rungeKutta.hpp

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// SPDX-License-Identifier: MIT
// SPDX-FileCopyrightText: 2023 NeoFOAM authors
 
#pragma once
 
#include <functional>
#include <memory>
 
#include "NeoFOAM/core/database/fieldCollection.hpp"
#include "NeoFOAM/core/database/oldTimeCollection.hpp"
#include "NeoFOAM/core/parallelAlgorithms.hpp"
#include "NeoFOAM/fields/field.hpp"
#include "NeoFOAM/timeIntegration/timeIntegration.hpp"
#include "NeoFOAM/timeIntegration/sundials.hpp"
 
 
namespace NeoFOAM::timeIntegration
{
 
template<typename SolutionFieldType>
class RungeKutta :
    public TimeIntegratorBase<SolutionFieldType>::template Register<RungeKutta<SolutionFieldType>>
{
public:
 
    using ValueType = SolutionFieldType::FieldValueType;
    using Expression = NeoFOAM::dsl::Expression;
    using Base =
        TimeIntegratorBase<SolutionFieldType>::template Register<RungeKutta<SolutionFieldType>>;
    using Base::dict_;
 
    RungeKutta() = default;
 
    ~RungeKutta() = default;
 
    RungeKutta(const Dictionary& dict) : Base(dict) {}
 
    RungeKutta(const RungeKutta& other);
 
    RungeKutta(RungeKutta&& other);
 
    // deleted because base class method deleted.
    RungeKutta& operator=(const RungeKutta& other) = delete;
 
    // deleted because base class method deleted.
    RungeKutta& operator=(RungeKutta&& other) = delete;
 
    static std::string name() { return "Runge-Kutta"; }
 
    static std::string doc() { return "Explicit time integration using the Runge-Kutta method."; }
 
    static std::string schema() { return "none"; }
 
    void
    solve(Expression& exp, SolutionFieldType& solutionField, scalar t, const scalar dt) override;
 
    std::unique_ptr<TimeIntegratorBase<SolutionFieldType>> clone() const override;
 
 
private:
 
    NeoFOAM::sundials::SKVector<ValueType>
        solution_; 
    NeoFOAM::sundials::SKVector<ValueType>
        initialConditions_; 
    std::shared_ptr<SUNContext> context_ {
        nullptr, sundials::SUN_CONTEXT_DELETER
    }; 
    std::unique_ptr<char, decltype(sundials::SUN_ARK_DELETER)> ODEMemory_ {
        nullptr, sundials::SUN_ARK_DELETER
    }; 
    std::unique_ptr<NeoFOAM::dsl::Expression> pdeExpr_ {nullptr
    }; 
    void initSUNERKSolver(Expression& exp, SolutionFieldType& field, const scalar t);
 
    void initExpression(const Expression& exp);
 
    void initSUNContext();
 
    void initSUNVector(const Executor& exec, size_t size);
 
    void initSUNInitialConditions(const SolutionFieldType& solutionField);
 
    void initODEMemory(const scalar t);
};
 
} // namespace NeoFOAM