On Wednesday 17 December 2008 19:20:11 Anders Logg wrote: > Ola and I have now finished up the first round of getting DOLFIN to > run in parallel. In short, we can now parse meshes from file in > parallel and partition meshes in parallel (using ParMETIS). > > We reused some good ideas that Niclas Jansson had implemented in > PXMLMesh before, but have also made some significant changes as > follows: > > 1. The XML reader does not handle any partitioning. > > 2. The XML reader just reads in a chunk of the mesh data on each > processor (in parallel) and stores that into a LocalMeshData object > (one for each processor). The data is just partitioned in blocks so > the vertices and cells may be completely unrelated. > > 3. The partitioning takes place in MeshPartitioning::partition, > which gets a LocalMeshData object on each processor. It then calls > ParMETIS to compute a partition (in parallel) and then redistributes > the data accordingly. Finally, a mesh is built on each processor using > the local data. > > 4. All direct MPI calls (except one which should be removed) have been > removed from the code. Instead, we mostly rely on dolfin::MPI::distribute > which handles most cases of parallel communication and works with STL > data structures. > > 5. There is just one ParMETIS call (no initial geometric > partitioning). It seemed like an unnecessary step, or are there good > reasons to perform the partitioning in two steps? > > For testing, go to sandbox/passembly, build and then run > > mpirun -n 4 ./demo > ./plot_partitions 4
Looks beautiful! I threw a 3D mesh of 160K vertices onto it, and it was partitioned nicely in some 10 s, on my 2 core laptop. Johan > Everyone interested in the parallel design and implementation is > encouraged to have a look at the following new classes: > > LocalMeshData: storage for local mesh data (not yet a mesh) > XMLLocalMeshData: parallel parser for local mesh data > MeshPartitioning: partitioning algorithm, calling ParMETIS _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
