[petsc-users] Get solution and rhs in the ts monitor

[Matthew Knepley]

On Thu, Nov 10, 2022 at 3:18 AM Tang, Qi <tangqi at msu.edu> wrote:

> Hi,
>
> How could I get rhs and solution in a ksp solve of ts?
>
> I am testing a linear problem (TS_Linear) using a bdf integrator. I tried
> to get the operator, rhs, and solution in the ts monitor through TSGetKSP
> and KSPGet***. But r = Ax-b is much larger than the ksp norm. I know the
> solver works fine.
>

Ax - b is the _unpreconditioned_ norm. By default we are printing the
preconditioned norm. You can see the difference by running with

  -ksp_monitor_true_residual

  Thanks,

     Matt


> Did I misunderstand something about how TS works here? Perhaps one of the
> vectors is changed after the ksp solve? If so, is there a simple way to get
> rhs and solution that ksp of ts solved?
>
> Thanks,
> Qi
>
>
>

-- 
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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