[MOAB-dev] Dense tag behavior

[Lorenzo Alessio Botti]

Hi all,

It seems that dense tag memory is allocated when the tag is set for at least one entity of a given type.

This is documented in the MOAB User's Guide. I missed it.        
"Storage for a given dense tag is not allocated until a tag value is set on an entity; memory for a given dense tag is allocated for all entities in a given sequence at the same time."

I would have expected the dense tag to be associated with the default value to all the entities in the mesh.

Thanks
Lorenzo



On May 12, 2011, at 4:43 PM, Tim Tautges wrote:

> Probably when the tag was created, it was not created with a default value.  This could be the case if the vtk reader created it upon finding it in the file.
> 
> One way around this would be to create a tag of the proper name/data type/storage type/default value before reading the vtk file; then the vtk reader will use that tag, and your quads will get the default value too.
> 
> The tris being set has to do with how storage for tags is allocated (based on sequences, the fundamental unit of storage in MOAB).
> 
> - tim
> 
> On 05/12/2011 09:31 AM, Lorenzo Botti wrote:
>> I'm noticing a strange behavior of dense tags.
>> 
>> I'm reading a hybrid tets+prisms+tris (tris represent the boundary mesh) vtk mesh where I have an id (type int) associated to each cell in order to define boundary conditions.
>> The ids are correctly represented in MOAB as a dense tag over the mesh elements.
>> 
>> However If I build 2D internal faces (tris and quads) with get_adjacencies only tris obtain the dense tag (set by default to 0?) while quads are tag free.
>> 
>> Does it work this way because no tags have been associated to quads?
>> 
>> Thanks
>> Lorenzo
>> 
>> 
> 
> -- 
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> 
>             Tim Tautges            Argonne National Laboratory
>         (tautges at mcs.anl.gov)      (telecommuting from UW-Madison)
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