On Mon, Jul 14, 2014 at 11:32 AM, Hodge, Neil E. <hod...@llnl.gov> wrote: > I recently sat down and read > > Kirk, "libMesh: a C++ library for adaptive mesh refinement/coarsening > simulations", Engineering with Computers, 2006. > > In that paper, I found the following: > > "On distributed memory machines, such as PC clusters, a complete copy of > the mesh is maintained independently on each processor. This design > decision limits practical 3D applications to on the order of 128 > processors because of the overhead associated with storing the global > mesh."
Wow, I had forgotten the paper said this! It's definitely not true any more, and the sentence leaves out something important, which is that the amount serial mesh "limits" you of course depends on the size of the Mesh. In practice I use SerialMesh for nearly all of my applications, and reserve ParallelMesh only for meshes which can't even be opened on a single node because they don't fit in the available system memory. In such cases, you have to use the Nemesis format and "split" your mesh in a preprocessing step before running your application. One of the nastier things that we've discovered within the last year or two is that std::map (which ParallelMesh uses to store its nodes and elements) imposes an incredible memory overhead relative to std::vectors, so that for small enough problems, running with ParallelMesh actually requires *more* memory than running with SerialMesh, even with the saving you get from parallelizing it factored in. > Is it possible to separate these two functionalities, i.e., to use the mesh > manipulation functionality, but not perform the element operations? Absolutely. -- John ------------------------------------------------------------------------------ Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck® Code Sight™ - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
