laplacianOperator.hpp

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// SPDX-FileCopyrightText: 2023 - 2025 NeoN authors
//
// SPDX-License-Identifier: MIT
 
#pragma once
 
#include "NeoN/core/executor/executor.hpp"
#include "NeoN/core/input.hpp"
#include "NeoN/core/runtimeSelectionFactory.hpp"
#include "NeoN/core/vector/vector.hpp"
#include "NeoN/dsl/operator.hpp"
#include "NeoN/linearAlgebra/linearSystem.hpp"
#include "NeoN/finiteVolume/cellCentred/fields/volumeField.hpp"
#include "NeoN/finiteVolume/cellCentred/fields/surfaceField.hpp"
#include "NeoN/mesh/unstructured/unstructuredMesh.hpp"
 
namespace NeoN::finiteVolume::cellCentred
{
 
/* @class Factory class to create divergence operators by a given name using
 * using NeoNs runTimeFactory mechanism
 */
template<typename ValueType>
class LaplacianOperatorFactory :
    public RuntimeSelectionFactory<
        LaplacianOperatorFactory<ValueType>,
        Parameters<const Executor&, const UnstructuredMesh&, const Input&>>
{
 
public:
 
    static std::unique_ptr<LaplacianOperatorFactory<ValueType>>
    create(const Executor& exec, const UnstructuredMesh& mesh, const Input& inputs)
    {
        std::string key = (std::holds_alternative<Dictionary>(inputs))
                            ? std::get<Dictionary>(inputs).get<std::string>("LaplacianOperator")
                            : std::get<TokenList>(inputs).next<std::string>();
        LaplacianOperatorFactory<ValueType>::keyExistsOrError(key);
        return LaplacianOperatorFactory<ValueType>::table().at(key)(exec, mesh, inputs);
    }
 
    static std::string name() { return "LaplacianOperatorFactory"; }
 
    LaplacianOperatorFactory(const Executor& exec, const UnstructuredMesh& mesh)
        : exec_(exec), mesh_(mesh), sparsityPattern_(la::SparsityPattern::readOrCreate(mesh)) {};
 
    virtual ~LaplacianOperatorFactory() {} // Virtual destructor
 
    virtual void laplacian(
        VolumeField<ValueType>& lapPhi,
        const SurfaceField<scalar>& gamma,
        VolumeField<ValueType>& phi,
        const dsl::Coeff operatorScaling
    ) = 0;
 
    virtual VolumeField<ValueType> laplacian(
        const SurfaceField<scalar>& gamma,
        VolumeField<ValueType>& phi,
        const dsl::Coeff operatorScaling
    ) const = 0;
 
    virtual void laplacian(
        Vector<ValueType>& lapPhi,
        const SurfaceField<scalar>& gamma,
        VolumeField<ValueType>& phi,
        const dsl::Coeff operatorScaling
    ) = 0;
 
    virtual void laplacian(
        la::LinearSystem<ValueType, localIdx>& ls,
        const SurfaceField<scalar>& gamma,
        VolumeField<ValueType>& phi,
        const dsl::Coeff operatorScaling
    ) = 0;
 
    // Pure virtual function for cloning
    virtual std::unique_ptr<LaplacianOperatorFactory<ValueType>> clone() const = 0;
 
    const la::SparsityPattern& getSparsityPattern() const { return sparsityPattern_; }
 
protected:
 
    const Executor exec_;
 
    const UnstructuredMesh& mesh_;
 
    const la::SparsityPattern& sparsityPattern_;
};
 
template<typename ValueType>
class LaplacianOperator : public dsl::OperatorMixin<VolumeField<ValueType>>
{
 
public:
 
    using VectorValueType = ValueType;
 
    // copy constructor
    LaplacianOperator(const LaplacianOperator& lapOp)
        : dsl::OperatorMixin<VolumeField<ValueType>>(
            lapOp.exec_, lapOp.coeffs_, lapOp.field_, lapOp.type_
        ),
          gamma_(lapOp.gamma_),
          laplacianOperatorStrategy_(
              lapOp.laplacianOperatorStrategy_ ? lapOp.laplacianOperatorStrategy_->clone() : nullptr
          ) {};
 
