[petsc-users] PCGASMSetLocalSubdomains

[Hui Zhang]

On Feb 15, 2012, at 11:19 AM, Hui Zhang wrote:

> Hi Dmitry,
> 
> thanks a lot! Currently, I'm not using ISColoring. Just comes another question
> on PCGASMSetModifySubMatrices(). The user provided function has the prototype
> 
>     func (PC pc,PetscInt nsub,IS *row,IS *col,Mat *submat,void *ctx);
> 
> I think the coloumns from the parameter 'col' are always the same as the rows 
> from the parameter 'row'. Because PCGASMSetLocalSubdomains() only accepts 
> index sets but not rows and columns. Has I misunderstood something?

As I tested, the row and col are always the same. 

I have a new question. Am I allowed to SetLocalToGlobalMapping() for the submat's
in the above func()?

thanks,
Hui

> 
> thanks,
> Hui
> 
> 
> On Feb 11, 2012, at 3:36 PM, Dmitry Karpeev wrote:
> 
>> Yes, that's right.
>> There is no good way to help the user assemble the subdomains at the moment beyond the 2D stuff.
>> It is expected that they are generated from mesh subdomains.
>> Each IS does carry the subdomains subcomm.
>> 
>> There is ISColoringToList() that is supposed to convert a "coloring" of indices to an array of ISs,
>> each having the indices with the same color and the subcomm that supports that color. It is
>> largely untested, though.  You could try using it and give us feedback on any problems you encounter.
>> 
>> Dmitry.
>> 
>> 
>> On Sat, Feb 11, 2012 at 6:06 AM, Hui Zhang <mike.hui.zhang at hotmail.com> wrote:
>> About PCGASMSetLocalSubdomains(), in the case of one subdomain supported by
>> multiple processors, shall I always create the arguments 'is[s]' and 'is_local[s]'
>> in a subcommunicator consisting of processors supporting the subdomain 's'?
>> 
>> The source code of PCGASMCreateSubdomains2D() seemingly does so.
>> 
>> Thanks,
>> Hui
>> 
>> 
> 

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