While not exactly ROMIO, the new HDF5 release comes with a nice optimization that benefits all MPI-IO implementations. In order to know where the objects, datastets, and other information in an HDF5 file is located on disk, a process needs to read the HDF5 metadata. This metadata is scattered across the file, so to find …
I’m itching to discard some of the little-used file system drivers in ROMIO. Keep: GPFS: IBM’s GPFS file system still sees several key deployments NFS: It’s everywhere, even though implementing MPI-IO consistency semantics over NFS is difficult at best TESTFS: I find this debugging-oriented file system useful occasionally. UFS: the generic Unix file system driver …
The IBM and Argonne teams have been digging into ROMIO’s collective I/O performance on the Mira supercomputer. These optimizations made it into the MPICH-3.1.1 release, so it seemed like a good time to write up a bit about these optimizations. no more “bglockless“: for Blue Gene /L and Blue Gene /P we wrote a ROMIO …
Update: in MPICH-3.1.1 we finally scrapped bglockless, (see this writeup on 3.1.1 and Blue Gene enhancements) but it’s still part of the system software on any BG /L BG /P or BG /Q machines. The following writeup is perhaps of historical interest, but it will be a while (maybe never) before mpich-3.1.1 is the default …
In ROMIO, setting hints looks like this: MPI_Info info; MPI_Info_create(&info); MPI_Info_set(“cb_buffer_size”, “8388608”); Setting these hints in the program can make sense in many cases — for example, you know something specific about the workload and wish to guide ROMIO’s optimizations a bit. But what if you want to explore the impact of hints on your …
To cite all of ROMIO, use “A Case for Using MPI’s Derived Datatypes to Improve I/O” @InProceedings{thakur:mpi, author = {Rajeev Thakur and William Gropp and Ewing Lusk}, title = {A Case for Using {MPI’s} Derived Datatypes to Improve {I/O} Performance}, booktitle = {Proceedings of SC98: High Performance Networking and Computing}, year = {1998}, month = …