Section: New Results

Task based asynchronous MPI collectives optimisation

Asynchronous collectives are more complex than plain non-blocking point-to-point communications. They need specific mechanisms for progression. Task based progression is a good way to improve the performance of applications with overlap.

We worked on a benchmarking tool [41] measuring specific collective overlapping, taking into account time shift between different nodes. Using this tool, we were able to experiment with different task execution policies in the NewMadeleine communication library.

We propose a progression policy consisting of a dedicated a core for progression tasks; modern processors have more and more cores, so it is profitable on that kind of processors. The only function of this core is to progress communications, so we use a particularly aggressive algorithm for this progression.