[Hdf-forum] HDF5 -- multithreading support or not?

Isaac Gerg isaac.gerg at gergltd.com
Mon Aug 29 10:51:02 CDT 2016


Thanks Dana, I see what you mean and where I misread.

On Mon, Aug 29, 2016 at 11:29 AM, Dana Robinson <derobins at hdfgroup.org>
wrote:

> Hi Isaac,
>
>
>
> It sounds like you want to call H5Fclose, not H5close. Try just closing
> the file and not calling H5close at all. Does that work?
>
>
>
> Dana
>
>
>
> *From:* Hdf-forum [mailto:hdf-forum-bounces at lists.hdfgroup.org] *On
> Behalf Of *Isaac Gerg
> *Sent:* Monday, August 29, 2016 11:25 AM
> *To:* HDF Users Discussion List <hdf-forum at lists.hdfgroup.org>
> *Subject:* Re: [Hdf-forum] HDF5 -- multithreading support or not?
>
>
>
> Hi Dana,
>
>
>
> I am not sure I understand your question.  In each thread, I open an hdf
> file, read from it, and then call H5close().
>
>
>
> > Normally, you don't need to call H5close() explicitly, btw. It will be
> called when the program exits.
>
>
>
> I did not know about this.
>
>
>
> In reading the documentation...
>
>
>
> > "This function is generally called when the application calls exit(),
> but may be called earlier in the event of an emergency shutdown or out of a
> desire to free all resources used by the HDF5 library."
>
> To me, "generally" implies that h5close() is not guaranteed to be called
> in exit() OR that its preferred by hdf library that the user calls
> H5close() right before calling exit().
>
>
>
> Thank you,
>
> Isaac
>
>
>
> On Mon, Aug 29, 2016 at 11:14 AM, Dana Robinson <derobins at hdfgroup.org>
> wrote:
>
> Hi Isaac,
>
>
>
> Are you calling H5close() from one thread and then expecting the other
> thread to make HDF5 calls? Because HDF5 calls are unlikely to be successful
> after you shut the library down :)
>
>
>
> Normally, you don't need to call H5close() explicitly, btw. It will be
> called when the program exits.
>
>
>
> From the reference manual (https://www.hdfgroup.org/
> HDF5/doc/RM/RM_H5.html#Library-Close ):
>
>
>
> "This function is generally called when the application calls exit(), but
> may be called earlier in the event of an emergency shutdown or out of a
> desire to free all resources used by the HDF5 library."
>
>
>
> Dana Robinson
>
> Software Engineer
>
> The HDF Group
>
>
>
> *From:* Hdf-forum [mailto:hdf-forum-bounces at lists.hdfgroup.org] *On
> Behalf Of *Isaac Gerg
> *Sent:* Friday, August 26, 2016 6:31 PM
> *To:* hdf-forum at lists.hdfgroup.org
> *Subject:* [Hdf-forum] HDF5 -- multithreading support or not?
>
>
>
> Hi Folks,
>
>
>
> I am a need for a windows application to have two threads read the same
> hdf5 file as read-only.  I have searched over months on the internet trying
> to determine if HDF5 can surely handle this case and have found conflicting
> results.
>
>
>
> I have built a test in C++, using the hdf5 C API, to determine if the read
> is possible.  The test occasional segfaults on H5Close().  I am trying to
> determine if the segfault is due to HDF5 or my own error.
>
>
>
> TL;DR - can HDF5 on windows support having 2 threads read from the same
> file as online documentation seems to be inconsistent.
>
>
>
> Thanks in advance,
>
> Isaac
>
>
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>
>
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