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BadFish/src/position.cpp
Marco Costalba 9446dd6da3 Move gamePly among the StateInfo data 
No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
2010-05-31 12:09:18 +01:00

2013 lines
60 KiB
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/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
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/>.
*/
////
//// Includes
////
#include <cassert>
#include <cstring>
#include <fstream>
#include <iostream>
#include "bitcount.h"
#include "mersenne.h"
#include "movegen.h"
#include "movepick.h"
#include "position.h"
#include "psqtab.h"
#include "san.h"
#include "tt.h"
#include "ucioption.h"
using std::string;
////
//// Variables
////
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];
static bool RequestPending = false;
/// Constructors
CheckInfo::CheckInfo(const Position& pos) {
Color us = pos.side_to_move();
Color them = opposite_color(us);
ksq = pos.king_square(them);
dcCandidates = pos.discovered_check_candidates(us);
checkSq[PAWN] = pos.attacks_from<PAWN>(ksq, them);
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] = EmptyBoardBB;
}
/// Position c'tors. Here we always create a slower but safer copy of
/// the original position or the FEN string, we want the new born Position
/// object do not depend on any external data. Instead if we know what we
/// are doing and we need speed we can create a position with default
/// c'tor Position() and then use just fast_copy().
Position::Position() {}
Position::Position(const Position& pos) {
memcpy(this, &pos, sizeof(Position));
detach(); // Always detach() in copy c'tor to avoid surprises
}
Position::Position(const string& fen) {
from_fen(fen);
}
/// Position::detach() copies the content of the current state and castling
/// masks inside the position itself. This is needed when the st pointee could
/// become stale, as example because the caller is about to going out of scope.
void Position::detach() {
startState = *st;
st = &startState;
st->previous = NULL; // as a safe guard
}
/// 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& fen) {
static const string pieceLetters = "KQRBNPkqrbnp";
static const Piece pieces[] = { WK, WQ, WR, WB, WN, WP, BK, BQ, BR, BB, BN, BP };
clear();
// Board
Rank rank = RANK_8;
File file = FILE_A;
size_t i = 0;
for ( ; fen[i] != ' '; i++)
{
if (isdigit(fen[i]))
{
// Skip the given number of files
file += (fen[i] - '1' + 1);
continue;
}
else if (fen[i] == '/')
{
file = FILE_A;
rank--;
continue;
}
size_t idx = pieceLetters.find(fen[i]);
if (idx == string::npos)
{
std::cout << "Error in FEN at character " << i << std::endl;
return;
}
Square square = make_square(file, rank);
put_piece(pieces[idx], square);
file++;
}
// Side to move
i++;
if (fen[i] != 'w' && fen[i] != 'b')
{
std::cout << "Error in FEN at character " << i << std::endl;
return;
}
sideToMove = (fen[i] == 'w' ? WHITE : BLACK);
// 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') allow_oo(WHITE);
else if (fen[i] == 'Q') allow_ooo(WHITE);
else if (fen[i] == 'k') allow_oo(BLACK);
else if (fen[i] == 'q') 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 (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) {
allow_ooo(WHITE);
initialQRFile = rookFile;
}
else {
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 (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) {
allow_ooo(BLACK);
initialQRFile = rookFile;
}
else {
allow_oo(BLACK);
initialKRFile = rookFile;
}
}
else {
std::cout << "Error in FEN at character " << i << std::endl;
return;
}
i++;
}
// Skip blanks
while (fen[i] == ' ')
i++;
// En passant square -- ignore if no capture is possible
if ( i <= fen.length() - 2
&& (fen[i] >= 'a' && fen[i] <= 'h')
&& (fen[i+1] == '3' || fen[i+1] == '6'))
{
Square fenEpSquare = square_from_string(fen.substr(i, 2));
Color them = opposite_color(sideToMove);
if (attacks_from<PAWN>(fenEpSquare, them) & this->pieces(PAWN, sideToMove))
st->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;
find_checkers();
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);
}
/// Position::to_fen() converts the position object to a FEN string. This is
/// probably only useful for debugging.
