> I am currently looking for a library that can work well with PETSc and can > provide me an FEM framework to handle a set of coupled nonlinear PDEs in 2 > and 3 dimensions. > > I hope to compare the usability of LibMesh and Deal II for this purpose.
Glad to help! > 2) What additional code changes would a user be required to make in order to > get matrix-free solution algorithms to work with LibMesh ? For example, only > local assemblies need be performed and global assemblies that require matrix > to be stored are not needed. For an iterative linear Krylov solve, this > would be done at every matvec product request. I'll go ahead and comment on this one... I assume you would like to compute the action of the matrix-vector product in some Krylov subspace method? PETSc provides support for the notion of 'user-provided' matrix vector product, where the user returns the result y=Kx given the vector x. In the PETSc nonlinear solvers (which we support but there is no explicit example using them at the moment) the user can provide a 'residual' function which can be used to perform matrix-free newton-krylov simulations. In libMesh this is as simple as providing a residual function and then using the -ksp_matrix_free or -ksp_mf_operator (I think) options to PETSc. Of course, you will still need to come up with a quality preconditioner to use such a scheme, and doing so may still require a matrix, depending on your PDE. > If somebody can provide me with some pointers for the scalability results > and possibly a sample code for even a simple 1-D diffusion problem, that > would be fantastic. I could probably be persuaded to add ex19 for this purpose, it is well overdue. John/Roy/Derek, if y'all could point me to a Laplace-Young matrix assembly routine this would be a good case to build the example on! -Ben ------------------------------------------------------------------------- SF.Net email is sponsored by: Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
