[petsc-users] Increasing norm with finer mesh

[Weizhuo Wang]

The code is attached in case anyone wants to take a look, I will try the
high frequency scenario later.

On Mon, Oct 8, 2018 at 7:58 PM Mark Adams <mfadams at lbl.gov> wrote:

>
>
> On Mon, Oct 8, 2018 at 6:58 PM Weizhuo Wang <weizhuo2 at illinois.edu> wrote:
>
>> The first plot is the norm with the flag -pc_type lu with respect to
>> number of grids in one axis (n), and the second plot is the norm without
>> the flag -pc_type lu.
>>
>
> So you are using the default PC w/o LU. The default is ILU. This will
> reduce high frequency effectively but is not effective on the low frequency
> error. Don't expect your algebraic error reduction to be at the same scale
> as the residual reduction (what KSP measures).
>
>
>>

-- 
Wang Weizhuo
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