[petsc-users] SNES update solution vector

[Bikash Kanungo]

Hi Barry,

So for Newton solvers that would work by explicitly setting the boundary
conditions in my gradient(function) and Jacobian vectors. But in
quasi-Newton solvers where the Jacobian is built from a history of previous
Jacobians and current gradient vector, I can't enforce a new boundary
condition. I can change the current gradient vector appropriately but I
don't see a way handle the the Jacobian.

Thanks,
Bikash



On Fri, Nov 3, 2017 at 6:20 PM, Smith, Barry F. <bsmith at mcs.anl.gov> wrote:

>
>
>   You should not need to "tamper" with the solution process to achieve
> this.
>
>   I would just change how my FormFunction and FormJacobian behave to
> implement the different boundary conditions. Why would that not work?
>
>    Barry
>
> > On Nov 3, 2017, at 4:39 PM, Bikash Kanungo <bikash at umich.edu> wrote:
> >
> > Hi Matt,
> >
> > I want to update the Dirichlet boundary condition on the solution vector
> on-the-fly. One way to do it is to destroy the current snes solver and
> create a new one with the new Dirichlet boundary condition (which means
> setting a new solution vector with a different size, size  = # of
> non-Dirichlet rows). But is it possible to work with the current snes and
> instead enforce the new Dirichlet boundary condition on the current
> solution vector?
> >
> > Thanks,
> > Bikash
> >
> > On Fri, Nov 3, 2017 at 5:19 PM, Matthew Knepley <knepley at gmail.com>
> wrote:
> > What do you want to do to it?
> >
> >   Matt
> >
> > On Fri, Nov 3, 2017 at 5:14 PM, Bikash Kanungo <bikash at umich.edu> wrote:
> > Hi,
> >
> > I'm trying to solve a nonlinear problem using BFGS Quasi-Newton solver.
> I would like to tamper the solution vector x on-the-fly, based on some
> criterion. Is there a way to do so? Will SNESGetSolution(SNES snes, Vec *
> x) allow me to do so for each SNES iteration?
> >
> > Thanks,
> > Bikash
> >
> > --
> > Bikash S. Kanungo
> > PhD Student
> > Computational Materials Physics Group
> > Mechanical Engineering
> > University of Michigan
> >
> >
> >
> >
> > --
> > What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> > -- Norbert Wiener
> >
> > https://www.cse.buffalo.edu/~knepley/
> >
> >
> >
> > --
> > Bikash S. Kanungo
> > PhD Student
> > Computational Materials Physics Group
> > Mechanical Engineering
> > University of Michigan
> >
>
>


-- 
Bikash S. Kanungo
PhD Student
Computational Materials Physics Group
Mechanical Engineering
University of Michigan
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