unsupported/Eigen/FFT - eigen - Git at Google

 // This file is part of Eigen, a lightweight C++ template library
 // for linear algebra.
 //
 // Copyright (C) 2009 Mark Borgerding mark a borgerding net
 //
 // This Source Code Form is subject to the terms of the Mozilla
 // Public License v. 2.0. If a copy of the MPL was not distributed
 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

 #ifndef EIGEN_FFT_MODULE_H
 #define EIGEN_FFT_MODULE_H

 #include <complex>
 #include <vector>
 #include <map>
 #include "../../Eigen/Core"


 /**
   * \defgroup FFT_Module Fast Fourier Transform module
   *
   * \code
   * #include <unsupported/Eigen/FFT>
   * \endcode
   *
   * This module provides Fast Fourier transformation, with a configurable backend
   * implementation.
   *
   * The default implementation is based on kissfft. It is a small, free, and
   * reasonably efficient default.
   *
   * There are currently four implementation backend:
   *
   * - kissfft(https://github.com/mborgerding/kissfft) : Simple and not so fast, BSD-3-Clause.
   *   It is a mixed-radix Fast Fourier Transform based up on the principle, "Keep It Simple, Stupid."
   *   Notice that:kissfft fails to handle "atypically-sized" inputs(i.e., sizes with large factors),a workaround is using fftw or pocketfft.
   * - fftw (http://www.fftw.org) : faster, GPL -- incompatible with Eigen in LGPL form, bigger code size.
   * - MKL (https://www.intel.com/content/www/us/en/developer/tools/oneapi/onemkl-download.html) : fastest, free -- may be incompatible with Eigen in GPL form.
   * - pocketfft (https://gitlab.mpcdf.mpg.de/mtr/pocketfft) : faster than kissfft, BSD 3-clause.
   *   It is a heavily modified implementation of FFTPack, with the following advantages:
   *   1.strictly C++11 compliant
   *   2.more accurate twiddle factor computation
   *   3.very fast plan generation
   *   4.worst case complexity for transform sizes with large prime factors is N*log(N), because Bluestein's algorithm is used for these cases
   *
   * \section FFTDesign Design
   *
   * The following design decisions were made concerning scaling and
   * half-spectrum for real FFT.
   *
   * The intent is to facilitate generic programming and ease migrating code
   * from  Matlab/octave.
   * We think the default behavior of Eigen/FFT should favor correctness and
   * generality over speed. Of course, the caller should be able to "opt-out" from this
   * behavior and get the speed increase if they want it.
   *
   * 1) %Scaling:
   * Other libraries (FFTW,IMKL,KISSFFT)  do not perform scaling, so there
   * is a constant gain incurred after the forward&inverse transforms , so
   * IFFT(FFT(x)) = Kx;  this is done to avoid a vector-by-value multiply.
   * The downside is that algorithms that worked correctly in Matlab/octave
   * don't behave the same way once implemented in C++.
   *
   * How Eigen/FFT differs: invertible scaling is performed so IFFT( FFT(x) ) = x.
   *
   * 2) Real FFT half-spectrum
   * Other libraries use only half the frequency spectrum (plus one extra
   * sample for the Nyquist bin) for a real FFT, the other half is the
   * conjugate-symmetric of the first half.  This saves them a copy and some
   * memory.  The downside is the caller needs to have special logic for the
   * number of bins in complex vs real.
   *
   * How Eigen/FFT differs: The full spectrum is returned from the forward
   * transform.  This facilitates generic template programming by obviating
   * separate specializations for real vs complex.  On the inverse
   * transform, only half the spectrum is actually used if the output type is real.
   */


 #include "../../Eigen/src/Core/util/DisableStupidWarnings.h"

 #ifdef EIGEN_FFTW_DEFAULT
 // FFTW: faster, GPL -- incompatible with Eigen in LGPL form, bigger code size
 #  include <fftw3.h>
 #  include "src/FFT/ei_fftw_impl.h"
    namespace Eigen {
      //template <typename T> typedef struct internal::fftw_impl  default_fft_impl; this does not work
      template <typename T> struct default_fft_impl : public internal::fftw_impl<T> {};
    }
 #elif defined EIGEN_MKL_DEFAULT
 // intel Math Kernel Library: fastest, free -- may be incompatible with Eigen in GPL form
 #  include "src/FFT/ei_imklfft_impl.h"
    namespace Eigen {
      template <typename T> struct default_fft_impl : public internal::imklfft::imklfft_impl<T> {};
    }
 #elif defined EIGEN_POCKETFFT_DEFAULT
 // internal::pocketfft_impl: a heavily modified implementation of FFTPack, with many advantages.
 # include<pocketfft_hdronly.h>
 # include"src/FFT/ei_pocketfft_impl.h"
   namespace Eigen {
      template <typename T>
       struct default_fft_impl : public internal::pocketfft_impl<T> {};
   }
 #else
 // internal::kissfft_impl:  small, free, reasonably efficient default, derived from kissfft
 # include "src/FFT/ei_kissfft_impl.h"
   namespace Eigen {
      template <typename T>
        struct default_fft_impl : public internal::kissfft_impl<T> {};
   }
 #endif