const string Position::to_fen() const {
static const string pieceLetters = " PNBRQK pnbrqk";
string fen;
int skip;
for (Rank rank = RANK_8; rank >= RANK_1; rank--)
{
skip = 0;
for (File file = FILE_A; file <= FILE_H; file++)
{
Square sq = make_square(file, rank);
if (!square_is_occupied(sq))
{ skip++;
continue;
}
if (skip > 0)
{
fen += (char)skip + '0';
skip = 0;
}
fen += pieceLetters[piece_on(sq)];
}
if (skip > 0)
fen += (char)skip + '0';
fen += (rank > RANK_1 ? '/' : ' ');
}
fen += (sideToMove == WHITE ? "w " : "b ");
if (st->castleRights != NO_CASTLES)
{
if (initialKFile == FILE_E && initialQRFile == FILE_A && initialKRFile == FILE_H)
{
if (can_castle_kingside(WHITE)) fen += 'K';
if (can_castle_queenside(WHITE)) fen += 'Q';
if (can_castle_kingside(BLACK)) fen += 'k';
if (can_castle_queenside(BLACK)) fen += 'q';
}
else
{
if (can_castle_kingside(WHITE))
fen += char(toupper(file_to_char(initialKRFile)));
if (can_castle_queenside(WHITE))
fen += char(toupper(file_to_char(initialQRFile)));
if (can_castle_kingside(BLACK))
fen += file_to_char(initialKRFile);
if (can_castle_queenside(BLACK))
fen += file_to_char(initialQRFile);
}
} else
fen += '-';
fen += ' ';
if (ep_square() != SQ_NONE)
fen += square_to_string(ep_square());
else
fen += '-';
return fen;
}
/// Position::print() prints an ASCII representation of the position to
/// the standard output. If a move is given then also the san is print.
void Position::print(Move m) const {
static const string pieceLetters = " PNBRQK PNBRQK .";
// Check for reentrancy, as example when called from inside
// MovePicker that is used also here in move_to_san()
if (RequestPending)
return;
RequestPending = true;
std::cout << std::endl;
if (m != MOVE_NONE)
{
Position p(*this);
string col = (color_of_piece_on(move_from(m)) == BLACK ? ".." : "");
std::cout << "Move is: " << col << move_to_san(p, m) << std::endl;
}
for (Rank rank = RANK_8; rank >= RANK_1; rank--)
{
std::cout << "+---+---+---+---+---+---+---+---+" << std::endl;
for (File file = FILE_A; file <= FILE_H; file++)
{
Square sq = make_square(file, rank);
Piece piece = piece_on(sq);
if (piece == EMPTY && square_color(sq) == WHITE)
piece = NO_PIECE;
char col = (color_of_piece_on(sq) == BLACK ? '=' : ' ');
std::cout << '|' << col << pieceLetters[piece] << col;
}
std::cout << '|' << std::endl;
}
std::cout << "+---+---+---+---+---+---+---+---+" << std::endl
<< "Fen is: " << to_fen() << std::endl
<< "Key is: " << st->key << std::endl;
RequestPending = false;
}
/// Position:hidden_checkers<>() returns a bitboard of all pinned (against the
/// king) pieces for the given color and for the given pinner type. Or, when
/// template parameter FindPinned is false, the pieces of the given color
/// candidate for a discovery check against the enemy king.
/// Bitboard checkersBB must be already updated when looking for pinners.
template<bool FindPinned>
Bitboard Position::hidden_checkers(Color c) const {
Bitboard result = EmptyBoardBB;
Bitboard pinners = pieces_of_color(FindPinned ? opposite_color(c) : c);
// Pinned pieces protect our king, dicovery checks attack
// the enemy king.
Square ksq = king_square(FindPinned ? c : opposite_color(c));
// Pinners are sliders, not checkers, that give check when candidate pinned is removed
pinners &= (pieces(ROOK, QUEEN) & RookPseudoAttacks[ksq]) | (pieces(BISHOP, QUEEN) & BishopPseudoAttacks[ksq]);
if (FindPinned && pinners)
pinners &= ~st->checkersBB;
while (pinners)
{
Square s = pop_1st_bit(&pinners);
Bitboard b = squares_between(s, ksq) & occupied_squares();
assert(b);
if ( !(b & (b - 1)) // Only one bit set?
&& (b & pieces_of_color(c))) // Is an our piece?
result |= b;
}
return result;
}
/// Position:pinned_pieces() returns a bitboard of all pinned (against the
/// king) pieces for the given color. Note that checkersBB bitboard must
/// be already updated.
Bitboard Position::pinned_pieces(Color c) const {
return hidden_checkers<true>(c);
}
/// Position:discovered_check_candidates() returns a bitboard containing all
/// pieces for the given side which are candidates for giving a discovered
/// check. Contrary to pinned_pieces() here there is no need of checkersBB
/// to be already updated.
Bitboard Position::discovered_check_candidates(Color c) const {
return hidden_checkers<false>(c);
}
/// Position::attackers_to() computes a bitboard containing all pieces which
/// attacks a given square.
Bitboard Position::attackers_to(Square s) const {
return (attacks_from<PAWN>(s, BLACK) & pieces(PAWN, WHITE))
| (attacks_from<PAWN>(s, WHITE) & pieces(PAWN, BLACK))
| (attacks_from<KNIGHT>(s) & pieces(KNIGHT))
| (attacks_from<ROOK>(s) & pieces(ROOK, QUEEN))
| (attacks_from<BISHOP>(s) & pieces(BISHOP, QUEEN))
| (attacks_from<KING>(s) & pieces(KING));
}
/// Position::attacks_from() computes a bitboard of all attacks
/// of a given piece put in a given square.
