scfft2dui,dzfft2dui(3F) scfft2dui,dzfft2dui(3F)NAME
scfft2dui, dzfft2dui - initialize the coefficient array for real-to-
complex 2D FFT modules.
SYNOPSYS
FORTRAN SPECIFICATION
subroutine SCFFT2DUI( n1, n2, coeff )
integer n1, n2
real coeff((n1+15) + 2*(n2+15))
subroutine DZFFT2DUI( n1, n2, coeff )
integer n1, n2
real*8 coeff((n1+15) + 2*(n2+15))
C SPECIFICATION
#include <fft.h>
float *scfft2dui( int n1, int n2, float *coeff);
double *dzfft2dui( int n1, int n2, double *coeff);
DESCRIPTION
Initialize, the coefficient array which is used in the 2D FFT modules.
This array contains the different twiddle factors and the factorization
of N1 and N2 into prime numbers.
As the FFT modules scfft2d or dzfft2d only read the coeff array, it may
be reused as many times as necessary once it has been initialized.
In C, if ptr is NULL, scfft2dui or dzfft2dui returns a pointer to an
allocated buffer.
SCFFT2DUI should be used to initialize the coefficient array before any
call to SCFFT2DU
DZFFT2DUI should be used to initialize the coefficient array before any
call to DZFFT2DU
PARAMETERS
N1 - Integer. Specifies the size of the first dimension of the 2D
sequence to be transformed. Unchanged on exit.
N2 - Integer. Specifies the size of the second dimension of the 2D
sequence to be transformed. Unchanged on exit.
COEFF - Array (C or Fortran) or NULL pointer(C).
Example of Calling Sequence
Initializing a coefficient array for real-to-complex FFTs of size 200 x
300.
Fortran :
real coeff((200+15)+2*(300+15))
call scfft2dui( 200, 300, coeff)
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scfft2dui,dzfft2dui(3F) scfft2dui,dzfft2dui(3F)
C :
#include <fft.h>
float *coeff;
coeff = scfft2dui( 200, 300, NULL);
SEE ALSO
fft, scfft2du, dzfft2du
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