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

[Barry Smith]

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)
>