fft3di(3F)

NAME
     cfft3di, zfft3di - initialize the coefficient array for complex-to-
     complex 3D FFT modules.

SYNOPSYS
     FORTRAN SPECIFICATION
     subroutine CFFT3DI( n1, n2, n3, coeff )
     integer                  n1, n2, n3
     complex             coeff((n1+15) + (n2+15) + (n3+15))

     subroutine ZFFT3DI( n1, n2, n3, coeff )
     integer                  n1, n2, n3
     double complex      coeff((n1+15) + (n2+15) + (n3+15))

     C SPECIFICATION
     #include <fft.h>
     complex *cfft3di( int n1, int n2, int n3, complex *coeff);

     zomplex *zfft3di( int n1, int n2, int n3, zomplex *coeff);


DESCRIPTION
     Initialize the coefficient array which is used in the 3D FFT modules.
     This array contains the different twiddle factors and the factorization
     of N1,N2 and N3 into prime numbers.
     As the FFT modules cfft3d or zfft3d 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, cfft3di or zfft3di returns a pointer to an
     allocated buffer.

     CFFT3DI should be used to initialize the coefficient array before any
     call to CFFT3D
     ZFFT3DI should be used to initialize the coefficient array before any
     call to ZFFT3D

PARAMETERS
     N1 - Integer, the first dimension size of the 3D sequence.  Unchanged on
     exit.

     N2 - Integer, the second dimension size of the 3D sequence.  Unchanged on
     exit.

     N3 Integer, the third dimension size of the 3D 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
     200x300X125
     Fortran :
          complex coeff((200+15)+(300+15)+(125+15))
          call cfft3di( 200, 300, 125, coeff)

     C :
          #include <fft.h>
          complex *coeff;
          coeff = cfft3di( 200, 300, 125, NULL);

SEE ALSO
          fft, cfft3d, zfft3d