Hi Bill and all,
> 1) What is the purpose of f77_wisdom.f90 and wisdom.c? I ask because
> they seem to duplicate functionality that is already available directly
> from the FFTW3 library in both C and Fortran form via the fftw3.h and
> fftw3f.f03 include files.
File fftw3f.f03 is apparently fairly new. It did not exist when last I
messed around with FFTW wisdom. Probably we can use it now; we made
wisdom.c because the older wrapper, invoked through f77_wisdom.f90,
failed on OS X.
> 2) I see that you have named the wisdom data file as jt9_wisdom.dat.
> Looking at the FFTW implementation it would seem that a single wisdom
> data file for all applications is not a great overhead. The default
> system wisdom data file (not available on Windows) is named
> /etc/fftw/{wisdomf,wisdom,wisdoml} and is intended to contain many
> optimized plan choices for various type and sizes of transform. I would
> have thought that a single wisdom data file for all WSJT-X programs and
> utilities would be sufficient. Was your intention to have a different
> wisdom data file for wsjt and jt9?
Revision 4617 also reads/writes wsjtx_wisdom.dat. We're presently
running two processes in parallel, jt9[.exe] and wsjtx[.exe]. We don't
want them writing to the same file, possibly over-writing information
that the other process wanted to save.
It will be trivial to change to one file if/when we change to a
single-process model.
System wisdom is convenient in *nix but not very convenient in Windows.
The whole idea is not particularly useful when we are using oddball
FFT lengths like some of those used in WSJT-X, e.g., 77175, 672000, and
884736.
> 3) I was also thinking of adding a header line to the exported wisdom
> data file including the program version. Something like:
>
> version:<last-change-svn-revision>{-dirty,-local}
Could be done, but my informed guess is that it's not worth the effort.
These optimizations lead to speed improvements that are rather minor.
The code is already carefully tuned and optimized; the FFTs do not
dominate execution times.
-- Joe
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