NektarFFT.h

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///////////////////////////////////////////////////////////////////////////////
//
// File NektarFFT.h
//
// For more information, please see: http://www.nektar.info
//
// The MIT License
//
// Copyright (c) 2006 Division of Applied Mathematics, Brown University (USA),
// Department of Aeronautics, Imperial College London (UK), and Scientific
// Computing and Imaging Institute, University of Utah (USA).
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//
// Description: Header file for the Fast Fourier Transform class in Nektar++
//
///////////////////////////////////////////////////////////////////////////////

#ifndef NEKTAR_LIB_UTILIITIES_FFT_NEKTARFFT_H
#define NEKTAR_LIB_UTILIITIES_FFT_NEKTARFFT_H

#include <LibUtilities/BasicConst/NektarUnivTypeDefs.hpp>
#include <LibUtilities/BasicUtils/NekFactory.hpp>
#include <LibUtilities/LibUtilitiesDeclspec.h>

namespace Nektar
{
    template <typename Dim, typename DataType>
    class Array;
    
    namespace LibUtilities
    {
        /**
         * The NektarFFT class is a virtual class to manage the use of the FFT to do Fwd/Bwd transformations
         * and convolutions. The function here defined will link to a proper implementation of the FFT algorithm.
         * Depending on the user definition the functions can link to a class which is a wrapper around the FFTW 
         * library or to a specific FFT implementation.
         */
        class NektarFFT;
        
        // A shared pointer to the NektarFFT object
        typedef std::shared_ptr<NektarFFT>  NektarFFTSharedPtr;
        
        /// Datatype of the NekFactory used to instantiate classes derived from
        /// the NektarFFT class.
        typedef LibUtilities::NekFactory< std::string, NektarFFT, int> NektarFFTFactory;
        
        LIB_UTILITIES_EXPORT NektarFFTFactory& GetNektarFFTFactory();

        class NektarFFT
        {
        public:
            
            /// Initialises NektarFFT class members.
            LIB_UTILITIES_EXPORT NektarFFT(int N);
            
            // Distructor
            LIB_UTILITIES_EXPORT  ~NektarFFT();
            
            /**
             * m_N is the dimension of the Fourier transform.
             * It means that the coefficient vector and the vector of the variable in physical
             * space have size m_N. It is becasue everything is managed just with real data.
             */
            int m_N;
        
            /**
             * Forward transformation to pass from physical to coefficient space using the FFT.
             * This method will take the place of the Matrix-Vector multiplication
             * input:
             * N         = number of Fourier points
             * inarray   = vector in physical space (length N)
             * output:
             * outarray  = vector in coefficient space (length N)
             */
            LIB_UTILITIES_EXPORT void FFTFwdTrans(Array<OneD,NekDouble> &phy, Array<OneD,NekDouble> &coef);
            
            /**
             * Backward transformation to pass from coefficient to physical space using the FFT.
             * This method will take the place of the Matrix-Vector multiplication
             * input:
             * N          = number of Fourier points
             * inarrray   = vector in coefficient space (length N)
             * output:
             * outarray   = vector in physical space (length N)
             */
            LIB_UTILITIES_EXPORT void FFTBwdTrans(Array<OneD,NekDouble> &coef, Array<OneD,NekDouble> &phys);
            
        protected:
            
            
            virtual void v_FFTFwdTrans(Array<OneD,NekDouble> &phys, Array<OneD,NekDouble> &coef);
                        
            virtual void v_FFTBwdTrans(Array<OneD,NekDouble> &coef, Array<OneD,NekDouble> &phys);
            
        private:
            
        };
    }//end namespace LibUtilities
}//end of namespace Nektar
#endif //NEKTAR_LIB_UTILIITIES_FFT_NEKTARFFT_H