fft2dui(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)
     C :
          #include <fft.h>
          float *coeff;
          coeff = scfft2dui( 200, 300, NULL);

SEE ALSO
          fft, scfft2du, dzfft2du