I have looked into that a bit more today and it seems there is everything we need available (finally). Then i'd have another question regarding the use of FEMSystem. What would be the actual use case of choosing FEMSystem vs. the approach in most examples? I have used the normal example approach because my projects were pretty much just "a single usecase". Our specific approach would be to have one physics model and then test and combine different algorithms from variying research fields (model order reduction / control theory) on that, so we would interact with the RHS and Jacobian matrices a lot (thats the reason we want to access the raw PETSc objects).
Julian On Wed, Aug 31, 2016 at 2:37 PM, Paul T. Bauman <ptbau...@gmail.com> wrote: > Hi Julian, > > On Wed, Aug 31, 2016 at 3:40 AM, Julian Andrej <j...@tf.uni-kiel.de> wrote: >> >> >> so we are elaborating FEM libraries for a project we are attempting. >> One requirement is, that we want to assemble FEM matrices/vector into >> PETSc objects, which libMesh obviously provides. Is there a way, to >> just assemble the matrices by providing element based loops, so that >> we can work with the plain PETSc Mat/Vec afterwards? >> >> Basically we want to hand off the FEM stuff to libMesh and do >> everything else on our own with the assembled objects. > > > If I understand what you're asking, then just about any of the examples > (http://libmesh.github.io/examples.html) should illustrate this, e.g. for > Poisson: > https://github.com/libMesh/libmesh/tree/master/examples/introduction/introduction_ex3. > In particular, if you built libMesh with PETSc, the NumericVector and > SparseMatrix objects will be PetscVector and PetscMatrix, respectively, so > you can cast and grab the raw Vec and Mat objects from the System::solution > and ImplicitSystem::matrix. > > HTH, > > Paul > > P.S. Note that we have interfaces to PETSc's solvers so you'll be able to do > all the command line foo for the PETSc solvers so you wouldn't need to > rewrite solvers yourself. Just my two cents. ------------------------------------------------------------------------------ _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
