[MOAB-dev] subdomains, sparse tags

[Grindeanu, Iulian R.]

Hi Nico,
If the tags are dense or sparse affects the way they are stored in memory or on the hdf5 file;
Sparse tags are kept in pairs <entity handle, value>
dense tags are kept in contiguous arrays, corresponding to entity sequences

I would use dense tags if possible;
On those entities on domains, do you need to identify domains or the value of the tag?

I mean, are you using the tag for grouping entities or they have the same value ?

In general, we create sets, and then "tag" them with a tag to identify/classify the sets.
(partition sets, or material sets, etc, which are usually sparse tags)

If every entity has a different value, you should use a dense tag defined on entities (not on sets)

If the tags are dense you can access them more efficiently with tag_iterate

there are some examples here

http://ftp.mcs.anl.gov/pub/fathom/moab-docs/DirectAccessWithHoles_8cpp-example.html

http://ftp.mcs.anl.gov/pub/fathom/moab-docs/DirectAccessNoHoles_8cpp-example.html

Not sure what you need exactly.
Iulian

________________________________
From: moab-dev-bounces at mcs.anl.gov [moab-dev-bounces at mcs.anl.gov] on behalf of Nico Schlömer [nico.schloemer at gmail.com]
Sent: Thursday, April 07, 2016 10:41 AM
To: moab-dev at mcs.anl.gov
Subject: Re: [MOAB-dev] subdomains, sparse tags

I'm kind of lost here on the tags side anyways. Is there a piece of code that uses tags that I can look at?

Cheers,
Nico

On Thu, Apr 7, 2016 at 3:13 PM Nico Schlömer <nico.schloemer at gmail.com<mailto:nico.schloemer at gmail.com>> wrote:
Hi everyone,

I'm just reading up on tags, all starting from the problem that I have mesh on which there are multiple subdomains which may or may not overlap, may or may not fill the the entire mesh. What I will need to do is to set those tags on the mesh and then to iterate over all entities with that tag (probably multiple times).

Do I see correctly that sparse tags [1] are the way to go then?

Cheers,
Nico

[1] https://www.mcs.anl.gov/~fathom/moab-docs/html/classmoab_1_1SparseTag.html
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