Bitboard Position::attacks_from(Piece p, Square s) const {
assert(square_is_ok(s));
switch (p)
{
case WP: return attacks_from<PAWN>(s, WHITE);
case BP: return attacks_from<PAWN>(s, BLACK);
case WN: case BN: return attacks_from<KNIGHT>(s);
case WB: case BB: return attacks_from<BISHOP>(s);
case WR: case BR: return attacks_from<ROOK>(s);
case WQ: case BQ: return attacks_from<QUEEN>(s);
case WK: case BK: return attacks_from<KING>(s);
default: break;
}
return false;
}
/// 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(move_is_ok(m));
assert(square_is_ok(s));
Square f = move_from(m), t = move_to(m);
assert(square_is_occupied(f));
if (bit_is_set(attacks_from(piece_on(f), t), s))
return true;
// Move the piece and scan for X-ray attacks behind it
Bitboard occ = occupied_squares();
Color us = color_of_piece_on(f);
clear_bit(&occ, f);
set_bit(&occ, t);
Bitboard xray = ( (rook_attacks_bb(s, occ) & pieces(ROOK, QUEEN))
|(bishop_attacks_bb(s, occ) & pieces(BISHOP, QUEEN))) & pieces_of_color(us);
// If we have attacks we need to verify that are caused by our move
// and are not already existent ones.
return xray && (xray ^ (xray & attacks_from<QUEEN>(s)));
}
/// 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::attackers_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() {
Color us = side_to_move();
st->checkersBB = attackers_to(king_square(us)) & pieces_of_color(opposite_color(us));
}
/// 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());
assert(move_is_ok(m));
assert(pinned == pinned_pieces(side_to_move()));
// Castling moves are checked for legality during move generation.
if (move_is_castle(m))
return true;
Color us = side_to_move();
Square from = move_from(m);
assert(color_of_piece_on(from) == us);
assert(piece_on(king_square(us)) == piece_of_color_and_type(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 (move_is_ep(m))
{
Color them = opposite_color(us);
Square to = move_to(m);
Square capsq = make_square(square_file(to), square_rank(from));
Bitboard b = occupied_squares();
Square ksq = king_square(us);
assert(to == ep_square());
assert(piece_on(from) == piece_of_color_and_type(us, PAWN));
assert(piece_on(capsq) == piece_of_color_and_type(them, PAWN));
assert(piece_on(to) == EMPTY);
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.
if (type_of_piece_on(from) == KING)
return !(attackers_to(move_to(m)) & pieces_of_color(opposite_color(us)));
// 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)
|| (direction_between_squares(from, king_square(us)) == direction_between_squares(move_to(m), king_square(us))));
}
/// Position::pl_move_is_evasion() tests whether a pseudo-legal move is a legal evasion
bool Position::pl_move_is_evasion(Move m, Bitboard pinned) const
{
assert(is_check());
Color us = side_to_move();
Square from = move_from(m);
Square to = move_to(m);
// King moves and en-passant captures are verified in pl_move_is_legal()
if (type_of_piece_on(from) == KING || move_is_ep(m))
return pl_move_is_legal(m, pinned);
Bitboard target = checkers();
Square checksq = pop_1st_bit(&target);
if (target) // double check ?
return false;
// Our move must be a blocking evasion or a capture of the checking piece
target = squares_between(checksq, king_square(us)) | checkers();
return bit_is_set(target, to) && pl_move_is_legal(m, pinned);
}
/// Position::move_is_check() tests whether a pseudo-legal move is a check
bool Position::move_is_check(Move m) const {
return move_is_check(m, CheckInfo(*this));
}
bool Position::move_is_check(Move m, const CheckInfo& ci) const {
assert(is_ok());
assert(move_is_ok(m));
assert(ci.dcCandidates == discovered_check_candidates(side_to_move()));
assert(color_of_piece_on(move_from(m)) == side_to_move());
assert(piece_on(ci.ksq) == piece_of_color_and_type(opposite_color(side_to_move()), KING));
Square from = move_from(m);
Square to = move_to(m);
PieceType pt = type_of_piece_on(from);
// 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)
||(direction_between_squares(from, ci.ksq) != direction_between_squares(to, ci.ksq)))
return true;
}
// Can we skip the ugly special cases ?
if (!move_is_special(m))
return false;
Color us = side_to_move();
Bitboard b = occupied_squares();
// Promotion with check ?
if (move_is_promotion(m))
{
clear_bit(&b, from);
switch (move_promotion_piece(m))
{
case KNIGHT:
return bit_is_set(attacks_from<KNIGHT>(to), ci.ksq);
case BISHOP:
return bit_is_set(bishop_attacks_bb(to, b), ci.ksq);
case ROOK:
return bit_is_set(rook_attacks_bb(to, b), ci.ksq);
case QUEEN:
return bit_is_set(queen_attacks_bb(to, b), ci.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.