 namespace Eigen {


 //
 template<typename T_SrcMat,typename T_FftIfc> struct fft_fwd_proxy;
 template<typename T_SrcMat,typename T_FftIfc> struct fft_inv_proxy;

 namespace internal {
 template<typename T_SrcMat,typename T_FftIfc>
 struct traits< fft_fwd_proxy<T_SrcMat,T_FftIfc> >
 {
   typedef typename T_SrcMat::PlainObject ReturnType;
 };
 template<typename T_SrcMat,typename T_FftIfc>
 struct traits< fft_inv_proxy<T_SrcMat,T_FftIfc> >
 {
   typedef typename T_SrcMat::PlainObject ReturnType;
 };
 }

 template<typename T_SrcMat,typename T_FftIfc>
 struct fft_fwd_proxy
  : public ReturnByValue<fft_fwd_proxy<T_SrcMat,T_FftIfc> >
 {
   typedef DenseIndex Index;

   fft_fwd_proxy(const T_SrcMat& src,T_FftIfc & fft, Index nfft) : m_src(src),m_ifc(fft), m_nfft(nfft) {}

   template<typename T_DestMat> void evalTo(T_DestMat& dst) const;

   Index rows() const { return m_src.rows(); }
   Index cols() const { return m_src.cols(); }
 protected:
   const T_SrcMat & m_src;
   T_FftIfc & m_ifc;
   Index m_nfft;
 };

 template<typename T_SrcMat,typename T_FftIfc>
 struct fft_inv_proxy
  : public ReturnByValue<fft_inv_proxy<T_SrcMat,T_FftIfc> >
 {
   typedef DenseIndex Index;

   fft_inv_proxy(const T_SrcMat& src,T_FftIfc & fft, Index nfft) : m_src(src),m_ifc(fft), m_nfft(nfft) {}

   template<typename T_DestMat> void evalTo(T_DestMat& dst) const;

   Index rows() const { return m_src.rows(); }
   Index cols() const { return m_src.cols(); }
 protected:
   const T_SrcMat & m_src;
   T_FftIfc & m_ifc;
   Index m_nfft;
 };


 template <typename T_Scalar,
          typename T_Impl=default_fft_impl<T_Scalar> >
 class FFT
 {
   public:
     typedef T_Impl impl_type;
     typedef DenseIndex Index;
     typedef typename impl_type::Scalar Scalar;
     typedef typename impl_type::Complex Complex;

     enum Flag {
       Default=0, // goof proof
       Unscaled=1,
       HalfSpectrum=2,
       // SomeOtherSpeedOptimization=4
       Speedy=32767
     };

     FFT( const impl_type & impl=impl_type() , Flag flags=Default ) :m_impl(impl),m_flag(flags) { }

     inline
     bool HasFlag(Flag f) const { return (m_flag & (int)f) == f;}

     inline
     void SetFlag(Flag f) { m_flag |= (int)f;}

     inline
     void ClearFlag(Flag f) { m_flag &= (~(int)f);}

     inline
     void fwd( Complex * dst, const Scalar * src, Index nfft)
     {
         m_impl.fwd(dst,src,static_cast<int>(nfft));
         if ( HasFlag(HalfSpectrum) == false)
           ReflectSpectrum(dst,nfft);
     }

     inline
     void fwd( Complex * dst, const Complex * src, Index nfft)
     {
         m_impl.fwd(dst,src,static_cast<int>(nfft));
     }

 #if defined EIGEN_FFTW_DEFAULT || defined EIGEN_POCKETFFT_DEFAULT || defined EIGEN_MKL_DEFAULT
     inline
     void fwd2(Complex * dst, const Complex * src, int n0,int n1)
     {
       m_impl.fwd2(dst,src,n0,n1);
     }
 #endif

     template <typename Input_>
     inline
     void fwd( std::vector<Complex> & dst, const std::vector<Input_> & src)
     {
       if ( NumTraits<Input_>::IsComplex == 0 && HasFlag(HalfSpectrum) )
         dst.resize( (src.size()>>1)+1); // half the bins + Nyquist bin
       else
         dst.resize(src.size());
       fwd(&dst[0],&src[0],src.size());
     }

