[Trilinos-Users] [EXTERNAL] NOX::Epetra::LinearSystemAztecOO

[Mike Sussman]

Thank you, Roger, for your reply.

In studying the example code, it had passed me by that the "Required"
interface appeared twice, once in constructing the Group and once in
constructing the LinearSystem.  Now I understand.  Thanks again.

On Mon, 2011-11-28 at 08:14 -0500, Roger Pawlowski wrote:
> Hi Mike,
> 
> The "Required" interface is required to construct the
> NOX::Epetra::Group, not to construct the LinearSystem.  The linear
> system object is used to access the Jacobian operator and its inverse
> operator for solving Newton based systems.  The four constructors in
> the linear system object support different use cases.  Essentially,
> the fourth constructor you refer to allows for a user to supply their
> own Jacobian operator and their own preconditioner.  The other
> contstructors are for the use cases where some of this information is
> not present.  In that case, the required interface will provide a
> residual evaluation that can be used to construct the missing
> information.  If the Jacobian operator is not supplied it will used
> Jacobian-free Newton-Krylov methods to approximate the Jacobian vector
> products.  If a preconditioner is missing, there are multiple options
> including using the residual evaluation to brute-force a colored
> finite differnce Jacobian to get preconditioner entries to hand off to
> Ifpack or ML.
> 
> Roger
> 
> 
> On 11/23/2011 09:49 PM, Mike Sussman wrote: 
> > Would someone please explain to me why the fourth constructor
> > in NOX::Epetra::LinearSystemAztecOO does NOT include the "required"
> > function evaluator computeF from NOX::Epetra::Interface::Required,
> > but only the Jacobian and preconditioner?  The words in the Detailed
> > Description seem to imply that the fourth constructor should include
> > NOX::Epetra::Interface::Required::computeF as a parameter.
> > 
> > 
> > -- 
> > Mike Sussman
> > 
> > _______________________________________________
> > Trilinos-Users mailing list
> > Trilinos-Users at software.sandia.gov
> > http://software.sandia.gov/mailman/listinfo/trilinos-users
> 

-- 
Mike Sussman