[Dune-devel] Semantics of {ghost,overlap}Size
Bernd Flemisch
bernd at iws.uni-stuttgart.de
Fri Jul 11 12:23:28 CEST 2014
Hi,
I would like to declare my interest to participate in such a meeting. I
will be present at the PDESoft on Wednesday and could come to the IWR on
Thursday or Friday.
Kind regards
Bernd
> Wow, a lot time has gone by without further action. It seems like many
> of the interested people will be at PDESoft in Heidelberg this month.
>
> Maybe we can seize the opportunity to hold a public informal meeting
> there around this theme. Maybe on the so-called coding days?
>
> Currently, it seems like there are even more issues coming up (at
> least judging from the list).
>
> Markus
>
> On Thu, Nov 07, 2013 at 08:55:06PM +0100, Martin Nolte wrote:
> >/ to be honest, I am not sure how much can be achieved with a single meeting.
> />/
> />/ The idea originated from the observation that the topic
> />/ "parallelism" was carefully avoided on the last "big" developer
> />/ meetings. It was my impression that on the one hand "only" around
> />/ 50% of the core developers are interested in this feature, while on
> />/ the other hand there are some extremely interested users (e.g.,
> />/ Bernd who has provided substantial contributions to parallel UG).
> />/
> />/ I think such a smaller group focussing entirely on this topic might
> />/ achieve more progress. It goes without saying that the "real
> />/ decisions" must be made by a formal vote of all core developers.
> />/
> />/ If there is enough interest in such a meeting, I suggest to set up a
> />/ page on the user wiki, so that we can collect the topics we're
> />/ interested in. We then might be able to judge the size of this
> />/ thing. We can always shorten the list, if it becomes too large.
> />/ Given interest, I would be prepared to organize such a meeting in
> />/ (or near) Freiburg.
> />/
> />/ Best,
> />/
> />/ Martin
> />/
> />/
> />/
> />/ On 11/07/2013 08:22 PM, Peter Bastian wrote:
> />/ >Dear all,
> />/ >
> />/ >clearly this has not been completely thought to the end once upon atime.
> />/ >
> />/ >I see that you need a specification of overlap for codim 0 and codim dim.
> />/ >
> />/ >Codim dim (vertices) is needed for standard overlapping DD methods.
> />/ >I would define two vertices as connected if they are subentites of a common
> />/ >codim 0 entity. With that Graph defined the distance ist clear.
> />/ >Then of course the data decomposition is still with respect to codim 0
> />/ >entites
> />/ >
> />/ >likewise two codim 0 entites are connected if they share an intersection.
> />/ >
> />/ >I am not sure whether the "overlap size" has any real application. In the numerical
> />/ >methods it is usually not needed.
> />/ >
> />/ >I am in favor of a meeting. Do you think about small cosmetic changes or something
> />/ >bigger? If it is bigger then we should also consider extensions due to hybrid
> />/ >parallelism, i.e. multithreading.
> />/ >
> />/ >
> />/ >-- Peter
> />/ >
> />/ >----------------------------------------
> />/ >Peter Bastian,
> />/ >IWR, Universität Heidelberg,
> />/ >INF 368, D-69120 Heidelberg
> />/ >
> />/ >>Am 07.11.2013 um 16:10 schrieb Martin Nolte <nolte at mathematik.uni-freiburg.de <http://lists.dune-project.org/mailman/listinfo/dune-devel>>:
> />/ >>
> />/ >>Hi,
> />/ >>
> />/ >>actually, I wonder whether anybody uses these methods at all (except for checking the return value for 0).
> />/ >>
> />/ >>Otherwise, I totally agree with Markus that semantics of the methods are completely unclear:
> />/ >>- They are not mentioned in the papers on dune-grid.
> />/ >>- The documentation of the interface does not give a definition
> />/ >> (what is the size of a "region"? Why is this integral?).
> />/ >>- The tests do not verify the result of these methods at all
> />/ >> (though it seems the information can be obtained by grid traversal).
> />/ >>
> />/ >>A mere hint in the documentation of YaspGrid is absolutely insufficient.
> />/ >>
> />/ >>Implementation node: SPGrid only implements these methods for codim 0, returning the number of elements in the corresponding partition. Up to now nobody complained about this.
> />/ >>
> />/ >>Given the current status, we might just replace these methods by capabilities like hasGhosts or hasOverlap.
> />/ >>
> />/ >>Anyway, in my opionion (as stated on the wish list for the developer meeting) the parallel part of the dune-grid interface should be revised in the near future. I think there are several points worth discussion. I was already thinking about a "small" meeting of those directly involved in the parallel interface (both on the user's and on the developer's side). What do the others feel?
> />/ >>
> />/ >>Best,
> />/ >>
> />/ >>Martin
> />/ >>
> />/ >>>On 11/07/2013 11:39 AM, Andreas Dedner wrote:
> />/ >>>Hi.
> />/ >>>I've wondered about that as well and am thinking that the method really only
> />/ >>>makes sense for codim 0 (where it the semantics seems clear enough).
> />/ >>>
> />/ >>>In DUNE everything boils down to codim 0 anyway (i.e. what leaf entities
> />/ >>>are for example). So if I have an overlap of 2 codim 0 entities then
> />/ >>>I would expect that the corresponding entities of higher codimension are
> />/ >>>there
> />/ >>>as well....
> />/ >>>
> />/ >>>Does anybody use that method for c>0?
> />/ >>>
> />/ >>>Best
> />/ >>>Andreas
> />/ >>>
> />/ >>>PS: should these method be deprecated on the grid class?
> />/ >>>
> />/ >>>>On 07/11/13 10:33, Markus Blatt wrote:
> />/ >>>>Hi,
> />/ >>>>
> />/ >>>>I recently looked at the documentation off these methodsbut this did
> />/ >>>>not help me understand what they are doing. It reads "Return size of
> />/ >>>>ghost region for a given codim on the leaf grid" but it is not clear
> />/ >>>>to me what this size is.
> />/ >>>>
> />/ >>>>In the documentation of yaspgrid it says that size is the distance in
> />/ >>>>graph, which is not really clearer. I assume that means the smallest
> />/ >>>>path between any two entities on different borders of that
> />/ >>>>region. Which still leaves the question open what the graph
> />/ >>>>of an enitity set of a given codim is. The vertices are of course the
> />/ >>>>codim entities. Seems like the edges would be the codim 1 entities for
> />/ >>>>elements and for all other entities with codim c the ones with codim c+1.
> />/ >>>>
> />/ >>>>Is there a precise definition somewhere?
> />/ >>>>
> />/ >>>>Markus
> />/ >>>
> />/ >>>
> />/ >>>_______________________________________________
> />/ >>>Dune-devel mailing list
> />/ >>>Dune-devel at dune-project.org <http://lists.dune-project.org/mailman/listinfo/dune-devel>
> />/ >>>http://lists.dune-project.org/mailman/listinfo/dune-devel
> />/ >>
> />/
> /
> --
> Do you need more support with DUNE or HPC in general?
>
> Dr. Markus Blatt - HPC-Simulation-Software & Serviceshttp://www.dr-blatt.de
> Hans-Bunte-Str. 8-10, 69123 Heidelberg, Germany
> Tel.: +49 (0) 160 97590858
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--
_______________________________________________________________
Bernd Flemisch phone: +49 711 685 69162
IWS, Universität Stuttgart fax: +49 711 685 60430
Pfaffenwaldring 61 email: bernd at iws.uni-stuttgart.de
D-70569 Stuttgart url: www.hydrosys.uni-stuttgart.de
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