On Tue, 29 Nov 2016, Michael Povolotskyi wrote: > I solve a system and I have to define some periodic boundary conditions > and some Dirichlet boundary conditions. > > My application is an old one, it was developed before > DirichletBoundaries and PeriodicBeoundaries existed in libmesh. So at > that time (around 2005) I developed the following solution. I added > constraints to the dof_map according to my boundary conditions. This was > not a very easy piece of code, since I had to add constraints in terms > of unconstrained DOFs only, but it was working. > > When I upgraded to libmesh 1.0.0, I found that in order to get correct > results, I had to call constrain_element_matrix and > constrain_element_vector with asymmetric_constraint_rows equal to false. > > Does it make sense to you?
I've been running my head around this for a while but I can't think of any obvious explanation. So let me try a bit harder to understand the problem. Were all your Dirichlet boundaries homogeneous? If not, how did you handle the offsets? What solver and preconditioner are you using? I assume it's something that can handle asymmetric operators, like the PETSc default GMRES+ILU? Is this a linear or nonlinear problem? If nonlinear, are you solving for the delta between two Newton iterates or solving directly for each Newton iterate? What are your linear solver tolerances? What's the smallest problem you can get this to replicate with? If you can exhibit it with a small code or with only a handful of elements then we might be able to dig into it ourselves. --- Roy ------------------------------------------------------------------------------ Developer Access Program for Intel Xeon Phi Processors Access to Intel Xeon Phi processor-based developer platforms. With one year of Intel Parallel Studio XE. Training and support from Colfax. Order your platform today.http://sdm.link/xeonphi _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
