On May 1, 2012, at 3:37 PM, Karthik Duraisamy wrote: > Hello, > > I have been using PETSc for a couple of years with good success, but > lately as my linear problems have become stiffer (condition numbers of the > order of 1.e20), I am looking to use better preconditioners. I tried using > PCMG with all the default options (i.e., I just specified my preconditioner > as PCMG and did not add any options to it) and I am immediately seeing better > convergence. > > What I am not sure of is why? I would like to know more about the > default parameters (the manual is not very explicit) and more importantly, > want to know why it is working even when I haven't specified any grid levels > and coarse grid operators. Any > help in this regard will be appreciated.
First run with -ksp_view to see what solver it is actually using. Barry > > Also, ultimately I want to use algebraic multigrid so is PCML a better > option than BoomerAMG? I tried BoomerAMG with mixed results. > > Thanks, > 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 > =======================================
