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262 lines
9.1 KiB
C++
262 lines
9.1 KiB
C++
// This file is part of Eigen, a lightweight C++ template library
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// for linear algebra.
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//
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// Copyright (C) 2009 Mark Borgerding mark a borgerding net
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//
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// Eigen is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Lesser General Public
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// License as published by the Free Software Foundation; either
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// version 3 of the License, or (at your option) any later version.
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//
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// Alternatively, you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as
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// published by the Free Software Foundation; either version 2 of
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// the License, or (at your option) any later version.
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//
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// Eigen is distributed in the hope that it will be useful, but WITHOUT ANY
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// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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// FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License or the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public
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// License and a copy of the GNU General Public License along with
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// Eigen. If not, see <http://www.gnu.org/licenses/>.
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#ifndef EIGEN_FFT_H
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#define EIGEN_FFT_H
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#include <complex>
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#include <vector>
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#include <map>
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#include <Eigen/Core>
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/** \ingroup Unsupported_modules
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* \defgroup FFT_Module Fast Fourier Transform module
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*
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* \code
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* #include <unsupported/Eigen/FFT>
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* \endcode
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*
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* This module provides Fast Fourier transformation, either using a built-in implementation
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* or as a frontend to various FFT libraries.
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*
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* The build-in implementation is based on kissfft. It is a small, free, and
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* reasonably efficient default.
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*
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* There are currently two frontends:
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*
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* - fftw (http://www.fftw.org) : faster, GPL -- incompatible with Eigen in LGPL form, bigger code size.
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* - MLK (http://en.wikipedia.org/wiki/Math_Kernel_Library) : fastest, commercial -- may be incompatible with Eigen in GPL form.
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*
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* \section FFTDesign Design
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*
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* The following design decisions were made concerning scaling and
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* half-spectrum for real FFT.
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*
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* The intent is to facilitate generic programming and ease migrating code
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* from Matlab/octave.
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* We think the default behavior of Eigen/FFT should favor correctness and
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* generality over speed. Of course, the caller should be able to "opt-out" from this
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* behavior and get the speed increase if they want it.
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*
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* 1) %Scaling:
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* Other libraries (FFTW,IMKL,KISSFFT) do not perform scaling, so there
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* is a constant gain incurred after the forward&inverse transforms , so
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* IFFT(FFT(x)) = Kx; this is done to avoid a vector-by-value multiply.
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* The downside is that algorithms that worked correctly in Matlab/octave
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* don't behave the same way once implemented in C++.
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*
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* How Eigen/FFT differs: invertible scaling is performed so IFFT( FFT(x) ) = x.
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*
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* 2) Real FFT half-spectrum
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* Other libraries use only half the frequency spectrum (plus one extra
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* sample for the Nyquist bin) for a real FFT, the other half is the
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* conjugate-symmetric of the first half. This saves them a copy and some
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* memory. The downside is the caller needs to have special logic for the
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* number of bins in complex vs real.
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*
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* How Eigen/FFT differs: The full spectrum is returned from the forward
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* transform. This facilitates generic template programming by obviating
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* separate specializations for real vs complex. On the inverse
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* transform, only half the spectrum is actually used if the output type is real.
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*/
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#ifdef EIGEN_FFTW_DEFAULT
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// FFTW: faster, GPL -- incompatible with Eigen in LGPL form, bigger code size
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# include <fftw3.h>
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namespace Eigen {
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# include "src/FFT/ei_fftw_impl.h"
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//template <typename T> typedef struct ei_fftw_impl default_fft_impl; this does not work
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template <typename T> struct default_fft_impl : public ei_fftw_impl<T> {};
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}
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#elif defined EIGEN_MKL_DEFAULT
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// TODO
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// intel Math Kernel Library: fastest, commercial -- may be incompatible with Eigen in GPL form
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namespace Eigen {
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# include "src/FFT/ei_imklfft_impl.h"
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template <typename T> struct default_fft_impl : public ei_imklfft_impl {};
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}
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#else
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// ei_kissfft_impl: small, free, reasonably efficient default, derived from kissfft
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//
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namespace Eigen {
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# include "src/FFT/ei_kissfft_impl.h"
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template <typename T>
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struct default_fft_impl : public ei_kissfft_impl<T> {};
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}
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#endif
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namespace Eigen {
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template <typename _Scalar,
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typename _Impl=default_fft_impl<_Scalar> >
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class FFT
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{
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public:
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typedef _Impl impl_type;
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typedef typename impl_type::Scalar Scalar;
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typedef typename impl_type::Complex Complex;
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enum Flag {
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Default=0, // goof proof
