Hey Jed, That makes sense now, thanks! It sounds like the correct way to do things is: For matrices: 1) for each set of coupled dofs, select 1 to be the master and modify the local to global maps such that all the local indices that previously pointed to the slave dofs now point to the master dof -> assembly doesn't produce anything for the slave rows 2) fill the rows for the slave dofs with a -1 in the master column and 1 in the slave column (since we are just enforcing slave = master). For residuals, just do 1) and then set slave dofs equal to the master dof. The star forest write up is exactly what I was looking for, thanks! Regards, Chris On Wed, Feb 22, 2017 at 5:37 PM, Jed Brown <[email protected]> wrote:

"Kong, Fande" <[email protected]> writes:

...

How about the inverse of SF? The original leaf becomes a new root, and the original leaf will map to multiple new leafs?

Chris has multiple local indices mapping to the same global index (this is the usual local-to-global map). He's eager to build a singular matrix and irritated that the tooling intentionally makes that harder to do by accident. ;-)

-- Chris Eldred https://www.math.univ-paris13.fr/~eldred/ Postdoctoral Fellow, LAGA, University of Paris 13 PhD, Atmospheric Science, Colorado State University, 2015 DOE Computational Science Graduate Fellow (Alumni) B.S. Applied Computational Physics, Carnegie Mellon University, 2009 [email protected]