changing default values in options database

Matthew Knepley knepley at
Fri Nov 7 12:12:52 CST 2008

I think you can just set those values before you call SetFromOptions()
and they will show up. However, I have not tried it.


On Fri, Nov 7, 2008 at 1:06 PM, Boyce Griffith <griffith at> wrote:
> Hi, Folks --
> I'm using some KSP solvers in a preconditioner (using FGMRES as the "outer"
> Krylov solver).  For these preconditioner KSPs, I generally want to use
> relatively loose relative convergence tolerances.
> Presently, I check to see if, e.g., -solver1_ksp_rtol, -solver2_ksp_atol,
> -solver3_max_it, etc., are set in the options database.  If a particular
> value is not set in the options database, I manually set that value to some
> value which is different from the default PETSc value.  Of course, when I
> use the `-help' flag, the help for each of the solvers indicates the default
> values for rtol, atol, max_it, etc. are the standard PETSc defaults.
> Is there a simple way to change these default values for individual solvers?
>  In particular, I would like to be able to ensure that the default values
> listed by `-help' correspond to the values that I'm specifying in the code.
> Thanks,
> -- Boyce

What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which
their experiments lead.
-- Norbert Wiener

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