Hi Tobias > What I had in mind has nothing to do with refinement. It is just a store > data, > do some quick work and restore data approach which will be useful for library > functions that work on a given fixed mesh and want to use user pointers or > indices without destroying the previous user data, whatever it may be.
that makes sense. it's a pity that there is this mutually exclusive relationship between user_pointer and user_indices. thanks for the explanation Regards Andrew On 28 Jul 2010, at 11:41 AM, Tobias Leicht wrote: > Hi Andrew, > >> When you say, the partitioning uses user_indices, you are referring to the >> partitioning across processors? > > Yes, exactly. It concerns the function that assigns subdomain IDs to cells. > >> Will this approach fail? (My code is not complete at present so I can't >> answer my own question just yet). > > It will fail if you call any function that uses user indices. A prominent > example is the already mentioned partitioning algorithm. > >>> Someone should implement a decent backup-and-restore functionality for >>> general user data, not indices or pointers. >> >> Agreed. More generally it should allow for projection on refinement as >> well. I would be happy to be involved. > > What I had in mind has nothing to do with refinement. It is just a store > data, > do some quick work and restore data approach which will be useful for library > functions that work on a given fixed mesh and want to use user pointers or > indices without destroying the previous user data, whatever it may be. > >> A silly question perhaps, but what Is the point of a cell user_index? > > Whenever you just want to save an integer per cell instead of a lot of data > it > is easier to just assign that integer directly instead of having a pointer to > it. I think that was the general idea. In the given example it is just set to > a global contiguous active cell index which deal.II does not offer otherwise. > (You could also use a dummy DoFHandler with a DG(0) element to achieve the > same thing.) > > Best, > Tobias _______________________________________________ dealii mailing list http://poisson.dealii.org/mailman/listinfo/dealii