if (move_is_ep(m))
{
Square capsq = make_square(square_file(to), square_rank(from));
clear_bit(&b, from);
clear_bit(&b, capsq);
set_bit(&b, to);
return (rook_attacks_bb(ci.ksq, b) & pieces(ROOK, QUEEN, us))
||(bishop_attacks_bb(ci.ksq, b) & pieces(BISHOP, QUEEN, us));
}
// Castling with check ?
if (move_is_castle(m))
{
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), ci.ksq);
}
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_is_check(m, ci));
}
void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveIsCheck) {
assert(is_ok());
assert(move_is_ok(m));
Key key = st->key;
// 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.
struct ReducedStateInfo {
Key pawnKey, materialKey;
int castleRights, rule50, gamePly, pliesFromNull;
Square epSquare;
Score value;
Value npMaterial[2];
};
memcpy(&newSt, st, sizeof(ReducedStateInfo));
newSt.previous = st;
st = &newSt;
// Save the current key to the history[] array, in order to be able to
// detect repetition draws.
history[st->gamePly++] = key;
// Update side to move
key ^= zobSideToMove;
// 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 (move_is_castle(m))
{
st->key = key;
do_castle_move(m);
return;
}
Color us = side_to_move();
Color them = opposite_color(us);
Square from = move_from(m);
Square to = move_to(m);
bool ep = move_is_ep(m);
bool pm = move_is_promotion(m);
Piece piece = piece_on(from);
PieceType pt = type_of_piece(piece);
PieceType capture = ep ? PAWN : type_of_piece_on(to);
assert(color_of_piece_on(from) == us);
assert(color_of_piece_on(to) == them || square_is_empty(to));
assert(!(ep || pm) || piece == piece_of_color_and_type(us, PAWN));
assert(!pm || relative_rank(us, to) == RANK_8);
if (capture)
do_capture_move(key, capture, them, to, ep);
// Update hash key
key ^= zobrist[us][pt][from] ^ zobrist[us][pt][to];
// Reset en passant square
if (st->epSquare != SQ_NONE)
{
key ^= zobEp[st->epSquare];
st->epSquare = SQ_NONE;
}
// Update castle rights, try to shortcut a common case
int cm = castleRightsMask[from] & castleRightsMask[to];
if (cm != ALL_CASTLES && ((cm & st->castleRights) != st->castleRights))
{
key ^= zobCastle[st->castleRights];
st->castleRights &= castleRightsMask[from];
st->castleRights &= castleRightsMask[to];
key ^= zobCastle[st->castleRights];
}
// Prefetch TT access as soon as we know key is updated
TT.prefetch(key);
// 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(&(byTypeBB[0]), move_bb); // HACK: byTypeBB[0] == occupied squares
board[to] = board[from];
board[from] = EMPTY;
// Update piece lists, note that index[from] is not updated and
// becomes stale. This works as long as index[] is accessed just
// by known occupied squares.
index[to] = index[from];
pieceList[us][pt][index[to]] = to;
// If the moving piece was a pawn do some special extra work
if (pt == PAWN)
{
// Reset rule 50 draw counter
st->rule50 = 0;
// Update pawn hash key
st->pawnKey ^= zobrist[us][PAWN][from] ^ zobrist[us][PAWN][to];
// Set en passant square, only if moved pawn can be captured
if ((to ^ from) == 16)
{
if (attacks_from<PAWN>(from + (us == WHITE ? DELTA_N : DELTA_S), us) & pieces(PAWN, them))
{
st->epSquare = Square((int(from) + int(to)) / 2);
key ^= zobEp[st->epSquare];
}
}
if (pm) // promotion ?
{
PieceType promotion = move_promotion_piece(m);
assert(promotion >= KNIGHT && promotion <= QUEEN);
// Insert promoted piece instead of pawn
clear_bit(&(byTypeBB[PAWN]), to);
set_bit(&(byTypeBB[promotion]), to);
board[to] = piece_of_color_and_type(us, promotion);
// Update piece counts
pieceCount[us][promotion]++;
pieceCount[us][PAWN]--;
// Update material key
st->materialKey ^= zobrist[us][PAWN][pieceCount[us][PAWN]];
st->materialKey ^= zobrist[us][promotion][pieceCount[us][promotion]-1];
// Update piece lists, move the last pawn at index[to] position
// and shrink the list. Add a new promotion piece to the list.
