[Dune] How to set boundary ids

[Oliver Sander]

Dear Dune!
As far as I know the question of who sets boundaryIds and how
is still unsettled.  Two days ago Peter, Christian, Benedikt and me
discussed this issue again.  We came up with a solution that was
acceptable to all four of us and combines (in our view) a consistent
interface with ease of use.

We propose that boundary ids should be consecutive and starting
from zero.  The user can influence the ordering by calling insert-
BoundarySegment in the desired order.  The second argument
(the segment geometry) will be made optional such that the user can
specify boundary segment orderings and still leave the geometry to the
implementation.I have described the solution in some more detail in
Sections 4.4 and 4.5 of the grid-howto.

We propose that the behavior described there be part of the official
Dune grid interface.  Please read it carefully and give us feedback.

Yours,
Oliver

-- 
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* Oliver Sander                ** email: sander at mi.fu-berlin.de        *
* Freie Universität Berlin     ** phone: + 49 (30) 838 75348           *
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