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Due to the current gap in continued funding from the U.S. National Science Foundation (NSF), the NSF Unidata Program Center has temporarily paused most operations. See NSF Unidata Pause in Most Operations for details.
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Hi Rob, On Sep 14, 2007, at 6:16 PM, Robert Latham wrote:
Hi. Bet you're going to get tired of me soon!
No, I'm happy to help you out, keep 'em coming... :-)
I'd really like to see all I/O calls using MPI-IO instead of posix fread (as in nc_check_for_hdf5). The HDF5 guys might recognize that I've bugged them about this last year :> ROMIO can take a file system prefix to override automatic file system detection. Such a prefix could be "testfs:" for our tracing file system driver (does no I/O, but logs which processes wrote how much) or it could be "pvfs2:" if we want to acess this userspace file system and do not happen to have the kernel component running. So for example, in nc_check_for_hdf5, instead of using fread, maybe use MPI_File_open and MPI_File_read when examining the magic number, and USE_PARALLEL_MPIIO is defined. Likewise, nc4_create_file, and nc_get_file_version use POSIX calls.
I think you might want the "MPI-POSIX" driver in HDF5 (look at H5Pset_fapl_mpiposix), but I don't know if the netCDF-4 library is exporting a way to use that in netCDF-4 applications. Hmm, but re- reading your note again, I'm not certain. Can you take a look at the MPI-POSIX file driver and see if that's what you want?
Quincey
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