kaiser.hpp

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#pragma once
 
#include <cstddef>
 
#include <sycl/sycl.hpp>
 
#include "kernels/elementwise_functions/i0.hpp"
 
namespace dpnp::kernels::kaiser
{
template <typename T>
class KaiserFunctor
{
private:
    T *res = nullptr;
    const std::size_t N;
    const T beta;
 
public:
    KaiserFunctor(T *res, const std::size_t N, const T beta)
        : res(res), N(N), beta(beta)
    {
    }
 
    void operator()(sycl::id<1> id) const
    {
        using dpnp::kernels::i0::cyl_bessel_i0;
 
        const auto i = id.get(0);
        const T alpha = (N - 1) / T(2);
        const T tmp = (i - alpha) / alpha;
        res[i] = cyl_bessel_i0(beta * sycl::sqrt(1 - tmp * tmp)) /
                 cyl_bessel_i0(beta);
    }
};
} // namespace dpnp::kernels::kaiser