[petsc-users] testing scalability for ksp/ex22.c

[Jed Brown]

Always send output with -log_summary for each run that you do.

On Thu, Feb 23, 2012 at 14:16, Francis Poulin <fpoulin at uwaterloo.ca> wrote:

> Hello,
>
> I am learning to use PetSc but am just a notice.  I have a rather basic
> question to ask and couldn't not find it on the achieves.
>
> I am wanting to test the scalability of a Multigrid solver to the 3D
> Poisson equation.  I found ksp/ex22.c that seems to solve the problem that
> I'm interested in.  I ran it on a large server using different processors.
>
> The syntax that I use to run using MPI was
>
> ./ex22 -da_grid_x 64 -da_grid_y 64 -da_grid_z 32
>

Which version of PETSc?


>
> I tested it using 2, 4, 8, 16 cpus and found that the time increases.  See
> below.  Clearly there is something that I don't understand since the time
> should be reduced.
>
> n               wtime
> ---------------------
> 2               3m58s
> 4               3m54s
> 8               5m51s
> 16              7m23s
>
> Any advice would be greatly appreciated.
>
> Best regrads,
> Francis
>
>
>
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