sfft_init, dfft_init, cfft_init, zfft_init 

Initialization step for fast fourier transform in one dimension

FORMAT

  status = {S,D,C,Z}FFT_INIT (n, fft_struct, stride_1_flag)

Arguments

  n                   integer*4
                      Specifies the number of values to be transformed, that
                      is, the length of the array to be transformed; n > 0.
                      For real operations, n must be even.

  fft_struct          record /dxml_s_fft_structure/ for single-precision real
                      operations
                      record /dxml_d_fft_structure/ for double-precision real
                      operations
                      record /dxml_c_fft_structure/ for single-precision
                      complex operations
                      record /dxml_z_fft_structure/ for double-precision
                      complex operations
                      You must include this argument but it needs no
                      additional definitions. The argument is declared in the
                      program before this routine.  See
                      the CXML Reference Guide  for more information.

  stride_1_flag       logical
                      Specifies the allowed distance between consecutive
                      elements in the input and output arrays:

                      TRUE: Stride must be 1.

                      FALSE: Stride is at least 1.

Description

  The _FFT_INIT functions build internal data structures needed to compute
  fast Fourier transforms of one-dimensional data. These routines are the
  first step in a three-step procedure.  They create the internal data
  structures, using attributes defined in the file CXMLDEF.FOR.

  Use the initialization routine that is appropriate for the data format.
  Then use the corresponding application and exit routines to complete the
  transform.  For example, use SFFT_INIT for the internal data structures
  used by SFFT_APPLY and end with the SFFT_EXIT routine.

Return Values

  0                  DXML_SUCCESS()

  4(real transforms only)
                     DXML_ILL_N_IS_ODD()

  8                  DXML_ILL_N_RANGE()

  12                 DXML_INS_RES()