On Thu, Aug 14, 2008 at 11:48:14AM +0200, Johan Hoffman wrote: > > On Wed, Aug 13, 2008 at 2:57 PM, Johan Hoffman <[EMAIL PROTECTED]> > > wrote: > > > >> > > >> > > >> > Johan Hoffman wrote: > >> >>> > >> >>> Anders Logg wrote: > >> >>>> On Tue, Jun 17, 2008 at 02:45:41PM +0100, Garth N. Wells wrote: > >> >>>>> It would be useful to lay out a plan for tackling DofMaps. Getting > >> >>>>> this > >> >>>>> right is the key to parallel assembly, assembly optimisations and > >> >>>>> applying Dirichlet boundary conditions by eliminating Dirichlet > >> dofs > >> >>>>> from the global system. > >> >>>>> > >> >>>>> I'm happy to take a look, but I'll need some time because I've > >> lost > >> >>>>> my > >> >>>>> overview of DofMaps. If someone else is already on top of it, I'd > >> be > >> >>>>> happy to provide feedback. > >> >>>>> > >> >>>>> Garth > >> >>>> I won't have time to look at it until after the summer and I > >> haven't > >> >>>> started. > >> >>>> > >> >>>> Anyway, I think we should wait until after the next release until > >> we > >> >>>> start messing with the dof maps. > >> >>>> > >> >>>> Are there any issues we need to sort out before releasing 0.8? I'm > >> >>>> thinking about a new release some time this or next week. > >> >>>> > >> >>>> One is to fix the bug in DirichletBC, but other than that? > >> >>>> > >> >>> Now would be a good time for a release so I can start messing with > >> >>> DofMaps. > >> >>> > >> >>> Garth > >> >> > >> >> Has anything more been done about the DofMap design? During the > >> summer > >> >> Niclas has extended to general elements his adaptive algorithm for > >> >> distributed parallel computing, so we are now ready to start messing > >> >> with > >> >> the DofMaps in order to implement his algorithm in DOLFIN. > >> >> > >> > > >> > It has been given some thought, but no changes have been made in the > >> > code yet. > >> > >> Ok. Any threads on the list to point to where this is discussed? > >> > >> If you have something already, I would suggest making it > >> > publicly available somewhere for feedback before starting work on > >> DOLFIN. > >> > >> It is a refinement and generalization of the thesis work of Niclas > >> Jansson > >> which was discussed on the list before the summer. Is is outlined in his > >> report: > >> > >> http://www.nada.kth.se/utbildning/grukth/exjobb/rapportlistor/2008/rapporter08/jansson_niclas_08051.pdf > >> > >> My announcement here was to initiate a discussion of the detailed > >> implementation, and to check if other DOLFIN-people were working on > >> similar stuff to avoid double/conflicting development. > >> > >> /Johan > >> > > > > Very good. We were about to start on this task, so now a good point in > > time > > to join forces. > > As a starting point, it would be nice to agreeing on what data is needed > > in > > addition to the partitioned meshes to construct the global dofmap. I.e. > > which MeshFunctions to construct during the mesh paritioning process. Are > > you people using the same {T,S,F} input as Anders describes in Algorithm 5 > > in his paper? > > We have discussed this, and it seems that for our adaptive algorithms we > need some more info. Basically, we have two aims: > > 1. Fully distributed computing (no collection of data on one processor) > 2. Possibility for dynamic load balancing > > To realize 1-2 we need information on the processor ownership of entities, > and for resdistributing the mesh we need global vertex numbering. That is, > we would need something like: {T,S,F,V,O}, where V is global vertex number > and O is information whether boundary (between processors) vertices are > own by the processor or if they are ghost nodes.
How do you deal with global edge or face numbers? My suggestion is to start without a global numbering and then build it (in parallel). > Possibly this is too much information, since for example S,F can be > computed from V,O, but by storing all info faster algorithms can be > constructed, so there is a trad-off between speed and memory. > > What do you say? If you have something that works, just send us a patch so we can try it. -- Anders
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