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Created by: bartgol

Currently, the ResidualModelEvaluator does not do anything to allow the use of W_prec. NOX has two ways to get a preconditioner from the model: through model_->create_W_prec() and through model_->get_W_factory()->getPreconditionerFactory()->createPrec() (assuming the prec factory is nonnull). Without the support for W_prec in ResidualModelEvaluator, in order to get NOX to use a preconditioner one must force his/her transientModel object to return a lows factory that does have a valid preconditioner factory

However, this is not always convenient/safe. One may want to always use his/her particular preconditioner for the problem at hand, and writing such a generic structure as a preconditioner factory for just one preconditioner seems too big of a hassle (besides not forcing the user to use the particular preconditioner for the problem). He/she may be better off writing the create_W_prec method in his/her model evaluator, and be done with it.

To fix this, I suggest to add the following lines to the method createOutArgsImpl of ResidualModelEvaluator

   MEB::OutArgsSetup<Scalar> transientOutArgs = transientModel_->createOutArgs();
   if (transientOutArgs.supports(MEB::OUT_ARG_W_prec))
   {
     outArgs.setSupports(MEB::OUT_ARG_W_prec);
   }

add this method to the class

     Teuchos::RCP<Thyra::PreconditionerBase<Scalar> > create_W_prec() const
          { return transientModel_->create_W_prec(); }

and finally add these lines in the evalModelImpl method (right before the call to evalModel of the transientModel)

   if (outArgs.supports(MEB::OUT_ARG_W_prec) && transientOutArgs.supports(MEB::OUT_ARG_W_prec))
   {
     transientOutArgs.set_W_prec(outArgs.get_W_prec());
   }

(the second part in the if may be redundant, I'm not sure).