Real to complex FFT using FFTW3. More...

Inheritance diagram for QRealComplexFFTW3:

Public Member Functions
	QRealComplexFFTW3 (const size_t size)
	constructor More...

	QRealComplexFFTW3 ()
	empty constructor More...

virtual	~QRealComplexFFTW3 ()
	destructor More...

virtual int	TransformToFreq (const QVector &data, QVectorC &FFT, bool compress=false)
	transform from the times to the frequencies More...

virtual int	TransformFromFreq (const QVectorC &FT, QVector &spectrum, bool compress=false)
	transform from the frequencies to the times More...

virtual void	SetWindowType (WindowType wt, int coherent=0)
	resize working table and space More...

Public Member Functions inherited from QFFT
	QFFT (const size_t size)
	constructor with its size More...

	QFFT ()
	empty constructor with its size More...

virtual	~QFFT ()
	destructor More...

int	GetWindowType () const
	Return the window type. More...

void	SetForward (bool isForward)
	virtual method. Must be implemented by daughter classes set the direction of the transform. More...

void	SetNormalized (bool isNormalized)
	virtual method. Must be implemented by daughter classes set the normalization of the transform. More...

Public Member Functions inherited from QFFTW3
	QFFTW3 ()
	ctor loads the wisdom singleton. More...

virtual	~QFFTW3 ()
	dtor does nothing. More...

bool	ExportWisdomToFile (const char *outFile)
	Save the accumulated wisdom to file. More...

bool	ImportWisdomFromFile (const char *inFile)
	Load wisdom from file. More...

bool	ImportSystemWisdom ()
	Load wisdom from a system file. More...

bool	ForgetWisdom (void)
	Forget any accumulated wisdom. More...

	ClassDef (QFFTW3, 0)

Protected Member Functions
virtual bool	CreatePlan (bool Forward)
	Create a plan for this FFT (or any of this size) More...

virtual bool	ClearCache (bool clearMem=true)
	Free the allocated memory. More...

virtual int	Transform (const QVector &data, QVector &result)
	Perform the transformation. More...

bool	CheckPlanCompatible (const QVector &data, const QVector &result) const
	Check to see if the fftw can be done without copying the data. More...

bool	Resize (size_t s)
	Resize the allocated memory. More...

	ClassDef (QRealComplexFFTW3, 0)

Protected Member Functions inherited from QFFT
void	IsPowerOf2 ()

	ClassDef (QFFT, 0)

Protected Attributes
bool	fSizeLock
	Lock the FFT size. More...

const int	fStride
	The stride of the arrays. More...

size_t	fAllocatedSize
	Size of the allocated array. More...

Protected Attributes inherited from QFFT
size_t	fSize

FFTDirection	fDirection

bool	fNormalized

bool	fIsPowerOf2

double *	fData

double *	fWindow

size_t	fWindowSize

WindowType	fWindowType

Additional Inherited Members
Public Types inherited from QFFT
enum	WindowType { WT_None = 0 , WT_Welch = 1 , WT_Rect = 2 , WT_Hann = 3 , WT_Hamming = 4 , WT_Cosinus = 5 , WT_BlackmanHarris = 6 , WT_Kaiser3 = 7 }
	window type More...

enum	ZeroPadSide { kMiddle = 0 , kSymmetric = 1 , kLeft = 2 , kRight = 3 }

enum	FFTDirection { kForward = 1 , kBackward = 0 }

Static Public Member Functions inherited from QFFT
static QVector	FFTAntiSym (const QVector &input)
	antisimmetrize time domain vector More...

static QVector	FFTSym (const QVector &input)
	simmetrize time domain vector More...

static QVector	ZeroPad (const QVector &input, size_t n_zeros, int Side=kMiddle, double zeroVal=0.)
	Add zeros to the input. More...

static QVectorC	ZeroPad (const QVectorC &input, size_t n_zeros, int Side=kMiddle, Diana::QComplex zeroVal=Diana::QComplex(0, 0))
	Add zeros to the input. More...

static WindowType	StrToWindowType (const std::string &winName)
	Convert string to window type. More...

static QVector	GetWindow (WindowType wt, size_t size, size_t zeros=0, int coherent=0, int param=0)
	create window and add zeros/2 to the left and zeros/2 to the right More...

static QVector	CutSides (const QVector &input, size_t ncut, bool isSym)
	cut left and right sides by ncut/2 More...

static bool	IsPowerOf2 (UInt_t Value)
	Is the input a power of 2. More...

static bool	IsPowerOf2 (UInt_t Value, UInt_t &Power, UInt_t &Remainder)
	Is the input a power of 2? More...

