb(to, occ) & pieces(BISHOP, QUEEN));
2011-11-12 20:44:06 +01:00
attackers &= occ; // Cut out pieces we've already done
2011-11-12 20:44:06 +01:00
// Add the new entry to the swap list
assert(slIndex < 32);
swapList[slIndex] = -swapList[slIndex - 1] + PieceValueMidgame[capturedType];
2011-11-12 20:44:06 +01:00
slIndex++;
// Remember the value of the capturing piece, and change the side to
// move before beginning the next iteration.
capturedType = pt;
stm = ~stm;
stmAttackers = attackers & pieces(stm);
2011-11-12 20:44:06 +01:00
// Stop before processing a king capture
if (capturedType == KING && stmAttackers)
{
assert(slIndex < 32);
swapList[slIndex++] = QueenValueMidgame*10;
break;
}
} while (stmAttackers);
// 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 (--slIndex)
swapList[slIndex-1] = std::min(-swapList[slIndex], swapList[slIndex-1]);
2011-11-12 20:44:06 +01:00
return swapList[0];
}
/// Position::clear() erases the position object to a pristine state, with an
/// empty board, white to move, and no castling rights.
void Position::clear() {
st = &startState;
memset(st, 0, sizeof(StateInfo));
st->epSquare = SQ_NONE;
memset(byColorBB, 0, sizeof(Bitboard) * 2);
memset(byTypeBB, 0, sizeof(Bitboard) * 8);
memset(pieceCount, 0, sizeof(int) * 2 * 8);
memset(index, 0, sizeof(int) * 64);
for (int i = 0; i < 8; i++)
for (int j = 0; j < 16; j++)
pieceList[0][i][j] = pieceList[1][i][j] = SQ_NONE;
for (Square sq = SQ_A1; sq <= SQ_H8; sq++)
{
board[sq] = NO_PIECE;
2011-11-12 20:44:06 +01:00
castleRightsMask[sq] = ALL_CASTLES;
}
2011-11-12 20:44:06 +01:00
sideToMove = WHITE;
nodes = 0;
occupied = 0;
2011-11-12 20:44:06 +01:00
}
/// Position::put_piece() puts a piece on the given square of the board,
/// updating the board array, pieces list, bitboards, and piece counts.
void Position::put_piece(Piece p, Square s) {
Color c = color_of(p);
PieceType pt = type_of(p);
2011-11-12 20:44:06 +01:00
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(&occupied, s);
2011-11-12 20:44:06 +01:00
}
/// 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 = zobCastle[st->castleRights];
for (Square s = SQ_A1; s <= SQ_H8; s++)
if (!square_is_empty(s))
result ^= zobrist[color_of(piece_on(s))][type_of(piece_on(s))][s];
2011-11-12 20:44:06 +01:00
if (ep_square() != SQ_NONE)
result ^= zobEp[ep_square()];
if (sideToMove == BLACK)
2011-11-12 20:44:06 +01:00
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 {
Bitboard b;
Key result = 0;
for (Color c = WHITE; c <= BLACK; c++)
{
b = pieces(PAWN, c);
while (b)
result ^= zobrist[c][PAWN][pop_1st_bit(&b)];
}
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 = 0;
for (Color c = WHITE; c <= BLACK; c++)
for (PieceType pt = PAWN; pt <= QUEEN; pt++)
for (int i = 0; i < piece_count(c, pt); i++)
2011-11-12 20:44:06 +01:00
result ^= zobrist[c][pt][i];
2011-11-12 20:44:06 +01:00
return result;
}
/// Position::compute_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.
Score Position::compute_value() const {
Bitboard b;
Score result = SCORE_ZERO;
for (Color c = WHITE; c <= BLACK; c++)
for (PieceType pt = PAWN; pt <= KING; pt++)
{
b = pieces(pt, c);
while (b)
result += pst(make_piece(c, pt), pop_1st_bit(&b));
2011-11-12 20:44:06 +01:00
}
result += (sideToMove == WHITE ? TempoValue / 2 : -TempoValue / 2);
2011-11-12 20:44:06 +01:00
return result;
}
/// Position::compute_non_pawn_material() computes the total non-pawn middle
/// game material value for the given side. Material values 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_ZERO;
for (PieceType pt = KNIGHT; pt <= QUEEN; pt++)
result += piece_count(c, pt) * PieceValueMidgame[pt];
return result;
}
/// 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.
template<bool SkipRepetition>
2011-11-12 20:44:06 +01:00
bool Position::is_draw() const {
// Draw by material?
if ( !pieces(PAWN)
&& (non_pawn_material(WHITE) + non_pawn_material(BLACK) <= BishopValueMidgame))
return true;
// Draw by the 50 moves rule?
if (st->rule50 > 99 && (!in_check() || MoveList<MV_LEGAL>(*this).size()))
2011-11-12 20:44:06 +01:00
return true;
// Draw by repetition?
if (!SkipRepetition)
{
int i = 4, e = std::min(st->rule50, st->pliesFromNull);
if (i <= e)
{
StateInfo* stp = st->previous->previous;
do {
stp = stp->previous->previous;
if (stp->key == st->key)
return true;
i +=2;
} while (i <= e);
}
}
2011-11-12 20:44:06 +01:00
return false;
}
// Explicit template instantiations
template bool Position::is_draw<false>() const;
template bool Position::is_draw<true>() const;
2011-11-12 20:44:06 +01:00
/// Position::init() is a static member function which initializes at startup
/// the various arrays used to compute hash keys and the piece square tables.
