Hi Bernd,
On Nov 15, 2011, at 4:51 PM, Bernd Rinn wrote:
> Hi all,
>
> I need to read an array of object references. I find the function
> H5Rget_name() quite slow. A loop like
>
> for (i = 0,refPR = refP; i < arrayLen; ++i,++refPR) {
>
> size = H5Rget_name((hid_t)loc_id, H5R_OBJECT, refPR, rName,
> rname_buf_size);
>
> } /* for (i = 0...) */
>
> takes about 19 seconds on my laptop for an array of length 3456 where
> loc_id is the object id of the object reference array. On the other hand,
>
> time h5dump Cells.AreaShape_Eccentricity.mat > /dev/null
>
> is finished after 1.6 seconds. h5dump not only lists the names of each
> reference of the object reference array (which is what the loop above is
> supposed to do), but also each referenced dataset, each of which is a
> float array with a couple of hundred elements. Still is is more than a
> factor of 10 faster. Unfortunately the source code of h5dump is not
> straight forward to read, so I hope someone can tell me the trick used
> by h5dump to get such good performance.
h5dump goes faster because it traverses the entire file, building a
list of all the objects in the file. Then each name is pulled from that table
when displayed later. Calling H5Rget_name individually will trigger a partial
traversal of the file to generate the path name...
Quincey
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