    LaplacianOperator(
        dsl::Operator::Type termType,
        const SurfaceField<scalar>& gamma,
        VolumeField<ValueType>& phi,
        Input input
    )
        : dsl::OperatorMixin<VolumeField<ValueType>>(phi.exec(), dsl::Coeff(1.0), phi, termType),
          gamma_(gamma),
          laplacianOperatorStrategy_(
              LaplacianOperatorFactory<ValueType>::create(this->exec_, phi.mesh(), input)
          ) {};
 
    LaplacianOperator(
        dsl::Operator::Type termType,
        const SurfaceField<scalar>& gamma,
        VolumeField<ValueType>& phi,
        std::unique_ptr<LaplacianOperatorFactory<ValueType>> laplacianOperatorStrategy
    )
        : dsl::OperatorMixin<VolumeField<ValueType>>(phi.exec(), dsl::Coeff(1.0), phi, termType),
          gamma_(gamma), laplacianOperatorStrategy_(std::move(laplacianOperatorStrategy)) {};
 
    LaplacianOperator(
        dsl::Operator::Type termType, const SurfaceField<scalar>& gamma, VolumeField<ValueType>& phi
    )
        : dsl::OperatorMixin<VolumeField<ValueType>>(phi.exec(), dsl::Coeff(1.0), phi, termType),
          gamma_(gamma), laplacianOperatorStrategy_(nullptr) {};
 
 
    void explicitOperation(Vector<ValueType>& source) const
    {
        NF_ASSERT(laplacianOperatorStrategy_, "LaplacianOperatorStrategy not initialized");
        const auto operatorScaling = this->getCoefficient();
        NeoN::Vector<ValueType> tmpsource(source.exec(), source.size(), zero<ValueType>());
        laplacianOperatorStrategy_->laplacian(tmpsource, gamma_, this->field_, operatorScaling);
        source += tmpsource;
    }
 
    void implicitOperation(la::LinearSystem<ValueType, localIdx>& ls) const
    {
        NF_ASSERT(laplacianOperatorStrategy_, "LaplacianOperatorStrategy not initialized");
        const auto operatorScaling = this->getCoefficient();
        laplacianOperatorStrategy_->laplacian(ls, gamma_, this->field_, operatorScaling);
    }
 
    // void laplacian(Vector<scalar>& lapPhi)
    // {
    //     laplacianOperatorStrategy_->laplacian(lapPhi, gamma_, getVector());
    // }
 
    // void laplacian(la::LinearSystem<scalar, localIdx>& ls)
    // {
    //     laplacianOperatorStrategy_->laplacian(ls, gamma_, getVector());
    // };
 
    void laplacian(VolumeField<scalar>& lapPhi)
    {
        const auto operatorScaling = this->getCoefficient();
        laplacianOperatorStrategy_->laplacian(lapPhi, gamma_, this->getVector(), operatorScaling);
    }
 
    VolumeField<scalar> laplacian()
    {
        const auto operatorScaling = this->getCoefficient();
        std::string name = "laplacian(" + gamma_.name + "," + this->field_.name + ")";
        VolumeField<scalar> lapPhi(
            this->exec_,
            name,
            this->field_.mesh(),
            createCalculatedBCs<VolumeBoundary<scalar>>(this->field_.mesh())
        );
        laplacianOperatorStrategy_->laplacian(lapPhi, gamma_, this->field_, operatorScaling);
        return lapPhi;
    }
 
    void read(const Input& input)
    {
        const UnstructuredMesh& mesh = this->field_.mesh();
        if (std::holds_alternative<NeoN::Dictionary>(input))
        {
            auto dict = std::get<NeoN::Dictionary>(input);
            std::string schemeName = "laplacian(" + gamma_.name + "," + this->field_.name + ")";
            auto tokens = dict.subDict("laplacianSchemes").get<NeoN::TokenList>(schemeName);
            laplacianOperatorStrategy_ =
                LaplacianOperatorFactory<ValueType>::create(this->exec(), mesh, tokens);
        }
        else
        {
            auto tokens = std::get<NeoN::TokenList>(input);
            laplacianOperatorStrategy_ =
                LaplacianOperatorFactory<ValueType>::create(this->exec(), mesh, tokens);
        }
    }
 
    std::string getName() const { return "LaplacianOperator"; }
 
private:
 
    const SurfaceField<scalar>& gamma_;
 
    std::unique_ptr<LaplacianOperatorFactory<ValueType>> laplacianOperatorStrategy_;
};
 
 
} // namespace NeoN