/// The latter is a two-step operation: First, the white halves of the tables
/// are copied from PSQT[] tables. Second, the black halves of the tables are
/// initialized by flipping and changing the sign of the white scores.
2011-11-12 20:44:06 +01:00
void Position::init() {
2011-11-12 20:44:06 +01:00
RKISS rk;
for (Color c = WHITE; c <= BLACK; c++)
for (PieceType pt = PAWN; pt <= KING; pt++)
for (Square s = SQ_A1; s <= SQ_H8; s++)
zobrist[c][pt][s] = rk.rand<Key>();
2011-11-12 20:44:06 +01:00
for (Square s = SQ_A1; s <= SQ_H8; s++)
zobEp[s] = rk.rand<Key>();
2011-11-12 20:44:06 +01:00
for (int i = 0; i < 16; i++)
2011-11-12 20:44:06 +01:00
zobCastle[i] = rk.rand<Key>();
zobSideToMove = rk.rand<Key>();
zobExclusion = rk.rand<Key>();
for (Piece p = W_PAWN; p <= W_KING; p++)
{
Score ps = make_score(PieceValueMidgame[p], PieceValueEndgame[p]);
2011-11-12 20:44:06 +01:00
for (Square s = SQ_A1; s <= SQ_H8; s++)
{
pieceSquareTable[p][s] = ps + PSQT[p][s];
pieceSquareTable[p+8][~s] = -pieceSquareTable[p][s];
}
}
2011-11-12 20:44:06 +01:00
}
/// Position::flip_me() flips position with the white and black sides reversed. This
2011-11-12 20:44:06 +01:00
/// is only useful for debugging especially for finding evaluation symmetry bugs.
void Position::flip_me() {
2011-11-12 20:44:06 +01:00
// Make a copy of current position before to start changing
const Position pos(*this, threadID);
clear();
threadID = pos.thread();
// Board
for (Square s = SQ_A1; s <= SQ_H8; s++)
if (!pos.square_is_empty(s))
put_piece(Piece(pos.piece_on(s) ^ 8), ~s);
2011-11-12 20:44:06 +01:00
// Side to move
sideToMove = ~pos.side_to_move();
2011-11-12 20:44:06 +01:00
// Castling rights
if (pos.can_castle(WHITE_OO))
set_castle_right(BLACK, ~pos.castle_rook_square(WHITE_OO));
if (pos.can_castle(WHITE_OOO))
set_castle_right(BLACK, ~pos.castle_rook_square(WHITE_OOO));
if (pos.can_castle(BLACK_OO))
set_castle_right(WHITE, ~pos.castle_rook_square(BLACK_OO));
if (pos.can_castle(BLACK_OOO))
set_castle_right(WHITE, ~pos.castle_rook_square(BLACK_OOO));
2011-11-12 20:44:06 +01:00
// En passant square
if (pos.st->epSquare != SQ_NONE)
st->epSquare = ~pos.st->epSquare;
2011-11-12 20:44:06 +01:00
// Checkers
st->checkersBB = attackers_to(king_square(sideToMove)) & pieces(~sideToMove);
2011-11-12 20:44:06 +01:00
// Hash keys
st->key = compute_key();
st->pawnKey = compute_pawn_key();
st->materialKey = compute_material_key();
// Incremental scores
st->value = compute_value();
// Material
st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
st->npMaterial[BLACK] = compute_non_pawn_material(BLACK);
assert(pos_is_ok());
2011-11-12 20:44:06 +01:00
}
/// Position::pos_is_ok() performs some consitency checks for the position object.
