fftw3: Wisdom of Fortran?
8.5 Wisdom of Fortran?
======================
In this section, we discuss how one can import/export FFTW wisdom (saved
plans) to/from a Fortran program; we assume that the reader is already
familiar with wisdom, as described in 
Words of Wisdom-Saving
Plans.
The basic problem is that is difficult to (portably) pass files and
strings between Fortran and C, so we cannot provide a direct Fortran
equivalent to the 'fftw_export_wisdom_to_file', etcetera, functions.
Fortran interfaces _are_ provided for the functions that do not take
file/string arguments, however: 'dfftw_import_system_wisdom',
'dfftw_import_wisdom', 'dfftw_export_wisdom', and 'dfftw_forget_wisdom'.
So, for example, to import the system-wide wisdom, you would do:
integer isuccess
call dfftw_import_system_wisdom(isuccess)
As usual, the C return value is turned into a first parameter;
'isuccess' is non-zero on success and zero on failure (e.g. if there is
no system wisdom installed).
If you want to import/export wisdom from/to an arbitrary file or
elsewhere, you can employ the generic 'dfftw_import_wisdom' and
'dfftw_export_wisdom' functions, for which you must supply a subroutine
to read/write one character at a time. The FFTW package contains an
example file 'doc/f77_wisdom.f' demonstrating how to implement
'import_wisdom_from_file' and 'export_wisdom_to_file' subroutines in
this way. (These routines cannot be compiled into the FFTW library
itself, lest all FFTW-using programs be required to link with the
Fortran I/O library.)
Info Catalog
fftw3: Fortran Examples
fftw3: Calling FFTW from Legacy Fortran