[petsc-users] Error Norm_2

[Smith, Barry F.]

   How are you computing the error norm? 

   You need to use the L2 norm in the computations, not the l2 norm. 

   Also you need to make sure the convergence criteria you use for the algebraic system is smaller than the descritzation error 


   Barry


> On Feb 25, 2019, at 1:55 PM, Fazlul Huq via petsc-users <petsc-users at mcs.anl.gov> wrote:
> 
> Hello PETSc Developers,
> 
> I have solved a very simple poisson problem with different matrix sizes (10 to 10^7).
> But when I have compared error norm_2 for the solution, I got the attached curve.
> It looks like error norm_2 increases with increasing matrix size. Shouldn't it decrease rather with increasing matrix size?
> 
> Thanks.
> 
> Sincerely,
> Huq
> -- 
> 
> Fazlul Huq
> Graduate Research Assistant
> Department of Nuclear, Plasma & Radiological Engineering (NPRE)
> University of Illinois at Urbana-Champaign (UIUC)
> E-mail: huq2090 at gmail.com
> <Error norm_2_withoutJacobi.png>