ir.hpp

// SPDX-FileCopyrightText: 2017 - 2025 The Ginkgo authors
//
// SPDX-License-Identifier: BSD-3-Clause
 
#ifndef GKO_PUBLIC_CORE_SOLVER_IR_HPP_
#define GKO_PUBLIC_CORE_SOLVER_IR_HPP_
 
 
#include <vector>
 
#include <ginkgo/core/base/exception_helpers.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/matrix/dense.hpp>
#include <ginkgo/core/matrix/identity.hpp>
#include <ginkgo/core/solver/solver_base.hpp>
#include <ginkgo/core/stop/combined.hpp>
#include <ginkgo/core/stop/criterion.hpp>
#include <ginkgo/core/stop/iteration.hpp>
 
 
namespace gko {
namespace solver {
 

template <typename ValueType = default_precision>
class Ir : public EnableLinOp<Ir<ValueType>>,
           public EnableSolverBase<Ir<ValueType>>,
           public EnableIterativeBase<Ir<ValueType>>,
           public EnableApplyWithInitialGuess<Ir<ValueType>>,
           public Transposable {
    friend class EnableLinOp<Ir>;
    friend class EnablePolymorphicObject<Ir, LinOp>;
    friend class EnableApplyWithInitialGuess<Ir>;
    GKO_ASSERT_SUPPORTED_VALUE_TYPE;
 
public:
    using value_type = ValueType;
    using transposed_type = Ir<ValueType>;
 
    std::unique_ptr<LinOp> transpose() const override;
 
    std::unique_ptr<LinOp> conj_transpose() const override;

    bool apply_uses_initial_guess() const override
    {
        return this->get_default_initial_guess() ==
               initial_guess_mode::provided;
    }

    std::shared_ptr<const LinOp> get_solver() const { return solver_; }

    void set_solver(std::shared_ptr<const LinOp> new_solver);

    Ir& operator=(const Ir&);

    Ir& operator=(Ir&&);

    Ir(const Ir&);

    Ir(Ir&&);
 
    class Factory;
 
    struct parameters_type
        : enable_iterative_solver_factory_parameters<parameters_type, Factory> {
        std::shared_ptr<const LinOpFactory> GKO_DEFERRED_FACTORY_PARAMETER(
            solver);

        std::shared_ptr<const LinOp> GKO_FACTORY_PARAMETER_SCALAR(
            generated_solver, nullptr);

        ValueType GKO_FACTORY_PARAMETER_SCALAR(relaxation_factor,
                                               value_type{1});

        initial_guess_mode GKO_FACTORY_PARAMETER_SCALAR(
            default_initial_guess, initial_guess_mode::provided);
    };
    GKO_ENABLE_LIN_OP_FACTORY(Ir, 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>());
 
protected:
    void apply_impl(const LinOp* b, LinOp* x) const override;
 
    template <typename VectorType>
    void apply_dense_impl(const VectorType* b, VectorType* x,
                          initial_guess_mode guess) const;
 
    void apply_impl(const LinOp* alpha, const LinOp* b, const LinOp* beta,
                    LinOp* x) const override;
 
    void apply_with_initial_guess_impl(const LinOp* b, LinOp* x,
                                       initial_guess_mode guess) const override;
 
    void apply_with_initial_guess_impl(const LinOp* alpha, const LinOp* b,
                                       const LinOp* beta, LinOp* x,
                                       initial_guess_mode guess) const override;
 
    void set_relaxation_factor(
        std::shared_ptr<const matrix::Dense<ValueType>> new_factor);
 
    explicit Ir(std::shared_ptr<const Executor> exec)
        : EnableLinOp<Ir>(std::move(exec))
    {}
 
    explicit Ir(const Factory* factory,
                std::shared_ptr<const LinOp> system_matrix)
        : EnableLinOp<Ir>(factory->get_executor(),
                          gko::transpose(system_matrix->get_size())),
          EnableSolverBase<Ir>{std::move(system_matrix)},
          EnableIterativeBase<Ir>{
              stop::combine(factory->get_parameters().criteria)},
          parameters_{factory->get_parameters()}
    {
        if (parameters_.generated_solver) {
            this->set_solver(parameters_.generated_solver);
        } else if (parameters_.solver) {
            this->set_solver(
                parameters_.solver->generate(this->get_system_matrix()));
        } else {
            this->set_solver(matrix::Identity<ValueType>::create(
                this->get_executor(), this->get_size()[0]));
        }
        this->set_default_initial_guess(parameters_.default_initial_guess);
        relaxation_factor_ = gko::initialize<matrix::Dense<ValueType>>(
            {parameters_.relaxation_factor}, this->get_executor());
    }
 
private:
    std::shared_ptr<const LinOp> solver_{};
    std::shared_ptr<const matrix::Dense<ValueType>> relaxation_factor_{};
};
 
 
template <typename ValueType = default_precision>
using Richardson = Ir<ValueType>;
 
 
template <typename ValueType>
struct workspace_traits<Ir<ValueType>> {
    using Solver = Ir<ValueType>;
    // number of vectors used by this workspace
    static int num_vectors(const Solver&);
    // number of arrays used by this workspace
    static int num_arrays(const Solver&);
    // array containing the num_vectors names for the workspace vectors
    static std::vector<std::string> op_names(const Solver&);
    // array containing the num_arrays names for the workspace vectors
    static std::vector<std::string> array_names(const Solver&);
    // array containing all varying scalar vectors (independent of problem size)
    static std::vector<int> scalars(const Solver&);
    // array containing all varying vectors (dependent on problem size)
    static std::vector<int> vectors(const Solver&);
 
    // residual vector
    constexpr static int residual = 0;
    // inner solution vector
    constexpr static int inner_solution = 1;
    // constant 1.0 scalar
    constexpr static int one = 2;
    // constant -1.0 scalar
    constexpr static int minus_one = 3;
 
    // stopping status array
    constexpr static int stop = 0;
};
 

template <typename ValueType>
auto build_smoother(std::shared_ptr<const LinOpFactory> factory,
                    size_type iteration = 1, ValueType relaxation_factor = 0.9)
{
    auto exec = factory->get_executor();
    return Ir<ValueType>::build()
        .with_solver(factory)
        .with_relaxation_factor(relaxation_factor)
        .with_criteria(gko::stop::Iteration::build().with_max_iters(iteration))
        .on(exec);
}

template <typename ValueType>
auto build_smoother(std::shared_ptr<const LinOp> solver,
                    size_type iteration = 1, ValueType relaxation_factor = 0.9)
{
    auto exec = solver->get_executor();
    return Ir<ValueType>::build()
        .with_generated_solver(solver)
        .with_relaxation_factor(relaxation_factor)
        .with_criteria(gko::stop::Iteration::build().with_max_iters(iteration))
        .on(exec);
}
 
 
}  // namespace solver
}  // namespace gko
 
 
#endif  // GKO_PUBLIC_CORE_SOLVER_IR_HPP_