[petsc-users] strong-scaling vs weak-scaling

[Justin Chang]

Thanks everyone. I still think there is a even better phrase for this,
like, static scaling? Because unlike strong/weak scaling, concurrency is
fixed (hence "static") and we only scale the problem, so this is a mix
between strong and weak scaling.

¯\_(ツ)_/¯

Anyway, what I really wanted to say is, it's good to know that these
"dynamic range/performance spectrum/static scaling" plots are designed to
go past the sweet spots. I also agree that it would be interesting to see a
time vs dofs*iterations/time plot. Would it then also be useful to look at
the step to setting up the preconditioner?

Justin

On Tue, Aug 30, 2016 at 1:55 PM, Jed Brown <jed at jedbrown.org> wrote:

> Mark Adams <mfadams at lbl.gov> writes:
> > I would guess it is the latter.
>
> In this case, definitely.
>
> > It is hard to get "rollover" to the right.  You could get it on KNL
> > (cache configuration of HBM) when you spill out of HBM.
>
> Yes, but the same occurs if you start repeatedly spilling from some
> level of cache, which can happen even if the overall data structure is
> much larger than cache.  Not all algorithms have the flexibility to
> choose tile sizes independently from problem size and specification;
> it's easy to forget that this luxury is not universal when focusing on
> dense linear algebra, for example.
>
> > Personally, if you are you going to go into this much detail (eg, more
> than
> > just one plot) I would show a plot of iteration count vs problem size,
> and
> > be done with it, and then fix the iteration count for the weak scaling
> and
> > dynamic range plot (I agree we could use a better name).
>
> Alternatively, plot the performance spectrum (dynamic range) for the
> end-to-end solve and per iteration.  The end user ultimately doesn't
> care about the cost per iteration (and it's meaningless when comparing
> to an algorithm that converges differently), so I'd prefer that the
> spectrum for the end-to-end application always be shown.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20160830/6d7ebc49/attachment.html>