[petsc-users] Using Finite Difference Jacobian with TS

[Matthew Knepley]

On Wed, Feb 2, 2022 at 6:08 PM Jorti, Zakariae via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Hello,
>
> I am using a TS to solve a differential algebraic equation (DAE).
> I do not provide the Jacobian matrix but instead set the TS to use a
> finite difference jacobian with coloring.
> For debugging, I only solve this DAE on one time step.
> Is there a way to output this finite difference jacobian in a matlab
> format (.m file)?
> I have already tried this flag : -mat_view ascii:ColFDJac.m:ascii_matlab ,
> but when I use it the test takes too long. My guess is that this flag  is
> trying to save all the matrices involved in the computations. I am  only
> interested in the jacobian though.
>

I tend to use -ksp_mat_view ascii:ColFDJac.m:ascii_matlab since that only
outputs the KSP system matrix.

  Thanks,

    Matt


> Thank you.
>
> Best,
>
> Zakariae
>
>

-- 
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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