Minimum cost adaptive synchronization: experiments with the ParaSol system

We present a novel adaptive synchronization algorithm, called the minimum average cost (MAC) algorithm, in the context of the parasol parallel simulation system. ParaSol is a multithreaded system for parallel simulation on shared- and distributed-memory environments, designed to support domain-specific Simulation Object Libraries. The proposed MAC algorithm is based on minimizing the cost of synchronization delay and rollback at a process, whenever its simulation driver must decide whether to either proceed optimistically or to delay processing. In the former case the risk is rollback cost, in the event of a straggler's arrival. In the latter case the risk is unnecessary delay, in the event a latecomer is not a straggler. In addition to the MAC algorithm and an optimal delay computation model, we report on some early experiments comparing the performance of MAC-based adaptive synchronization to optimistic synchronization.