cg.hpp

// SPDX-FileCopyrightText: 2017 - 2026 The Ginkgo authors
//
// SPDX-License-Identifier: BSD-3-Clause
 
#ifndef GKO_PUBLIC_CORE_SOLVER_CG_HPP_
#define GKO_PUBLIC_CORE_SOLVER_CG_HPP_
 
 
#include <vector>
 
#include <ginkgo/core/base/array.hpp>
#include <ginkgo/core/base/exception_helpers.hpp>
#include <ginkgo/core/base/lin_op.hpp>
#include <ginkgo/core/base/math.hpp>
#include <ginkgo/core/base/types.hpp>
#include <ginkgo/core/config/config.hpp>
#include <ginkgo/core/config/registry.hpp>
#include <ginkgo/core/config/type_descriptor.hpp>
#include <ginkgo/core/log/logger.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>
 
 
namespace gko {
namespace solver {
 
 
template <typename ValueType = default_precision>
class Cg : public LinOp,
           public EnablePreconditionedIterativeSolver<ValueType, Cg<ValueType>>,
           public Transposable {
    GKO_ASSERT_SUPPORTED_VALUE_TYPE;
 
public:
    using value_type = ValueType;
    using transposed_type = Cg<ValueType>;
 
    std::unique_ptr<LinOp> transpose() const override;
 
    std::unique_ptr<LinOp> conj_transpose() const override;
 
    bool apply_uses_initial_guess() const override { return true; }
 
    class Factory;
 
    struct parameters_type
        : enable_preconditioned_iterative_solver_factory_parameters<
              parameters_type, Factory> {};
 
    GKO_ENABLE_LIN_OP_FACTORY(Cg, 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) const;
 
    void apply_impl(const LinOp* alpha, const LinOp* b, const LinOp* beta,
                    LinOp* x) const override;
 
    explicit Cg(std::shared_ptr<const Executor> exec) : LinOp(std::move(exec))
    {}
 
    explicit Cg(const Factory* factory,
                std::shared_ptr<const LinOp> system_matrix)
        : LinOp(factory->get_executor(),
                gko::transpose(system_matrix->get_size())),
          EnablePreconditionedIterativeSolver<ValueType, Cg<ValueType>>{
              std::move(system_matrix), factory->get_parameters()},
          parameters_{factory->get_parameters()}
    {}
};
 
 
template <typename ValueType>
struct nullspace_traits<Cg<ValueType>> {
    static constexpr bool is_supported = true;
    static constexpr bool requires_hermitian = true;
    static constexpr bool two_sided_projection = false;
};
 
 
template <typename ValueType>
struct workspace_traits<Cg<ValueType>> {
    using Solver = Cg<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 r = 0;
    // preconditioned residual vector
    constexpr static int z = 1;
    // p vector
    constexpr static int p = 2;
    // q vector
    constexpr static int q = 3;
    // beta scalar
    constexpr static int beta = 4;
    // previous rho scalar
    constexpr static int prev_rho = 5;
    // current rho scalar
    constexpr static int rho = 6;
    // constant 1.0 scalar
    constexpr static int one = 7;
    // constant -1.0 scalar
    constexpr static int minus_one = 8;
    // right-hand side projected onto the range of the system matrix
    constexpr static int proj_rhs = 9;
 
    // stopping status array
    constexpr static int stop = 0;
    // reduction tmp array
    constexpr static int tmp = 1;
};
 
 
}  // namespace solver
}  // namespace gko
 
 
#endif  // GKO_PUBLIC_CORE_SOLVER_CG_HPP_