Re: [Libmesh-users] Question about unique_ids

[David K. <dav...@ak...>]

On Wed, Jan 10, 2018 at 3:07 PM, John Peterson <jwp...@gm...> wrote:

>
>
> On Wed, Jan 10, 2018 at 12:38 PM, David Knezevic <
> dav...@ak...> wrote:
>
>> I'd like to use unique_ids to identify elements and nodes without worrying
>> about renumbering, but before I do that I'd like to understand a bit more
>> about how unique_ids are defined.
>>
>> In particular, what is the idea behind how we generate the unique_ids?
>> From
>> the code in replicated_mesh.C, for example, it looks like the unique_ids
>> are set in add_node and add_elem, with _next_unique_id being incremented
>> each time a new ID is set. This looks simple enough, but I was wondering
>> if
>> there's anything else to it?
>>
>
> That's pretty much all there is to it, at least as far as I know.
>
>
> One concrete question I have is if I create two Mesh objects by reading in
>> the same mesh exodus file twice, will those two meshes have matching
>> unique_ids? I guess they will simply because "add_node" and "add_elem"
>> will
>> be called in the same order during those two read operations.
>>
>
> Yes, the unique ids are only unique per mesh, as the _next_unique_id is
> owned by MeshBase.
>
> I can't see why two meshes created in exactly the same way wouldn't have
> the exact same unique ids for all nodes and elems.
>


OK, thanks!

David