[mumps-dev] Re: Question on using MUMPS in PETSC

[Jean-Yves L Excellent]

Hi,

Clearly in MUMPS processor 0 uses more memory during
the analysis step because the analysis is sequential.
So until we provide a parallel analysis, processor 0
is gathering the graph of the matrix from all other
processors to perform the analysis. But that memory
is freed at the end of the analysis so it should
not affect the factorization.

Thanks for letting us know if you have more information.

Regards,
Jean-Yves

Hong Zhang wrote:
> 
> Randy,
> The petsc interface does not create much of extra
> memories.
> The analysis phase of MUMPS solver is sequential - which might causes 
> one process blow up with memory.
> I'm forwarding this email to the mumps developer
> for their input.
> 
> Jean-Yves,
> What do you think about the reported problem
> (see attached below)?
> 
> Thanks,
> 
> Hong
> 
> On Thu, 31 Jul 2008, Randall Mackie wrote:
> 
>> Barry,
>>
>> I don't think it's the matrix - I saw the same behavior when I ran your
>> ex2.c program and set m=n=5000.
>>
>> Randy
>>
>>
>> Barry Smith wrote:
>>>
>>>    If m and n are the number of rows and columns of the sparse matrix 
>>> (i.e. it is
>>> tiny problem) then please
>>> send us matrix so we can experiment with it to petsc-maint at mcs.anl.log
>>>
>>>   You can send us the matrix by simply running with -ksp_view_binary and
>>> sending us the file binaryoutput.
>>>
>>>    Barry
>>>
>>> On Jul 31, 2008, at 5:56 PM, Randall Mackie wrote:
>>>
>>>> When m = n = small (like 50), it works fine. When I set m=n=5000, I see
>>>> the same thing, where one process on the localhost is taking >4 G of 
>>>> RAM,
>>>> while all other processes are taking 137 M.
>>>>
>>>> Is this the standard behavior for MUMPS? It seems strange to me.
>>>>
>>>> Randy
>>>>
>>>>
>>>> Matthew Knepley wrote:
>>>>> Does it work on KSP ex2?
>>>>>  Matt
>>>>> On Thu, Jul 31, 2008 at 4:35 PM, Randall Mackie 
>>>>> <rlmackie862 at gmail.com> wrote:
>>>>>> I've compiled PETSc with MUMPS support, and I'm trying to run a 
>>>>>> small test
>>>>>> problem, but I'm having some problems. It seems to begin just 
>>>>>> fine, but
>>>>>> what I notice is that on one process (out of 64), the memory just 
>>>>>> keeps
>>>>>> going up and up and up until it crashes, while on the other 
>>>>>> processes,
>>>>>> the memory usage is reasonable. I'm wondering if anyone might have 
>>>>>> any idea
>>>>>> why? By the way, my command file is like this:
>>>>>>
>>>>>> -ksp_type preonly
>>>>>> -pc_type lu
>>>>>> -mat_type aijmumps
>>>>>> -mat_mumps_cntl_4 3
>>>>>> -mat_mumps_cntl_9 1
>>>>>>
>>>>>>
>>>>>> Randy
>>>>>>
>>>>>> ps. This happens after the analysis stage and in the factorization 
>>>>>> stage.
>>>>>>
>>>>>>
>>>>
>>>