2011-11-12 20:44:06 +01:00
/// This is meant to be helpful when debugging.
bool Position::pos_is_ok(int* failedStep) const {
2011-11-12 20:44:06 +01:00
// What features of the position should be verified?
const bool debugAll = false;
const bool debugBitboards = debugAll || false;
const bool debugKingCount = debugAll || false;
const bool debugKingCapture = debugAll || false;
const bool debugCheckerCount = debugAll || false;
const bool debugKey = debugAll || false;
const bool debugMaterialKey = debugAll || false;
const bool debugPawnKey = debugAll || false;
const bool debugIncrementalEval = debugAll || false;
const bool debugNonPawnMaterial = debugAll || false;
const bool debugPieceCounts = debugAll || false;
const bool debugPieceList = debugAll || false;
const bool debugCastleSquares = debugAll || false;
if (failedStep) *failedStep = 1;
// Side to move OK?
if (sideToMove != WHITE && sideToMove != BLACK)
2011-11-12 20:44:06 +01:00
return false;
// Are the king squares in the position correct?
if (failedStep) (*failedStep)++;
if (piece_on(king_square(WHITE)) != W_KING)
2011-11-12 20:44:06 +01:00
return false;
if (failedStep) (*failedStep)++;
if (piece_on(king_square(BLACK)) != B_KING)
2011-11-12 20:44:06 +01:00
return false;
// Do both sides have exactly one king?
if (failedStep) (*failedStep)++;
if (debugKingCount)
{
int kingCount[2] = {0, 0};
for (Square s = SQ_A1; s <= SQ_H8; s++)
if (type_of(piece_on(s)) == KING)
kingCount[color_of(piece_on(s))]++;
2011-11-12 20:44:06 +01:00
if (kingCount[0] != 1 || kingCount[1] != 1)
return false;
}
// Can the side to move capture the opponent's king?
if (failedStep) (*failedStep)++;
if (debugKingCapture)
{
Color us = sideToMove;
Color them = ~us;
2011-11-12 20:44:06 +01:00
Square ksq = king_square(them);
if (attackers_to(ksq) & pieces(us))
2011-11-12 20:44:06 +01:00
return false;
}
// Is there more than 2 checkers?
if (failedStep) (*failedStep)++;
if (debugCheckerCount && popcount<Full>(st->checkersBB) > 2)
2011-11-12 20:44:06 +01:00
return false;
// Bitboards OK?
if (failedStep) (*failedStep)++;
if (debugBitboards)
{
// The intersection of the white and black pieces must be empty
if (!(pieces(WHITE) & pieces(BLACK)))
2011-11-12 20:44:06 +01:00
return false;
// The union of the white and black pieces must be equal to all
// occupied squares
if ((pieces(WHITE) | pieces(BLACK)) != occupied_squares())
2011-11-12 20:44:06 +01:00
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 && (pieces(p1) & pieces(p2)))
return false;
}
// En passant square OK?
if (failedStep) (*failedStep)++;
if (ep_square() != SQ_NONE)
{
// The en passant square must be on rank 6, from the point of view of the
// side to move.
if (relative_rank(sideToMove, ep_square()) != RANK_6)
2011-11-12 20:44:06 +01:00
return false;
}
// Hash key OK?
if (failedStep) (*failedStep)++;
if (debugKey && st->key != compute_key())
return false;
// Pawn hash key OK?
if (failedStep) (*failedStep)++;
if (debugPawnKey && st->pawnKey != compute_pawn_key())
return false;
// Material hash key OK?
if (failedStep) (*failedStep)++;
if (debugMaterialKey && st->materialKey != compute_material_key())
return false;
// Incremental eval OK?
if (failedStep) (*failedStep)++;
if (debugIncrementalEval && st->value != compute_value())
return false;
// Non-pawn material OK?
if (failedStep) (*failedStep)++;
if (debugNonPawnMaterial)
{
if (st->npMaterial[WHITE] != compute_non_pawn_material(WHITE))
return false;
if (st->npMaterial[BLACK] != compute_non_pawn_material(BLACK))
return false;
}
// Piece counts OK?
if (failedStep) (*failedStep)++;
if (debugPieceCounts)
for (Color c = WHITE; c <= BLACK; c++)
for (PieceType pt = PAWN; pt <= KING; pt++)
if (pieceCount[c][pt] != popcount<Full>(pieces(pt, c)))
2011-11-12 20:44:06 +01:00
return false;
if (failedStep) (*failedStep)++;
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 (piece_on(piece_list(c, pt)[i]) != make_piece(c, pt))
2011-11-12 20:44:06 +01:00
return false;
if (index[piece_list(c, pt)[i]] != i)
2011-11-12 20:44:06 +01:00
return false;
}
if (failedStep) (*failedStep)++;
if (debugCastleSquares)
for (CastleRight f = WHITE_OO; f <= BLACK_OOO; f = CastleRight(f << 1))
2011-11-12 20:44:06 +01:00
{
if (!can_castle(f))
continue;
Piece rook = (f & (WHITE_OO | WHITE_OOO) ? W_ROOK : B_ROOK);
2011-11-12 20:44:06 +01:00
if ( castleRightsMask[castleRookSquare[f]] != (ALL_CASTLES ^ f)
|| piece_on(castleRookSquare[f]) != rook)
2011-11-12 20:44:06 +01:00
return false;
}
if (failedStep) *failedStep = 0;
return true;
}