GFFTDianelsonLanczos.cpp File Reference

#include "GFFTDianelsonLanczos.hh"

Functions
bool	GFFTCheckDim (u_int n)
u_int	GFFTGetPower2Dim (u_int n)
int	GFFTBaseComplex (double data[], u_int n, bool inv)
int	GFFTComplex (double f_in[], double f_out[], u_int n, bool inv)
int	GFFTReal2 (double f_in1[], double f_in2[], double f_out1[], double f_out2[], u_int n, bool inv)
int	GFFTBaseReal (double data[], u_int n, bool inv)
int	GFFTReal (double f_in[], double f_out[], u_int n, bool inv)

Detailed Description

Source file for the Fast Fourier Transform (FFT) functions using the Danielson-Lanczos algorithm (see Danielson-Lanczos algorithm for FFT).

Function Documentation

int GFFTBaseComplex	(	double	data[],
		u_int	n,
		bool	inv
	)

Function implementing the Danielson-Lanczos algorithm for the FFT of a complex numbers array. The function returns 0 (no error check!). For n complex numbers, the array has length 2*n, in the following order: Re[0], Im[0], Re[1], Im[1], ... Re[n-1], Im[n-1]. The size of the data array must be at least 2*n.

Warning: the function works for a dimension that is a power of 2; this is not checked.

Parameters

data	input sample and transform result as output
n	number of complex values
inv	transformation type: false for FFT, true for inverse FFT

References FFT_2PI, and SWAP_DOUBLE.

Referenced by GFFTBaseReal(), GFFTComplex(), and GFFTReal2().

int GFFTBaseReal	(	double	data[],
		u_int	n,
		bool	inv
	)

Function implementing the Danielson-Lanczos algorithm for the FFT of a real numbers array. The function returns 0 (no error check!).

For the FFT, the f_in array contains the real data array as input (n real values), and the f_out array receives de complex Fourier transform as output (n/2 complex values). For the inverse FFT, the f_in array contains the complex Fourier transform as input, and the f_out array receives the real samples as output.

The FFT array (complex) has length n, in the following order: Re[0], Im[0], Re[1], Im[1], ... Re[n/2-1], Im[n/2-1]. Since the sampled function is real, the transform terms 0 and n/2 are pure reals (no imaginary part), and Im[0] contains Re[n/2].

Warning: the function works for a dimension that is a power of 2; this is not checked.

Parameters

data	input sample and transform result as output
n	number of real values
inv	transformation type: false for FFT, true for inverse FFT

References FFT_PI, and GFFTBaseComplex().

Referenced by GFFTReal().

bool GFFTCheckDim

(

u_int

n

)

Function that recursively tests the input number to check whether it is a power of 2. This function is used to check the dimension of the arrays for the FFT functions.

Parameters

n	input number

References GFFTCheckDim().

Referenced by GFFTCheckDim(), GFFTComplex(), GFFTReal(), GFFTReal2(), and GBaseSampleFFT::InitData().

int GFFTComplex	(	double	f_in[],
		double	f_out[],
		u_int	n,
		bool	inv
	)

FFT for a complex sampling of n (being a power of 2) complex values. For n complex numbers, the arrays have length 2*n, in the following order: Re[0], Im[0], Re[1], Im[1], ... Re[n-1], Im[n-1]. The function returns 0 if no error occured.

Parameters

f_in	input samples
f_out	transform result
n	sample size (number of complex values)
inv	transformation type: false for FFT, true for inverse FFT

References GFFT_DIM_ERROR, GFFTBaseComplex(), and GFFTCheckDim().

u_int GFFTGetPower2Dim

(

u_int

n

)

Return the integer value larger or equal to n that is a power of 2.

Parameters

n	initial dimension (must be at least 2)

Referenced by GBaseSampleFFT::InitData(), and GBaseSampleFFT::ResizeData().

int GFFTReal	(	double	f_in[],
		double	f_out[],
		u_int	n,
		bool	inv
	)

FFT for a sampled real function.

For the FFT, the f_in array contains the real data array as input (n real values), and the f_out array receives de complex Fourier transform as output (n/2 complex values). For the inverse FFT, the f_in array contains the complex Fourier transform as input, and the f_out array receives the real samples as output.

The FFT array (complex) has length n, in the following order: Re[0], Im[0], Re[1], Im[1], ... Re[n/2-1], Im[n/2-1]. Since the sampled function is real, the transform terms 0 and n/2 are pure reals (no imaginary part), and Im[0] contains Re[n/2].

Parameters

f_in	input samples
f_out	transform result
n	sample size (number of real values)
inv	transformation type: false for FFT, true for inverse FFT

References GFFT_DIM_ERROR, GFFTBaseReal(), and GFFTCheckDim().

Referenced by GRealSampleFFT::ComputeFunctionData(), and GRealSampleFFT::ComputeTransformData().

int GFFTReal2	(	double	f_in1[],
		double	f_in2[],
		double	f_out1[],
		double	f_out2[],
		u_int	n,
		bool	inv
	)

Simultaneous FFT for 2 real samples of n (being a power of 2) real values. The function uses the complex samples FFT algorithm. The function returns 0 if no error occured. The input and output arrays have a dimension n.

For the FFT, the f_in arrays contain the real data array as input (n real values), and the f_out arrays receive de complex Fourier transform as output (n/2 complex values). For the inverse FFT, the f_in arrays contain the complex Fourier transform as input, and the f_out arrays receive the real samples as output.

The FFT arrays contains n/2 complex values, in the following order: Re[0], Im[0], Re[1], Im[1], ... Re[n/2-1], Im[n/2-1]. Since the sampled functions are real, the transform terms 0 and n/2 are pure reals (no imaginary part), and Im[0] contains Re[n/2].

Parameters

f_in1	function 1 samples (input)
f_in2	function 2 samples (input)
f_out1	transform 1 function result (output)
f_out2	transform 2 function result (output)
n	sample size (number of complex values)
inv	transformation type: false for FFT, true for inverse FFT

References GFFT_DIM_ERROR, GFFTBaseComplex(), and GFFTCheckDim().