On Thu, Aug 25, 2016 at 11:57 AM, Boris Boutkov <boris...@buffalo.edu> wrote:
> Hello all, (apologies in advance for the double post, looks like I wasn't > subscribed properly earlier), > > Ive been working on some libMesh/GRINS/PETSc Multigrid code and have been > getting some unexpected convergence results that don't quite line up with > theory. > > Currently I am uniformly refining a simple square grid with Dirichlet BCs > and manually element-wise constructing L2 projected interpolation matrices > between mesh levels while constraining each projection using the four > argument version of constrain_element_matrix. As a naive first attempt I > turned asymmetric_constrain_rows to false, as it helped me get past the > `!constraint_row.empty()' assertion which I didn't quite understand. > > Having now seen some of the convergence results I think maybe I was too > hasty in turning this asymmetric switch off as my iterative solvers are > having some difficulties on some mesh levels while being OK on others, my > hunch is this might be related to projections of hanging boundary nodes I > introduce while refining - but this leaves me stuck on the above assert. > You said you were doing uniform refinement? I'm confused by "hanging boundary nodes". -- John
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