Parallel ISCreateGeneral()

[Tim Stitt]

OK Matt...will try that out. Thanks.

Matthew Knepley wrote:
> On Nov 18, 2007 12:21 PM, Tim Stitt <timothy.stitt at ichec.ie> wrote:
>   
>> Oh...ok I am now officially confused.
>>
>> I have developed a serial code for getting the first k rows of an
>> inverted sparse matrix..thanks to PETSC users/developers help this past
>> week.
>>
>> In that code I was calling MatLUFactorSymbolic() and
>> MatLUFactorNumeric() to factor the sparse matrix and then calling
>> MatSolve for each of the first k columns in the identity matrix as the
>> RHS. I then varied the matrix type from the command line to test MUMPS,
>> SUPERLU etc. for the best performance.
>>
>> Now I just want to translate the code into a parallel version...so I now
>> assemble rows in a distributed fashion and now working on translating
>> the MatLUFactorSymbolic() and MatLUFactorNumeric() calls which require
>> index sets...hence my original question.
>>
>> Are you saying that I now shouldn't be calling those routines?
>>     
>
> You can certainly do it that way, but it is much easier to just use a KSP.
> You set the Mat using KSPSetOperators, then KSPSetType(ksp, KSPPREONLY),
> and PCSetType(pc, PCLU) (or MUMPS or whatever). Then KSPSolve() with the
> identity columns. We handle everything else.
>
>   Matt
>
>   
>> Tim.
>>
>> Matthew Knepley wrote:
>>     
>>> On Nov 18, 2007 11:52 AM, Tim Stitt <timothy.stitt at ichec.ie> wrote:
>>>
>>>       
>>>> Matt,
>>>>
>>>> It is in setup for MatLUFactorSymbolic() and MatLUFactorNumeric() calls
>>>> which require index sets. I have distributed my rows across the
>>>> processes and now just a bit confused about the arguments to the
>>>> ISCreateGeneral() routine to set up the IS sets used by the Factor
>>>> routines in parallel.
>>>>
>>>> So my basic question is what in general is the length and integers that
>>>> get passed to ISCreateGeneral() when doing this type of calculation in
>>>> parallel? Are they local index values (0..#rows on process-1) or do they
>>>> refer to the distributed indices of the global matrix?
>>>>
>>>>         
>>> To be consistent, these would be local sizes and global numberings. However,
>>> I am not sure why you would be doing this. I do not believe any of the parallel
>>> LU packages accept an ordering from the user (they calculate their own),
>>> and I would really only use them from a KSP (or PC at the least).
>>>
>>>   Matt
>>>
>>>
>>>       
>>>> Tim.
>>>>
>>>>
>>>> Matthew Knepley wrote:
>>>>
>>>>         
>>>>> On Nov 18, 2007 11:34 AM, Tim Stitt <timothy.stitt at ichec.ie> wrote:
>>>>>
>>>>>
>>>>>           
>>>>>> OK..so I should be using the aggregate length returned by
>>>>>> MatGetOwnershipRange() routine?
>>>>>>
>>>>>>
>>>>>>             
>>>>> If you are using it to permute a Mat, yes.
>>>>>
>>>>>   Matt
>>>>>
>>>>>
>>>>>
>>>>>           
>>>>>> Thanks Matt for you help.
>>>>>>
>>>>>>
>>>>>> Matthew Knepley wrote:
>>>>>>
>>>>>>
>>>>>>             
>>>>>>> IS are not really parallel, so all the lengths, etc. only refer to local things.
>>>>>>>
>>>>>>>   Matt
>>>>>>>
>>>>>>> On Nov 18, 2007 11:22 AM, Tim Stitt <timothy.stitt at ichec.ie> wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>               
>>>>>>>> Hi all,
>>>>>>>>
>>>>>>>> Just wanted to know if the "the length of the index set" for a call to
>>>>>>>> ISCreateGeneral() in a parallel code, is a global length, or the length
>>>>>>>> of the local elements on each process?
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>> Tim.
>>>>>>>>
>>>>>>>> --
>>>>>>>> Dr. Timothy Stitt <timothy_dot_stitt_at_ichec.ie>
>>>>>>>> HPC Application Consultant - ICHEC (www.ichec.ie)
>>>>>>>>
>>>>>>>> Dublin Institute for Advanced Studies
>>>>>>>> 5 Merrion Square - Dublin 2 - Ireland
>>>>>>>>
>>>>>>>> +353-1-6621333 (tel) / +353-1-6621477 (fax)
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>                 
>>>>>>>               
>>>>>> --
>>>>>> Dr. Timothy Stitt <timothy_dot_stitt_at_ichec.ie>
>>>>>> HPC Application Consultant - ICHEC (www.ichec.ie)
>>>>>>
>>>>>> Dublin Institute for Advanced Studies
>>>>>> 5 Merrion Square - Dublin 2 - Ireland
>>>>>>
>>>>>> +353-1-6621333 (tel) / +353-1-6621477 (fax)
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>             
>>>>>
>>>>>           
>>>> --
>>>> Dr. Timothy Stitt <timothy_dot_stitt_at_ichec.ie>
>>>> HPC Application Consultant - ICHEC (www.ichec.ie)
>>>>
>>>> Dublin Institute for Advanced Studies
>>>> 5 Merrion Square - Dublin 2 - Ireland
>>>>
>>>> +353-1-6621333 (tel) / +353-1-6621477 (fax)
>>>>
>>>>
>>>>
>>>>         
>>>
>>>
>>>       
>> --
>> Dr. Timothy Stitt <timothy_dot_stitt_at_ichec.ie>
>> HPC Application Consultant - ICHEC (www.ichec.ie)
>>
>> Dublin Institute for Advanced Studies
>> 5 Merrion Square - Dublin 2 - Ireland
>>
>> +353-1-6621333 (tel) / +353-1-6621477 (fax)
>>
>>
>>     
>
>
>
>   


-- 
Dr. Timothy Stitt <timothy_dot_stitt_at_ichec.ie>
HPC Application Consultant - ICHEC (www.ichec.ie)

Dublin Institute for Advanced Studies
5 Merrion Square - Dublin 2 - Ireland

+353-1-6621333 (tel) / +353-1-6621477 (fax)