Research On Time Management In Large Scale Distributed And Parallel Simulation System

Time management is an important way to ensure the causality of events’ dealing correct in distributed and parallel simulation. It is the hot topic of the research in distributed and parallel simulation. With the topology and interaction of simulation nodes becomes more and more complex. How to reduce the occupation of communication resources in conservative protocol driven by step and the probability of rollback avalanche in optimistic protocol driven by event has become the hot topic of research in distributed and parallel simulation, which is studied by this paper.Firstly, the paper introduces some basic knowledge of distributed and parallel simulation and analyies how to choose the best value of Lookahead in conservative protocol driven by step and the relation of rollback probability and optimistic extent in optimistic protocol driven by event. the problem of communication congestion in conservative protocol driven by step and the problem of rollback avalanche in optimistic protocol driven by event are analyzed. The research status at home and abroad is introduced, and the paper points out the shortages of those methods existed.Secondly, To solve the problem of communication congestion in conservative protocol driven by step, the paper designs and tests three algorithms, which is the time management algorithm based on Time Tree, the time management algorithm based on Step Agency Module and the Time Tree algorithm based on Step Agency Modules. By sending messages layer by layer, converting the network communication between members to the shared memory communication between Step Agency Modules and mixing them, those algorithms reduce the load of network and server’s portThirdly, To solve the problem of rollback avalanche in optimistic protocol driven by event, the paper designs and tests an advanced optimistic protocol based on Time Dams, which reduces the rollback probability and keeps the optimism of simulation to some extent by dividing every Logic Processes’ Local Virtual Time into some parts and limit any Rollback in one part. This protocol has been applied for the national patent. The paper proposed a way to adjust the interval between two dams adaptivly, which is based on the effective of simulation time promoting. The paper discusses how to implement this protocol based HLA.Lastly, the paper designs and realizes two models, the model of the against between red and blue and the model of parts processing, by the Time Tree algorithm based on Step Agency Module and the advanced optimistic protocol based on Time Dams. The results show that those two algorithms reduce the probability of communication congestion and rollback avalanche, and the both two algorithms can manage time effectively.