[petsc-users] KSP linear solver returns inf

[Matthew Knepley]

On Thu, Mar 26, 2015 at 9:21 AM, Manav Bhatia <bhatiamanav at gmail.com> wrote:

> Hi,
>
>   I am using the KSP linear solver for my system of equations, without any
> command line options at this point. I have checked that the L1 norms of my
> system matrix and the force vector are finite values, but the KSP solver is
> returning with an “inf” residual in the very first iteration.
>
>   The problem has 6.7M dofs and I have tried this on multiple machines
> with different number of nodes with the same result.
>
>    Is there a reason why the solver would return after the first iteration
> with an inf?
>
>    I am not sure on where to start debugging this case, so I would
> appreciate any pointers.
>

For all solver questions, we want to see the output of

  -ksp_view -ksp_monitor_true_residual -ksp_converged_reason

The problem here would be that there is an error, so we would never see the
output
of -ksp_view and know what solver you are using. If you are using something
complex,
can you try using

  -pc_type jacobi

and send the output from the options above? Then we can figure out why the
other solver
gets an inf.

  Thanks,

     Matt


> Thanks,
> Manav
>
>
>


-- 
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
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