Square lastPawnSquare = pieceList[us][PAWN][pieceCount[us][PAWN]];
index[lastPawnSquare] = index[to];
pieceList[us][PAWN][index[lastPawnSquare]] = lastPawnSquare;
pieceList[us][PAWN][pieceCount[us][PAWN]] = SQ_NONE;
index[to] = pieceCount[us][promotion] - 1;
pieceList[us][promotion][index[to]] = to;
// Partially revert hash keys update
key ^= zobrist[us][PAWN][to] ^ zobrist[us][promotion][to];
st->pawnKey ^= zobrist[us][PAWN][to];
// Partially revert and update incremental scores
st->value -= pst(us, PAWN, to);
st->value += pst(us, promotion, to);
// Update material
st->npMaterial[us] += piece_value_midgame(promotion);
}
}
// Update incremental scores
st->value += pst_delta(piece, from, to);
// Set capture piece
st->capture = capture;
// Update the key with the final value
st->key = key;
// Update checkers bitboard, piece must be already moved
st->checkersBB = EmptyBoardBB;
if (moveIsCheck)
{
if (ep | pm)
st->checkersBB = attackers_to(king_square(them)) & pieces_of_color(us);
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>(ci.ksq) & pieces(ROOK, QUEEN, us));
if (pt != BISHOP)
st->checkersBB |= (attacks_from<BISHOP>(ci.ksq) & pieces(BISHOP, QUEEN, us));
}
}
}
// Finish
sideToMove = opposite_color(sideToMove);
st->value += (sideToMove == WHITE ? TempoValue : -TempoValue);
assert(is_ok());
}
/// Position::do_capture_move() is a private method used to update captured
/// piece info. It is called from the main Position::do_move function.
void Position::do_capture_move(Key& key, PieceType capture, Color them, Square to, bool ep) {
assert(capture != KING);
Square capsq = to;
// If the captured piece was a pawn, update pawn hash key,
// otherwise update non-pawn material.
if (capture == PAWN)
{
if (ep) // en passant ?
{
capsq = (them == BLACK)? (to - DELTA_N) : (to - DELTA_S);
assert(to == st->epSquare);
assert(relative_rank(opposite_color(them), to) == RANK_6);
assert(piece_on(to) == EMPTY);
assert(piece_on(capsq) == piece_of_color_and_type(them, PAWN));
board[capsq] = EMPTY;
}
st->pawnKey ^= zobrist[them][PAWN][capsq];
}
else
st->npMaterial[them] -= piece_value_midgame(capture);
// Remove captured piece
clear_bit(&(byColorBB[them]), capsq);
clear_bit(&(byTypeBB[capture]), capsq);
clear_bit(&(byTypeBB[0]), capsq);
// Update hash key
key ^= zobrist[them][capture][capsq];
// Update incremental scores
st->value -= pst(them, capture, capsq);
// Update piece count
pieceCount[them][capture]--;
// Update material hash key
st->materialKey ^= zobrist[them][capture][pieceCount[them][capture]];
// Update piece list, move the last piece at index[capsq] position
//
// WARNING: This is a not perfectly 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 lastPieceSquare = pieceList[them][capture][pieceCount[them][capture]];
index[lastPieceSquare] = index[capsq];
pieceList[them][capture][index[lastPieceSquare]] = lastPieceSquare;
pieceList[them][capture][pieceCount[them][capture]] = SQ_NONE;
// Reset rule 50 counter
st->rule50 = 0;
}
/// 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) {
assert(move_is_ok(m));
assert(move_is_castle(m));
Color us = side_to_move();
Color them = opposite_color(us);
// Reset capture field
st->capture = NO_PIECE_TYPE;
// Find source squares for king and rook
Square kfrom = move_from(m);
Square rfrom = move_to(m); // HACK: See comment at beginning of function
Square kto, rto;
assert(piece_on(kfrom) == piece_of_color_and_type(us, KING));
assert(piece_on(rfrom) == piece_of_color_and_type(us, ROOK));
// 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
Piece king = piece_of_color_and_type(us, KING);
Piece rook = piece_of_color_and_type(us, ROOK);
board[kfrom] = board[rfrom] = EMPTY;
board[kto] = king;
board[rto] = rook;
// Update piece lists
pieceList[us][KING][index[kfrom]] = kto;
pieceList[us][ROOK][index[rfrom]] = rto;
int tmp = index[rfrom]; // In Chess960 could be rto == kfrom
index[kto] = index[kfrom];
index[rto] = tmp;
// 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];
// Reset rule 50 counter
st->rule50 = 0;
// Update checkers BB
st->checkersBB = attackers_to(king_square(them)) & pieces_of_color(us);
// Finish
sideToMove = opposite_color(sideToMove);
st->value += (sideToMove == WHITE ? TempoValue : -TempoValue);
assert(is_ok());
}
/// 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());
assert(move_is_ok(m));
sideToMove = opposite_color(sideToMove);
if (move_is_castle(m))
{
undo_castle_move(m);
return;
}
Color us = side_to_move();
Color them = opposite_color(us);
Square from = move_from(m);
Square to = move_to(m);
bool ep = move_is_ep(m);
bool pm = move_is_promotion(m);
PieceType pt = type_of_piece_on(to);
assert(square_is_empty(from));
assert(color_of_piece_on(to) == us);
assert(!pm || relative_rank(us, to) == RANK_8);
assert(!ep || to == st->previous->epSquare);
assert(!ep || relative_rank(us, to) == RANK_6);
assert(!ep || piece_on(to) == piece_of_color_and_type(us, PAWN));
if (pm) // promotion ?
