combination.hpp

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#ifndef GKO_CORE_BASE_COMBINATION_HPP_
#define GKO_CORE_BASE_COMBINATION_HPP_


#include <vector>


#include <ginkgo/core/base/lin_op.hpp>


namespace gko {


template <typename ValueType = default_precision>
class Combination : public EnableLinOp<Combination<ValueType>>,
                    public EnableCreateMethod<Combination<ValueType>> {
    friend class EnablePolymorphicObject<Combination, LinOp>;
    friend class EnableCreateMethod<Combination>;

public:
    using value_type = ValueType;

    const std::vector<std::shared_ptr<const LinOp>> &get_coefficients() const
        noexcept
    {
        return coefficients_;
    }

    const std::vector<std::shared_ptr<const LinOp>> &get_operators() const
        noexcept
    {
        return operators_;
    }

protected:
    explicit Combination(std::shared_ptr<const Executor> exec)
        : EnableLinOp<Combination>(exec)
    {}

    template <
        typename CoefficientIterator, typename OperatorIterator,
        typename = xstd::void_t<
            typename std::iterator_traits<
                CoefficientIterator>::iterator_category,
            typename std::iterator_traits<OperatorIterator>::iterator_category>>
    explicit Combination(CoefficientIterator coefficient_begin,
                         CoefficientIterator coefficient_end,
                         OperatorIterator operator_begin,
                         OperatorIterator operator_end)
        : EnableLinOp<Combination>([&] {
              if (operator_begin == operator_end) {
                  throw OutOfBoundsError(__FILE__, __LINE__, 1, 0);
              }
              return (*operator_begin)->get_executor();
          }()),
          coefficients_(coefficient_begin, coefficient_end),
          operators_(operator_begin, operator_end)
    {
        for (const auto &c : coefficients_) {
            GKO_ASSERT_EQUAL_DIMENSIONS(c, dim<2>(1, 1));
        }
        this->set_size(operators_[0]->get_size());
        for (const auto &o : operators_) {
            GKO_ASSERT_EQUAL_DIMENSIONS(o, this->get_size());
        }
    }

    template <typename... Rest>
    explicit Combination(std::shared_ptr<const LinOp> coef,
                         std::shared_ptr<const LinOp> oper, Rest &&... rest)
        : Combination(std::forward<Rest>(rest)...)
    {
        GKO_ASSERT_EQUAL_DIMENSIONS(coef, dim<2>(1, 1));
        GKO_ASSERT_EQUAL_DIMENSIONS(oper, this->get_size());
        coefficients_.insert(begin(coefficients_), coef);
        operators_.insert(begin(operators_), oper);
    }

    explicit Combination(std::shared_ptr<const LinOp> coef,
                         std::shared_ptr<const LinOp> oper)
        : EnableLinOp<Combination>(oper->get_executor(), oper->get_size()),
          coefficients_{coef},
          operators_{oper}
    {}

    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;

private:
    std::vector<std::shared_ptr<const LinOp>> coefficients_;
    std::vector<std::shared_ptr<const LinOp>> operators_;

    // TODO: solve race conditions when multithreading
    mutable struct cache_struct {
        cache_struct() = default;
        cache_struct(const cache_struct &other) {}
        cache_struct &operator=(const cache_struct &other) { return *this; }

        std::unique_ptr<LinOp> zero;
        std::unique_ptr<LinOp> one;
        std::unique_ptr<LinOp> intermediate_x;
    } cache_;
};


}  // namespace gko


#endif  // GKO_CORE_BASE_COMBINATION_HPP_