Matrix creation/destruction

[John Fettig]

Another similar question.  Running src/snes/examples/tutorials/ex1 on 2
processors with -log_summary shows

VecScatterBegin       91 1.0 1.2181e-03 1.3 0.00e+00 0.0 3.8e+01 8.0e+00
0.0e+00  4  0 49 40  0   4  0 49 40  0     0
VecScatterEnd         19 1.0 3.5119e-04 3.5 0.00e+00 0.0 0.0e+00 0.0e+00
0.0e+00  1  0  0  0  0   1  0  0  0  0     0

There are 91 Begins but only 19 Ends.  The calls are matched in the driver,
so why aren't they matched when it runs?

John

On Tue, Aug 25, 2009 at 1:42 PM, John Fettig <john.fettig at gmail.com> wrote:

> Barry,
>
> Thanks for the quick reply, that definitely clears it up.
>
> John
>
>
> On Tue, Aug 25, 2009 at 1:38 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>>
>>   The ILU factorization requires a matrix that is created inside the KSP
>> operations. Plus it counts sequential matrices that are contained inside the
>> parallel matrices so the matrix numbers will often be hard to understand.
>>
>>   The VecScatter is created in the MatAssembly and used in the matrix
>> vector products and then destroyed when the matrix is destroy that is why
>> its creation and destruction are in different states.
>>
>>   The index sets in the assembly are used to create the vecscatter. The
>> index sets in the main stage a probably related to the preconditioner
>> building.
>>
>>  Barry
>>
>> On Aug 25, 2009, at 1:25 PM, John Fettig wrote:
>>
>>  I'm trying to understand where matrices get created and destroyed,
>>> because I have a mismatch in the -log_summary of my code but I can't figure
>>> out where.  Running ksp/ksp/examples/tutorials/ex2 with 4 processors, the
>>> log summary looks like:
>>>
>>>
>>>
>>> Object Type          Creations   Destructions   Memory  Descendants' Mem.
>>>
>>> --- Event Stage 0: Main Stage
>>>
>>>              Matrix     4              4      11408     0
>>>                 Vec    20             21      29264     0
>>>         Vec Scatter     0              1        868     0
>>>           Index Set     3              3       1704     0
>>>       Krylov Solver     2              2      18880     0
>>>      Preconditioner     2              2       1408     0
>>>
>>> --- Event Stage 1: Assembly
>>>
>>>                 Vec     2              1       1304     0
>>>         Vec Scatter     1              0          0     0
>>>           Index Set     2              2       1052     0
>>>
>>> ========================================================================================================================
>>>
>>>
>>> Why are there 4 matrices created/destroyed?  Where does this happen?  I
>>> only see one matrix being created/destroyed in the source, so it must be
>>> happening someplace in the KSP/PC.  Also, there is a mismatch in the Vec and
>>> Vec Scatter counts in each of the stages, even though it would seem that
>>> (e.g.) all the Vec Scatters should be contained to the assembly stage.
>>>
>>> John
>>>
>>>
>>
>
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