On Fri, May 11, 2012 at 4:47 PM, Karthik Duraisamy <dkarthik at stanford.edu>wrote:
> Dear all, > > I have been able to use AMG (using ML) for some of my problems and am > looking to delve deeper into the workings of the algorithm to better > understand how to use it for larger and more complex problems. Since my > problems are hyperbolic and involve sharp gradients, I think there is a > possibility that coarse level operators are not very stable in some > problems. I see evidence of this because in many cases, I need to use lu or > a very high k ilu(k) on coarser levels to keep the iterative solver from > diverging. > > In this regard, I am wondering whether it is possible to obtain the > coarse grid operators (or at the very least, the eigenstructure at these > levels). Right now, I am doing the monitoring at the baseline level but I > am looking for additional information. > You can get the smoother http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/PC/PCMGGetSmoother.html This has the operator, and you can use the Krylov eigen approximation. You should have complete control. Matt > Regards, > Karthik. > > -- > > ======================================= > Karthik Duraisamy > Assistant Professor (Consulting) > Durand Building Rm 357 > Dept of Aeronautics and Astronautics > Stanford University > Stanford CA 94305 > > Phone: 650-721-2835 > Web: www.stanford.edu/~dkarthik > ======================================= > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120511/9f8ed363/attachment.htm>
