[petsc-users] KSP Tolerances for SNES

[Matthew Knepley]

On Mon, Jan 20, 2014 at 3:58 PM, Dharmendar Reddy
<dharmareddy84 at gmail.com>wrote:

> Hello,
>         I want to set KSP Tolerances for an SNES solver for F(X) = 0
>
> as absTolKSP = maxval ( norm2F, absTolF_SNES)
>
> I am doing the above step based on Corollary 4 in the paper
> (
> http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.10.8477&rep=rep1&type=pdf
> )
>

It appears that Mike's paper was published before the reference everyone
uses for this:

S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an inexact
Newton method", SISC 17 (1), pp.16-32, 1996.

We have it in PETSc:


http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/SNES/SNESKSPSetUseEW.html

  Thanks,

     Matt


> Since norm2(F) chnages as the simulation progress, how to change the
> tolerence for the ksp ?
>
> I am trying via KSPConvergenceTest by doing the following calls inside
> the test funciton
>
>  call KSPSetTolerances
>  call KSPDefaultConverged
>
> now for the second call i need to pass KSPDefaultConvergedCtx , how do
> i do this from Fortran ?
>
> Thanks
> Reddy
>



-- 
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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