ilu.hpp

// SPDX-FileCopyrightText: 2017 - 2025 The Ginkgo authors
//
// SPDX-License-Identifier: BSD-3-Clause
 
#ifndef GKO_PUBLIC_CORE_FACTORIZATION_ILU_HPP_
#define GKO_PUBLIC_CORE_FACTORIZATION_ILU_HPP_
 
 
#include <memory>
 
#include <ginkgo/core/base/composition.hpp>
#include <ginkgo/core/base/lin_op.hpp>
#include <ginkgo/core/base/types.hpp>
#include <ginkgo/core/config/config.hpp>
#include <ginkgo/core/config/registry.hpp>
#include <ginkgo/core/factorization/incomplete_factorization.hpp>
#include <ginkgo/core/matrix/csr.hpp>
 
 
namespace gko {
namespace factorization {
 
 
template <typename ValueType = gko::default_precision,
          typename IndexType = gko::int32>
class Ilu : public Composition<ValueType> {
public:
    using value_type = ValueType;
    using index_type = IndexType;
    using matrix_type = matrix::Csr<ValueType, IndexType>;
 
    std::shared_ptr<const matrix_type> get_l_factor() const
    {
        // Can be `static_cast` since the type is guaranteed in this class
        return std::static_pointer_cast<const matrix_type>(
            this->get_operators()[0]);
    }
 
    std::shared_ptr<const matrix_type> get_u_factor() const
    {
        // Can be `static_cast` since the type is guaranteed in this class
        return std::static_pointer_cast<const matrix_type>(
            this->get_operators()[1]);
    }
 
    // Remove the possibility of calling `create`, which was enabled by
    // `Composition`
    template <typename... Args>
    static std::unique_ptr<Composition<ValueType>> create(Args&&... args) =
        delete;
 
    GKO_CREATE_FACTORY_PARAMETERS(parameters, Factory)
    {
        std::shared_ptr<typename matrix_type::strategy_type>
            GKO_FACTORY_PARAMETER_SCALAR(l_strategy, nullptr);
 
        std::shared_ptr<typename matrix_type::strategy_type>
            GKO_FACTORY_PARAMETER_SCALAR(u_strategy, nullptr);
 
        bool GKO_FACTORY_PARAMETER_SCALAR(skip_sorting, false);
 
        incomplete_algorithm GKO_FACTORY_PARAMETER_SCALAR(
            algorithm, incomplete_algorithm::sparselib);
    };
    GKO_ENABLE_LIN_OP_FACTORY(Ilu, parameters, Factory);
    GKO_ENABLE_BUILD_METHOD(Factory);
 
    static parameters_type parse(
        const config::pnode& config, const config::registry& context,
        const config::type_descriptor& td_for_child =
            config::make_type_descriptor<ValueType, IndexType>());
 
protected:
    Ilu(const Factory* factory, std::shared_ptr<const gko::LinOp> system_matrix)
        : Composition<ValueType>{factory->get_executor()},
          parameters_{factory->get_parameters()}
    {
        if (parameters_.l_strategy == nullptr) {
            parameters_.l_strategy =
                std::make_shared<typename matrix_type::classical>();
        }
        if (parameters_.u_strategy == nullptr) {
            parameters_.u_strategy =
                std::make_shared<typename matrix_type::classical>();
        }
        generate_l_u(system_matrix, parameters_.skip_sorting)->move_to(this);
    }
 
    std::unique_ptr<Composition<ValueType>> generate_l_u(
        const std::shared_ptr<const LinOp>& system_matrix,
        bool skip_sorting) const;
};
 
 
}  // namespace factorization
}  // namespace gko
 
 
#endif  // GKO_PUBLIC_CORE_FACTORIZATION_ILU_HPP_