Hey remember a long time ago when I went through ROMIO to make it “big data” clean? ( Large transfers in ROMIO or this paper about fun with datatypes https://ieeexplore.ieee.org/document/7018162 ) . So I thought I was done when MPI-4 introduced new “large count” routines that now take an MPI_Count type for counts of items …
For years I’ve had a little tool in my home directory that does an MPI_File_open and reads out all the hints associated with that file. It was so simple and dumb I never put it on github. Now a new crop of machines has me realizing it might be useful to more people. So here …
I don’t have a lot of first-hand experience with the Quobyte file system but the developers contributed a file system driver for ROMIO, making them my new best friends. https://www.quobyte.com/product I think a lot about how to converge the worlds of HPC storage and data center storage. Looks like this new ROMIO driver might be …
I was surprised to find I hadn’t written anything about the environment variables one can set in ROMIO. I don’t think I have a well-thought-out theory of when to use an environment variable vs when to use an MPI_Info key. In this post, I’ll talk about ROMIO environment variables in general. The GPFS, PVFS2, and …
It has been a while since the last official MPICH release, but shortly before US Thanksgiving, the MPICH team released MPICH-3.3. ROMIO’s most noteworthy changes include wholesale reformatting of all the code to the same coding styles. Sorry about your fork or branch. use the MPL utility library already used in MPICH. Eliminates a lot …
If you would like to learn more about I/O in High Performance Computing, come check out our SC 2018 tutorial Parallel I/O in Practice. We will cover the hardware and software that makes up the software stack on large parallel computers. MPI-IO takes up a big chunk of time, as do the I/O libraries which …
It is an error for multiple MPI processes to write to the same or to overlapping regions of a file. ROMIO will let you get away with this but if your processes are writing different data, I can’t tell you what will end up in the file in the end. What about reads, though? ROMIO’s …
Data Direct has a storage product called “Infinte Memory Engine“. You can access this accelerated storage through POSIX but there is also a library-level native interface. DDN recently contributed a ROMIO driver to use the IME “native” interfaces, and I have merged this into MPICH master for an upcoming release. Thanks! For most people, this …
Getting the best performance out of Lustre can be a bit of a challenge. Here are some things to check if you tried out ROMIO on a Lustre file system and did not see the performance you were expecting. The zeroth step in tuning Lustre is “consult your site-specific documentation”. Your admins will have information …
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 …