Hi Quincy,
thanks for taking the time answering!
On Mon, Oct 11, 2010 at 08:04:28AM -0500, Quincey Koziol wrote:
> On Oct 10, 2010, at 5:12 PM, Jens Thoms Toerring wrote:
> > I am using the C++ API and trying to figure out how to
> > find out what an object that could be either a group or a
> > symbolic link really is. Unfortunately it seems that all
> > the functions that do that (like H5::CommonFG::getObjinfo())
> > are deprecated in 1.8 (and I would prefer not to use any
> > deprecated features). At least I haven't been able yet to
> > find any function/method that tells me if an object that
> > I got a name for is a link. Perhaps I did overlook it,
> > so I would be grateful for some hints.
> >
> > At the moment I thus resorted to just calling getLinkval()
> > and catch the error one gets if the name passed to it isn't
> > a link. That works but I noticed something strange: since I
> > didn't have a good idea what the second 'size' argument is
> > supposed to be good for I simply left it out, relying on the
> > default value of 0 (which I guess is supposed to indicate:
> > give me the whole name of what the link is pointing to). But
> > then i observed that the amount of memory consumed by the
> > program jumps up with each call of the function with incre-
> > ments in the order of 800 kB to about 7.5 MB. And that memory
> > never seems to become deallocated. This doesn't happen when
> > instead of leaving the argument out (or passing 0) I use a
> > fixed value - in that case memory consumption doesn't change
> > at all. This, of course, has the disadvantage that things
> > will go wrong badly if I haven't a good guess on the upper
> > bould of the length of the name linked to...
>
> You probably want to use H5Lexists(), along with H5Oget_info() to check
> this sort of thing.
So I guess there are no functions in the C++ API left for that
kind of thing? And I unfortunately haven't been able to figure
out how to use the functions you mention. H5Lexists() returns
TRUE no matter if the object I am interested in is a group or a
link. And I don't see anything in what I obtain from H5Oget_info()
(or H5Oget_info_by_name()) that would help me. The 'type' field
in the H5O_info_t structure doesn't seem to tell me if this
is a softlink or a group and I also have found nothing that
would indicate how long the resulting name is when following
the link, which seems to be needed for the getLinkval() call
(the default of 0 looking like resulting in a memory leak).
I'm probably missing the obvious but at the moment I have no
ideas left how to proceed.
> > Finally, there's another thing perhaps someone can help me
> > with: I tried to create some 120.000 1D data sets, about
> > 200 bytes large and each in it's own group. This resulted
> > in a huge overhead in the file: instead of the expected file
> > size of arond 24 MB (of course plus a bit for overhead) the
> > files were about 10 times larger than expected. Using a number
> > (30) of 2D data sets (with 4000 rows) took care of this but I
> > am curious why this makes such a big difference.
>
> Did you create them as chunked datasets? And, what were the dimensions
> of the chunk sizes you used?
No, those were simple 1-dimensional data sets, written out in a
single call immediately after creation and then closed. Perhps
having them all in their own group makes a difference? What I
noticed was that h5dump on the resulting file told me under
Storage information/Groups that for B-tree/List about 140 MB
were used...
Thanks and best regards, Jens
--
\ Jens Thoms Toerring ________ [email protected]
\_______________________________ http://toerring.de
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