Just curious,  but I've been wondering if it was possible to implement non-linear ODE's using the PETSC interface to PVODE (http://www.llnl.gov/CASC/sundials/)?


On 2/20/07, Ingo Schmidt <ingo.schmidt@tuhh.de> wrote:
Hi Roy, Ben and to whom it may concern, too,

I've started to implement the (linear) wave equation for structural
mechanics (well known: M d2u/dt2+Ku = f) into the
NonlinearImplicitSystem framework of libmesh, just to gain some
experiences with that stuff. The foundation is the code of example 13
but I'd like to use the NonlinearSolver classes (instead of
(implementing) Newton's method + linear_solve) and let PETSc handle the
equilibrium iteration at each time step.
So, exists there, may be an inofficial, example of libmesh following
that idea I can use as "help resource"?
If not, what are the reasons of reimplementing Newton's method and doing
linear solve instead of using SNES? Something specific with that
libmesh-petsc Interface or is it just that complex and horrible SNES

The last thing which is the last question (see below) of my last mail  I
directly adress to Ben upon the advice of Roy.
>> Thirdly, the TransientSystem<TransientNonlinearImplicitSystem> following
>> ex13 will be the best alternative to the FEMSystem for me. But is there
>> a chance to include the SNESSetUpdate
>> (http://www-unix.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/SNES/SNESSetUpdate.html )
>> -Option into libmesh at the PetscNonlinearSolver.solve() ? That's a
>> really general but also important option necessary for residuals
>> depending on the "current" solution ( e.g. nonlinear constitutive laws).
> You'll have to ask Ben about that - I think he's currently the only
> one who's done any work with PETSc's nonlinear solvers... and it can't
> have been too much work, if he's still got that hand-rolled Newton
> loop in ex13!  He's probably slacking off, finishing his dissertation
> and graduating next month and such.
> ---
> Roy
O.K. thanks a lot in advice especially to Ben and all the best for your

Best regards


PS: Actually, is there really no one who's solving structural mechanics
problems with libmesh??

Dipl.-Ing. Ingo Schmidt
Institute of Modelling and Computation

Hamburg University of Technology
Building L/ room: 3032
21075 Hamburg


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