[Wien] FFTW compiling

[Pavel Ondračka]

Maybe Gavin can clarify but I'm not actually sure if the instructions
in the mentioned email are 100% correct. FFTW there is compiled with
the default static libs (libfftw3.a and libfftw3_mpi.a), but the actual
-lfftw3 -lfftw3_mpi flags used for linking are for the dynamic library
(libfftw3.so and libfftw3_mpi.so). My guess is that it worked for Gavin
due to having another dynamic fftw somewhere in the path (e.g., the
system fftw libraries)?

Anyway, if you can get libfftw3.a but not libfftw3_mpi.a even when you
pass --enable-mpi to fftw configure, there is likely some problem with
your MPI installation. Were there any warnings during fftw configure?
BTW on some distributions like Fedora, only installing openmpi or mpich
is not enough you must also load it to set all the paths properly (for
example on Fedora with "module load openmpi"). This is distribution
specific though.

To get the dynamic library, just pass --enable-shared to fftw
configure, the Wien2k flags should work than (provided you can figure
out the missing mpi fftw lib). However I would highly recommend to get
the fftw from distribution repositories (something like libfftw3-mpi-
dev and libfftw3-dev package is needed, but specific package names vary
with distribution as well), unless you are on some enterprise systemwith legacy fftw version. 

Best regards
Pavel

On Wed, 2019-07-03 at 14:57 +0530, Riyajul Islam wrote:
> Hellow wien2k users,
> I am facing a problem in compiling FFTW in sitecofiguration. I have
> followed all the steps as in "
> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg18664.html
> ". But could nopt acces the
> "/home/username/fftw3/mpi/.libs/libfftw3_mpi.a" as in in mailing
> list.
> the current settings for FFTW is 
> F   FFTW options:            -DFFTW3 -I/home/edison1/fftw3/include
>       FFTW-LIBS:               -L/home/edison1/fftw3/lib64 -lfftw3
>       FFTW-PLIBS:              NOT FOUND!
> 
> How can I solve this issue?
> 
> Regards,
> Riyajul Islam
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