     template<typename InputDerived, typename ComplexDerived>
     inline
     void fwd( MatrixBase<ComplexDerived> & dst, const MatrixBase<InputDerived> & src, Index nfft=-1)
     {
       typedef typename ComplexDerived::Scalar dst_type;
       typedef typename InputDerived::Scalar src_type;
       EIGEN_STATIC_ASSERT_VECTOR_ONLY(InputDerived)
       EIGEN_STATIC_ASSERT_VECTOR_ONLY(ComplexDerived)
       EIGEN_STATIC_ASSERT_SAME_VECTOR_SIZE(ComplexDerived,InputDerived) // size at compile-time
       EIGEN_STATIC_ASSERT((internal::is_same<dst_type, Complex>::value),
             YOU_MIXED_DIFFERENT_NUMERIC_TYPES__YOU_NEED_TO_USE_THE_CAST_METHOD_OF_MATRIXBASE_TO_CAST_NUMERIC_TYPES_EXPLICITLY)
       EIGEN_STATIC_ASSERT(int(InputDerived::Flags)&int(ComplexDerived::Flags)&DirectAccessBit,
             THIS_METHOD_IS_ONLY_FOR_EXPRESSIONS_WITH_DIRECT_MEMORY_ACCESS_SUCH_AS_MAP_OR_PLAIN_MATRICES)

       if (nfft<1)
         nfft = src.size();

       if ( NumTraits< src_type >::IsComplex == 0 && HasFlag(HalfSpectrum) )
         dst.derived().resize( (nfft>>1)+1);
       else
         dst.derived().resize(nfft);

       if ( src.innerStride() != 1 || src.size() < nfft ) {
         Matrix<src_type,1,Dynamic> tmp;
         if (src.size()<nfft) {
           tmp.setZero(nfft);
           tmp.block(0,0,src.size(),1 ) = src;
         }else{
           tmp = src;
         }
         fwd( &dst[0],&tmp[0],nfft );
       }else{
         fwd( &dst[0],&src[0],nfft );
       }
     }

     template<typename InputDerived>
     inline
     fft_fwd_proxy< MatrixBase<InputDerived>, FFT<T_Scalar,T_Impl> >
     fwd( const MatrixBase<InputDerived> & src, Index nfft=-1)
     {
       return fft_fwd_proxy< MatrixBase<InputDerived> ,FFT<T_Scalar,T_Impl> >( src, *this,nfft );
     }

     template<typename InputDerived>
     inline
     fft_inv_proxy< MatrixBase<InputDerived>, FFT<T_Scalar,T_Impl> >
     inv( const MatrixBase<InputDerived> & src, Index nfft=-1)
     {
       return  fft_inv_proxy< MatrixBase<InputDerived> ,FFT<T_Scalar,T_Impl> >( src, *this,nfft );
     }

     inline
     void inv( Complex * dst, const Complex * src, Index nfft)
     {
       m_impl.inv( dst,src,static_cast<int>(nfft) );
       if ( HasFlag( Unscaled ) == false)
         scale(dst,Scalar(1./nfft),nfft); // scale the time series
     }

     inline
     void inv( Scalar * dst, const Complex * src, Index nfft)
     {
       m_impl.inv( dst,src,static_cast<int>(nfft) );
       if ( HasFlag( Unscaled ) == false)
         scale(dst,Scalar(1./nfft),nfft); // scale the time series
     }

     template<typename OutputDerived, typename ComplexDerived>
     inline
     void inv( MatrixBase<OutputDerived> & dst, const MatrixBase<ComplexDerived> & src, Index nfft=-1)
     {
       typedef typename ComplexDerived::Scalar src_type;
       typedef typename ComplexDerived::RealScalar real_type;
       typedef typename OutputDerived::Scalar dst_type;
       const bool realfft= (NumTraits<dst_type>::IsComplex == 0);
       EIGEN_STATIC_ASSERT_VECTOR_ONLY(OutputDerived)
       EIGEN_STATIC_ASSERT_VECTOR_ONLY(ComplexDerived)
       EIGEN_STATIC_ASSERT_SAME_VECTOR_SIZE(ComplexDerived,OutputDerived) // size at compile-time
       EIGEN_STATIC_ASSERT((internal::is_same<src_type, Complex>::value),
             YOU_MIXED_DIFFERENT_NUMERIC_TYPES__YOU_NEED_TO_USE_THE_CAST_METHOD_OF_MATRIXBASE_TO_CAST_NUMERIC_TYPES_EXPLICITLY)
       EIGEN_STATIC_ASSERT(int(OutputDerived::Flags)&int(ComplexDerived::Flags)&DirectAccessBit,
             THIS_METHOD_IS_ONLY_FOR_EXPRESSIONS_WITH_DIRECT_MEMORY_ACCESS_SUCH_AS_MAP_OR_PLAIN_MATRICES)

       if (nfft<1) { //automatic FFT size determination
         if ( realfft && HasFlag(HalfSpectrum) )
           nfft = 2*(src.size()-1); //assume even fft size
         else
           nfft = src.size();
       }
       dst.derived().resize( nfft );

       // check for nfft that does not fit the input data size
       Index resize_input= ( realfft && HasFlag(HalfSpectrum) )
         ? ( (nfft/2+1) - src.size() )
         : ( nfft - src.size() );

       if ( src.innerStride() != 1 || resize_input ) {
         // if the vector is strided, then we need to copy it to a packed temporary
         Matrix<src_type,1,Dynamic> tmp;
         if ( resize_input ) {
           size_t ncopy = (std::min)(src.size(),src.size() + resize_input);
           tmp.setZero(src.size() + resize_input);
           if ( realfft && HasFlag(HalfSpectrum) ) {
             // pad at the Nyquist bin
             tmp.head(ncopy) = src.head(ncopy);
             tmp(ncopy-1) = real(tmp(ncopy-1)); // enforce real-only Nyquist bin
           }else{
             size_t nhead,ntail;
             nhead = 1+ncopy/2-1; // range  [0:pi)
             ntail = ncopy/2-1;   // range (-pi:0)
             tmp.head(nhead) = src.head(nhead);
             tmp.tail(ntail) = src.tail(ntail);
             if (resize_input<0) { //shrinking -- create the Nyquist bin as the average of the two bins that fold into it
               tmp(nhead) = ( src(nfft/2) + src( src.size() - nfft/2 ) )*real_type(.5);
             }else{ // expanding -- split the old Nyquist bin into two halves
               tmp(nhead) = src(nhead) * real_type(.5);
               tmp(tmp.size()-nhead) = tmp(nhead);
             }
           }
         }else{
           tmp = src;
         }
         inv( &dst[0],&tmp[0], nfft);
       }else{
         inv( &dst[0],&src[0], nfft);
       }
     }

     template <typename Output_>
     inline
     void inv( std::vector<Output_> & dst, const std::vector<Complex> & src,Index nfft=-1)
     {
       if (nfft<1)
         nfft = ( NumTraits<Output_>::IsComplex == 0 && HasFlag(HalfSpectrum) ) ? 2*(src.size()-1) : src.size();
       dst.resize( nfft );
       inv( &dst[0],&src[0],nfft);
     }


 #if defined EIGEN_FFTW_DEFAULT || defined EIGEN_POCKETFFT_DEFAULT || defined EIGEN_MKL_DEFAULT
     inline
     void inv2(Complex * dst, const Complex * src, int n0,int n1)
     {
       m_impl.inv2(dst,src,n0,n1);
       if ( HasFlag( Unscaled ) == false)
           scale(dst,1./(n0*n1),n0*n1);
     }
 #endif


     inline
     impl_type & impl() {return m_impl;}
   private:

     template <typename T_Data>
     inline
     void scale(T_Data * x,Scalar s,Index nx)
     {
 #if 1
       for (int k=0;k<nx;++k)
         *x++ *= s;
 #else
       if ( ((ptrdiff_t)x) & 15 )
         Matrix<T_Data, Dynamic, 1>::Map(x,nx) *= s;
       else
         Matrix<T_Data, Dynamic, 1>::MapAligned(x,nx) *= s;
          //Matrix<T_Data, Dynamic, Dynamic>::Map(x,nx) * s;
 #endif
     }

     inline
     void ReflectSpectrum(Complex * freq, Index nfft)
     {
       // create the implicit right-half spectrum (conjugate-mirror of the left-half)
       Index nhbins=(nfft>>1)+1;
       for (Index k=nhbins;k < nfft; ++k )
         freq[k] = conj(freq[nfft-k]);
     }

     impl_type m_impl;
     int m_flag;
 };

 template<typename T_SrcMat,typename T_FftIfc>
 template<typename T_DestMat> inline
 void fft_fwd_proxy<T_SrcMat,T_FftIfc>::evalTo(T_DestMat& dst) const
 {
     m_ifc.fwd( dst, m_src, m_nfft);
 }

 template<typename T_SrcMat,typename T_FftIfc>
 template<typename T_DestMat> inline
 void fft_inv_proxy<T_SrcMat,T_FftIfc>::evalTo(T_DestMat& dst) const
 {
     m_ifc.inv( dst, m_src, m_nfft);
 }

 }

 #include "../../Eigen/src/Core/util/ReenableStupidWarnings.h"

