Simulation of Asynchronous Iterative Algorithms Using SimGrid

Synchronous iterative algorithms are often less scalable than asynchronous iterative ones. Performing large scale experiments with different kind of network parameters is not easy because with supercomputers such parameters are fixed. So, one solution consists in using simulations first in order to analyze what parameters could influence or not the behavior of an algorithm. In this paper, we show that it is interesting to use SimGrid to simulate the behavior of asynchronous iterative algorithms. For that, we compare the behavior of a synchronous GMRES algorithm with an asynchronous multisplitting one with simulations which let us easily choose some parameters. Both codes are real MPI codes and simulations allow us to see when the asynchronous multisplitting algorithm can be more efficient than the GMRES one to solve a 3D Poisson problem.