scaled_reordered.hpp

// SPDX-FileCopyrightText: 2017 - 2025 The Ginkgo authors
//
// SPDX-License-Identifier: BSD-3-Clause
 
#ifndef GKO_PUBLIC_CORE_REORDER_SCALED_REORDERED_HPP_
#define GKO_PUBLIC_CORE_REORDER_SCALED_REORDERED_HPP_
 
 
#include <ginkgo/core/base/abstract_factory.hpp>
#include <ginkgo/core/base/executor.hpp>
#include <ginkgo/core/base/lin_op.hpp>
#include <ginkgo/core/base/types.hpp>
#include <ginkgo/core/matrix/dense.hpp>
#include <ginkgo/core/matrix/diagonal.hpp>
#include <ginkgo/core/matrix/identity.hpp>
#include <ginkgo/core/matrix/permutation.hpp>
#include <ginkgo/core/reorder/reordering_base.hpp>
 
 
namespace gko {
namespace experimental {
namespace reorder {
 

template <typename ValueType = default_precision, typename IndexType = int32>
class ScaledReordered
    : public EnableLinOp<ScaledReordered<ValueType, IndexType>> {
    friend class EnableLinOp<ScaledReordered, LinOp>;
    friend class EnablePolymorphicObject<ScaledReordered, LinOp>;
    GKO_ASSERT_SUPPORTED_VALUE_AND_INDEX_TYPE;
 
public:
    using value_type = ValueType;
    using index_type = IndexType;
    using ReorderingBaseFactory =
        AbstractFactory<gko::reorder::ReorderingBase<IndexType>,
                        gko::reorder::ReorderingBaseArgs>;
 
    std::shared_ptr<const LinOp> get_system_matrix() const
    {
        return system_matrix_;
    }
 
    std::shared_ptr<const LinOp> get_inner_operator() const
    {
        return inner_operator_;
    }
 
    GKO_CREATE_FACTORY_PARAMETERS(parameters, Factory)
    {
        std::shared_ptr<const LinOpFactory> GKO_FACTORY_PARAMETER_SCALAR(
            inner_operator, nullptr);

        std::shared_ptr<const ReorderingBaseFactory>
            GKO_FACTORY_PARAMETER_SCALAR(reordering, nullptr);

        std::shared_ptr<const matrix::Diagonal<value_type>>
            GKO_FACTORY_PARAMETER_SCALAR(row_scaling, nullptr);

        std::shared_ptr<const matrix::Diagonal<value_type>>
            GKO_FACTORY_PARAMETER_SCALAR(col_scaling, nullptr);
    };
    GKO_ENABLE_LIN_OP_FACTORY(ScaledReordered, parameters, Factory);
    GKO_ENABLE_BUILD_METHOD(Factory);
 
protected:
    explicit ScaledReordered(std::shared_ptr<const Executor> exec)
        : EnableLinOp<ScaledReordered>(std::move(exec)),
          permutation_array_{exec}
    {}
 
    explicit ScaledReordered(const Factory* factory,
                             std::shared_ptr<const LinOp> system_matrix)
        : EnableLinOp<ScaledReordered>(factory->get_executor(),
                                       system_matrix->get_size()),
          parameters_{factory->get_parameters()},
          permutation_array_{factory->get_executor()}
    {
        // For now only support square matrices.
        GKO_ASSERT_IS_SQUARE_MATRIX(system_matrix);
 
        auto exec = this->get_executor();
 
        system_matrix_ = gko::clone(exec, system_matrix);
 
        // Scale the system matrix if scaling coefficients are provided
        if (parameters_.row_scaling) {
            GKO_ASSERT_EQUAL_DIMENSIONS(parameters_.row_scaling,
                                        system_matrix_);
            row_scaling_ = parameters_.row_scaling;
            row_scaling_->apply(system_matrix_, system_matrix_);
        }
        if (parameters_.col_scaling) {
            GKO_ASSERT_EQUAL_DIMENSIONS(parameters_.col_scaling,
                                        system_matrix_);
            col_scaling_ = parameters_.col_scaling;
            col_scaling_->rapply(system_matrix_, system_matrix_);
        }
 
        // If a reordering factory is provided, generate the reordering and
        // permute the system matrix accordingly.
        if (parameters_.reordering) {
            auto reordering = parameters_.reordering->generate(system_matrix_);
            permutation_array_ = reordering->get_permutation_array();
            system_matrix_ = as<Permutable<index_type>>(system_matrix_)
                                 ->permute(&permutation_array_);
        }
 
        // Generate the inner operator with the scaled and reordered system
        // matrix. If none is provided, use the Identity.
        if (parameters_.inner_operator) {
            inner_operator_ =
                parameters_.inner_operator->generate(system_matrix_);
        } else {
            inner_operator_ = gko::matrix::Identity<value_type>::create(
                exec, this->get_size()[0]);
        }
    }
 
    void apply_impl(const LinOp* b, LinOp* x) const override;
 
    void apply_impl(const LinOp* alpha, const LinOp* b, const LinOp* beta,
                    LinOp* x) const override;

    void set_cache_to(const LinOp* b, const LinOp* x) const
    {
        if (cache_.inner_b == nullptr ||
            cache_.inner_b->get_size() != b->get_size()) {
            const auto size = b->get_size();
            cache_.inner_b =
                matrix::Dense<value_type>::create(this->get_executor(), size);
            cache_.inner_x =
                matrix::Dense<value_type>::create(this->get_executor(), size);
            cache_.intermediate =
                matrix::Dense<value_type>::create(this->get_executor(), size);
        }
        cache_.inner_b->copy_from(b);
        if (inner_operator_->apply_uses_initial_guess()) {
            cache_.inner_x->copy_from(x);
        }
    }
 
private:
    std::shared_ptr<LinOp> system_matrix_{};
    std::shared_ptr<const LinOp> inner_operator_{};
    std::shared_ptr<const matrix::Diagonal<value_type>> row_scaling_{};
    std::shared_ptr<const matrix::Diagonal<value_type>> col_scaling_{};
    array<index_type> permutation_array_{};

    mutable struct cache_struct {
        cache_struct() = default;
 
        ~cache_struct() = default;
 
        cache_struct(const cache_struct&) {}
 
        cache_struct(cache_struct&&) {}
 
        cache_struct& operator=(const cache_struct&) { return *this; }
 
        cache_struct& operator=(cache_struct&&) { return *this; }
 
        std::unique_ptr<matrix::Dense<value_type>> inner_b{};
        std::unique_ptr<matrix::Dense<value_type>> inner_x{};
        std::unique_ptr<matrix::Dense<value_type>> intermediate{};
    } cache_;
};
 
 
}  // namespace reorder
}  // namespace experimental
}  // namespace gko
 
 
#endif  // GKO_PUBLIC_CORE_REORDER_SCALED_REORDERED_HPP_