 #endif
	// This file is part of Eigen, a lightweight C++ template library
	// for linear algebra.
	//
	// Copyright (C) 2009 Mark Borgerding mark a borgerding net
	//
	// This Source Code Form is subject to the terms of the Mozilla
	// Public License v. 2.0. If a copy of the MPL was not distributed
	// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

	#ifndef EIGEN_FFT_MODULE_H
	#define EIGEN_FFT_MODULE_H

	#include <complex>
	#include <vector>
	#include <map>
	#include "../../Eigen/Core"


	/**
	* \defgroup FFT_Module Fast Fourier Transform module
	*
	* \code
	* #include <unsupported/Eigen/FFT>
	* \endcode
	*
	* This module provides Fast Fourier transformation, with a configurable backend
	* implementation.
	*
	* The default implementation is based on kissfft. It is a small, free, and
	* reasonably efficient default.
	*
	* There are currently four implementation backend:
	*
	* - kissfft(https://github.com/mborgerding/kissfft) : Simple and not so fast, BSD-3-Clause.
	* It is a mixed-radix Fast Fourier Transform based up on the principle, "Keep It Simple, Stupid."
	* Notice that:kissfft fails to handle "atypically-sized" inputs(i.e., sizes with large factors),a workaround is using fftw or pocketfft.
	* - fftw (http://www.fftw.org) : faster, GPL -- incompatible with Eigen in LGPL form, bigger code size.
	* - MKL (https://www.intel.com/content/www/us/en/developer/tools/oneapi/onemkl-download.html) : fastest, free -- may be incompatible with Eigen in GPL form.
	* - pocketfft (https://gitlab.mpcdf.mpg.de/mtr/pocketfft) : faster than kissfft, BSD 3-clause.
	* It is a heavily modified implementation of FFTPack, with the following advantages:
	* 1.strictly C++11 compliant
	* 2.more accurate twiddle factor computation
	* 3.very fast plan generation
	* 4.worst case complexity for transform sizes with large prime factors is N*log(N), because Bluestein's algorithm is used for these cases
	*
	* \section FFTDesign Design
	*
	* The following design decisions were made concerning scaling and
	* half-spectrum for real FFT.
	*
	* The intent is to facilitate generic programming and ease migrating code
	* from Matlab/octave.
	* We think the default behavior of Eigen/FFT should favor correctness and
	* generality over speed. Of course, the caller should be able to "opt-out" from this
	* behavior and get the speed increase if they want it.
	*
	* 1) %Scaling:
	* Other libraries (FFTW,IMKL,KISSFFT) do not perform scaling, so there
	* is a constant gain incurred after the forward&inverse transforms , so
	* IFFT(FFT(x)) = Kx; this is done to avoid a vector-by-value multiply.
	* The downside is that algorithms that worked correctly in Matlab/octave
	* don't behave the same way once implemented in C++.
	*
	* How Eigen/FFT differs: invertible scaling is performed so IFFT( FFT(x) ) = x.
	*
	* 2) Real FFT half-spectrum
	* Other libraries use only half the frequency spectrum (plus one extra
	* sample for the Nyquist bin) for a real FFT, the other half is the
	* conjugate-symmetric of the first half. This saves them a copy and some
	* memory. The downside is the caller needs to have special logic for the
	* number of bins in complex vs real.
	*
	* How Eigen/FFT differs: The full spectrum is returned from the forward
	* transform. This facilitates generic template programming by obviating
	* separate specializations for real vs complex. On the inverse
	* transform, only half the spectrum is actually used if the output type is real.
	*/


	#include "../../Eigen/src/Core/util/DisableStupidWarnings.h"

	#ifdef EIGEN_FFTW_DEFAULT
	// FFTW: faster, GPL -- incompatible with Eigen in LGPL form, bigger code size
	# include <fftw3.h>
	# include "src/FFT/ei_fftw_impl.h"
	namespace Eigen {
	//template <typename T> typedef struct internal::fftw_impl default_fft_impl; this does not work
	template <typename T> struct default_fft_impl : public internal::fftw_impl<T> {};
	}
	#elif defined EIGEN_MKL_DEFAULT
	// intel Math Kernel Library: fastest, free -- may be incompatible with Eigen in GPL form
	# include "src/FFT/ei_imklfft_impl.h"
	namespace Eigen {
	template <typename T> struct default_fft_impl : public internal::imklfft::imklfft_impl<T> {};
	}
	#elif defined EIGEN_POCKETFFT_DEFAULT
	// internal::pocketfft_impl: a heavily modified implementation of FFTPack, with many advantages.
	# include<pocketfft_hdronly.h>
	# include"src/FFT/ei_pocketfft_impl.h"
	namespace Eigen {
	template <typename T>
	struct default_fft_impl : public internal::pocketfft_impl<T> {};
	}
	#else
	// internal::kissfft_impl: small, free, reasonably efficient default, derived from kissfft
	# include "src/FFT/ei_kissfft_impl.h"
	namespace Eigen {
	template <typename T>
	struct default_fft_impl : public internal::kissfft_impl<T> {};
	}
	#endif

