blas2_matrix_vector_product.hpp

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// SPDX-License-Identifier: BSL-1.0
// SPDX-FileCopyrightText: Copyright (C) 2023 Tobias Hienzsch
 
#ifndef TETL_LINALG_BLAS2_MATRIX_VECTOR_PRODUCT_HPP
#define TETL_LINALG_BLAS2_MATRIX_VECTOR_PRODUCT_HPP
 
#include <etl/_contracts/check.hpp>
#include <etl/_linalg/exposition.hpp>
 
namespace etl::linalg {
 
/// \ingroup linalg
template <in_matrix InMat, in_vector InVec, out_vector OutVec>
constexpr auto matrix_vector_product(InMat a, InVec x, OutVec y) noexcept -> void
{
    TETL_PRECONDITION(a.extent(1) == x.extent(0));
    TETL_PRECONDITION(a.extent(0) == y.extent(0));
 
    using index_type = detail::common_index_type_t<InMat, InVec, OutVec>;
 
    for (index_type i{0}; i < static_cast<index_type>(a.extent(0)); ++i) {
        y(i) = typename OutVec::element_type{};
        for (index_type j{0}; j < static_cast<index_type>(a.extent(1)); ++j) {
            y(i) += a(i, j) * x(j);
        }
    }
}
 
} // namespace etl::linalg
 
#endif // TETL_LINALG_BLAS2_MATRIX_VECTOR_PRODUCT_HPP