Hi,
Sorry, this question has probably been asked before, but I couldn't
find anything in the docs, and there doesn't seem to be an archive of
this mailing list.
Are there known practical limitations on the number of objects
(e.g., groups or datasets)? I'm asking because I've written some test
programs, and the HDF5 performance seems to start non-linearly degrading
once the number of objects grows above approximately 50000-100000
objects. Are there parameter settings that can improve this?
I have two test programs that I'm using to test HDF5:
Program 1:
Create a new HDF5 file, and write 100000 chunked datasets of
size (6,2,2) (native double) into the top level. In this test,
the chunk dimensions are the same as the entire dataset.
Program 2:
Create a new HDF5 file, create 1000 groups, and write 100
chunked datasets of size (6,2,2) (native double) into each
group. In this test, the chunk dimensions are the same as the
entire dataset.
I'm using chunked datasets, because the next test after this would
extend the dataset sizes from (6,2,2) to (N,2,2), for varying values of
N. I've tried using the split file driver, but the performance of that
is comparable.
Also, to get better performance, I've had to twiddle various symbol
and storage parameters, but I really have no idea what I'm doing, here:
status = H5Pset_istore_k(fcpl, 1);
status = H5Pset_sym_k(fcpl, 20, 50);
[ What I'm really trying to do is figure out a reasonable way of storing
ragged arrays of ragged arrays of ragged arrays of .... The nesting
can go pretty deep, and so I was wondering if I could use groups to
help with the nesting. Unfortunately, with this approach, the number
of groups used by my program could be on the order of a trillion or
more, worst-case. I could use alternative encodings (e.g.,
concatenate all my datasets), but, at that point, I don't know if it's
worthwhile to use HDF5 any more. ;-( ]
···
--
Darryl Okahata
darrylo@soco.agilent.com
DISCLAIMER: this message is the author's personal opinion and does not
constitute the support, opinion, or policy of Agilent Technologies, or
of the little green men that have been following him all day.
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