{
PieceType promotion = move_promotion_piece(m);
pt = PAWN;
assert(promotion >= KNIGHT && promotion <= QUEEN);
assert(piece_on(to) == piece_of_color_and_type(us, promotion));
// Replace promoted piece with a pawn
clear_bit(&(byTypeBB[promotion]), to);
set_bit(&(byTypeBB[PAWN]), to);
// Update piece counts
pieceCount[us][promotion]--;
pieceCount[us][PAWN]++;
// Update piece list replacing promotion piece with a pawn
Square lastPromotionSquare = pieceList[us][promotion][pieceCount[us][promotion]];
index[lastPromotionSquare] = index[to];
pieceList[us][promotion][index[lastPromotionSquare]] = lastPromotionSquare;
pieceList[us][promotion][pieceCount[us][promotion]] = SQ_NONE;
index[to] = pieceCount[us][PAWN] - 1;
pieceList[us][PAWN][index[to]] = to;
}
// 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(&(byTypeBB[0]), move_bb); // HACK: byTypeBB[0] == occupied squares
board[from] = piece_of_color_and_type(us, pt);
board[to] = EMPTY;
// Update piece list
index[from] = index[to];
pieceList[us][pt][index[from]] = from;
if (st->capture)
{
Square capsq = to;
if (ep)
capsq = (us == WHITE)? (to - DELTA_N) : (to - DELTA_S);
assert(st->capture != KING);
assert(!ep || square_is_empty(capsq));
// Restore the captured piece
set_bit(&(byColorBB[them]), capsq);
set_bit(&(byTypeBB[st->capture]), capsq);
set_bit(&(byTypeBB[0]), capsq);
board[capsq] = piece_of_color_and_type(them, st->capture);
// Update piece count
pieceCount[them][st->capture]++;
// Update piece list, add a new captured piece in capsq square
index[capsq] = pieceCount[them][st->capture] - 1;
pieceList[them][st->capture][index[capsq]] = capsq;
}
// Finally point our state pointer back to the previous state
st = st->previous;
assert(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) {
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.
Color us = side_to_move();
// Find source squares for king and rook
Square kfrom = move_from(m);
Square rfrom = move_to(m); // HACK: See comment at beginning of function
Square kto, rto;
// 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(piece_on(kto) == piece_of_color_and_type(us, KING));
assert(piece_on(rto) == piece_of_color_and_type(us, ROOK));
// 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] = piece_of_color_and_type(us, ROOK);
board[kfrom] = piece_of_color_and_type(us, KING);
// Update piece lists
pieceList[us][KING][index[kto]] = kfrom;
pieceList[us][ROOK][index[rto]] = rfrom;
int tmp = index[rto]; // In Chess960 could be rto == kfrom
index[kfrom] = index[kto];
index[rfrom] = tmp;
// Finally point our state pointer back to the previous state
st = st->previous;
assert(is_ok());
}
/// 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(StateInfo& backupSt) {
assert(is_ok());
assert(!is_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 a new state to be used.
backupSt.key = st->key;
backupSt.epSquare = st->epSquare;
backupSt.value = st->value;
backupSt.previous = st->previous;
backupSt.pliesFromNull = st->pliesFromNull;
st->previous = &backupSt;
// Save the current key to the history[] array, in order to be able to
// detect repetition draws.
history[st->gamePly++] = st->key;
// Update the necessary information
if (st->epSquare != SQ_NONE)
st->key ^= zobEp[st->epSquare];
st->key ^= zobSideToMove;
TT.prefetch(st->key);
sideToMove = opposite_color(sideToMove);
st->epSquare = SQ_NONE;
st->rule50++;
st->pliesFromNull = 0;
st->value += (sideToMove == WHITE) ? TempoValue : -TempoValue;
}
/// Position::undo_null_move() unmakes a "null move".
void Position::undo_null_move() {
assert(is_ok());
assert(!is_check());
// Restore information from the our backup StateInfo object
StateInfo* backupSt = st->previous;
st->key = backupSt->key;
st->epSquare = backupSt->epSquare;
st->value = backupSt->value;
st->previous = backupSt->previous;
st->pliesFromNull = backupSt->pliesFromNull;
// Update the necessary information
sideToMove = opposite_color(sideToMove);
st->rule50--;
st->gamePly--;
}
/// 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(Square to) const {
assert(square_is_ok(to));
return see(SQ_NONE, to);
}
int Position::see(Move m) const {
assert(move_is_ok(m));
return see(move_from(m), move_to(m));
}
int Position::see_sign(Move m) const {
assert(move_is_ok(m));
Square from = move_from(m);
Square to = move_to(m);
// Early return if SEE cannot be negative because capturing piece value
// is not bigger then captured one.
