[petsc-users] Mat/Vec with empty ranks

[Matthew Knepley]

On Mon, Oct 2, 2017 at 6:21 AM, Florian Lindner <mailinglists at xgm.de> wrote:

> Hello,
>
> I have a matrix and vector that live on 4 ranks, but only rank 2 and 3
> have values:
>
> e.g.
>
> Vec Object: 4 MPI processes
>   type: mpi
> Process [0]
> Process [1]
> 1.1
> 2.5
> 3.
> 4.
> Process [2]
> 5.
> 6.
> 7.
> 8.
> Process [3]
>
>
> Doing a simple LSQR solve does not converge. However, when the values are
> distributed equally, it converges within 3
> iterations.
>
> What can I do about that?
>
> I have attached a simple program and creates the matrix and vector or
> loads them from a file.
>

There are a few problems with this program. I am attaching a cleaned up
version. However, convergence still differs starting
at iteration 2. It appears that LSQR has a problem with this system, or we
have a bug that I cannot see.

  Thanks,

    Matt


> Thanks,
> Florian
>



-- 
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.caam.rice.edu/~mk51/>
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