[Trilinos-Users] AztecOO::Iterate error code -3: loss of precision

[Heroux, Mike]

Denis,

This message is generated when the iterative method detects numerical
breakdown.  Although it can in principle come from coding errors,
especially if you have logic errors in formulating your linear system that
might make the matrix or RHS values incorrect, it is more likely a symptom
of a naturally poorly conditioned system.  This is almost certainly the
case if you have other systems for which the solver works.

In these situations, you can experiment with different preconditioners
that might be more robust.  Also, you could consider GMRES in this case,
perhaps without restart.  It can be more robust in these situations.

Mike


On 5/15/15, 1:55 PM, "Denis Davydov" <davydden at gmail.com> wrote:

>Dear all, 
>
>I am getting this error when solving a poisson equation discretized with
>hp-FEM and Lagrange basis functions.
>The solver is CG. 
>Any idea what could that be?
>
>p.s. the error appears only for a very particular combination of h and p
>refinement, 
>perhaps it could be related to a particularly bad condition number of the
>matrix?
>
>Kind regards,
>Denis 
>
>_______________________________________________
>Trilinos-Users mailing list
>Trilinos-Users at trilinos.org
>https://trilinos.org/mailman/listinfo/trilinos-users