	namespace Eigen {


	//
	template<typename T_SrcMat,typename T_FftIfc> struct fft_fwd_proxy;
	template<typename T_SrcMat,typename T_FftIfc> struct fft_inv_proxy;

	namespace internal {
	template<typename T_SrcMat,typename T_FftIfc>
	struct traits< fft_fwd_proxy<T_SrcMat,T_FftIfc> >
	{
	typedef typename T_SrcMat::PlainObject ReturnType;
	};
	template<typename T_SrcMat,typename T_FftIfc>
	struct traits< fft_inv_proxy<T_SrcMat,T_FftIfc> >
	{
	typedef typename T_SrcMat::PlainObject ReturnType;
	};
	}

	template<typename T_SrcMat,typename T_FftIfc>
	struct fft_fwd_proxy
	: public ReturnByValue<fft_fwd_proxy<T_SrcMat,T_FftIfc> >
	{
	typedef DenseIndex Index;

	fft_fwd_proxy(const T_SrcMat& src,T_FftIfc & fft, Index nfft) : m_src(src),m_ifc(fft), m_nfft(nfft) {}

	template<typename T_DestMat> void evalTo(T_DestMat& dst) const;

	Index rows() const { return m_src.rows(); }
	Index cols() const { return m_src.cols(); }
	protected:
	const T_SrcMat & m_src;
	T_FftIfc & m_ifc;
	Index m_nfft;
	};

	template<typename T_SrcMat,typename T_FftIfc>
	struct fft_inv_proxy
	: public ReturnByValue<fft_inv_proxy<T_SrcMat,T_FftIfc> >
	{
	typedef DenseIndex Index;

	fft_inv_proxy(const T_SrcMat& src,T_FftIfc & fft, Index nfft) : m_src(src),m_ifc(fft), m_nfft(nfft) {}

	template<typename T_DestMat> void evalTo(T_DestMat& dst) const;

	Index rows() const { return m_src.rows(); }
	Index cols() const { return m_src.cols(); }
	protected:
	const T_SrcMat & m_src;
	T_FftIfc & m_ifc;
	Index m_nfft;
	};


	template <typename T_Scalar,
	typename T_Impl=default_fft_impl<T_Scalar> >
	class FFT
	{
	public:
	typedef T_Impl impl_type;
	typedef DenseIndex Index;
	typedef typename impl_type::Scalar Scalar;
	typedef typename impl_type::Complex Complex;

	enum Flag {
	Default=0, // goof proof
	Unscaled=1,
	HalfSpectrum=2,
	// SomeOtherSpeedOptimization=4
	Speedy=32767
	};

	FFT( const impl_type & impl=impl_type() , Flag flags=Default ) :m_impl(impl),m_flag(flags) { }

	inline
	bool HasFlag(Flag f) const { return (m_flag & (int)f) == f;}

	inline
	void SetFlag(Flag f) { m_flag \|= (int)f;}

	inline
	void ClearFlag(Flag f) { m_flag &= (~(int)f);}

	inline
	void fwd( Complex * dst, const Scalar * src, Index nfft)
	{
	m_impl.fwd(dst,src,static_cast<int>(nfft));
	if ( HasFlag(HalfSpectrum) == false)
	ReflectSpectrum(dst,nfft);
	}

	inline
	void fwd( Complex * dst, const Complex * src, Index nfft)
	{
	m_impl.fwd(dst,src,static_cast<int>(nfft));
	}

	#if defined EIGEN_FFTW_DEFAULT \|\| defined EIGEN_POCKETFFT_DEFAULT \|\| defined EIGEN_MKL_DEFAULT
	inline
	void fwd2(Complex * dst, const Complex * src, int n0,int n1)
	{
	m_impl.fwd2(dst,src,n0,n1);
	}
	#endif

	template <typename Input_>
	inline
	void fwd( std::vector<Complex> & dst, const std::vector<Input_> & src)
	{
	if ( NumTraits<Input_>::IsComplex == 0 && HasFlag(HalfSpectrum) )
	dst.resize( (src.size()>>1)+1); // half the bins + Nyquist bin
	else
	dst.resize(src.size());
	fwd(&dst[0],&src[0],src.size());
	}

