code_saturne User's Forum

Hello,

I would like to know if, given a number of meshes in a certain order in the GUI xml file, the cells ID after the joining and the partitioning for parallel run remain ordered following the order of the preprocessed meshes.

Giving a glance to some previous cases, it seems that in each parallel domain the local "iel" follows this order. Though, I don't know if this is just a coincidence or if it's true for any kind of joining and partitioning.

Thank you very much


Jacopo

Hello Jacopo,

Mesh joining does not change cell ids (only face and vertex ids), so the ids do remain the same after joining.

Partitioning is more tricky: the local order for the subset assigned to a given is unchanged, but of course the local ids may not match the global ids for all cells.

With version 4.0, a local cell renumbering option (to improve performance) will also change the numbering (but is not activated by default).

Whenever partitioning or renumbering is used, global cell ids are added to the mesh structure, to maintain the initial (pre-partitioning/reumbering) cell ids (using 1 to n instead of 0 to n-1 numbering).

So global numbers are "stable", while local numbers usually maintain the same order, but this is not guaranteed (in the future, basing global numbers in a space-filling curve instead of the initial numbering could have some advantages, but would break compatibility with older restart files, so even if that is added at some future point, an option for deactivating it would probably be added).

Cheers,

Yvan