fft Class Reference

Fast fourier transform using the fftw library. More...

#include <fft.H>

Public Types
enum	transformDirection { FORWARD_TRANSFORM = -1 , REVERSE_TRANSFORM = 1 }

Static Public Member Functions
static void	fftRenumberRecurse (List< complex > &data, List< complex > &renumData, const UList< int > &nn, label nnprod, label ii, label l1, label l2)
static void	fftRenumber (List< complex > &data, const UList< int > &nn)
	fftRenumber: fold the n-d data array to get the fft components in the right places.
static tmp< complexField >	realTransform1D (const scalarField &field)
	Transform real-value data.
static tmp< complexField >	realTransform1D (const tmp< scalarField > &field)
	Transform real-value data.
static void	transform (complexField &field, const UList< int > &nn, transformDirection fftDirection)
	Transform complex-value data.
static tmp< complexField >	forwardTransform (const tmp< complexField > &field, const UList< int > &nn)
static tmp< complexField >	reverseTransform (const tmp< complexField > &field, const UList< int > &nn)
static tmp< complexVectorField >	forwardTransform (const tmp< complexVectorField > &field, const UList< int > &nn)
static tmp< complexVectorField >	reverseTransform (const tmp< complexVectorField > &field, const UList< int > &nn)

Detailed Description

Fast fourier transform using the fftw library.

The complex transform field is returned in the field supplied. The direction of transform is supplied as an argument (-1 = forward, 1 = reverse). The dimensionality and organisation of the array of values in space is supplied in the nn indexing array.

Note

The fftw library uses int only (no longs) for its dimensionality.

Source files

• fft.H
• fft.C

Definition at line 51 of file fft.H.

Member Enumeration Documentation

transformDirection

enum transformDirection

Enumerator
FORWARD_TRANSFORM	The sign -1 = FFTW_FORWARD.
REVERSE_TRANSFORM	The sign +1 = FFTW_BACKWARD.

Definition at line 56 of file fft.H.

Member Function Documentation

fftRenumberRecurse()

void fftRenumberRecurse ( List< complex > & data, List< complex > & renumData, const UList< int > & nn, label nnprod, label ii, label l1, label l2 )

static

Definition at line 27 of file fft.C.

References fftRenumberRecurse(), and UList< T >::size().

Referenced by fftRenumber(), and fftRenumberRecurse().

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fftRenumber()

void fftRenumber ( List< complex > & data, const UList< int > & nn )

static

fftRenumber: fold the n-d data array to get the fft components in the right places.

Definition at line 87 of file fft.C.

References fftRenumberRecurse(), and forAll.

Referenced by transform().

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realTransform1D() [1/2]

Foam::tmp< Foam::complexField > realTransform1D ( const scalarField & field )

static

Transform real-value data.

• uses the fftw real to half-complex method
• result size is field.size()/2 + 1

Definition at line 113 of file fft.C.

References UList< T >::data(), field(), n, and tmp< T >::New().

Referenced by noiseFFT::Pf(), noiseModel::Pf(), and realTransform1D().

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realTransform1D() [2/2]

Foam::tmp< Foam::complexField > realTransform1D ( const tmp< scalarField > & field )

static

Transform real-value data.

• uses the fftw real to half-complex method
• result size is field.size()/2 + 1

Definition at line 160 of file fft.C.

References tmp< T >::clear(), and realTransform1D().

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transform()

void transform ( complexField & field, const UList< int > & nn, transformDirection fftDirection )

static

Transform complex-value data.

Definition at line 171 of file fft.C.

References UList< T >::begin(), fftRenumber(), field(), forAll, FORWARD_TRANSFORM, N(), REVERSE_TRANSFORM, and UList< T >::size().

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forwardTransform() [1/2]

Foam::tmp< Foam::complexField > forwardTransform ( const tmp< complexField > & field, const UList< int > & nn )

static

Definition at line 235 of file fft.C.

References tmp< T >::clear(), FORWARD_TRANSFORM, tmp< T >::New(), and Foam::transform().

Referenced by energySpectrum::calcAndWriteSpectrum(), Foam::calcEk(), and forwardTransform().

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reverseTransform() [1/2]

Foam::tmp< Foam::complexField > reverseTransform ( const tmp< complexField > & field, const UList< int > & nn )

static

Definition at line 251 of file fft.C.

References tmp< T >::clear(), tmp< T >::New(), REVERSE_TRANSFORM, and Foam::transform().

Referenced by reverseTransform(), and turbGen::U().

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forwardTransform() [2/2]

Foam::tmp< Foam::complexVectorField > forwardTransform ( const tmp< complexVectorField > & field, const UList< int > & nn )

static

Definition at line 267 of file fft.C.

References tmp< T >::clear(), Foam::component(), forwardTransform(), VectorSpace< Form, Cmpt, Ncmpts >::nComponents, and tmp< T >::New().

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reverseTransform() [2/2]

Foam::tmp< Foam::complexVectorField > reverseTransform ( const tmp< complexVectorField > & field, const UList< int > & nn )

static

Definition at line 290 of file fft.C.

References tmp< T >::clear(), Foam::component(), VectorSpace< Form, Cmpt, Ncmpts >::nComponents, tmp< T >::New(), and reverseTransform().

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The documentation for this class was generated from the following files:

• src/randomProcesses/fft/fft.H
• src/randomProcesses/fft/fft.C