TimeDiscretization.h

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// SPDX-FileCopyrightText: Copyright (c) OpenGeoSys Community (opengeosys.org)
// SPDX-License-Identifier: BSD-3-Clause
 
#pragma once
 
#include <vector>
 
#include "MathLib/LinAlg/LinAlg.h"
#include "NumLib/DOF/GlobalMatrixProviders.h"
#include "Types.h"
 
namespace NumLib
{

class TimeDiscretization
{
public:
    TimeDiscretization() = default;

    virtual void setInitialState(const double t0) = 0;

    virtual void nextTimestep(const double t, const double delta_t) = 0;

    virtual double getCurrentTime() const = 0;

    virtual double getCurrentTimeIncrement() const = 0;

    virtual double getPreviousTimeIncrement() const = 0;

    virtual void getWeightedOldX(
        GlobalVector& y, GlobalVector const& x_old) const = 0;  // = x_old
 
    virtual ~TimeDiscretization() = default;
};

class BackwardEuler final : public TimeDiscretization
{
public:
    void setInitialState(const double t0) override { _t = t0; }
    void nextTimestep(const double t, const double delta_t) override
    {
        _delta_t_prev = _delta_t;
        _t = t;
        _delta_t = delta_t;
    }
 
    double getCurrentTime() const override { return _t; }
    double getCurrentTimeIncrement() const override { return _delta_t; }
    double getPreviousTimeIncrement() const override { return _delta_t_prev; }
    void getWeightedOldX(GlobalVector& y,
                         GlobalVector const& x_old) const override;
 
private:
    double _t = std::numeric_limits<double>::quiet_NaN();  
    double _delta_t =
        std::numeric_limits<double>::quiet_NaN();  

    double _delta_t_prev = std::numeric_limits<double>::quiet_NaN();
};

}  // namespace NumLib