On Tue, 13 Mar 2018, Vasileios Vavourakis wrote:
I would like to run (in parallel mode) a piece of libMesh code where on each processor, a libMesh::Mesh is initialised & stored locally and, hence, subsequently initialise the EquationSystems accordingly, and for each processor independently. The FE mesh, may be same for all processors, or different, but in principle the information need to be stored independently (and partitioned in one subdomain/partition) without any problems when running things in parallel. I have tried to enforce the partitioning of the mesh via, e.g.: LibMeshInit init(argc, argv); Mesh msh(init.comm(), 1); //...import the mesh... msh.prepare_for_use(); msh.partition(1); // EquationSystems es(msh); // ...add a system here... es.init(); // ...solve the system, etc... However, I noticed that should I run the code in that many processes as many as the number of elements of the mesh, then it is ok; else it freezes (especially at a point where I "update_global_solution". Does this make sense to you?
Yes, I'm afraid so. Although you might have told the mesh to give every element to processor 0, when you created the mesh with init.comm(), you made every processor on that communicator (i.e. every processor in this case, since init defaults to MPI_COMM_WORLD) an owner of that mesh. When you do collective operations on a mesh, even processors who don't own any elements on the mesh must be involved if they're part of that mesh's communicator.
Any suggestions / tips? I am afraid there might be an easy way to do it, however, I wanted to have your opinion about it.
I *think* the thing to do would be to create a new Parallel::Communicator wrapper around MPI_COMM_SELF, then use that to create a local Mesh. I've never done that before, though. If you do it and it works, we'd love to have a unit test to make sure it *stays* working through future library updates. If you do it and it doesn't work, let us know and (especially if you can set up a failing test case) I'll try to help figure out what's wrong. --- Roy ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
