source: trunk/WRF.COMMON/WRFV3/external/fftpack/fftpack5/README

FFTPACK5 - a FORTRAN library of fast Fourier transforms

Copyright (C) 1995-2004, Scientific Computing Division,
University Corporation for Atmospheric Research
Licensed under the GNU General Public License (GPL)

Authors:  Paul N. Swarztrauber and Richard A. Valent

$Id: README,v 1.2 2004/06/17 21:59:51 rodney Exp $

Website
-------

http://www.scd.ucar.edu/css/software/fftpack5


Documentation
-------------

Documentation is provided in PDF format in the file fftpack5.pdf.
This information is also available in HTML format at the above
website.  Information about building the library follows below,
as well as a synopsis of the library.


Compiling Library
-----------------   

[Editor's note - this refers to the original build, 
not the WRF modified build.]

The included Makefile if configured to build a static
library on most currently availble unix and unix-like
operating systems.  The given make targets (type "make"
without any arguments for a list of targets) correspond
to compiler names; e.g. intel = Intel F95 compiler, 
gnu = GNU g77 compiler, sun = Sun Solaris compiler, etc.

The source code is by default configured for single precision
real numbers.  If double precision is desired, the Makefile must
be modified with the appropriate compiler options for promoting
real to double precision as well as promoting constants to double
precision (this is often "-r8" on some, but not all, compilers).


Complex Transform Routines
__________________________

CFFT1I    1D complex initialization
CFFT1B    1D complex backward
CFFT1F    1D complex forward

CFFT2I    2D complex initialization
CFFT2B    2D complex backward
CFFT2F    2D complex forward

CFFTMI    multiple complex initialization
CFFTMB    multiple complex backward
CFFTMF    multiple complex forward


Real Transform Routines
_______________________

RFFT1I    1D real initialization
RFFT1B    1D real backward
RFFT1F    1D real forward

RFFT2I    2D real initialization
RFFT2B    2D real backward
RFFT2F    2D real forward

RFFTMI    multiple real initialization
RFFTMB    multiple real backward
RFFTMF    multiple real forward


Real Cosine Transform Routines
______________________________

COST1I    1D real cosine initialization
COST1B    1D real cosine backward
COST1F    1D real cosine forward

COSTMI    multiple real cosine initialization
COSTMB    multiple real cosine backward
COSTMF    multiple real cosine forward


Real Sine Transform Routines
____________________________

SINT1I    1D real sine initialization
SINT1B    1D real sine backward
SINT1F    1D real sine forward

SINTMI    multiple real sine initialization
SINTMB    multiple real sine backward
SINTMF    multiple real sine forward


Real Quarter-Cosine Transform Routines
______________________________________

COSQ1I    1D real quarter-cosine initialization
COSQ1B    1D real quarter-cosine backward
COSQ1F    1D real quarter-cosine forward

COSQMI    multiple real quarter-cosine initialization
COSQMB    multiple real quarter-cosine backward
COSQMF    multiple real quarter-cosine forward


Real Quarter-Sine Transform Routines
____________________________________

SINQ1I    1D real quarter-sine initialization
SINQ1B    1D real quarter-sine backward
SINQ1F    1D real quarter-sine forward

SINQMI    multiple real quarter-sine initialization
SINQMB    multiple real quarter-sine backward
SINQMF    multiple real quarter-sine forward


Library FFTPACK5 contains 1D, 2D, and multiple fast Fourier
subroutines, written in Fortran 77, for transforming real and complex
data, real even and odd wave data, and real even and odd quarter-wave
data.

All of the FFTPACK5 routines listed above are grouped in triplets
e.g. {CFFT1I, CFFT1F, CFFT1B}.  The suffix "I" denotes "initialize",
"F" denotes "forward" (as in "forward transform") and "B" denotes
"backward".  In an application program, before calling "B" or "F"
routines for the first time, or before calling them with a different
length, users must initialize an array by calling the "I" routine of
the appropriate pair or triplet.  Note that "I" routines need not be
called each time before a "B" or "F" routine is called.

All of the transform routines in FFTPACK5 are normalized.

Error messages are written to unit 6 by routine XERFFT.  The
standard version of XERFFT issues an error message and halts execution,
so that no FFTPACK routine will return to the calling program with
error return IER different than zero.  Users may consider modifying the
STOP statement in order to call system-specific exception-handling
facilities.

FFTPACK5 is written in standard Fortran 77 except for several
instances where arrays of type REAL or COMPLEX are passed to a
subroutine and used as a different type.

 (1) "Vectorizing the Fast Fourier Transforms", by Paul Swarztrauber,
     Parallel Computations, G. Rodrigue, ed., Academic Press,
     New York 1982.

 (2) "Fast Fourier Transforms Algorithms for Vector Computers", by
     Paul Swarztrauber, Parallel Computing, (1984) pp.45-63.