Matrix creation/destruction

[John Fettig]

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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