[petsc-users] PCGASMSetLocalSubdomains

[Dmitry Karpeev]

Hui,
There've been several changes to PCGASM ahead of the new release.
Let me go back and see if it affected the convergence problem.
Dmitry.

On Thu, May 10, 2012 at 4:16 AM, Hui Zhang <mike.hui.zhang at hotmail.com>wrote:

> 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>
>>>> 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
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120510/8b4dfb2b/attachment.htm>