24 ms·

No, computing is happening in parallel with data being sent/received

• gnufx 6y ago
  What fraction of communication on a typical HPC system is overlapped with computation? My guess is rather little, despite the Mellanox sales pitch. I do wish people commonly made cluster-global profiling-type measurements to be able to answer that sort of question and do optimization.
  • fluffything 6y ago
    Heavily depends on the application. Many applications running on a Top 10 system of the Top 500 are required to show good single threaded performance and good weak and strong scalings up to a big part of the system. Checking all these 3 check boxes is hard to do if your communication is not fully overlapped by computation. The smaller your problem, the better your single threaded performance (e.g. at some point your problem fits in L3), and the larger fraction of execution time that communication dominates. Even the poorest applications on these systems use non-blocking MPI to overlap communication with computation nowadays.