Hi,
Thanks for your reply.
I am attaching part of my code that does the parallel write.
Points to notice are:
1. for 'nprocs' processors, there are 'nend' diagonal processors that are
actually doing the write, where:
nprocs = nend * (nend+1) / 2
2. the subroutine for parallel write, 'phdfwrite' is present in the file hdfmodule.f
3. This subroutine is called only by the diagonal processors(nend)
Please find attached the source files. I also notice that for 265875 real nos.,
there is no speed difference even between INDEPENDENT and COLLECTIVE IO. Is this
because of the small size of the array. Also do you find anything that I may be
doing which reduces the speed ?
Best Regards,
Nikhil
Hi Nikhil,
> Hi All,
>
> I am writing a HDF5 file in parallel. But to my surprise, the
> performance of the
> parallel write isn't better compared to the serial binary write
> operation. To
> write 265875 real numbers, my HDF write takes about 0.1 seconds
> whereas the
> serial binary operation takes around 0.07 seconds. This is
> surprising as
> parallel should be atleast as fast as serial if not any faster.
>
> Can anybody give me any suggestions as to what can be done to
> noticably speedup
> this write operation ?
Hmm, are you using collective or independent parallel I/O? Also,
that's a pretty small dataset, so you are not likely to see much
difference either way.
> Will the performance of HDF5 write be better than binary for very
> large arrays ?
Our goal is to make HDF5 writes be equivalent to binary for large raw
data I/O operations, but to make the files produced self-describing,
portable, etc. also.
> If not how can I bring any substantial speedup ?
This is a very hard question to answer without more details... 
Quincey
>
>
> Regards,
> Nikhil
>
>
>
>
> ----------------------------------------------------------------------
> This mailing list is for HDF software users discussion.
> To subscribe to this list, send a message to hdf-forum-subscribe@hdfgroup.org
> .
> To unsubscribe, send a message to hdf-forum-unsubscribe@hdfgroup.org.
>
>
----------------------------------------------------------------------
This mailing list is for HDF software users discussion.
To subscribe to this list, send a message to hdf-forum-subscribe@hdfgroup.org.
To unsubscribe, send a message to hdf-forum-unsubscribe@hdfgroup.org.
Regards,
Nikhil
···
On Jul 9, 2008, at 6:39 PM, Nikhil Laghave wrote:
----------------------------------------------------------------------
This mailing list is for HDF software users discussion.
To subscribe to this list, send a message to hdf-forum-subscribe@hdfgroup.org.
To unsubscribe, send a message to hdf-forum-unsubscribe@hdfgroup.org.