MCFFT (3sciport)

Applies multiple Fast Fourier Transforms (FFTs)

SYNOPSIS

  Call MCFFT( isign, n, lot, scale, x, inc1x, inc2x, y, inc1y, inc2y,
              table, ntable, work, nwork )

ARGUMENTS

  isign           Integer.
                  Specifies whether to initialize the coefficient table,
                  perform a forward FFT, perform an inverse FFT, or activate
                  an escape mechanism. Legitimate values for isign are:

                  0  overlay table with a CXML FFT structure,
                  +1 compute a  forward transform, and
                  -1 compute an inverse transform.

                  If isign is equal to '80FF0FF0FF0FF0FF'X, then free the
                  CXML structure overlaying table.

  n               Integer.
                  The order of the FFTs.

  lot             Integer.
                  The number of transforms to be computed.

  scale           Real.
                  Each element of the complex output vectors of matrix y is
                  multipled by scale after the FFTs are performed.

  x               Complex matrix.
                  The complex input vectors to be transformed.

  inc1x           Integer.
                  The increment between elements within the vectors of matrix
                  x.

  inc2x           Integer.
                  The increment between starting elements of the vectors of
                  matrix x.

  y               Complex matrix.
                  The complex output vectors. If output vectors overlay input
                  vectors exactly, in-place FFTs are performed.

  inc1y           Integer.
                  The increment between elements within the vectors of matrix
                  y.

  inc2y           Integer.
                  The increment between starting elements of the vectors of
                  matrix y.

  table           Real vector.
                  A vector of constants used by the FFT algorithm. The table
                  is written only when isign is zero. Only the first 121
                  locations are used by the SCIPORT implementation.

  ntable          Integer.
                  The length of the table vector. ntable must be at least
                  121.

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

  nwork           Integer.
                  A vestigial argument ignored by the SCIPORT implementation.

DESCRIPTION

  MCFFT computes a group of Fourier Transforms using the complex data matrix
  x and the coefficient vector table as inputs and the complex matrix y as
  output.

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

NOTE

  Calling MCFFT with isign 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 MCFFT for which the status of
  table 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.