How to use OpenMpAssembler in dolfin (C++)

Dear friends,

I am trying to use OpenMpAssembler function in dolfin 1.1.0 (C++). I have include header file:

include <dolfin/fem/OpenMpAssembler.h>

but when I use:
dolfin::OpenMpAssembler omp_assembler;
omp_assembler.assemble(A,a);

It gives out the following error:
error: ‘OpenMpAssembler’ is not a member of ‘dolfin’|

Did I miss something? Thanks.

asked Jul 10, 2013 by xzhao99 FEniCS Novice (270 points)

1 Answer

Best answer

Your DOLFIN is probably compiled without OpenMP. Check by has_openmp() in python or by HAS_OPENMP C++ macro.

answered Jul 10, 2013 by Jan Blechta FEniCS Expert (51,420 points)
selected Jul 19, 2013 by Jan Blechta

Hi Jan,

Thank you for your answer. I am curious why dolfin use "HAS_OPENMP", I also find this macro in OpenMpAssembler.h file. When I make the test, I write

ifdef HAS_OPENMP

std::cout<<"openmp"<<std::endl;

endif

ifndef HAS_OPENMP

std::cout<<"NO openmp"<<std::endl;

endif

But it still shows "NO openmp" for the output. If I use #ifdef _OPENMP, it clearly shows that the openmp is compiled! Since OpenMpAssembler.h also uses HAS_OPENMP, I think this is the reason why OpenMpAssembler is not implemented!

Does DOLFIN define its own macro here? How can I compile FEniCS with OpenMP. During my installation, I just followed the standard instruction for Ubuntu.
Thank you very much.

commented Jul 12, 2013 by xzhao99 FEniCS Novice (270 points)

How can I compile FEniCS with OpenMP.

You probably need to install FEniCS from source. I don't know whether precompiled binaries can work with OpenMP. Johannes would know but he is on holiday.

commented Jul 12, 2013 by Jan Blechta FEniCS Expert (51,420 points)

Yes, the precompiled binaries are compiled with OpenMP.

commented Aug 1, 2013 by johannr FEniCS Expert (17,350 points)

And, how I can to change the compiler in mac to get openmp fron the source?

commented Jul 18, 2014 by ljofre FEniCS Novice (720 points)