2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2021 The Stockfish developers (see AUTHORS file)
5 Stockfish is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Stockfish is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
19 //Definition of input features HalfKP of NNUE evaluation function
23 #include "../../position.h"
25 namespace Stockfish::Eval::NNUE::Features {
27 // Orient a square according to perspective (rotates by 180 for black)
28 inline Square HalfKP::orient(Color perspective, Square s) {
29 return Square(int(s) ^ (bool(perspective) * 63));
32 // Index of a feature for a given king position and another piece on some square
33 inline IndexType HalfKP::make_index(Color perspective, Square s, Piece pc, Square ksq) {
34 return IndexType(orient(perspective, s) + PieceSquareIndex[perspective][pc] + PS_NB * ksq);
37 // Get a list of indices for active features
38 void HalfKP::append_active_indices(
41 ValueListInserter<IndexType> active
43 Square ksq = orient(perspective, pos.square<KING>(perspective));
44 Bitboard bb = pos.pieces() & ~pos.pieces(KING);
47 Square s = pop_lsb(bb);
48 active.push_back(make_index(perspective, s, pos.piece_on(s), ksq));
53 // append_changed_indices() : get a list of indices for recently changed features
55 void HalfKP::append_changed_indices(
59 ValueListInserter<IndexType> removed,
60 ValueListInserter<IndexType> added
62 const auto& dp = st->dirtyPiece;
63 Square oriented_ksq = orient(perspective, ksq);
64 for (int i = 0; i < dp.dirty_num; ++i) {
65 Piece pc = dp.piece[i];
66 if (type_of(pc) == KING) continue;
67 if (dp.from[i] != SQ_NONE)
68 removed.push_back(make_index(perspective, dp.from[i], pc, oriented_ksq));
69 if (dp.to[i] != SQ_NONE)
70 added.push_back(make_index(perspective, dp.to[i], pc, oriented_ksq));
74 int HalfKP::update_cost(StateInfo* st) {
75 return st->dirtyPiece.dirty_num;
78 int HalfKP::refresh_cost(const Position& pos) {
79 return pos.count<ALL_PIECES>() - 2;
82 bool HalfKP::requires_refresh(StateInfo* st, Color perspective) {
83 return st->dirtyPiece.piece[0] == make_piece(perspective, KING);
86 } // namespace Stockfish::Eval::NNUE::Features