dolfin team mailing list archive

[Matthew Knepley <knepley@xxxxxxxxx>]

On Tue, Apr 28, 2009 at 3:05 PM, Robert Kirby <robert.c.kirby@xxxxxxxxx>wrote:

> Hi all,it's my understanding that the way ufc ordering works is for
> adjacent cells to
> alternate orientation so that they traverse edges (and faces in 3d) the
> same global
> way.  It seems that in 2d this is equivalent to two-coloring a graph (each
> cell is either
> clockwise or counterclockwise)
>
> Has there been any thought to issues at imposing ufc ordering in parallel,
> where each
> process has to assign an orientation to the first local cell, and different
> processors
> might disagree?
>

How would this disagreement come about? Maybe I do not understand what UFC
is doing
here is how I do it:

  1) Values are associated with Sieve points. If there are multiple values
on an edge, these
       values are ordered here.

  2) Every Sieve arrow has an orientation. This orientation produced by a
traversal concatenates
      these orientations, and is relative to orientation to the initial
orientation in the Sieve.

  3) I do not see the parallel problem because all data is just traded
between shared sieve
      points, and thus has identical orientations. However, I use the
traversals to construct
      ordered arrays of data. Maybe UFC does something else.

  Matt


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What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
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