sfft_apply_3d, dfft_apply_3d, cfft_apply_3d, zfft_apply_3d 


  Real transform: status = {S,D}FFT_APPLY_3D (input_format, output_format,
  direction, in, out, lda_i, lda_j, fft_struct, ni_stride, nj_stride,

  Complex transforms in complex format: status = {C,Z}FFT_APPLY_3D
  (input_format, output_format, direction, in, out, lda_i, lda_j, fft_struct,
  ni_stride, nj_stride, nk_stride)

  Complex transform in real data format: status = {C,Z}FFT_APPLY_3D
  (input_format, output_format, direction, in_real, in_imag, out_real,
  out_imag, lda_i, lda_j, fft_struct, ni_stride, nj_stride, nk_stride)


  input_format, output_format
                      Identifies the data type of the input and the format to
                      be used to store the data, regardless of the data type.
                      For example, a complex sequence can be stored in real

                      The character 'R' specifies the format as real; the
                      character 'C' specifies the format as complex. As
                      convenient, use either upper- or lowercase characters,
                      and either spell out or abbreviate the word.

                      The following table shows the valid values:

  Subprogram   Input Format   Output Format   Direction

  {S,D}        'R'            'C'             'F'

               'C'            'R'             'B'

               'R'            'R'             'F' or 'B'

  {C,Z}        'R'            'R'             'F' or 'B'

               'C'            'C'             'F' or 'B'

       For complex data, the type of data determines what other arguments are
       needed.  When both the input and output data are real, the complex
       routines store the data as separate arrays for imaginary and real data
       so additional arguments are needed.

  direction           character*(*)
                      Specifies the operation as either the forward or
                      inverse transform. Use 'F' or 'f' to specify the
                      forward transform. Use 'B' or 'b' to specify the
                      inverse transform.

  in, out             real*4 | real*8 | complex*8 | complex*16
                      Both the arguments are three-dimensional arrays.  The
                      input and output arrays can be the same array. The IN
                      array contains the data to be transformed. The OUT
                      array  contains the transformed data.

  in_real, out_real, in_imag, out_imag
                      REAL*4 | REAL*8
                      Use these arguments when performing a complex transform
                      on real data format and storing the result in a real
                      data format.

  lda_i, lda_j        integer*4
                      Specifies the number of rows and columns in the IN and
                      OUT arrays; lda_i >= ni, lda_j >= nj.  For {S,D}
                      routines, lda_i >= ni+2 when the input format is 'R'
                      and the output format is 'C' or the input format is 'C'
                      and the output format is 'R'.

  fft_struct          record /dxml_s_fft_structure_3d/ for single-precision
                      real operations
                      record /dxml_d_fft_structure_3d/ for double-precision
                      real operations
                      record /dxml_c_fft_structure_3d/ for single-precision
                      complex operations
                      record /dxml_z_fft_structure_3d/ for double-precision
                      complex operations
                      The argument refers to the structure created by the
                      _INIT routine.

  ni_stride, nj_stride, nk_stride
                      Specifies the distance between consecutive elements in
                      the IN and OUT arrays; the valid stride depends on the
                      _INIT routine. ni_stride >= 1, nj_stride >= 1,
                      nk_stride >= 1.


  The _FFT_APPLY_3D routines compute the fast Fourier transform of three-
  dimensional data in either the forward or backward direction.  These
  routines are the second step of the three-step procedure for the fast
  Fourier transform of three-dimensional data.  They compute the fast forward
  or inverse Fourier transform, using the internal data structures created by
  the _FFT_3D_INIT subroutine.

  Use the _APPLY_3D routines with their corresponding _INIT_3D and _EXIT_3D
  routines. For example, use SFFT_APPLY after the SFFT_INIT and end with the
  SFFT_EXIT routine.  See the CXML Reference Manual's chapter on "Using the
  Signal Processing Subprograms" for an explanation of real and complex data

Return Values

  0                  DXML_SUCCESS()

  11                 DXML_ILL_LDA()

  12                 DXML_INS_RES()

  13                 DXML_BAD_STRIDE()

  18 (for real transform only)

  15                 DXML_BAD_DIRECTION_STRING()

  16                 DXML_BAD_FORMAT_STRING()


  REAL*8 A(130,128,128), B(130,128,128)
  N_I = 128
  N_J = 128
  N_K = 128
  LDA_I = 130
  LDA_J = 128

  This FORTRAN code computes the forward, three-dimensional, real FFT of a
  128x128x128 matrix A.  The result of the transform is stored in B in
  complex form. Note that the leading dimension of B is 130 to hold the extra
  complex values (see section on data storage).  Note also that the input
  matrix A requires a leading dimension of at least 130.

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