[petsc-users] MatGetRowMinAbs returns negative number

[Dominik Szczerba]

Do you think this issue can potentially explain a behavior I observe:

In my big block shell matrix there are two blocks submatrices: (say) B
and B transposed. MaxAbs is exact same for both submatrices, MinAbs is
zero for B (as expected), but small negative for the other
(unexpected).

Now question: do I have a bug (that I do not immediately see) or this
can be hopefully only a trick in MinAbs?

Thanks a lot.

On Wed, Jan 4, 2012 at 6:05 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> On Wed, Jan 4, 2012 at 11:02, Matthew Knepley <knepley at gmail.com> wrote:
>>
>> Okay, here is what is wrong with the logic:
>>
>> 1) Its not a shift, it ignores values < 1.0e-12
>
>
> you wrote that in the commit message
>
>>
>>
>> 2) The problem is on line 2.17 of the diff where it takes the first value
>> as minimum, but does not take the absolute value
>
>
> good catch