[MOAB-dev] Question about getting entities with tag data

[Paul Wilson]

Jason Kraftcheck wrote:
> Paul Wilson wrote:
>> Hi there,
>>
>> I have been digging through the interface and I can't seem to find a 
>> function that will return an MBRange of entities formed by matching a 
>> single tag against a set of tag values.  As far as I can tell, 
>> get_entities_by_type_and_tag will return an MBRange of entities 
>> formed by matching N tags against N corresponding values, but will 
>> not match 1 tag against M values.
>>
>> Is there such a function?  If not, is there a recommended way to 
>> resolve this? 
>
> You can call the existing function m times, passing the 
> MBInterface::UNITE flag (or INTERSECT if that's what you want.)  Or 
> pass in m copies of the tag handle.
>
>> My first attempt was to get each entity one at a time, but that is 
>> extremely slow.  Perhaps better to get the tag data for all possible 
>> entities and then throw out the ones that are not needed?
>>
>
> MOAB's search of tag values is O(n).  If you need something faster, 
> you'll have to construct your own map or hash table from value to handle.
That's what I did - got all tag values, put it into 
map<tag_value,MBEntityHandle> and used STL algorithms to achieve what I 
needed.

Paul

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