[petsc-users] Setting absolute tolerance on ksp solver

[Amal Sahai]

The problem still persists. The solver keeps iterating till the maximum
number of iterations is reached despite absolute convergence criteria being
met long before that.

Regards
Amal

On Tue, Sep 8, 2015, 22:50 Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>   Instead of setting rtol to default you should set it zero so it never
> gets triggered.
>
> > On Sep 8, 2015, at 10:38 PM, Amal Sahai <amalsahai at gmail.com> wrote:
> >
> > I have been setting the tolerance for a ksp solver using
> KSPSetTolerances. I would like to set my convergence criteria using only
> the absolute convergence parameter. I use the following command to set this
> up:
> >
> > KSPSetTolerances( ksp, PETSC_DEFAULT, atol, PETSC_DEFAULT, maxits)
> >
> > The problem is my ksp solver considers only the value of rtol while
> stopping the iterative solve. I tried changing the value of rtol to some
> other parameter instead of PETSC_DEFAULT (while making sure that atol is
> the more stringent condition requiring more iterations) but to no avail.
> >
> > How can I fix this?
> >
> > Regards
> > Amal
>
>
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