fft1di(3F)

NAME
     cfft1di, zfft1di - initialize the coefficient array for Complex-to-
     Complex 1D FFT modules.

SYNOPSYS
     FORTRAN SPECIFICATION
     subroutine CFFT1DI( n, coeff )
     integer             n
     complex             coeff(n+15)

     subroutine ZFFT1DI( n, coeff )
     integer             n
     double complex      coeff(n+15)

     C SPECIFICATION
     #include <fft.h>
     complex *cfft1di( int n, complex *coeff);

     zomplex *zfft1di( int n, zomplex *coeff);


DESCRIPTION
     Initialize the coefficient array which is used in the FFT modules.  This
     array contains the different twiddle factors and the factorization of N
     into prime numbers.
     As the FFT modules cfft1d or zfft1d only read the coeff array, it may be
     reused as long as necessary once it has been initialized.

     In C, if ptr is NULL, cfft1di or zfft1di returns a pointer to an
     allocated buffer.

     CFFT1DI should be used to initialize the coeeficient array before any
     call to CFFT1D
     ZFFT1DI should be used to initialize the coeeficient array before any
     call to ZFFT1D

PARAMETERS
     N - Integer. Specifies the length of the 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 complex-to-complex FFTs of size 200.

     Fortran :
          complex coeff(200+15)
          call cfft1di( 200, coeff)

     C :
          #include <fft.h>
          complex *coeff;
         coeff = cfft1di( 200, NULL);

SEE ALSO
          fft, cfft1d, zfft1d