	template<typename InputDerived, typename ComplexDerived>
	inline
	void fwd( MatrixBase<ComplexDerived> & dst, const MatrixBase<InputDerived> & src, Index nfft=-1)
	{
	typedef typename ComplexDerived::Scalar dst_type;
	typedef typename InputDerived::Scalar src_type;
	EIGEN_STATIC_ASSERT_VECTOR_ONLY(InputDerived)
	EIGEN_STATIC_ASSERT_VECTOR_ONLY(ComplexDerived)
	EIGEN_STATIC_ASSERT_SAME_VECTOR_SIZE(ComplexDerived,InputDerived) // size at compile-time
	EIGEN_STATIC_ASSERT((internal::is_same<dst_type, Complex>::value),
	YOU_MIXED_DIFFERENT_NUMERIC_TYPES__YOU_NEED_TO_USE_THE_CAST_METHOD_OF_MATRIXBASE_TO_CAST_NUMERIC_TYPES_EXPLICITLY)
	EIGEN_STATIC_ASSERT(int(InputDerived::Flags)&int(ComplexDerived::Flags)&DirectAccessBit,
	THIS_METHOD_IS_ONLY_FOR_EXPRESSIONS_WITH_DIRECT_MEMORY_ACCESS_SUCH_AS_MAP_OR_PLAIN_MATRICES)

	if (nfft<1)
	nfft = src.size();

	if ( NumTraits< src_type >::IsComplex == 0 && HasFlag(HalfSpectrum) )
	dst.derived().resize( (nfft>>1)+1);
	else
	dst.derived().resize(nfft);

	if ( src.innerStride() != 1 \|\| src.size() < nfft ) {
	Matrix<src_type,1,Dynamic> tmp;
	if (src.size()<nfft) {
	tmp.setZero(nfft);
	tmp.block(0,0,src.size(),1 ) = src;
	}else{
	tmp = src;
	}
	fwd( &dst[0],&tmp[0],nfft );
	}else{
	fwd( &dst[0],&src[0],nfft );
	}
	}

	template<typename InputDerived>
	inline
	fft_fwd_proxy< MatrixBase<InputDerived>, FFT<T_Scalar,T_Impl> >
	fwd( const MatrixBase<InputDerived> & src, Index nfft=-1)
	{
	return fft_fwd_proxy< MatrixBase<InputDerived> ,FFT<T_Scalar,T_Impl> >( src, *this,nfft );
	}

	template<typename InputDerived>
	inline
	fft_inv_proxy< MatrixBase<InputDerived>, FFT<T_Scalar,T_Impl> >
	inv( const MatrixBase<InputDerived> & src, Index nfft=-1)
	{
	return fft_inv_proxy< MatrixBase<InputDerived> ,FFT<T_Scalar,T_Impl> >( src, *this,nfft );
	}

	inline
	void inv( Complex * dst, const Complex * src, Index nfft)
	{
	m_impl.inv( dst,src,static_cast<int>(nfft) );
	if ( HasFlag( Unscaled ) == false)
	scale(dst,Scalar(1./nfft),nfft); // scale the time series
	}

	inline
	void inv( Scalar * dst, const Complex * src, Index nfft)
	{
	m_impl.inv( dst,src,static_cast<int>(nfft) );
	if ( HasFlag( Unscaled ) == false)
	scale(dst,Scalar(1./nfft),nfft); // scale the time series
	}

	template<typename OutputDerived, typename ComplexDerived>
	inline
	void inv( MatrixBase<OutputDerived> & dst, const MatrixBase<ComplexDerived> & src, Index nfft=-1)
	{
	typedef typename ComplexDerived::Scalar src_type;
	typedef typename ComplexDerived::RealScalar real_type;
	typedef typename OutputDerived::Scalar dst_type;
	const bool realfft= (NumTraits<dst_type>::IsComplex == 0);
	EIGEN_STATIC_ASSERT_VECTOR_ONLY(OutputDerived)
	EIGEN_STATIC_ASSERT_VECTOR_ONLY(ComplexDerived)
	EIGEN_STATIC_ASSERT_SAME_VECTOR_SIZE(ComplexDerived,OutputDerived) // size at compile-time
	EIGEN_STATIC_ASSERT((internal::is_same<src_type, Complex>::value),
	YOU_MIXED_DIFFERENT_NUMERIC_TYPES__YOU_NEED_TO_USE_THE_CAST_METHOD_OF_MATRIXBASE_TO_CAST_NUMERIC_TYPES_EXPLICITLY)
	EIGEN_STATIC_ASSERT(int(OutputDerived::Flags)&int(ComplexDerived::Flags)&DirectAccessBit,
	THIS_METHOD_IS_ONLY_FOR_EXPRESSIONS_WITH_DIRECT_MEMORY_ACCESS_SUCH_AS_MAP_OR_PLAIN_MATRICES)

	if (nfft<1) { //automatic FFT size determination
	if ( realfft && HasFlag(HalfSpectrum) )
	nfft = 2*(src.size()-1); //assume even fft size
	else
	nfft = src.size();
	}
	dst.derived().resize( nfft );

