[petsc-users] Solutions different after program restart

[Jed Brown]

On Sun, Jun 3, 2012 at 8:30 AM, Niceno Bojan <bojan.niceno at psi.ch> wrote:

> Residual norm obtained from a call to "KSPGetResidualNorm(ksp, &rnorm);",
> gives:
>
> - First run: 1.98077e-02
> - Second run: 2.61329e-02
>
> The tolerances I request from KSP's gmres solver are:
>
> - Linear solver relative tolerance = 0.001;
> - Linear solver absolute tolerance = 1.0e-5;
>
> Does it tell you something?  It does not to me :-(
>

Is the initial residual about 30?


> > For some codes, the domain decomposition will not be identical on
> restart;
> > that changes the algorithm.
>
> That is clear, but what I am comparing are two sequential runs.
>

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.
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