[petsc-users] Increasing norm with finer mesh

[Weizhuo Wang]

I also tried to divide the norm by m*n , which is the number of grids, the
trend of norm still increases.

Thanks!

Weizhuo

Matthew Knepley <knepley at gmail.com> 于2018年10月1日周一 下午7:45写道：

> On Mon, Oct 1, 2018 at 6:31 PM Weizhuo Wang <weizhuo2 at illinois.edu> wrote:
>
>> Hi!
>>
>> I'm recently trying out the example code provided with the KSP solver
>> (ex12.c). I noticed that the mean norm of the grid increases as I use finer
>> meshes. For example, the mean norm is 5.72e-8 at m=10 n=10. However at
>> m=100, n=100, mean norm increases to 9.55e-6. This seems counter intuitive,
>> since most of the time error should decreases when using finer grid. Am I
>> doing this wrong?
>>
>
> The norm is misleading in that it is the l_2 norm, meaning just the sqrt
> of the sum of the squares of
> the vector entries. It should be scaled by the volume element to
> approximate a scale-independent
> norm (like the L_2 norm).
>
>   Thanks,
>
>      Matt
>
>
>> Thanks!
>> --
>> Wang Weizhuo
>>
>
>
> --
> 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/>
>


-- 
Wang Weizhuo
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