[petsc-users] Imbalance in ParMETIS

[Eda Oktay]

Dear Matt,

You were right, I confused concepts. By setting vertex weights, I am able
to get different number of edge cuts.

Thanks,

Eda

Matthew Knepley <knepley at gmail.com>, 1 Tem 2019 Pzt, 13:10 tarihinde şunu
yazdı:

> On Mon, Jul 1, 2019 at 3:00 AM Eda Oktay <eda.oktay at metu.edu.tr> wrote:
>
>> Dear Matt,
>>
>> In order to get a nice cut, I am trying to change the balance, that is
>> why I tried to change ubvec. But still I couldn't understand why it didn't
>> change anything.
>>
>> I tried to change vertex weights but it only made Max and Min change but
>> it didn't change the cut.
>>
>
> I think you are confusing concepts. The "cut" is the number of edges
> discarded when you divide the mesh
> into pieces, but each piece is supposed to have an equal size. The only
> way you can get the partitioner to
> divide the mesh into pieces of unequal size is to use vertex weights.
>
>   Thanks,
>
>      Matt
>
>
>> Thanks,
>>
>> Eda
>>
>>
>> On Fri, Jun 28, 2019, 1:49 PM Matthew Knepley <knepley at gmail.com> wrote:
>>
>>> On Fri, Jun 28, 2019 at 5:38 AM Eda Oktay via petsc-users <
>>> petsc-users at mcs.anl.gov> wrote:
>>>
>>>> Hello everyone,
>>>>
>>>> I am trying to change load balance in ParMETIS in order to give
>>>> different number of elements to different processors. In the manual, it
>>>> states that changing "ubvec" parameter should work. So, instead of 1.05, I
>>>> gave 1.2,1.5 and so on but load balance didn't change. I always get Max 5
>>>> Min 5 when I view load balance. The partitioning part of my code is:
>>>>
>>>
>>> ParMetis is always balancing. ubvec changes the balance between having
>>> even partitions and a nice cut. If
>>> you want unbalanced partitions, you have to change the vertex weights.
>>>
>>>   Thanks,
>>>
>>>     Matt
>>>
>>>
>>>>  ierr = MatConvert(A,MATMPIADJ,MAT_INITIAL_MATRIX,&AL);CHKERRQ(ierr);
>>>>
>>>>   ierr = MatPartitioningCreate(MPI_COMM_WORLD,&part);CHKERRQ(ierr);
>>>>   ierr = MatPartitioningSetAdjacency(part,AL);CHKERRQ(ierr);
>>>>
>>>>   ierr = MatPartitioningSetFromOptions(part);CHKERRQ(ierr);
>>>>   ierr = MatPartitioningApply(part,&partitioning);CHKERRQ(ierr);
>>>>   MatPartitioningViewImbalance(part,partitioning);
>>>>
>>>> What should I do? Why changing ubvec didn't change anything, am I
>>>> missing something?
>>>>
>>>> Thanks,
>>>>
>>>> Eda
>>>>
>>>
>>>
>>> --
>>> What most experimenters take for granted before they begin their
>>> experiments is infinitely more interesting than any results to which their
>>> experiments lead.
>>> -- Norbert Wiener
>>>
>>> https://www.cse.buffalo.edu/~knepley/
>>> <http://www.cse.buffalo.edu/~knepley/>
>>>
>>
>
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
>
> https://www.cse.buffalo.edu/~knepley/
> <http://www.cse.buffalo.edu/~knepley/>
>
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