Detailed Description

Real to complex FFT using FFTW3.

Author: J. Ouellet

This is an adaptation of QRealComplexFFT to use a FFTW3 library. This carries with it several advantages.

First, if an FFT of on size is to be performed many many times, this algorithm does not need to reallocate memory multiple times (so long as the instance is persistant, the memory is deallocated upon deletion of the object).

The bigger advantage is the use of FFTW3, since FFTW3 makes a plan for how it will perform and FFT and stores that plan the time to complete the FFT is much much faster (once the plan has been estabilished). FFTW3 needs to make two plans, one plan for a forward FFT, one plan for a backward FFT, these are made only when needed. Once the plans are made, they persist for the lifetime of the program (not just the object). This is the FFTW3 wisdom. The biggest speed up is for arrays whose size is a multiple of a large prime (like say 626=2*313). Here FFTW3 chooses the fastest algorithm to perform the FFT and can result in a factor of 10 speedup of the code.

Limitations: For a single instance of the object, the size of the array is fixed. If you wish to perform an FFT of another size, you must create a new instance of QRealComplexFFTW3. (Reallocate the memory, and replan the FFT).

For this class to be implemented, the os must be able to find the FFTW3 headers. If those are not found, this class will just be an alias of QRealComplexFFT using the gsl headers.

Definition at line 54 of file QRealComplexFFTW3.hh.

Constructor & Destructor Documentation

◆ QRealComplexFFTW3() [1/2]

QRealComplexFFTW3::QRealComplexFFTW3 ( const size_t size )

constructor

Parameters

size	is the length of the real vector to be transformed

Definition at line 11 of file QRealComplexFFTW3.cc.

References fAllocatedSize, QFFT::fDirection, QFFT::fNormalized, QFFT::fSize, fSizeLock, QFFT::fWindow, QFFT::fWindowType, QFFT::kForward, QERR_UNKNOWN_ERR, Resize(), and QFFT::WT_None.

◆ QRealComplexFFTW3() [2/2]

QRealComplexFFTW3::QRealComplexFFTW3 ( )

empty constructor

Definition at line 32 of file QRealComplexFFTW3.cc.

References fAllocatedSize, QFFT::fData, QFFT::fSize, fSizeLock, QFFT::fWindow, QFFT::fWindowType, QERR_UNKNOWN_ERR, and QFFT::WT_None.

◆ ~QRealComplexFFTW3()

QRealComplexFFTW3::~QRealComplexFFTW3 ( )

virtual

destructor

Definition at line 52 of file QRealComplexFFTW3.cc.

References ClearCache().

Member Function Documentation

◆ CheckPlanCompatible()

bool QRealComplexFFTW3::CheckPlanCompatible	(	const QVector &	data,
		const QVector &	result
	)		const

inlineprotected

Check to see if the fftw can be done without copying the data.

Normally, this class creates a plan which FFTs data back and forth between fData<->fComplexData. However, this means that data must be copied between the original vector and the local memory slot. This check determines if the fft can be done without moving the data.

There are a few requirements:

The real/complex vectors must have the same stride as fData/fComplexData (in this case fStride=1).
The real/complex vectors must have the same alignment in memory as fData/fComplex data. The easiest way to achieve this is using fftw_malloc as is implemented in QVector.

However, as of FFTW 3.3.3, this code actually caused significant slow down. Currently, this function returns false, forcing the memory copy.

Definition at line 149 of file QRealComplexFFTW3.hh.

◆ ClassDef()

QRealComplexFFTW3::ClassDef	(	QRealComplexFFTW3	,
		0
	)

protected

◆ ClearCache()

bool QRealComplexFFTW3::ClearCache ( bool clearMem = true )

protectedvirtual

Free the allocated memory.

This occurs on destruction of the object and resizing

Parameters

clearMem If true, also free the memory

Definition at line 238 of file QRealComplexFFTW3.cc.

References QVector::ArrayFree(), and QFFT::fData.

Referenced by Resize(), and ~QRealComplexFFTW3().

◆ CreatePlan()

bool QRealComplexFFTW3::CreatePlan ( bool Forward )

protectedvirtual

Create a plan for this FFT (or any of this size)

Definition at line 165 of file QRealComplexFFTW3.cc.

References QFFT::fData, and QFFT::fSize.

Referenced by TransformFromFreq(), and TransformToFreq().

◆ Resize()

bool QRealComplexFFTW3::Resize ( size_t s )

protectedvirtual

Resize the allocated memory.

