dolfin team mailing list archive

[Niclas Jansson <njansson@xxxxxx>]

On Mon, 3 Dec 2007 09:53:23 +0100 (MET)
"Johan Hoffman" <jhoffman@xxxxxxxxxx> wrote:

> > On Sun, Dec 02, 2007 at 06:17:35PM +0100, Johan Hoffman wrote:
> >> >
> >> >
> >> > Johan Hoffman wrote:
> >> >>> Johan Hoffman wrote:
> >> >>>> Hi all,
> >> >>>>
> >> >>>> Connected to this discussion is also the msc thesis work on
> >dolfin> >>>> parallization of Nicklas Jansson at KTH. He has now
> >started working> on
> >> >>>> this based on the updated TODO list of dolfin. He has tried to
> >send> an
> >> >>>> email to this list (dolfin-dev@xxxxxxxxxx) but it appears that
> >it> is
> >> >>>> stuck
> >> >>>> in a filter awaiting moderator approval.
> >> >>> If he joins the list, he'll be able to make posts.
> >> >>
> >> >> Ok.
> >> >>
> >> >>> Maybe someone (a moderator) could
> >> >>>> help out so that we can get past this, to better coordinate
> >> >>>> parallelization efforts?
> >> >>>>
> >> >>> One point on the TODO list: we discussed some time ago the mesh
> >> >>> partitioning, and decided against ParMETIS or METIS because
> >they do> not
> >> >>> use a GPL (compatible) license. Magnus has implemented a nice
> >> >>> partitioning interface which uses SOCTCH which does have a GPL
> >> >>> compatible license.
> >> >>
> >> >> Ok. Does the switch to LGPL licence for dolfin make any
> >difference?> Or
> >> >> is
> >> >> it still a conflict?
> >> >>
> >> >
> >> > There is still a conflict. The METIS license basically says that
> >it> can
> >> > be used for non-profit purposes only, and permission is required
> >to> > re-distribute it.
> >>
> >> Ok, then there is a problem.
> >>
> >> >> About Scotch; the argument was that it lacked parallel
> >partitioning,> and
> >> >> a
> >> >> few other nice features of parMetis. But it seems that Scotch
> >v5.0 is> >> moving towards a parallel implementation as well?
> >> >>
> >> >
> >> > It does have it now. That said, I can't see us using or needing
> >> parallel
> >> > partitioning in the short- to medium-term future.
> >>
> >> Ok. Maybe we'll manage with Scotch for now then.
> >>
> >> As for parallel assembly, we will need this in the coming months,
> >so we> will push the fully parallel approach within Nicklas' msc
> >project,> including parallel redistribution for adaptively refined
> >meshes (which> parMetis seems to support nicely).
> >>
> >> /Johan
> >
> > Sounds very good, but if major changes to the Mesh classes are
> > necessary (which seems likely), I suspect I will be somewhat
> > sensitive to having all those changes pushed at once. So it would be
> > good to discuss plans for the design as early as possible so we can
> > all feel comfortable with the changes.
> >
> > --
> > Anders
> 
> I agree. That's why the TODO list was added in the dolfin rep, and an
> accompanying dolfin-dev post was sent (...which got stuck in the
> filter). With a fresh dolfin-dev membership, Nicklas can resend his
> post where the strategy is presented in more detail, which then anyone
> can comment on.
> 
> I would expect the plan to be rather uncontroversial, and it will fit
> nicely with the work of Magnus.
> 
> /Johan
> 

It's a different strategy that uses point to point instead of collective
communication. However the plan for parallel assembly should be more or
less the same.

I attached the more detailed TODO list, it should explain the necessary
changes to the Mesh classes.

Niclas

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