[Dune] Dune::IdSet

[Markus Blatt]

On Mon, Feb 15, 2010 at 02:46:58PM +0100, Christian Engwer wrote:
> On Mon, Feb 15, 2010 at 02:43:06PM +0100, Markus Blatt wrote:
> > On Mon, Feb 15, 2010 at 02:11:22PM +0100, Guo  Hua wrote:
> > > But how to get a global index set(consecutive of course). Any
> > > suggestions to do that?
> > 
> > There is no such global index set. You have to compute it yourself.
> 
> Actually, it is not available, because it should never be
> necessary. If you want to do parallel computations, then you should
> only store that data that is necessary for your local coputations,
> thus you only have an local IndexSet. The IdSet is used for
> identification and for communication, not for storing data.
> 

Maybe he wants to use some external solvers?
There are a lot of parallel linear algebra packages out there that
have the concept of parallel (global) matrix and vectors
incorporated. These need global consecutive indices. That is each dof
has a unique index and looking at the indices of all dof (all
processors), they need to start from 0 and be consecutive.

Markus