[petsc-users] How/where to update DASetStencilWidth() info

[Jed Brown]

To keep the stencil small for matrix preallocation, you can create two
DMDAs.
On Jan 6, 2012 9:07 PM, "Barry Smith" <bsmith at mcs.anl.gov> wrote:

>
> On Jan 6, 2012, at 4:43 PM, Xuefeng Li wrote:
>
> > On Fri, 6 Jan 2012, Matthew Knepley wrote:
> >
> >> On Fri, Jan 6, 2012 at 4:32 PM, Xuefeng Li <li at loyno.edu> wrote:
> >>
> >>> However, is there a way to change/adjust the stencil width
> >>> AFTER the DA has been created and set up to a DMMG? Or,
> >>> in general, can we attach different DA objects to a DMMG
> >>> at different times?
> >>>
> >>
> >> 1) You cannot change this after setting up the DA. Just make another DA,
> >> since
> >>   they are very lightweight.
> >>
> >> 2) I think structuring new code around DMMG is wrong. It has been
> removed in
> >>   petsc-dev and is deprecated in 3.2. What are you trying to do?
> >>
> > I am just trying to use the ghost points to share
> > data among neighboring processes at one step
> > during the whole iteration. At that particular
> > step, the stencil width needs to be bigger.
> >
> > One can always set the stencil width to be big
> > enough so that one does not need to adjust it.
> > But this is just not as efficient as it can be.
>
>   Just create a bigger-stencil DMDA that you use during those "special"
> steps.
>
>   Barry
>
> >
> > Thanks again.
> >
> > Regards,
> >
> > --Xuefeng Li, (504)865-3340(phone)
> >  Like floating clouds, the heart rests easy
> >  Like flowing water, the spirit stays free
> >       http://www.loyno.edu/~li/home
> >  New Orleans, Louisiana (504)865-2051(fax)
> >
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120108/55f99085/attachment.htm>