Re: [patch] Use fftw if available

[Mumit Khan]

On Tue, 1 May 2001, Trond Varslot wrote:

> Hello,
> I think it would be a great idea to give the option of using FFTW if this is 
> installed on the computer. It should be included in the main octave tree, 
> though, and not distributed as a separate patch. Octave is able to use BLAS 
> and LAPACK. FFTW should be

 treated the same way.

That was the point of the patch. However, the configuration is obviously
not doing what I had planned on.

> 
> Now, my problems emerged when trying your patch out. It applies fine, but 
> somehow I get lots of compilation errors of the sort
> 
> >/usr/src/build/octave-2.1.33/liboctave/dMatrix.cc:761: undefined reference 
> >to `cffti_'

This means that (1) configure couldn't find fftw/dfftw.h and/or
libfftw/libdfftw, but (2) told libcruft/Makefile not to build fftpack,
which is obviously not correct. The config.log file should have some
details on what's going on.

Here're a few questions:

1. Did you rebuild the auto-generated files such configure, config.h.in,
etc?
2. Did you specify --with-fftw when configuring?
3. Can your compiler find fftw headers and libraries without extra
options (eg., -I/usr/local/include and -L/usr/local/lib)? config.log
should have that info.

My gut feeling tells me that, unless something is obviously amiss in
the patch, you had skipped step 1 above. 

If not, could you send me the following info?

1. machine info (<srcdir>/config.guess)
2. locations of fftw header and libraries and whether you have dfftw.h or
fftw.h there.
3. Makeconf -- there is a variable called FFTW_LIBS that should be
filled in.
4. config.h -- there are a few FFTW related variables there that configure
is supposed to set.
5. config.log

The answer is in there somewhere.

> I have not had time to look into what causes these problems, but octave 
> compiles nicely without your patch, so it must be introducing something.
> Which version of octave was this patch done against? Which version of fftw 
> did you use? I tried this on octave-2.1.33 with fftw-2.1.3.
> 

I use Octave from CVS, so don't know what would happen if you tried this
with octave-2.1.33 (did you have trouble applying the patch, and then
did you re-create all the generated files such configure, config.h.in,
etc?). I'm using fftw-2.1.3 as well.

> I would really like to try it out, as I am currently doing some work which 
> depends rather heavily on fft.
> 

You may have to try out the CVS tree if we can't figure out why configure
is not doing what it's expected to do. I probably won't have the time to
investigate problem with 2.1.33, but will certainly help fix whatever
problems there may be with Octave CVS tree (octave web site has info on
how to check out a copy).

Regards,
Mumit