Causal order based time warp: a tradeoff of optimism

The optimistic synchronization paradigm, time warp, allows logical processes to advance aggressively. In the circumstances where the violation of the local causality constraint (LCC) is prone to occurring, this optimism may introduce substantial rollbacks and, as a consequence, significant overhead in recovering from erroneous computations. In this paper, a new approach, COBTW, is proposed, where the happen before relation is employed to capture the potential violations of LCC and causal order is applied to regulate the advancement of logical processes. Due to the difference between causal order and time-stamp order, there are discrepancies between them. Solutions to remove the discrepancies are proposed. Experiments conducted in a cluster and an emulated WAN suggest that COBTW reduces rollbacks caused by violations of LCC and empirically results in better performance, in comparison with the time warp protocol.