FancyFFTs Namespace Reference

My implementation of a wrapper for FFTW for use with ROOT thing. More...

Enumerations
enum	conventionFlag {   kSum = 0, kAverage = 1, kTimeIntegral = 2, kPowSpecDensity = 3,   kPowSpecDensity_dBm = 4 }
	Flag to pass to FancyFFT functions specifying normalization of power spectra.

Functions
complex< double > *	doFFT (int len, double *input, bool copyOutputToNewArray, int threadInd=0)
	Does a forward fast fourier transform on a real input array. More...
complex< double > *	doFFT (int len, double *input, complex< double > *output, int threadInd=0)
	Does a forward fast fourier transform on a real input array. More...
complex< double > *	doFFT (int len, double *input, complex< double > *output, bool copyOutputToNewArray, int threadInd=0)
	Does a forward fast fourier transform on a real input array. More...
double *	doInvFFT (int len, complex< double > *input, bool copyOutputToNewArray, int threadInd=0)
	Does an inverse fast fourier transform on an array of complex<double>s. More...
double *	doInvFFT (int len, complex< double > *input, double *output, int threadInd=0)
	Does an inverse fast fourier transform on an array of complex<double>s. More...
double *	doInvFFT (int len, complex< double > *input, double *output, bool copyOutputToNewArray, int threadInd=0)
	Does an inverse fast fourier transform on an array of complex<double>s. More...
double *	getPowerSpectrum (int len, double *input, double dt, conventionFlag normFlag, int threadInd=0)
	Creates the power spectrum in an array of doubles of length (len/2 + 1). More...
double *	getPowerSpectrum (int len, double *input, double dt, conventionFlag normFlag, double *outputPtr, int threadInd=0)
	Creates the power spectrum in an array of doubles of length (len/2 + 1). More...
TGraph *	getPowerSpectrumTGraph (int len, double *input, double dt, conventionFlag normFlag, bool dBScale, int threadInd=0)
	Creates a power spectrum TGraph from an array of doubles. More...
double *	getFreqArray (int len, double dt)
	Get the array of frequencies to go with FFT output, determined by the tranform length and dt. More...
int	getNumFreqs (int len)
	Get the number of frequencies from the number of samples. More...
int	printListOfKeys ()
	Prints the list of keys of plans to stdout.
double *	crossCorrelate (int len, double *v1, double *v2, int threadInd=0)
	Cross correlates the two input arrays. More...
double *	crossCorrelate (int len, complex< double > *fft1, complex< double > *fft2, int threadInd=0)
	Cross correlates the two input arrays. More...
double *	crossCorrelate (int len, complex< double > *fft1, complex< double > *fft2, double *output, int threadInd=0)
	Cross correlates the two input arrays. More...
int	extendToPowerOfTwo (int len)
	Find the next highest power of two. More...
complex< double > *	zeroPadFFT (complex< double > *fft, int numSamples, int numSamplesUpsampled)
	Zero padds FFTts,. More...
complex< double > *	zeroPadFFT (complex< double > *fft, complex< double > *output, int numSamples, int numSamplesUpsampled)
	Zero padds FFTts,. More...
bool	makeNewPlanIfNeeded (int len, int threadInd=0)
	Creates new fftw plan to handle 1D transforms of length len if they haven't been allocated already. More...
double *	getRealArray (std::pair< Int_t, Int_t > key)
	Get the real array of the internal fftw memory. Do not delete this! More...

Detailed Description

My implementation of a wrapper for FFTW for use with ROOT thing.

Most functionality has been merged into FFTtools, except some of the threading options. Hopefully that will get done at some point in the future and this namespace can be done away with.

Function Documentation

double * FancyFFTs::crossCorrelate	(	int	len,
		double *	v1,
		double *	v2,
		int	threadInd = 0
	)

Cross correlates the two input arrays.

Parameters

len	is the length of both arrays, v1 and 2.
v1	is the first input array.
v2	is the second input array.
threadInd	uses a particular threads plans to do the ffts.

Returns

a pointer to an array of doubles containing the cross correlations.

Definition at line 541 of file FancyFFTs.cxx.

double * FancyFFTs::crossCorrelate	(	int	len,
		complex< double > *	fft1,
		complex< double > *	fft2,
		int	threadInd = 0
	)

Cross correlates the two input arrays.

Parameters

len	is the length of both arrays, v1 and 2.
fft1	is the fft of the first input array.
fft2	is the fft of the second input array.
threadInd	uses a particular threads plans to do the ffts.

Returns

a pointer to an array of doubles containing the cross correlations.

