[Dune] GridFactory and parallel grids (and boundary adaptation)

[Jö Fahlke]

Hi!

I'm preparing for the the Heidelberg Dune Course this month and was wondering
about the status of the GridFactory with parallel grids.  I'm also wondering
aout boundary adaptation and parallel grids (I usually get some questions
about that during the lecture).

With regard to loading a parallel grid with the GridFactory, the current
informal standard seems to be inserting on rank 0 only, inserting nothing on
the other ranks, and following that by a loadBalance().  I know that worked
with the old ALUGrid, and apparently UG supports that too[1].  Is that still
the way to go with dune-alugrid or are there better ways (so long as you want
to keep using the GridFactory?).

GmshReader seems seems to be be similar: it doesn't seem to know anything
about MPI, so you have to create an empty GridFactory, fill it with GmshReader
on rank 0 only, create the grid, and then loadBalance.  I'm assuming there are
no specializations of GmshReader out the, please point me to them if I'm
wrong.

Now about boundary adaptation: UG states[1]

  Warning:
    To use a parametrized boundary on a parallel machine you need to hand over
    the boundary segments to the grid factory on all processes.  This behavior
    violates the Dune grid interface specification and will be corrected in
    the future.

I'm assuming that means create a GridFactory on all ranks and insert each
boundary segment on each rank.  But do I have to insert the vertices (and
elements) on each rank too, to do I just make sure to use the same vertex
numbers as on rank 0?

What is ALUGrid doing about boundary adaptation and loadBalance()?  (I faintly
remember something about interpolating the boundary segment into a polynomial,
but I may be quite mistaken there.)

[1] http://www.dune-project.org/doc/doxygen/html/classDune_1_1GridFactory_3_01UGGrid_3_01dimworld_01_4_01_4.html

-- 
Jorrit (Jö) Fahlke, Institute for Computational und Applied Mathematics,
University of Münster, Orleans-Ring 10, D-48149 Münster
Tel: +49 251 83 35146 Fax: +49 251 83 32729

Der Horizont vieler Menschen ist ein Kreis mit Radius Null - und das
nennen sie ihren Standpunkt.
-- A. Einstein
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 828 bytes
Desc: Digital signature
URL: <https://lists.dune-project.org/pipermail/dune/attachments/20150210/d398d213/attachment.sig>