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Unscaled=1,
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HalfSpectrum=2,
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// SomeOtherSpeedOptimization=4
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Speedy=32767
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};
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FFT( const impl_type & impl=impl_type() , Flag flags=Default ) :m_impl(impl),m_flag(flags) { }
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inline
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bool HasFlag(Flag f) const { return (m_flag & (int)f) == f;}
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inline
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void SetFlag(Flag f) { m_flag |= (int)f;}
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inline
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void ClearFlag(Flag f) { m_flag &= (~(int)f);}
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inline
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void fwd( Complex * dst, const Scalar * src, int nfft)
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{
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m_impl.fwd(dst,src,nfft);
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if ( HasFlag(HalfSpectrum) == false)
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ReflectSpectrum(dst,nfft);
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}
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inline
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void fwd( Complex * dst, const Complex * src, int nfft)
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{
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m_impl.fwd(dst,src,nfft);
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}
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template <typename _Input>
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inline
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void fwd( std::vector<Complex> & dst, const std::vector<_Input> & src)
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{
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if ( NumTraits<_Input>::IsComplex == 0 && HasFlag(HalfSpectrum) )
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dst.resize( (src.size()>>1)+1);
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else
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dst.resize(src.size());
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fwd(&dst[0],&src[0],static_cast<int>(src.size()));
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}
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template<typename InputDerived, typename ComplexDerived>
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inline
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void fwd( MatrixBase<ComplexDerived> & dst, const MatrixBase<InputDerived> & src)
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{
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EIGEN_STATIC_ASSERT_VECTOR_ONLY(InputDerived)
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EIGEN_STATIC_ASSERT_VECTOR_ONLY(ComplexDerived)
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EIGEN_STATIC_ASSERT_SAME_VECTOR_SIZE(ComplexDerived,InputDerived) // size at compile-time
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EIGEN_STATIC_ASSERT((ei_is_same_type<typename ComplexDerived::Scalar, Complex>::ret),
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YOU_MIXED_DIFFERENT_NUMERIC_TYPES__YOU_NEED_TO_USE_THE_CAST_METHOD_OF_MATRIXBASE_TO_CAST_NUMERIC_TYPES_EXPLICITLY)
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EIGEN_STATIC_ASSERT(int(InputDerived::Flags)&int(ComplexDerived::Flags)&DirectAccessBit,
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THIS_METHOD_IS_ONLY_FOR_EXPRESSIONS_WITH_DIRECT_MEMORY_ACCESS_SUCH_AS_MAP_OR_PLAIN_MATRICES)
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if ( NumTraits< typename InputDerived::Scalar >::IsComplex == 0 && HasFlag(HalfSpectrum) )
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dst.derived().resize( (src.size()>>1)+1);
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else
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dst.derived().resize(src.size());
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fwd( &dst[0],&src[0],src.size() );
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}
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inline
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void inv( Complex * dst, const Complex * src, int nfft)
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{
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m_impl.inv( dst,src,nfft );
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if ( HasFlag( Unscaled ) == false)
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scale(dst,1./nfft,nfft);
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}
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inline
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void inv( Scalar * dst, const Complex * src, int nfft)
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{
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m_impl.inv( dst,src,nfft );
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if ( HasFlag( Unscaled ) == false)
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scale(dst,1./nfft,nfft);
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}
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template<typename OutputDerived, typename ComplexDerived>
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inline
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void inv( MatrixBase<OutputDerived> & dst, const MatrixBase<ComplexDerived> & src)
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{
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EIGEN_STATIC_ASSERT_VECTOR_ONLY(OutputDerived)
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EIGEN_STATIC_ASSERT_VECTOR_ONLY(ComplexDerived)
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EIGEN_STATIC_ASSERT_SAME_VECTOR_SIZE(ComplexDerived,OutputDerived) // size at compile-time
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EIGEN_STATIC_ASSERT((ei_is_same_type<typename ComplexDerived::Scalar, Complex>::ret),
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YOU_MIXED_DIFFERENT_NUMERIC_TYPES__YOU_NEED_TO_USE_THE_CAST_METHOD_OF_MATRIXBASE_TO_CAST_NUMERIC_TYPES_EXPLICITLY)
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EIGEN_STATIC_ASSERT(int(OutputDerived::Flags)&int(ComplexDerived::Flags)&DirectAccessBit,
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THIS_METHOD_IS_ONLY_FOR_EXPRESSIONS_WITH_DIRECT_MEMORY_ACCESS_SUCH_AS_MAP_OR_PLAIN_MATRICES)
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int nfft = src.size();
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int nout = HasFlag(HalfSpectrum) ? ((nfft>>1)+1) : nfft;
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dst.derived().resize( nout );
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inv( &dst[0],&src[0],src.size() );
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}
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template <typename _Output>
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inline
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void inv( std::vector<_Output> & dst, const std::vector<Complex> & src)
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{
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if ( NumTraits<_Output>::IsComplex == 0 && HasFlag(HalfSpectrum) )
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dst.resize( 2*(src.size()-1) );
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else
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dst.resize( src.size() );
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inv( &dst[0],&src[0],static_cast<int>(dst.size()) );
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}
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// TODO: multi-dimensional FFTs
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// TODO: handle Eigen MatrixBase
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// ---> i added fwd and inv specializations above + unit test, is this enough? (bjacob)
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inline
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impl_type & impl() {return m_impl;}
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private:
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template <typename _It,typename _Val>
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inline
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void scale(_It x,_Val s,int nx)
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{
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for (int k=0;k<nx;++k)
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*x++ *= s;
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}
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inline
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void ReflectSpectrum(Complex * freq,int nfft)
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{
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// create the implicit right-half spectrum (conjugate-mirror of the left-half)
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int nhbins=(nfft>>1)+1;
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for (int k=nhbins;k < nfft; ++k )
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freq[k] = conj(freq[nfft-k]);
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}
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impl_type m_impl;
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int m_flag;
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};
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}
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#endif
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/* vim: set filetype=cpp et sw=2 ts=2 ai: */
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