Definition at line 593 of file FancyFFTs.cxx.

double * FancyFFTs::crossCorrelate	(	int	len,
		complex< double > *	fft1,
		complex< double > *	fft2,
		double *	output,
		int	threadInd = 0
	)

Cross correlates the two input arrays.

Parameters

len	is the length of the time domain input (not the length of the ffts).
fft1	is the fft of the first input array.
fft2	is the fft of the second input array.
output	is a pointer to copy the outputted cross correlations to.
threadInd	uses a particular threads plans to do the ffts.

Returns

a pointer to an array of doubles containing the cross correlations.

Definition at line 612 of file FancyFFTs.cxx.

complex< double > * FancyFFTs::doFFT	(	int	len,
		double *	input,
		bool	copyOutputToNewArray,
		int	threadInd = 0
	)

Does a forward fast fourier transform on a real input array.

Parameters

len	is the length of the input.
input	is a pointer to an array of doubles of length len.
copyOutputToNewArray	leave output in internal memory (false) or allocate new memory and copy (true).
threadInd	uses a particular threads plans to do the ffts.

Returns

a pointer to an array of complex<double>s containing the fft.

Definition at line 212 of file FancyFFTs.cxx.

complex< double > * FancyFFTs::doFFT	(	int	len,
		double *	input,
		complex< double > *	output,
		int	threadInd = 0
	)

Does a forward fast fourier transform on a real input array.

Parameters

len	is the length of the input.
input	is a pointer to an array of doubles of length len.
output	is a pointer to an array of complex<double> to copy the output to.
threadInd	uses a particular threads plans to do the ffts.

Returns

a pointer to an array of complex<double>s containing the fft.

Definition at line 228 of file FancyFFTs.cxx.

complex< double > * FancyFFTs::doFFT	(	int	len,
		double *	input,
		complex< double > *	output,
		bool	copyOutputToNewArray,
		int	threadInd = 0
	)

Does a forward fast fourier transform on a real input array.

Parameters

len	is the length of the input.
input	is a pointer to an array of doubles of length len.
output	is a pointer to an array of complex<double> to copy the output to.
copyOutputToNewArray	leave output in internal memory (false) or allocate new memory and copy (true).
threadInd	uses a particular threads plans to do the ffts.

Returns

a pointer to an array of complex<double>s containing the fft.

Definition at line 245 of file FancyFFTs.cxx.

double * FancyFFTs::doInvFFT	(	int	len,
		complex< double > *	input,
		bool	copyOutputToNewArray,
		int	threadInd = 0
	)

Does an inverse fast fourier transform on an array of complex<double>s.

Parameters

len	is the length of the real output array.
input	is a pointer to an array of complex<double>s of length (len/2 +1).
copyOutputToNewArray	leave output in internal memory (false) or allocate new memory and copy (true).
threadInd	uses a particular threads plans to do the ffts.

Returns

a pointer to an array of doubles containing the (real) inverse FFT.

Definition at line 288 of file FancyFFTs.cxx.

double * FancyFFTs::doInvFFT	(	int	len,
		complex< double > *	input,
		double *	output,
		int	threadInd = 0
	)

Does an inverse fast fourier transform on an array of complex<double>s.

Parameters

len	is the length of the real output array.
input	is a pointer to an array of complex<double>s of length (len/2 +1).
output	is a pointer to an array of doubles to copy the output to.
threadInd	uses a particular threads plans to do the ffts.

Returns

a pointer to an array of doubles containing the (real) inverse FFT.

Definition at line 306 of file FancyFFTs.cxx.

double * FancyFFTs::doInvFFT	(	int	len,
		complex< double > *	input,
		double *	output,
		bool	copyOutputToNewArray,
		int	threadInd = 0
	)

Does an inverse fast fourier transform on an array of complex<double>s.

Parameters

len	is the length of the real output array.
input	is a pointer to an array of complex<double>s of length (len/2 +1).
output	is a pointer to an array of doubles to copy the output to.
copyOutputToNewArray	leave output in internal memory (false) or allocate new memory and copy (true).
threadInd	uses a particular threads plans to do the ffts.

Returns

a pointer to an array of doubles containing the (real) inverse FFT.

Definition at line 325 of file FancyFFTs.cxx.

int FancyFFTs::extendToPowerOfTwo

(

int

len

)

Find the next highest power of two.

Parameters

len	is the number to find the next highest power of two.

Returns

the next highest power of two.

Definition at line 377 of file FancyFFTs.cxx.

double * FancyFFTs::getFreqArray	(	int	len,
		double	dt
	)

Get the array of frequencies to go with FFT output, determined by the tranform length and dt.

