NFFT.h

// -*- C++ -*-
// -*- coding: utf-8 -*-
//
// Author: Brian Hawkins
// Copyright 2019-
//

#pragma once

#include "forward.h"

#include <cmath>
#include <valarray>

#include <isce3/core/Constants.h>
#include <isce3/core/Kernels.h>
#include "Signal.h"

template<class T>
class isce3::signal::NFFT {
    public:
        NFFT(size_t m, size_t n, size_t fft_size);

        void execute(const std::valarray<std::complex<T>> &spectrum,
                     const std::valarray<double> &times,
                     std::valarray<std::complex<T>> &out);

        void execute(size_t isize, size_t istride,
                     const std::complex<T> *spectrum,
                     size_t tsize, size_t tstride,
                     const double *times,
                     size_t osize, size_t ostride,
                     std::complex<T> *out);

        void execute_adjoint(const std::valarray<std::complex<T>> &time_series,
                             const std::valarray<double> &times,
                             std::valarray<std::complex<T>> &spectrum);

        void execute_adjoint(size_t isize, size_t istride,
                             const std::complex<T> *time_series,
                             size_t tsize, size_t tstride,
                             const double *times,
                             size_t osize, size_t ostride,
                             std::complex<T> *spectrum);


        void set_spectrum(const std::valarray<std::complex<T>> &x);

        void set_spectrum(size_t size, size_t stride, const std::complex<T> *x);

        std::complex<T> interp(double t) const;

        size_t size_kernel() const {return 2*_m+1;}
        size_t size_spectrum() const {return _n;}
        size_t size_transform() const {return _fft_size;}

    private:
        size_t _m, _n, _fft_size;
        std::valarray<std::complex<T>> _xf, _xt;
        std::valarray<T> _weights;
        isce3::core::NFFTKernel<T> _kernel;
        isce3::signal::Signal<T> _fft;
};