[Trilinos-Users] DAE's in Piro

Roger Pawlowski rppawlo at sandia.gov
Mon Aug 29 09:00:17 MDT 2011

Hi Chris,

I believe that the Implicit BDF Stepper in rythmos is a reimplementation 
of the IDA stepper.

DAE's are handled by the user.  When you write your model evaluator, you 
assemble the nonlinear equations including the mass matrix, so you can 
just leave out the terms that do not have a mass matrix contribution.  
During an evaluate call, rythmos will provide time derivatives for all 
degrees of freedom, but you are not required to use them all to form the 
equation set.


On 08/28/2011 10:36 PM, Christopher Parmer wrote:
> Hi All,
> I'm moving my model into DAE form and have two quick questions:
>     * Is the IDA BDF stepper supported in Piro?
>     * How are DAEs handled in Rythmos/Piro. Is there an option for a
>       mass matrix? How does outArgs know which residuals are
>       differential and which are algebraic?
> Thanks,
> Chris
> -- 
> (802) 343-5897
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> Trilinos-Users at software.sandia.gov
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