Hi Werner,

On May 21, 2014, at 6:23 AM, Werner Benger 
<[email protected]<mailto:[email protected]>> wrote:
What is the quickest way to open attributes in a callback from H5Aiterate2() ?

It would seem that in the callback function there is the option to either call

H5Aopen_by_idx()  or H5Aopen_by_name() .

Since the callback function receives an H5A_info_t 
a<http://www.hdfgroup.org/HDF5/doc/RM/RM_H5A.html#Annot-OpenByIdx>s parameter, 
one might
expect that using its corder member to open the attribute by index would be
faster than going via another name lookup. However, our experiments it is
30x slower to go via the index than via the name.

Is this expected behavior? Are the alternatives?

Hmm, did you create the object with the "index the creation order info" flag as 
well as the "track the creation order info" flag?

Quincey


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