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official-stockfish
GitHub Repository: official-stockfish/Stockfish
 Path: blob/master/src/nnue/features/half_ka_v2_hm.cpp
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/*

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  Stockfish, a UCI chess playing engine derived from Glaurung 2.1

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  Copyright (C) 2004-2026 The Stockfish developers (see AUTHORS file)

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  Stockfish is free software: you can redistribute it and/or modify

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  it under the terms of the GNU General Public License as published by

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  the Free Software Foundation, either version 3 of the License, or

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  (at your option) any later version.

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  Stockfish is distributed in the hope that it will be useful,

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  but WITHOUT ANY WARRANTY; without even the implied warranty of

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  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

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  GNU General Public License for more details.

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  You should have received a copy of the GNU General Public License

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  along with this program.  If not, see <http://www.gnu.org/licenses/>.

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*/

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//Definition of input features HalfKAv2_hm of NNUE evaluation function

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#include "half_ka_v2_hm.h"

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#include "../../bitboard.h"

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#include "../../position.h"

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#include "../../types.h"

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#include "../nnue_common.h"

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namespace Stockfish::Eval::NNUE::Features {

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// Index of a feature for a given king position and another piece on some square

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IndexType HalfKAv2_hm::make_index(Color perspective, Square s, Piece pc, Square ksq) {

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    const IndexType flip = 56 * perspective;

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    return (IndexType(s) ^ OrientTBL[ksq] ^ flip) + PieceSquareIndex[perspective][pc]

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         + KingBuckets[int(ksq) ^ flip];

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}

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// Get a list of indices for active features

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void HalfKAv2_hm::append_active_indices(Color perspective, const Position& pos, IndexList& active) {

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    Square   ksq = pos.square<KING>(perspective);

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    Bitboard bb  = pos.pieces();

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    while (bb)

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    {

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        Square s = pop_lsb(bb);

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        active.push_back(make_index(perspective, s, pos.piece_on(s), ksq));

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    }

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}

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// Get a list of indices for recently changed features

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void HalfKAv2_hm::append_changed_indices(

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  Color perspective, Square ksq, const DiffType& diff, IndexList& removed, IndexList& added) {

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    removed.push_back(make_index(perspective, diff.from, diff.pc, ksq));

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    if (diff.to != SQ_NONE)

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        added.push_back(make_index(perspective, diff.to, diff.pc, ksq));

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    if (diff.remove_sq != SQ_NONE)

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        removed.push_back(make_index(perspective, diff.remove_sq, diff.remove_pc, ksq));

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    if (diff.add_sq != SQ_NONE)

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        added.push_back(make_index(perspective, diff.add_sq, diff.add_pc, ksq));

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}

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bool HalfKAv2_hm::requires_refresh(const DiffType& diff, Color perspective) {

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    return diff.pc == make_piece(perspective, KING);

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}

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}  // namespace Stockfish::Eval::NNUE::Features

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