[petsc-users] Performance of ISCreateGeneral()

[Mark Adams]

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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