Time Warp cancellation optimizations on high latency networks

We investigate the performance of the time warp kernel APSIS when running on various communication layers, in particular on a wide-area grid. Several cancellation strategies are tried, among them the lazy cancellation and a little known bulk anti-messages optimization. Our experiments with an Ising spin simulation indicate that the slowdown caused by high latency networks, while significant, is not catastrophic; and that it can be significantly reduced using the lazy cancellation. Experiments suggest that further improvements can be expected if a more elaborate communication infrastructure is put in place.