AndersonAcceleration.h

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// SPDX-FileCopyrightText: Copyright (c) OpenGeoSys Community (opengeosys.org)
// SPDX-License-Identifier: BSD-3-Clause
 
#pragma once
 
#include <Eigen/Core>
#include <vector>
 
#include "MathLib/LinAlg/GlobalMatrixVectorTypes.h"
 
namespace NumLib
{
class AndersonAcceleration final
{
public:
    static constexpr int min_mixing_depth = 2;

    explicit AndersonAcceleration(int depth);
 
    ~AndersonAcceleration();
 
    AndersonAcceleration(AndersonAcceleration const&) = delete;
    AndersonAcceleration& operator=(AndersonAcceleration const&) = delete;

    void accelerate(GlobalVector const& x_old, GlobalVector& x_new);

    void dropLastStep();
 
private:
    struct HistoryEntry
    {
        GlobalVector* x;
        GlobalVector* f;
    };

    static void releaseHistoryEntry(HistoryEntry const& entry);

    int const _depth;

    std::vector<HistoryEntry> _history;

    Eigen::MatrixXd _gram;
};
 
}  // namespace NumLib