	// check for nfft that does not fit the input data size
	Index resize_input= ( realfft && HasFlag(HalfSpectrum) )
	? ( (nfft/2+1) - src.size() )
	: ( nfft - src.size() );

	if ( src.innerStride() != 1 \|\| resize_input ) {
	// if the vector is strided, then we need to copy it to a packed temporary
	Matrix<src_type,1,Dynamic> tmp;
	if ( resize_input ) {
	size_t ncopy = (std::min)(src.size(),src.size() + resize_input);
	tmp.setZero(src.size() + resize_input);
	if ( realfft && HasFlag(HalfSpectrum) ) {
	// pad at the Nyquist bin
	tmp.head(ncopy) = src.head(ncopy);
	tmp(ncopy-1) = real(tmp(ncopy-1)); // enforce real-only Nyquist bin
	}else{
	size_t nhead,ntail;
	nhead = 1+ncopy/2-1; // range [0:pi)
	ntail = ncopy/2-1; // range (-pi:0)
	tmp.head(nhead) = src.head(nhead);
	tmp.tail(ntail) = src.tail(ntail);
	if (resize_input<0) { //shrinking -- create the Nyquist bin as the average of the two bins that fold into it
	tmp(nhead) = ( src(nfft/2) + src( src.size() - nfft/2 ) )*real_type(.5);
	}else{ // expanding -- split the old Nyquist bin into two halves
	tmp(nhead) = src(nhead) * real_type(.5);
	tmp(tmp.size()-nhead) = tmp(nhead);
	}
	}
	}else{
	tmp = src;
	}
	inv( &dst[0],&tmp[0], nfft);
	}else{
	inv( &dst[0],&src[0], nfft);
	}
	}

	template <typename Output_>
	inline
	void inv( std::vector<Output_> & dst, const std::vector<Complex> & src,Index nfft=-1)
	{
	if (nfft<1)
	nfft = ( NumTraits<Output_>::IsComplex == 0 && HasFlag(HalfSpectrum) ) ? 2*(src.size()-1) : src.size();
	dst.resize( nfft );
	inv( &dst[0],&src[0],nfft);
	}


	#if defined EIGEN_FFTW_DEFAULT \|\| defined EIGEN_POCKETFFT_DEFAULT \|\| defined EIGEN_MKL_DEFAULT
	inline
	void inv2(Complex * dst, const Complex * src, int n0,int n1)
	{
	m_impl.inv2(dst,src,n0,n1);
	if ( HasFlag( Unscaled ) == false)
	scale(dst,1./(n0n1),n0n1);
	}
	#endif


	inline
	impl_type & impl() {return m_impl;}
	private:

	template <typename T_Data>
	inline
	void scale(T_Data * x,Scalar s,Index nx)
	{
	#if 1
	for (int k=0;k<nx;++k)
	x++ = s;
	#else
	if ( ((ptrdiff_t)x) & 15 )
	Matrix<T_Data, Dynamic, 1>::Map(x,nx) *= s;
	else
	Matrix<T_Data, Dynamic, 1>::MapAligned(x,nx) *= s;
	//Matrix<T_Data, Dynamic, Dynamic>::Map(x,nx) * s;
	#endif
	}

	inline
	void ReflectSpectrum(Complex * freq, Index nfft)
	{
	// create the implicit right-half spectrum (conjugate-mirror of the left-half)
	Index nhbins=(nfft>>1)+1;
	for (Index k=nhbins;k < nfft; ++k )
	freq[k] = conj(freq[nfft-k]);
	}

	impl_type m_impl;
	int m_flag;
	};

	template<typename T_SrcMat,typename T_FftIfc>
	template<typename T_DestMat> inline
	void fft_fwd_proxy<T_SrcMat,T_FftIfc>::evalTo(T_DestMat& dst) const
	{
	m_ifc.fwd( dst, m_src, m_nfft);
	}

	template<typename T_SrcMat,typename T_FftIfc>
	template<typename T_DestMat> inline
	void fft_inv_proxy<T_SrcMat,T_FftIfc>::evalTo(T_DestMat& dst) const
	{
	m_ifc.inv( dst, m_src, m_nfft);
	}

	}

	#include "../../Eigen/src/Core/util/ReenableStupidWarnings.h"

	#endif