[petsc-users] PCGASMSetLocalSubdomains

[Dmitry Karpeev]

You should be able to. 
This behavior is the same as in PCASM,
except in GASM the matrices live on subcommunicators.
I am in transit right now, but I can take a closer look in Friday.

Dmitry



On Feb 15, 2012, at 8:07, Hui Zhang <mike.hui.zhang at hotmail.com> wrote:

> 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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