[petsc-dev] Matrix-free preconditioners

[Chris Eldred]

Hey Jed,

That's what I thought, thanks for the clarification!

Regards,
Chris Eldred

On Sat, Jan 28, 2017 at 2:58 PM, Jed Brown <jed at jedbrown.org> wrote:
> That's pretty much it.  You can probably easily apply the local part of
> the operator so you can do a block Jacobi by running an iterative method
> on subdomains.  Depending on the preconditioner, you might be able to
> apply Neumann subdomain operators -- a research topic would be to set up
> a BDDC-type method without explicit subdomain matrices.
>
> Chris Eldred <chris.eldred at gmail.com> writes:
>
>> Hey Petsc Dev,
>>
>> I had some questions about preconditioners, and I was hoping the list
>> could help me out. Specifically, if I have a MatShell with the ability
>> to compute the diagonal of the matrix; and a geometric multigrid
>> hierarchy with appropriate operators defined; what are my
>> preconditioner options?
>>
>> From reading the manual and the doc pages, it appears that my options are
>> 1) Jacobi (and block variants)
>> 2) Multigrid
>> plus the ability to use Fieldsplit for block matrices. Then within
>> multigrid, any iterative KSP (ie one that requires only matrix-vector
>> products) can be used as a smoother, with the basic ones being
>> Chebyshev and Richardson using Jacobi as a preconditioner.
>>
>> Is this correct? Is there anything else?
>>
>> Regards,
>> Chris Eldred
>>
>> --
>> Chris Eldred
>> https://www.math.univ-paris13.fr/~eldred/
>> Postdoctoral Fellow, LAGA, University of Paris 13
>> PhD, Atmospheric Science, Colorado State University, 2015
>> DOE Computational Science Graduate Fellow (Alumni)
>> B.S. Applied Computational Physics, Carnegie Mellon University, 2009
>> chris.eldred at gmail.com



-- 
Chris Eldred
https://www.math.univ-paris13.fr/~eldred/
Postdoctoral Fellow, LAGA, University of Paris 13
PhD, Atmospheric Science, Colorado State University, 2015
DOE Computational Science Graduate Fellow (Alumni)
B.S. Applied Computational Physics, Carnegie Mellon University, 2009
chris.eldred at gmail.com