[alcf-discuss] [Fwd: Re: [Fwd: Re: Parallel hdf5 I/O of strided data]]

[Rob Latham]

On Wed, May 06, 2009 at 04:16:02PM -0500, Tim Tautges wrote:
> ???

Hi Tim, Jason.  Sorry for the confusion.  I was perhaps too brief with
my response to John.

Jason's correct.   Property lists are passed in to the HDF5 read and
write calls.  Maybe John's code sets up a property list further on and
he didn't show that part when I asked about HDF5 tuning?   

http://www.hdfgroup.org/HDF5/Tutor/parallel.html

HDF5 makes the distinction between parallel and collective access to
an HDF5 file and to an HDF5 dataset, a distinction I omitted in my
response to John.. 

Hope that is more clear.

HDF5 disables collective I/O to a dataset by default, which is not
ideal on bluegene. 

==rob


> -------- Original Message --------
> Subject: Re: [Fwd: Re: [alcf-discuss] Parallel hdf5 I/O of strided data]
> Date: Wed, 06 May 2009 15:52:53 -0500
> From: Jason Kraftcheck <kraftche at cae.wisc.edu>
> To: Tim Tautges <tautges at mcs.anl.gov>
> References: <4A01F6CB.3040107 at mcs.anl.gov>
>
> Tim Tautges wrote:
>> Are you using the collective property in the parallel hdf5 writer?  (See
>> below...)
>>
>
> The comment below seems to be inconsistent with the documentation.  If you
> follow the link below to the description of H5Pset_dxpl_mpio, note the part
> where it says "The property list can then be used to control the I/O
> transfer mode during data I/O operations."  That seems to imply that the
> property is to be passed to things like H5Dread and H5Dwrite (data I/O)
> rather than H5Fcreate.
>
> The Parallel HDF5 documentation (what there is of it) also says that this
> property gets passed to H5Dread and H5Dwrite
> (http://www.hdfgroup.org/HDF5/Tutor/pcrtaccd.html).  It never mentions the
> property in connection with H5Fcreate or H5Fopen, nor can I find such a
> usage in any of the examples.



-- 
Rob Latham
Mathematics and Computer Science Division
Argonne National Lab, IL USA