[petsc-users] Increasing norm with finer mesh

[Smith, Barry F.]

   Please send your version of the example that computes the mean norm of the grid; I suspect we are talking apples and oranges

   Barry



> On Oct 1, 2018, at 7:51 PM, Weizhuo Wang <weizhuo2 at illinois.edu> wrote:
> 
> 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/
> 
> 
> -- 
> Wang Weizhuo