Hm - uniform refinement, yes. Are the boundary nodes on the outside edges of refined elements not considered to be hanging nodes? Apologies if I'm misusing the term.
On Thu, Aug 25, 2016 at 5:28 PM, John Peterson <jwpeter...@gmail.com> wrote: > > > 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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