[petsc-users] force ksp to continue if divergence or increase divergence tol, how ?

[Barry Smith]

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.
> 
>