[petsc-users] KSPBuildSolution

[Jed Brown]

On Wed, Feb 16, 2011 at 16:18, Juha Jäykkä <juhaj at iki.fi> wrote:

> So the "solution" in the KSP should actually be identically zero for a
> converged result?
>

Yes


>
> > defect. If the initial guess is zero, then it would normally pick up your
> > Dirichlet boundary conditions on the first iteration and all subsequent
> > solves would have zero in those locations.
>
> It is not zero initially. But, on the other hand, it has zeros at both ends
> even at the very first iteration. If I understood your reply correctly,
> this
> would be expected for an initial guess which has correct values at the
> boundaries and it should only pick them up on the first iteration if they
> were
> not correct to begin with.
>
> Having ruled out a possibility of a bug in KSP, I need to continue my hunt
> for
> DIVERGED_LINEAR_SOLVE... None of the convergence tolerances seem to make
> any
> difference, it always diverges. The funny thing is, it diverges even if I
> start with an *exact* *solution*...
>

This is a problem. Run with -ksp_converged_reason to find out why it's
diverging.
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