Hmm. If I understand the question, I really cannot imagine a scenario where parallel I/O would be "faster" than MPI send/recv calls.
However, there may be a practicality issue here. It may be the case that the data processor k needs is on processor j but processor k doesn't know that processor j has it and processor j doesn't know that processor k needs it. So, there has to be some communication to for the processors to learn that. And, if those processors are 'somewhere else' in their execution, then you have a significant issue in programming to take advantage of the fact that you could use MPI send/recv to move the data anyways. In the end, it just might be more practical to just read data from the file, even if it is quite a bit slower. I am not sure I answered the question you asked though ;) Mark -- Mark C. Miller, Lawrence Livermore National Laboratory ================!!LLNL BUSINESS ONLY!!================ mille...@llnl.gov<mailto:mille...@llnl.gov> urgent: markcmille...@gmail.com T:8-6 (925)-423-5901 M/W/Th:7-12,2-7 (530)-753-8511 From: Suman Vajjala <suman.g...@gmail.com<mailto:suman.g...@gmail.com>> Reply-To: HDF Users Discussion List <hdf-forum@hdfgroup.org<mailto:hdf-forum@hdfgroup.org>> Date: Monday, April 8, 2013 9:38 PM To: HDF Users Discussion List <hdf-forum@hdfgroup.org<mailto:hdf-forum@hdfgroup.org>> Subject: [Hdf-forum] Performance query Hi, I have a question regarding the performance of parallel I/O vs MPI communication based calls. I have data which needs to be accessed by different processors. If the data is in memory then MPI calls (Send/Recv) does the job. In an another scenario the data is written to a H5 file and different processors access the respective data using parallel I/O. Would MPI calls be faster than HDF5 parallel I/O? (data access could be unstructured) Regards Suman Vajjala
_______________________________________________ Hdf-forum is for HDF software users discussion. Hdf-forum@hdfgroup.org http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org
