Thanks. It’s really helpful for me. I have another question about local nodes and local elements.
A process can only access one part of solution vectors. This part of vectors contains the solution of all local nodes, is it right? If it’s right, when there is a local element contains a node that is not owned by this process, how to get the solution vector of this node without requesting other process? And can point_value() be executed to get the value of a point located in this element since some nodes are not owned by the process? > On Jun 27, 2016, at 1:33 PM, John Peterson <jwpeter...@gmail.com> wrote: > > > > On Mon, Jun 27, 2016 at 10:24 AM, 张江 <zhangjiang.d...@gmail.com > <mailto:zhangjiang.d...@gmail.com>> wrote: > Hi, > > I have a few questions about reading data in parallel using libmesh. The > program is running on n processes, and I wish to have n partitions on this > mesh which means each data partition is assigned to one process. > > 1. How to make sure that each process just contains one part of the entire > mesh and the corresponding nodal values? > 2. How can each process maintain the data values of ghost nodes since its > local elements may contains the nodes that are not in its local nodes? > > Here is the initialization code. It seems that each process can access the > entire mesh and the entire nodal solution. Does it mean that each process > hold the entire data? > > I'm not sure what reason you have for thinking this... if you look at the > code for ExodusII_IO::copy_nodal_solution() you can see that it reads the > nodal values on every processor, but it only sets the values for which it is > responsible. > > Generally speaking, you should only access dofs which fall in the half-open > range > [system.solution->first_local_index(), system.solution->last_local_index()) > > > > libMesh::UnstructuredMesh *_mesh; > libMesh::ExodusII_IO *_exio; > libMesh::EquationSystems *_eqsys; > libMesh::System *_asys; > libMesh::PointLocatorTree *_locator; > > _mesh = new Mesh(comm()); > _exio = new ExodusII_IO(*_mesh); > _exio->read(filename); > _mesh->allow_renumbering(false); > _mesh->prepare_for_use(); > > General comment: don't use "new" and "delete" unless you have an explicit > reason for doing so. > > > > unsigned int _Vx_var, _Vy_var, _Vz_var; > _eqsys = new EquationSystems(*_mesh); > _asys = &(_eqsys->add_system<System>("Velocity")); > _Vx_var = _asys->add_variable("Vx", FIRST, LAGRANGE); > _Vy_var = _asys->add_variable("Vy", FIRST, LAGRANGE); > _Vz_var = _asys->add_variable("Vz", FIRST, LAGRANGE); > > _eqsys->init(); > > _locator = new PointLocatorTree(*_mesh); > > _exio->copy_nodal_solution(*_asys, "Vx", varnames[0]); // velocityX > _exio->copy_nodal_solution(*_asys, "Vy", varnames[1]); // velocityY > _exio->copy_nodal_solution(*_asys, "Vz", varnames[2]); // velocityZ > > libMesh::UniquePtr<libMesh::NumericVector<libMesh::Number> > _as = > _asys->current_local_solution->clone(); > > You are making a copy of the entire current_local_solution vector here, which > is almost certainly not what you want. > > -- > John ------------------------------------------------------------------------------ Attend Shape: An AT&T Tech Expo July 15-16. Meet us at AT&T Park in San Francisco, CA to explore cutting-edge tech and listen to tech luminaries present their vision of the future. This family event has something for everyone, including kids. Get more information and register today. http://sdm.link/attshape _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
