Error in importing python module that uses fftw3 library: undefined symbol: dfftw_destroy_plan_

[jishnub]

I have a module shtools that I am trying to import in julia. It is a collection of fortran codes that comes with a python f2py wrapper. I am being able to import it correctly in python, but using @pyimport to import it in julia fails. I am using julia 0.4.5.

$ python -c "import pyshtools as shtools"
loading shtools documentation
$ julia
julia> using PyCall
julia> @pyimport pyshtools
ERROR: PyError (:PyImport_ImportModule) <type 'exceptions.ImportError'>
ImportError('/home/jishnu/lib/SHTOOLS-3.0/pyshtools/_SHTOOLS.so: undefined symbol: dfftw_destroy_plan_',)
  File "/home/jishnu/lib/SHTOOLS-3.0/pyshtools/__init__.py", line 31, in <module>
    load_documentation()
  File "/home/jishnu/lib/SHTOOLS-3.0/pyshtools/__init__.py", line 13, in load_documentation
    from . import _SHTOOLS

 [inlined code] from /home/jishnu/.julia/v0.4/PyCall/src/exception.jl:81
 in pyimport at /home/jishnu/.julia/v0.4/PyCall/src/PyCall.jl:341

From what I can see, the path to libfftw3.so is present in LD_LIBRARY_PATH. libfftw3.so is also present in julia's lib directory.

$ python -c 'import sys,os;print filter(lambda x: os.path.exists(x) and "libfftw3.so" in os.listdir(x),sys.argv[1].split(":"))' $LD_LIBRARY_PATH
['/home/apps/fftw-3.2/lib']

I have built shtools and pycall using the same version of python (version 2.7 from anaconda2). Is there a way to tell julia how to find this library?

[stevengj]

The problem is that the default Julia builds FFTW using the --disable-fortran, so it doesn't have the Fortran-callable wrappers that are needed by your code, and since this libfftw is already linked it is the one found by your Fortran code.

The simplest workaround is to rebuild Julia, either to use a different fftw library or to enable the Fortran wrappers.

In the longer run, it is probably worthwhile to build libfftw with the Fortran-callable wrappers by default (since they take hardly any space and don't pull in any Fortran code). This would require a patch for Julia. Can you open an issue?