Izaak, I have the answer for 4), 1-3) will leave to others (but for 2) see also http://www.hdfgroup.org/HDF5/doc/RM/CollectiveCalls.html, I think it answers your question) On Oct 13, 2011, at 5:44 PM, Zaak Beekman wrote:
> My apologies if I have asked this before, or if this info is available in the > documentation; I have searched through the online documentation and cannot > find the answer. > The documentation for H5Pset_fapl_mpio says: > > ' H5Pset_fapl_mpio stores the user-supplied MPI IO parameters comm, for > communicator, and info, for information, in the file access property list > fapl_id. That property list can then be used to create and/or open a file. > H5Pset_fapl_mpio is available only in the parallel HDF5 library and is not a > collective function. > comm is the MPI communicator to be used for file open, as defined in > MPI_FILE_OPEN of MPI-2. This function makes a duplicate of the communicator, > so modifications to comm after this function call returns have no effect on > the file access property list. > ... > If the file access property list already contains previously-set communicator > and Info values, those values will be replaced and the old communicator and > Info object will be freed.' > > Does this mean that: > 1) HDF5 now has a copy of the communicator passed to H5Pset_fapl_mpio so that > I am free to use the communicator I passed in for computations without > worrying about communication collisions? > 2) If 'H5Pset_fapl_mpio...is not a collective function,' does that mean it > should only be called by one MPI rank? > 3) If I want to open and work with multiple files simultaneously, using the > same or different communicators, then the only way to do this is to create > one file access property list per file using H5Pset_fapl_mpio, right? One > does this instead of reusing the same file access property list (if the > communicator is the same) or placing another call to H5Pset_fapl_mpio and > passing in the the old property list, but the new communicator (if the > communicator is different), correct? (If I am reading the documentation > correctly then opening multiple files with the same access property list > means that they will all use the same communicator and messages may collide, > alternatively if one uses a new file-access-property list then each open file > has a unique communicator/communication context.) > > Dimension scales: > 4) Also, are there Fortran bindings for the high-level dimension scales API? > If not, one should be able to follow the specification document to implement > dimension scales using lower level HDF5 API calls, right? > Yes, Fortran wrappers for dimension scales will be part of the HDF5 1.8.8 release coming in mid November. We hope to announce pre-release testing early next week. Elena > Sorry to have so many questions, i just want to make sure that I am > understanding the semantics correctly. > Izaak Beekman > =================================== > (301)244-9367 > Princeton University Doctoral Candidate > Mechanical and Aerospace Engineering > [email protected] > > UMD-CP Visiting Graduate Student > Aerospace Engineering > [email protected] > [email protected] > _______________________________________________ > Hdf-forum is for HDF software users discussion. > [email protected] > http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org
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