[Dune-devel] Grid-Entity ownership in distributed ALUGrid or UGGrid

[Simon Praetorius]

Hi everyone,

Recently in a dune-functions meeting we wanted to explore the 
design-space of how we can support users with the parallelization of 
their code, i.e., using a dune-functions basis on a distributed grid, in 
combination with, e.g., the dune-istl data-structures. When working on 
some examples, I noticed that one of the first steps seems always to be 
to identify unique ownership of grid entities, i.e., can we assign 
uniquely a processor rank that "owns" a given grid entity or can we tell 
whether we are the master over a local entity. This is the basis for 
building up a communication pattern for the actual DOFs in a 
discretization. In multiple frameworks this ownership identification is 
implemented a similar way, e.g. in dune-pdelab, AMDiS, and 
dune/grid/utility/globalindexset.hh . I was wondering: the information 
on which other rank an entity is present and the identification of one 
master rank should be actually available in the grid implementation 
already, to build up the grid communication. However, the public grid 
interface does not provide access to this information. It is probably 
encoded in different ways in each grid manager.

My question is: can the information about entity ownership, or the set 
of other ranks an entity belongs to, be extracted in the specific 
implementation of some grids, e.g. ALUGrid, or UGGrid, or YaspGrid, or 
SPGrid, maybe also in the ParallelGrid meta-grid wrapper? Without 
additional communication? If so, maybe we could discuss a common 
interface and develop a utility for dune-grid to easily provide this 
information. A fallback implementation can be provided using 
communication and is part of the implementation details of 
GlobalIndexSet of dune-grid. I think, this is a necessary utility for 
implementing parallel frameworks on top of the grid module, without 
reinventing the wheel.

Best regards,
Simon

-- 
Dr. Simon Praetorius
Technische Universität Dresden
Institute of Scientific Computing
phone: +49 351 463-34432
mail: simon.praetorius at tu-dresden.de
web: https://tu-dresden.de/mn/math/wir/das-institut/beschaeftigte/simon-praetorius


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