cfft2di,zfft2di(3F) cfft2di,zfft2di(3F)NAME
cfft2di, zfft2di - initialize the coefficient array for complex-to-
complex 2D FFT modules.
SYNOPSYS
FORTRAN SPECIFICATION
subroutine CFFT2DI( n1, n2, coeff )
integer n1, n2
complex coeff((n1+15) + (n2+15))
subroutine ZFFT2DI( n1, n2, coeff )
integer n1, n2
double complex coeff((n1+15) + (n2+15))
C SPECIFICATION
#include <fft.h>
complex *cfft2di( int n1, int n2, complex *coeff);
zomplex *zfft2di( int n1, int n2, zomplex *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 cfft2d or zfft2d only read the coeff array, it may be
reused as long as necessary once it has been initialized.
In C, if ptr is NULL, cfft2di or zfft2di returns a pointer to an
allocated buffer.
CFFT2DI should be used to initialize the coefficient array before any
call to CFFT2D
ZFFT2DI should be used to initialize the coefficient array before any
call to ZFFT2D
PARAMETERS
N1 - Integer, the first dimension size of the 2D sequence.
Unchanged on exit.
N2 - Integer, the second dimension size of the 2D sequence.
Unchanged on exit.
COEFF - Array (C or Fortran) or NULL pointer(C).
Example of Calling Sequence
Initializing a coefficient array for complex-to-complex FFTs of size 200
x 300.
Fortran :
complex coeff((200+15)+(300+15))
call cfft2di( 200, 300, coeff)
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cfft2di,zfft2di(3F) cfft2di,zfft2di(3F)
C :
#include <fft.h>
complex *coeff;
coeff = cfft2di( 200, 300, NULL);
SEE ALSO
fft, cfft2d, zfft2d
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