kronecker_product.hpp

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// SPDX-License-Identifier: BSD-2-Clause
 
#ifndef pRC_CORE_TENSOR_FUNCTIONS_KRONECKER_PRODUCT_H
#define pRC_CORE_TENSOR_FUNCTIONS_KRONECKER_PRODUCT_H
 
#include <prc/core/functors/mul.hpp>
#include <prc/core/tensor/declarations.hpp>
 
namespace pRC
{
    template<class XA, class XB, IsTensorish RA = RemoveReference<XA>,
        IsTensorish RB = RemoveReference<XB>>
        requires(RA::Dimension == RB::Dimension) &&
        IsInvocable<Mul, ResultOf<XA, typename RA::Subscripts>,
            ResultOf<XB, typename RB::Subscripts>>
    static inline constexpr auto kroneckerProduct(XA &&a, XB &&b)
    {
        return expand(makeSeries<Index, RA::Dimension>(),
            [&a, &b](auto const... seq)
            {
                return hadamardProduct(
                    inflate<RB::size(seq)...>(forward<XA>(a)),
                    broadcast<RA::size(seq)...>(forward<XB>(b)));
            });
    }
}
#endif // pRC_CORE_TENSOR_FUNCTIONS_KRONECKER_PRODUCT_H