dolfin team mailing list archive

["Johan Hoffman" <jhoffman@xxxxxxxxxx>]

> On Mon, Dec 03, 2007 at 09:53:23AM +0100, Johan Hoffman 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.
>> >
>>
>> 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
>
> ok, sounds good.
>
> Magnus is finishing his thesis at the end of January and before then
> we'd like to have partitioning, communication and parallel assembly in
> place. We are not planning to distribute the mesh, only to broadcast
> it from one processor to all others and then the assembler skips those
> cells which are not on the current processor.

Ok.

> Then Nicklas can expand it to distributed meshes. (And of course the
> work on the two approaches can happen in parallel.)

Good. We'll keep updated through the mailinglist.

/Johan


> --
> Anders
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