On Mon, Sep 14, 2015 at 3:46 AM, Stephan Herb < inf74...@stud.uni-stuttgart.de> wrote:
> Hello, > > I wrote a code to compute displacements and drilling moments for flat > shell elements with FEM. It imports a mesh file (xda or msh), assembles > the system matrix and RHS, solves the system and exports the results as > vtk files. > When I run my program with one processor it all works fine and the > displacements are correct. The problem occurs with more than one processor. > Simple example: Plane mesh (e.g. 8x8 quadrilaterals). Left edge is > clamped, the force is applied at the right edge and only at this edge. > If I run this example with e.g. 2 processors the partitioning cut halves > the mesh in a left and a right part. The result looks as follows: The > left part has no displacement at all, while the right part has a huge > displacement. > So you implemented a new type of shell finite element in libmesh? It would be great if this is something you could share with us in a branch on GitHub... > I studied your example codes and couldn't see any special code fragments > that is needed for a parallelized version of the code, so I thought: > 'Hey, libmesh seems to handle the parallelization internally - that's > great!'. But when I look at my results; in my opinion every processor > solves its own partial system with its own boundary condition, mesh > nodes and RHS and produces its own solution - so no communication or > exchange between the processes at all... > Are you using PETSc? Please send me (or share on google docs) your config.log file so I can take a look at your system's configuration. Now to my questions: Do I need additional configurations in my code to > make it work (at the LinearImplicitSystem, the mesh, the system matrix, > etc.)? Additional MPI code to exchange values/vectors/matrices by my > own? Libmesh seems to use MPI communication extensively internally and > it's difficult for me right now to see where the problem is. Perhaps you > can give me a hint to be back on track soon. > You shouldn't need to do anything too special. One big thing is to make sure you use "active_local" element iterators instead of "active" ones in your assembly routine if you are writing non-FEMSystem style libmesh code. ------------------------------------------------------------------------------ _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
