[petsc-users] Problem with large grid size

[Smith, Barry F.]

> On Nov 29, 2018, at 1:46 PM, Fazlul Huq via petsc-users <petsc-users at mcs.anl.gov> wrote:
> 
> Hello PETSc Developers,
> 
> I am trying to run the code (attached herewith) with the following command and it works until the size of the matrix is 99999X99999. But when I try to run with 999999X999999 then I got weird result.

   What is that "weird result"? 

   My guess is for problems that large you need to ./configure PETSc with the additional option --with-64-bit-indices since for such large problems 32 bit integers are not large enough to contain values needed for storing and accessing the sparse matrix.

   Barry

> 
> The command is: 
> ./poisson_m -n 999999 -pc_type hypre -pc_hypre_type boomeramg -ksp_view_solution
> Any suggestions is appreciated.
> 
> 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
> <poisson_m.c>