[petsc-users] Performance of ISCreateGeneral()

[Junchao Zhang]

Shidi,
  Rethink the comm passed to your ISCreateGeneral().   Could you do it with
PETSC_COMM_SELF?

--Junchao Zhang

On Sun, Jul 5, 2020 at 3:27 PM Mark Adams <mfadams at lbl.gov> wrote:

> The column after the time in the PETSC output, on the  ISCreateGeneral
> row, with -log_view, shows the ratio of the max time (shown) to min time.
> If you are using your own timers just report the min and max time that you
> measure.
> You can also put an MPI_Barrier before the call to ISCreateGeneral to get
> clean data.
> And I trust that the problem is well load balance, that is, all processors
> have the same amount of data.
>
> On Sun, Jul 5, 2020 at 4:00 PM Y. Shidi <ys453 at cam.ac.uk> wrote:
>
>> Thank you for your reply Mark.
>> What do you mean by ratio (max/min)?
>> Do I need to turn on some options for this?
>>
>> Kind regards,
>> Shidi
>>
>> On 2020-07-05 20:15, Mark Adams wrote:
>> > ISCreateGeneral just takes your indices and caches them. But it is a
>> > synch point. What ratio (max/min) is PETSc reporting in this data?
>> >
>> > On Sun, Jul 5, 2020 at 1:51 PM Y. Shidi <ys453 at cam.ac.uk> wrote:
>> >
>> >> Dear developers,
>> >>
>> >> I am currently doing a weak scaling test, and find that
>> >> the weak scaling results for ISCreateGeneral() is very bad.
>> >> For 2, 4, 8 processors, the running times for completing
>> >> ISCreateGeneral() are:
>> >> 0.687494, 3.00597 and 10.0613.
>> >> I am not sure if this is normal.
>> >>
>> >> Thank you for your time.
>> >>
>> >> Kind Regards,
>> >> Shidi
>>
>
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