For performance reasons, it can be very efficient to bind mpi processes to cores. You should read the mpirun manual and the binding section.
Here is the command line to bind the processes:
mpirun -np 4 -bind-to-core feelpp_qs_laplacian
On Ubuntu systems and possibly others, locale (language, money, ...) information might be set and we don't handle that very well at the moment. You might get the following message at the execution of any Feel++ applications
terminate called after throwing an instance of 'std::runtime_error' what(): locale::facet::_S_create_c_locale name not valid
To fix this, we suggest that you `unset` all environment variables related to locale information. It includes `LANG`, `LC_CTYPE` and `LC_ALL`.
Just type
unset LANG LC_CTYPE LC_ALL
then the Feel++ application should execute without problems.