[petsc-users] PCGASMSetLocalSubdomains

[Hui Zhang]

Hi Dmitry,

is there any news about PCGASM? 

thanks,
Hui

On Feb 20, 2012, at 6:38 PM, Dmitry Karpeev wrote:

> Okay, thanks.
> I'll take a look.
> 
> Dmitry.
> 
> On Mon, Feb 20, 2012 at 11:30 AM, Hui Zhang <mike.hui.zhang at hotmail.com> wrote:
> For reference, my results are attached.
> 
> asm1.txt for asm with 1 process,
> asm2.txt for asm with 2 processes,
> gasm1.txt for gasm with 1 process, (with the iteration numbers different from others)
> gasm2.txt for gasm with 2 processes
> 
> 
> 
> 
> 
> 
> thank you,
> Hui
> 
> On Feb 20, 2012, at 3:06 PM, Dmitry Karpeev wrote:
> 
>> 
>> 
>> On Mon, Feb 20, 2012 at 12:59 AM, Hui Zhang <mike.hui.zhang at hotmail.com> wrote:
>> 
>> On Feb 20, 2012, at 12:41 AM, Dmitry Karpeev wrote:
>> 
>>> 
>>> 
>>> On Sun, Feb 19, 2012 at 3:08 PM, Hui Zhang <mike.hui.zhang at hotmail.com> wrote:
>>> I have a new problem: the results from ASM and GASM are different and it seems
>>> GASM has something wrong with SetModifySubMatrices. Numerical tests are with 
>>> each subdomain supported only by one subdomain. There are no problems when
>>> I did not modify submatrices.  But when I modify submatrices, there are problems
>>> with GASM but no problems with ASM. 
>>> 
>>> For example, I use two subdomains. In the first case each subdomain is supported by
>>> one processor and there seems no problem with GASM. But when I use run my program 
>>> with only one proc. so that it supports both of the two subdomains, the iteration 
>>> number is different from the first case and is much larger.  On the other hand
>>> ASM has no such problem.
>>>  
>>> Are the solutions the same?
>>> What problem are you solving?
>> 
>> Yes, the solutions are the same. That's why ASM gives the same results with one or
>> two processors. But GASM did not.  
>> Sorry, I wasn't clear: ASM and GASM produced different solutions in the case of two domains per processor?
>> I'm solving the Helmholtz equation.  Maybe 
>> I can prepare a simpler example to show this difference.
>> That would be helpful.  
>> Thanks.
>> 
>> Dmitry. 
>> 
>>> 
>>> Dmitry. 
>>> 
>>> 
>>> On Feb 15, 2012, at 6:46 PM, Dmitry Karpeev wrote:
>>> 
>>>> 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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