On Jul 29, 2011, at 10:10 AM, Pierre-Yves Aquilanti wrote:
> Hello,
>
> I'm using a preconditionner of my construction which has the particularity to
> make the norm of the residual vector increase suddently (from 1e-1 to 1e+6).
> The problem is that if that PETSc concludes to divergence after applying my
> preconditionner.
>
> Also, i setted the -ksp_divtol flag to 100 (random value to make it works)
> and also used the KSPSetTolerances function with the same value.
100 is not enough. In your case you need to use something like 10^8. The
value you put in this parameter is the maximum ratio the residual norm is
allowed to increase before it is declared diverged.
Barry
>
> I'm probably missing some point but can't figure out which one.
>
> Do someone has an idea ?
>
> Thanks a lot.
>
>
