[petsc-users] Solutions different after program restart

[Jed Brown]

On Sun, Jun 3, 2012 at 8:37 AM, Niceno Bojan <bojan.niceno at psi.ch> wrote:

> I don't know.  Is there a way to find out?
>

-ksp_monitor or -ksp_monitor_true_residual


>
>
> > In that case, check that the system being solved is identical. You can
> save
> > it with -ksp_view_binary. Load it with
> > src/ksp/ksp/examples/tutorials/ex10.c as an independent test. Also be
> sure
> > to use the same initial guess.
>
> Thanks.  I was checking norms of matrix "A" and "x" and "b" vectors (2nd
> order) and they ARE the same before and after restart.  Does the same norm
> ensure the matrices and and vectors are the same?
>

They could be ordered differently. A different ordering would change the
ILU algorithm. You can also run with -pc_type jacobi to avoid this source
of variation (norms are still order-dependent up to rounding error).
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