if ( midgame_value_of_piece_on(from) <= midgame_value_of_piece_on(to)
&& type_of_piece_on(from) != KING)
return 1;
return see(from, to);
}
int Position::see(Square from, Square to) const {
// Material values
static const int seeValues[18] = {
0, PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
RookValueMidgame, QueenValueMidgame, QueenValueMidgame*10, 0,
0, PawnValueMidgame, KnightValueMidgame, BishopValueMidgame,
RookValueMidgame, QueenValueMidgame, QueenValueMidgame*10, 0,
0, 0
};
Bitboard attackers, stmAttackers, b;
assert(square_is_ok(from) || from == SQ_NONE);
assert(square_is_ok(to));
// Initialize colors
Color us = (from != SQ_NONE ? color_of_piece_on(from) : opposite_color(color_of_piece_on(to)));
Color them = opposite_color(us);
// Initialize pieces
Piece piece = piece_on(from);
Piece capture = piece_on(to);
Bitboard occ = occupied_squares();
// King cannot be recaptured
if (type_of_piece(piece) == KING)
return seeValues[capture];
// Handle en passant moves
if (st->epSquare == to && type_of_piece_on(from) == PAWN)
{
assert(capture == EMPTY);
Square capQq = (side_to_move() == WHITE)? (to - DELTA_N) : (to - DELTA_S);
capture = piece_on(capQq);
assert(type_of_piece_on(capQq) == PAWN);
// Remove the captured pawn
clear_bit(&occ, capQq);
}
while (true)
{
// 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 = (rook_attacks_bb(to, occ) & pieces(ROOK, QUEEN))
| (bishop_attacks_bb(to, occ) & pieces(BISHOP, QUEEN))
| (attacks_from<KNIGHT>(to) & pieces(KNIGHT))
| (attacks_from<KING>(to) & pieces(KING))
| (attacks_from<PAWN>(to, WHITE) & pieces(PAWN, BLACK))
| (attacks_from<PAWN>(to, BLACK) & pieces(PAWN, WHITE));
if (from != SQ_NONE)
break;
// If we don't have any attacker we are finished
if ((attackers & pieces_of_color(us)) == EmptyBoardBB)
return 0;
// Locate the least valuable attacker to the destination square
// and use it to initialize from square.
stmAttackers = attackers & pieces_of_color(us);
PieceType pt;
for (pt = PAWN; !(stmAttackers & pieces(pt)); pt++)
assert(pt < KING);
from = first_1(stmAttackers & pieces(pt));
piece = piece_on(from);
}
// If the opponent has no attackers we are finished
stmAttackers = attackers & pieces_of_color(them);
if (!stmAttackers)
return seeValues[capture];
attackers &= occ; // Remove the moving piece
// 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.
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; !(stmAttackers & pieces(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 = stmAttackers & pieces(pt);
occ ^= (b & (~b + 1));
attackers |= (rook_attacks_bb(to, occ) & pieces(ROOK, QUEEN))
| (bishop_attacks_bb(to, occ) & pieces(BISHOP, QUEEN));
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);
stmAttackers = attackers & pieces_of_color(c);
// Stop after a king capture
if (pt == KING && stmAttackers)
{
assert(n < 32);
swapList[n++] = 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 (--n)
swapList[n-1] = Min(-swapList[n], swapList[n-1]);
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 < 64; i++)
board[i] = EMPTY;
for (int i = 0; i < 8; i++)
for (int j = 0; j < 16; j++)
pieceList[0][i][j] = pieceList[1][i][j] = SQ_NONE;
sideToMove = WHITE;
initialKFile = FILE_E;
initialKRFile = FILE_H;
initialQRFile = FILE_A;
}
/// 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() {
st->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]++;
}
/// 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) {
st->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) {
st->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 (square_is_occupied(s))
result ^= zobrist[color_of_piece_on(s)][type_of_piece_on(s)][s];
if (ep_square() != SQ_NONE)
result ^= zobEp[ep_square()];
result ^= zobCastle[st->castleRights];
if (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 = pieces(PAWN, 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 = piece_count(c, pt);
for (int i = 0; i < count; i++)
result ^= zobrist[c][pt][i];
}
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 {
Score result = make_score(0, 0);
Bitboard b;
Square s;
for (Color c = WHITE; c <= BLACK; c++)
for (PieceType pt = PAWN; pt <= KING; pt++)
{
b = pieces(pt, c);
while (b)
{
s = pop_1st_bit(&b);
assert(piece_on(s) == piece_of_color_and_type(c, pt));
result += pst(c, pt, s);
}
}
result += (side_to_move() == WHITE ? TempoValue / 2 : -TempoValue / 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);
for (PieceType pt = KNIGHT; pt <= QUEEN; pt++)
{
Bitboard b = pieces(pt, c);
while (b)
{
assert(piece_on(first_1(b)) == piece_of_color_and_type(c, pt));
pop_1st_bit(&b);
result += piece_value_midgame(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.
