util.c File Reference

Utility functions needed for transforms. More...

#include "s2kit/util.h"
#include <math.h>
#include <stdlib.h>

Go to the source code of this file.

Functions
void	ComplexMult (const double x, const double y, const double u, const double v, double *real_result, double *imag_result)
	Multiplies two complex numbers. More...
int	IndexOfHarmonicCoeff (const int m, const int l, const int bw)
	Gives the position of the coefficient f-hat(m,l) in the one-row array. More...
void	TransMult (double *rdatacoeffs, double *idatacoeffs, double *rfiltercoeffs, double *ifiltercoeffs, double *rres, double *ires, const int bw)
	Multiplies harmonic coefficients of a function and a filter. More...

Detailed Description

Utility functions needed for transforms.

Definition in file util.c.

Function Documentation

ComplexMult()

void ComplexMult ( const double  x, const double  y, const double  u, const double  v, double *  real_result, double *  imag_result  )

inline

Multiplies two complex numbers.

The result is stored separately for real and imaginary part.

Parameters

x	real part of the first number
y	imaginary part of the first number
u	real part of the second number
v	imaginary part of the second number
real_result	real part of the result
imag_result	imaginary part of the result

Definition at line 23 of file util.c.

IndexOfHarmonicCoeff()

int IndexOfHarmonicCoeff	(	const int	m,
		const int	l,
		const int	bw
	)

Gives the position of the coefficient f-hat(m,l) in the one-row array.

Returns the position of the coefficient f-hat(m,l) in the one-row array with the spherical coefficients. It helps to preserve the symmetry that the coefficients have:

f-hat(l,-m) = (-1)^m * conjugate( f-hat(l,m) )

Parameters

m	order
l	degree
bw	bandwidth

Definition at line 42 of file util.c.

TransMult()

void TransMult	(	double *	rdatacoeffs,
		double *	idatacoeffs,
		double *	rfiltercoeffs,
		double *	ifiltercoeffs,
		double *	rres,
		double *	ires,
		const int	bw
	)

Multiplies harmonic coefficients of a function and a filter.

See convolution theorem of Driscoll and Healy for details.

Parameters

rdatacoeffs	real data coefficients
idatacoeffs	imaginary data coefficients
rfiltercoeffs	real filter coefficients
ifiltercoeffs	imaginary filter coefficients
rres	array of real result
ires	array of imaginary result
bw	bandwidth of problem

Note

datacoeffs should be output of an SHT (e.g. FSTSemiMemo())

filtercoeffs should be output of an SHT (e.g. FZTSemiMemo())

All arrays must be of length bw*bw

Definition at line 68 of file util.c.