A conservative parallel simulation algorithm for entity-oriented modeling

Conservative parallel simulation protocols are such that each logical process (LP) in the simulation execute events only when it is certain that there will not be any time-order causality violation. Examples of conservative protocols include the asynchronous ChandyMisra-Bryant (CMB) algorithm [2], and synchronous algorithms such as that described in [1,6]. In all these protocols, time-guarantee (or time-bound) information for an LP is computed from the other LP’s (e.g. in CMB protocol, an LPi sends lookahead information to a next LPj, to give a lower time-bound for future events arriving at LPj from LPi.) In this paper, we propose a variant form of conservative parallel simulation protocol in which the timeguarantee for an LP is computed from the existing events in the system. The difference is this: in an algorithm such as the CMB protocol, an LPi may process different types of events, each of which may generate different events that proceed on to different LP’s. It can be difficult for LPi to guarantee different time-bounds to its next LP’s. The time-bounds to some LP’s may be more restrictive than necessary. If the time-bounds are provided by the entities (events) going through the system (as in our proposed algorithm), an event E at LPi can independently supply time-bounds only to those LP’s which may receive events generated by E. So even if LPj is one of LPi’s next LP’s, if E’s generated events cannot arrive at LPj, LPj is not restricted by E’s time-bound. We will describe the algorithm, outline a proof of its correctness and discuss its possible strengths and weaknesses.