Parameters

len	is the length of the real fft input.
dt	is the time between real input samples.

Returns

a pointer to an array of doubles containing the frequencies.

Definition at line 394 of file FancyFFTs.cxx.

int FancyFFTs::getNumFreqs

(

int

len

)

Get the number of frequencies from the number of samples.

Parameters

len	is the length of the real fft input.

Returns

the number of frequencies.

Definition at line 416 of file FancyFFTs.cxx.

double * FancyFFTs::getPowerSpectrum	(	int	len,
		double *	input,
		double	dt,
		FancyFFTs::conventionFlag	normFlag,
		int	threadInd = 0
	)

Creates the power spectrum in an array of doubles of length (len/2 + 1).

Parameters

len	is the length of the input.
input	is a pointer to an array of doubles of length len.
dt	is the time step between samples.
normFlag	is a flag specifying how to normalize the output TGraph.
threadInd	uses a particular threads plans to do the ffts.

Returns

a pointer to the array containing the power spectrum.

Definition at line 77 of file FancyFFTs.cxx.

double * FancyFFTs::getPowerSpectrum	(	int	len,
		double *	input,
		double	dt,
		FancyFFTs::conventionFlag	normFlag,
		double *	outputPtr,
		int	threadInd = 0
	)

Creates the power spectrum in an array of doubles of length (len/2 + 1).

Parameters

len	is the length of the input.
input	is a pointer to an array of doubles of length len.
dt	is the time step between samples.
normFlag	is a flag specifying how to normalize the output TGraph.
threadInd	uses a particular threads plans to do the ffts.
outputPtr	can be used to direct FancyFFTs to copy the output into pre-allocatred memory.

Returns

a pointer to the array containing the power spectrum.

Definition at line 98 of file FancyFFTs.cxx.

TGraph * FancyFFTs::getPowerSpectrumTGraph	(	int	len,
		double *	input,
		double	dt,
		FancyFFTs::conventionFlag	normFlag,
		bool	dBScale,
		int	threadInd = 0
	)

Creates a power spectrum TGraph from an array of doubles.

Parameters

len	is the length of the input.
input	is a pointer to an array of doubles of length len.
dt	is the time step between samples.
normFlag	is a flag specifying how to normalize the output TGraph.
dBScale	specifies whether to return the TGraph in dB or linear scale.
threadInd	specifies the thread index of the fftw plans to use.

Returns

the power spectrum TGraph.

Definition at line 52 of file FancyFFTs.cxx.

double * FancyFFTs::getRealArray

(

std::pair< Int_t, Int_t >

key

)

Get the real array of the internal fftw memory. Do not delete this!

Parameters

key	is an std::pair of the real array length and the thread index of the plan.

Returns

a pointer to fftw's internal real array. DO NOT DELETE THIS!

Definition at line 673 of file FancyFFTs.cxx.

bool FancyFFTs::makeNewPlanIfNeeded	(	int	len,
		int	threadInd = 0
	)

Creates new fftw plan to handle 1D transforms of length len if they haven't been allocated already.

Parameters

len	is the length of the input.
threadInd	is the index of the thread that needs an fftw plan.

Definition at line 19 of file FancyFFTs.cxx.

complex< double > * FancyFFTs::zeroPadFFT	(	complex< double > *	fft,
		int	numSamples,
		int	numSamplesUpsampled
	)

Zero padds FFTts,.

Parameters

fft	is the unpadded fft.
numSamples	is the length of the time domain of the fft (i.e. NOT the number of frequency bins)
numSamplesUpsampled	is the length of the time domain of the padded fft (i.e. NOT the number of frequency bins)

Returns

the a pointer to an array of complex<doubles> containing the padded fft.

This is for doing interpolation in the time domain. Zero padding in the time/frequency domain is equivelent to interpolation in the time/frequency domain.

Definition at line 436 of file FancyFFTs.cxx.

complex< double > * FancyFFTs::zeroPadFFT	(	complex< double > *	fft,
		complex< double > *	output,
		int	numSamples,
		int	numSamplesUpsampled
	)

Zero padds FFTts,.

Parameters

fft	is the unpadded fft.
numSamples	is the length of the time domain of the fft (i.e. NOT the number of frequency bins)
numSamplesUpsampled	is the length of the time domain of the padded fft (i.e. NOT the number of frequency bins)
output	is where the padded fft should be copied to.

Returns

the a pointer to an array of complex<doubles> containing the padded fft.

This is for doing interpolation in the time domain. Zero padding in the time/frequency domain is equivelent to interpolation in the time/frequency domain.

Definition at line 457 of file FancyFFTs.cxx.