[petsc-users] Failure of MUMPS

[Matthew Knepley]

On Fri, Oct 5, 2018 at 9:08 PM Mike Wick <michael.wick.1980 at gmail.com>
wrote:

> Hello PETSc team:
>
> I am trying to solve a PDE problem with high-order finite elements. The
> matrix is getting denser and my experience is that MUMPS just outperforms
> iterative solvers.
>

If the problem is elliptic, there is a lot of evidence that the P1
preconditioner is descent for the system. Some people
just project the system to P1, invert that with multigrid, and use that as
the PC for Krylov. It should be worth trying.
Moreover, as Jed will tell you, forming matrices for higher order is
counterproductive. You should apply those matrix-free.

  Thanks,

     Matt


> For certain problems, MUMPS just fail in the middle for no clear reason. I
> just wander if there is any suggestion to improve the robustness of MUMPS?
> Or in general, any suggestion for interative solver with very high-order
> finite elements?
>
> Thanks!
>
> Mike
>


-- 
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

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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