If fSizeLock == true this returns false.

Implements QFFT.

Definition at line 207 of file QRealComplexFFTW3.cc.

References QVector::ArrayAlloc(), ClearCache(), fAllocatedSize, QFFT::fData, QFFT::fSize, and fSizeLock.

Referenced by QRealComplexFFTW3(), TransformFromFreq(), and TransformToFreq().

◆ SetWindowType()

void QRealComplexFFTW3::SetWindowType	(	WindowType	wt,
		int	coherent = `0`
	)

virtual

resize working table and space

Parameters

s	is the size of the real array to be transformed

Implements QFFT.

Definition at line 259 of file QRealComplexFFTW3.cc.

References QFFT::fSize, QFFT::fWindow, QFFT::fWindowSize, QFFT::fWindowType, and QFFT::GetWindow().

Referenced by QRealComplexFFT::SetWindowType(), TransformFromFreq(), and TransformToFreq().

◆ Transform()

int QRealComplexFFTW3::Transform	(	const QVector &	data,
		QVector &	result
	)

protectedvirtual

Perform the transformation.

This method takes the input data vector and performs a forward or backward transform to the result vector. If this is a forward transformation result must have size 2*fSize. If this is a reverse transformation, data needs to be (at least) size fSize+(fSize % 2 ? 1 : 2) i.e. the next even number larger than fSize.

This method is different from QRealComplexFFTGSL, in that the latter class requires the complex vector to be of size 2*fSize, and be formatted with the real terms first, followed by the complex terms. On the other hand, this class requires that the complex vector be interleaved. (This is more efficient since, that is the way the data are arranged after both gsl and fftw algorithms.)

Implements QFFT.

Definition at line 162 of file QRealComplexFFTW3.cc.

◆ TransformFromFreq()

int QRealComplexFFTW3::TransformFromFreq	(	const QVectorC &	FT,
		QVector &	spectrum,
		bool	compress = `false`
	)

virtual

transform from the frequencies to the times

Parameters

result stores the spectra size of the FFT is size of @FFF

Returns: 0 upon success

Definition at line 110 of file QRealComplexFFTW3.cc.

References CreatePlan(), QFFT::fData, QFFT::fSize, QFFT::fWindow, QFFT::fWindowType, Im(), QERR_UNKNOWN_ERR, Re(), Resize(), QFFT::SetForward(), and SetWindowType().

Referenced by QRealComplexFFT::TransformFromFreq().

◆ TransformToFreq()

int QRealComplexFFTW3::TransformToFreq	(	const QVector &	data,
		QVectorC &	FFT,
		bool	compress = `false`
	)

virtual

transform from the times to the frequencies

Parameters

result stores the fft size of the FFT is size of @data

Returns: 0 upon success

Definition at line 56 of file QRealComplexFFTW3.cc.

References CreatePlan(), QFFT::fData, QFFT::fSize, QFFT::fWindow, QFFT::fWindowType, Im(), QERR_UNKNOWN_ERR, Re(), Resize(), QFFT::SetForward(), and SetWindowType().

Referenced by QRealComplexFFT::TransformToFreq().

Member Data Documentation

◆ fAllocatedSize

size_t QRealComplexFFTW3::fAllocatedSize

protected

Size of the allocated array.

Definition at line 172 of file QRealComplexFFTW3.hh.

Referenced by QRealComplexFFTW3(), and Resize().

◆ fSizeLock

bool QRealComplexFFTW3::fSizeLock

protected

Lock the FFT size.

Definition at line 165 of file QRealComplexFFTW3.hh.

Referenced by QRealComplexFFTW3(), and Resize().

◆ fStride

const int QRealComplexFFTW3::fStride

protected

The stride of the arrays.

Definition at line 170 of file QRealComplexFFTW3.hh.

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

pkg/mathtools/QRealComplexFFTW3.hh
pkg/mathtools/QRealComplexFFTW3.cc

Public Member Functions

Protected Member Functions

Protected Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ QRealComplexFFTW3() [1/2]

◆ QRealComplexFFTW3() [2/2]

◆ ~QRealComplexFFTW3()

Member Function Documentation

◆ CheckPlanCompatible()

◆ ClassDef()

◆ ClearCache()

◆ CreatePlan()

◆ Resize()

◆ SetWindowType()

◆ Transform()

◆ TransformFromFreq()

◆ TransformToFreq()

Member Data Documentation

◆ fAllocatedSize

◆ fSizeLock

◆ fStride