CFFTMLT (3sciport)

Applies complex to complex Fast Fourier Transforms (FFTs) on multiple input vectors

SYNOPSIS

  Call CFFTMLT( ar, ai, work, trigs ,ifax, inc, jump, n, lot, isign )

ARGUMENTS

  ar              Real matrix.
                  An input/output matrix containing the n*lot real parts of
                  lot complex vectors, each of length n. The real parts of
                  FFT output overwrite ar.

  ai              Real matrix.
                  An input/output matrix containing the n*lot imaginary parts
                  of lot complex vectors, each of length n. The imaginary
                  parts of FFT output overwrite ai.

  work            Real vector.
                  A vestigial argument ignored by the SCIPORT implementation.

  trigs           Real vector.
                  A vector overlaid by the CXML FFT structure. The trigs
                  vector must contain at least 121 elements. Before being
                  used, trigs must be initialized by the following call:

                  CALL CFTFAX( n,ifax,trigs ).

                  When CFTFAX is called with ifax equal to
                  '80FF0FF0FF0FF0FF'X, the FFT structure overlaying trigs is
                  freed.

  ifax            Integer vector.
                  A vestigial argument ignored by the SCIPORT implementation.

  inc             Integer.
                  The increment between elements within each length n data
                  vector of ar and ai.

  jump            Integer.
                  The increment between starting elements of real vectors
                  within ar.  The increment between starting elements of
                  imaginary vectors within ai.

  n               Integer.
                  The length of the data vectors.

  lot             Integer.
                  The number of data vectors.

  isign           Integer.
                  +1 for Fourier analysis
                  -1 for Fourier synthesis

DESCRIPTION

  CFFTMLT applies a complex to complex FFT to lot data vectors, each of
  length n, simultaneously.

  For equations and other information, see Volume 3: UNICOS Math and
  Scientific Library Reference Manual SR-2081 7.0, Cray Research, Inc.

NOTE

  Before CFFTMLT is called the first time, the trigs vector must be
  initialized by calling CFTFAX as shown below:

          Call CFTFAX( n,ifax,trigs )

  Thereafter, the vector trigs must not be written to. However, it can be
  used by CCFTMLT any number of times, as long as the length n is not
  changed.

  Calling CFTFAX with ifax set to '80FF0FF0FF0FF0FF'X initiates an escape.
  Please see the sciport man page for details. The escape mechanism should be
  inserted immediately after the last call to CFFTMLT for which the status of
  trigs is known. This mechanism should be used sparingly. Its use implies
  frequent re-initializations of the sine and cosine tables - which are quite
  costly.

  See also sciport.