[petsc-users] Zeroed solution after 0 iterations

[John Mousel]

Barry,

I've attached a small example that replicates this behavior.

John

On Wed, Apr 13, 2016 at 9:25 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>    John,
>
>     We'll need the full code to debug this. It doesn't see this should
> happen.
>
>    Barry
>
> > On Apr 13, 2016, at 7:11 AM, John Mousel <john.mousel at gmail.com> wrote:
> >
> > I have a colleague who is trying to run some simple test cases. He
> noticed if he provides the solution vector as the exact solution with a
> non-zero guess tagged, that the solution vector is zeroed upon return after
> 0 iterations. The system is just a 5x5 matrix corresponding to a heat
> equation with Dirichlet BCs. I've copied the KSPView below. He's using
> petsc-3.6.3.
> >
> > John
> >
> > solution before kspsolve:Vec Object: 1 MPI processes
> >   type: mpi
> > Process [0]
> > 300
> > 300
> > 300
> > 300
> > 300
> > KSP Object: 1 MPI processes
> >   type: bcgs
> >   maximum iterations=100
> >   tolerances:  relative=1e-15, absolute=1e-50, divergence=10000
> >   right preconditioning
> >   using nonzero initial guess
> >   using UNPRECONDITIONED norm type for convergence test
> > PC Object: 1 MPI processes
> >   type: ilu
> >     ILU: out-of-place factorization
> >     0 levels of fill
> >     tolerance for zero pivot 2.22045e-14
> >     matrix ordering: natural
> >     factor fill ratio given 1, needed 1
> >       Factored matrix follows:
> >         Mat Object:         1 MPI processes
> >           type: seqaij
> >           rows=5, cols=5
> >           package used to perform factorization: petsc
> >           total: nonzeros=25, allocated nonzeros=25
> >           total number of mallocs used during MatSetValues calls =0
> >             using I-node routines: found 1 nodes, limit used is 5
> >   linear system matrix = precond matrix:
> >   Mat Object:   1 MPI processes
> >     type: seqaij
> >     rows=5, cols=5
> >     total: nonzeros=25, allocated nonzeros=25
> >     total number of mallocs used during MatSetValues calls =0
> >       using I-node routines: found 1 nodes, limit used is 5
> > solution after kspsolve:Vec Object: 1 MPI processes
> >   type: mpi
> > Process [0]
> > 0
> > 0
> > 0
> > 0
> > 0
>
>
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