// FIXME: Currently we are not handling 50 move rule correctly when in check
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 > 100 || (st->rule50 == 100 && !is_check()))
return true;
// Draw by repetition?
for (int i = 4, e = Min(Min(st->gamePly, st->rule50), st->pliesFromNull); i <= e; i += 2)
if (history[st->gamePly - i] == st->key)
return true;
return false;
}
/// Position::is_mate() returns true or false depending on whether the
/// side to move is checkmated.
bool Position::is_mate() const {
MoveStack moves[256];
return is_check() && (generate_moves(*this, moves, false) == moves);
}
/// Position::has_mate_threat() tests whether a given color has a mate in one
/// from the current position.
bool Position::has_mate_threat(Color c) {
StateInfo st1, st2;
Color stm = side_to_move();
if (is_check())
return false;
// If the input color is not equal to the side to move, do a null move
if (c != stm)
do_null_move(st1);
MoveStack mlist[120];
bool result = false;
Bitboard pinned = pinned_pieces(sideToMove);
// Generate pseudo-legal non-capture and capture check moves
MoveStack* last = generate_non_capture_checks(*this, mlist);
last = generate_captures(*this, last);
// Loop through the moves, and see if one of them is mate
for (MoveStack* cur = mlist; cur != last; cur++)
{
Move move = cur->move;
if (!pl_move_is_legal(move, pinned))
continue;
do_move(move, st2);
if (is_mate())
result = true;
undo_move(move);
}
// Undo null move, if necessary
if (c != stm)
undo_null_move();
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();
zobExclusion = genrand_int64();
}
/// 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);
PieceSquareTable[p][s] = make_score(MgPST[p][s] + i, EgPST[p][s] + i);
}
for (Square s = SQ_A1; s <= SQ_H8; s++)
for (Piece p = BP; p <= BK; p++)
PieceSquareTable[p][s] = -PieceSquareTable[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());
clear();
// Board
for (Square s = SQ_A1; s <= SQ_H8; s++)
if (!pos.square_is_empty(s))
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)) allow_oo(BLACK);
if (pos.can_castle_queenside(WHITE)) allow_ooo(BLACK);
if (pos.can_castle_kingside(BLACK)) allow_oo(WHITE);
if (pos.can_castle_queenside(BLACK)) 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.st->epSquare != SQ_NONE)
st->epSquare = flip_square(pos.st->epSquare);
// Checkers
find_checkers();
// 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(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(int* failedStep) 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;
static const bool debugCastleSquares = false;
if (failedStep) *failedStep = 1;
// Side to move OK?
if (!color_is_ok(side_to_move()))
return false;
// Are the king squares in the position correct?
if (failedStep) (*failedStep)++;
if (piece_on(king_square(WHITE)) != WK)
return false;
if (failedStep) (*failedStep)++;
if (piece_on(king_square(BLACK)) != BK)
return false;
// Castle files OK?
if (failedStep) (*failedStep)++;
if (!file_is_ok(initialKRFile))
return false;
if (!file_is_ok(initialQRFile))
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)]++;
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 = side_to_move();
Color them = opposite_color(us);
Square ksq = king_square(them);
if (attackers_to(ksq) & pieces_of_color(us))
return false;
}
// Is there more than 2 checkers?
if (failedStep) (*failedStep)++;
if (debugCheckerCount && count_1s(st->checkersBB) > 2)
return false;
// Bitboards OK?
if (failedStep) (*failedStep)++;
if (debugBitboards)
{
// The intersection of the white and black pieces must be empty
if ((pieces_of_color(WHITE) & pieces_of_color(BLACK)) != EmptyBoardBB)
return false;
// The union of the white and black pieces must be equal to all
// occupied squares
if ((pieces_of_color(WHITE) | pieces_of_color(BLACK)) != 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 && (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(side_to_move(), ep_square()) != RANK_6)
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] != count_1s(pieces(pt, c)))
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)) != piece_of_color_and_type(c, pt))
return false;
if (index[piece_list(c, pt, i)] != i)
return false;
}
}
if (failedStep) (*failedStep)++;
if (debugCastleSquares) {
for (Color c = WHITE; c <= BLACK; c++) {
if (can_castle_kingside(c) && piece_on(initial_kr_square(c)) != piece_of_color_and_type(c, ROOK))
return false;
if (can_castle_queenside(c) && piece_on(initial_qr_square(c)) != piece_of_color_and_type(c, ROOK))
return false;
}
if (castleRightsMask[initial_kr_square(WHITE)] != (ALL_CASTLES ^ WHITE_OO))
return false;
if (castleRightsMask[initial_qr_square(WHITE)] != (ALL_CASTLES ^ WHITE_OOO))
return false;
if (castleRightsMask[initial_kr_square(BLACK)] != (ALL_CASTLES ^ BLACK_OO))
return false;
if (castleRightsMask[initial_qr_square(BLACK)] != (ALL_CASTLES ^ BLACK_OOO))
return false;
}
if (failedStep) *failedStep = 0;
return true;
}
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