octave-3.2.0 configure and fftw3

[Jaroslav Hajek]

On Fri, Jul 3, 2009 at 7:23 PM, Wolfgang
Pichl<wolfgang.pichl at univie.ac.at> wrote:
> Hi,
> there seems to be a bug in the octave-3.2.0 configure script which
> inhibits using an installed fftw3 library. In config.log I find the
> following:
>
> configure:10240: checking for fftw_plan_dft_1d in -lfftw3
> configure:10275: gcc -o conftest -g -O2    conftest.c -lfftw3  -lhdf5 -lz
> -lm  >&5
> configure:10281: $? = 0
> configure:10299: result: yes
> configure:10303: checking for fftwf_plan_dft_1d in -lfftw3f
> configure:10338: gcc -o conftest -g -O2    conftest.c -lfftw3f  -lhdf5 -lz
> -lm
>>&5
> /usr/lib64/gcc/x86_64-slamd64-linux/4.2.4/../../../../x86_64-slamd64-linux/bin/ld:
> cannot find -lfftw3f
> collect2: ld returned 1 exit status
>
> and at the end:
>
> configure:34554: WARNING: FFTW library not found.  Octave will use the
> (slower)
> FFTPACK library instead.
>
> As far as I understand, this means: configure first checks the standard
> libfftw3 (which is double precision). It is present and detected, but
> after that the single-precision version libfftw3f is also searched. Of
> course, it does not exist, the fftw3 package does not allow to build and
> install versions for different precisions at the same time (at least not
> without nasty tricks). So configure decides to disable support for the
> external fftw3. './configure --help' does not show any option to override
> this behaviour.
>
> I have tested this on x86_64 Linux (Slamd64 distribution), with fftw3
> built from the source and installed in /usr/local. Anyway, the problem
> looks quite platform-independent. Octave-3.0.5 does not have
> this problem, the fftw3 library is detected out of the box.
>
> best regards
> Wolfgang Pichl
>

Octave 3.2.0 supports single precision, that's why it needs single
precision support in FFTW.
I built FFTW 3.1.2 from sources some six months ago, and both libfftw3
and libfftw3f are installed without problems. I really don't recall
doing any nasty tricks beyond the standard holy trio (configure; make;
make install).
Also, the fftw3 package from my Ubuntu distro provides both precision.
So, recompiling FFTW3 with support for both precisions should be your
easiest way forward.

regards

-- 
RNDr. Jaroslav Hajek
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz