[petsc-users] Imbalance in ParMETIS

[Matthew Knepley]

On Fri, Jul 19, 2019 at 1:58 AM Eda Oktay <eda.oktay at metu.edu.tr> wrote:

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

Great! I am glad it works now.

  Thanks,

    Matt


> 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/>
>>
>

-- 
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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