Groups   98 of 99+      julia-users › Calling Clanguage from Julia with OpenMP  Windows  3 posts by 2 authors      pokerho... googlemail.com    Jan 19     Hi,   I am trying to call Clanguage code from Julia.It works for 'regular' Clanguage code but now I have code that  potentially  uses OpenMP which causes trouble. I am trying to interpolate a function using a spline approximation. In short, if I type:  gcc -shared -O3 nspline_omp.c -o libcspline.dll -ffast-math   and then call one of the functions in the library from Julia using ccall, it works. But judging from the speed and comparison with other languages, only 1 thread is used. The code certainly supports multi-threading, for a my friend of mine on his Mac, it worked. If I type:  gcc -shared -O3 nspline_omp.c -o libcspline2.dll -ffast-math -fopenmp   iand try to call it from Julia, it doesn't work anymore, in particular:  LoadError: error compiling spline: could not load library  libcspline2.dll   The specified module could not be found.   Libdl.dlopen  libcspline2.dll    gives the same error. As an example, consider:   include omp.h   int banana int hello     int nt;  pragma omp parallel    nt   omp_get_num_threads  ;    return nt;      include  stdio.h  int main     printf   d\n , banana 12  ;     which perfectly works when compiled as .exe  gcc helloworld.c -fopenmp . When I try to compile    include  stdlib.h   include  omp.h   int banana int hello     int nt;  pragma omp parallel     nt   omp_get_num_threads  ;     return nt;    as a shared library using  gcc -shared -O3 helloworld2.c -o libcpsline3.dll -ffast-math -fopenmp  and then in Julia:  Libdl.dlopen  libcspline3.dll   LoadError: could not load library  libcspline3.dll   The specified module could not be found.   Finally, I am new to Julia and Clanguage and basically I have not much of an idea what I am doing, so it could be an obvious mistake. Thanks for your help.         Tony Kelman    Jan 19   Take a look at the libcspline3.dll in Dependency Walker. You're likely missing a libgomp dll which you'll need to copy from your compiler installation and put it next to libcspline3.dll. Where did you install the gcc compiler from and are you calling it from inside an environment like cygwin or msys 2 ?      pokerho... googlemail.com    Jan 20   copying the libgomp.dll into my working directory worked! Thanks!