Dear Daniel, If appropriate, you could also consider using MPI_Comm_split() <https://www.mpich.org/static/docs/v3.2/www3/MPI_Comm_split.html> to create a new communicator based off of a subset of the world / master communicator, and pass that along to all classes / functions in your FEM code.
Best, Jean-Paul > On 21 Jan 2019, at 05:41, Wolfgang Bangerth <[email protected]> wrote: > > On 1/19/19 1:09 PM, Daniel wrote: >> >> After compiling I get the following behavior: >> >> bash-3.2$ mpirun -np 4 ./step-18 >> >> fem group size: 3 comm:3 >> >> fem group size: 3 comm:3 >> >> fem group size: 3 comm:3 >> >> fem group size: 3 comm:32766 > > The problem here is that only 3 of the processes participate in the > communicator. But you ask the question of the group size on all processes: > MPI_Comm_size( FEM_Comm ,&size_fem_comm); > Here, FEM_Comm is a communicator object that is really only initialized on > the > three participating processes, whereas it is uninitialized on the fourth and > consequently you are getting pointless answers there. > > You have the same problem again at the end of the same block, where every > process creates a TopLevel object using FEM_Comm, but really only on three of > the processes is this object valid. > > After creating the subset communicator, you need to have an if statement of > the form > if (this process is participating in the subset communicator) > { > do everything else > } > > Best > W. > > -- > ------------------------------------------------------------------------ > Wolfgang Bangerth email: [email protected] > www: http://www.math.colostate.edu/~bangerth/ > > -- > The deal.II project is located at http://www.dealii.org/ > For mailing list/forum options, see > https://groups.google.com/d/forum/dealii?hl=en > --- > You received this message because you are subscribed to the Google Groups > "deal.II User Group" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
