[petsc-users] [Libmesh-users] Convergence rate for petsc virs

Jed Brown jedbrown at mcs.anl.gov
Mon Aug 13 12:00:40 CDT 2012

On Mon, Aug 13, 2012 at 9:14 AM, Ataollah Mesgarnejad <
amesga1 at tigers.lsu.edu> wrote:

> You see this is really bad for a case like mine where essentially I am
> solving a quadratic problem with box constraints (Jac and Constraints are
> constant during each solve). Is there anything we can do to use this
> structure shouldn't we be able to get a quadratic convergence ?

Your problem is not smooth, thus you cannot expect quadratic convergence in
a general setting. The active set/reduced space methods (SNESVIRS) change
in a discrete way as the bound constraints are activated or deactivate,
therefore they do not generally converge quadratically until the constraint
set has been identified. You can try semismooth Newton methods (SNESVISS)
for a method that has a better chance of converging quadratically.
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