Hi Jens,
On Oct 12, 2010, at 2:24 PM, Jens Thoms Toerring wrote:
> Hi Quincey,
>
> 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.
Hmm, sorry, I missed that you wanted to check for a soft link. You
need to use H5Lget_info() for that.
>>> 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...
This is very weird, can you send a sample program that shows this
result?
Thanks,
Quincey
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