[petsc-users] Multigrid

[Karthik Duraisamy]

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.

        Also, ultimately I want to use algebraic multigrid so is PCML a better option than BoomerAMG? I tried BoomerAMG with mixed results.

Thanks,
Karthik



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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
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