[petsc-users] Convergence rate for spatially varying Helmholtz system

[Ramakrishnan Thirumalaisamy]

We fixed the issue. The linear operator in the matrix-free solver was set
up correctly, whereas the linear operator in the preconditioner was not set
up correctly (it was lagging in time). After setting the linear operators
correctly, we see that the diagonal system is solved in 1 iteration. Thank
you.

On Thu, Sep 30, 2021 at 5:49 PM Matthew Knepley <knepley at gmail.com> wrote:

> On Thu, Sep 30, 2021 at 6:58 PM Amneet Bhalla <mail2amneet at gmail.com>
> wrote:
>
>>
>>
>>>
>>>    For a diagonal system with this modest range of values Jacobi should
>>> converge in a single iteration.
>>>
>>
>> This is what I wanted to confirm (and my expectation also). There could
>> be a bug in the way we are setting up the linear operators in the
>> preconditioner and the matrix-free solver. We need to do some debugging.
>>
>> (with regard to the diagonal).
>>
>> We have printed the matrix and viewed it in Matlab. It is a diagonal
>> matrix.
>>
>
> Can you send us the matrix? This definitely should converge in 1 iterate
> now, so something I do not understand is going on.
> I will take any format you've got :)
>
>   Thanks,
>
>      Matt
>
> --
> 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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