Thank you Lawrence.


The 1-layer case is non-singular so the 2-layer should also be non-singular, I would think.


I made the change you suggested and that seemed to help a lot.  Now I need to understand the solution.


Cheers, Francis



------------------
Francis Poulin                    
Associate Professor
Department of Applied Mathematics
University of Waterloo

email:           fpoulin@uwaterloo.ca
Web:            https://uwaterloo.ca/poulin-research-group/
Telephone:  +1 519 888 4567 x32637

From: firedrake-bounces@imperial.ac.uk <firedrake-bounces@imperial.ac.uk> on behalf of Lawrence Mitchell <lawrence.mitchell@imperial.ac.uk>
Sent: Wednesday, June 21, 2017 12:54:53 PM
To: firedrake@imperial.ac.uk
Subject: Re: [firedrake] problem solving a linear system
 


On 21/06/17 17:00, Francis Poulin wrote:
>
> Saving file at /QG2L-Stommel-psi-u-q.ipynb
>   Linear firedrake_0_ solve did not converge due to
> DIVERGED_PCSETUP_FAILED iterations 0
>                  PCSETUP_FAILED due to FACTOR_NUMERIC_ZEROPIVOT

This is your problem.  You have a 0 on the diagonal of your operator.

If you are sure it is non-singular, try adding:

"pc_factor_mat_solver_package": "mumps"

to your solver options.

Lawrence

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