[petsc-dev] any way to detect if a matrix is singular?

[Hong]

Fande,
'-pc_factor_shift_amount 1' is huge.
Try use petsc default shift amount '1.e-14' by
 '-pc_factor_shift_type  nonzero' only.

Hong

On Tue, Oct 10, 2017 at 9:40 AM, Matthew Knepley <knepley at gmail.com> wrote:

> On Tue, Oct 10, 2017 at 10:36 AM, Kong, Fande <fande.kong at inl.gov> wrote:
>
>> Hi Developers,
>>
>> I am trying to use the native LU in PETSc to compute a matrix (arising
>> from a fluid-structure interaction problem). I encounter a zero pivot. The
>> matrix gives the wrong Newton direction when using "-pc_factor_shift_type
>>  nonzero -pc_factor_shift_amount 1".  I hence guess the matrix is
>> singular.
>>
>> Any easy way to detect if or not the matrix is singular??
>>
>
> That is the easiest way, namely having LU fail. You can catch the failure
> and do something useful.
>
>   Matt
>
>
>> Fande,
>>
>
>
>
> --
> 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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