Checkpointing in a time warp synchronized parallel simulator is a necessary and potentially expensive operation. In the simple case, a time warp simulator checkpoints every χ events, for some fixed value χ. For larg...
详细信息
ISBN:
(纸本)9780818671203
Checkpointing in a time warp synchronized parallel simulator is a necessary and potentially expensive operation. In the simple case, a time warp simulator checkpoints every χ events, for some fixed value χ. For larger values of χ, the simulator requires less overhead for saving the state, but incurs an increased latency during rollback. Thus, the problem is to balance the time to save states against the time to coast forward upon rollback. Unfortunately, a static determination of a optimal value for χ is very difficult and can vary widely, even between closely related instances of a time warp simulator. Furthermore, the optimal checkpoint interval may actually vary over the lifetime of the *** address these problems, several investigators have proposed dynamically adjusting the checkpoint interval χ as the simulation progresses. This paper analyzes three previous techniques for dynamically sizing checkpoint intervals and presents a new, heuristic algorithm for this purpose. All four techniques are implemented in a common application domain (digital system simulation from VHDL descriptions) and a direct comparison between the algorithms is performed. The results show a significant difference in the performance of the implemented algorithms. However, in virtually all cases, the dynamic algorithms performed near or better than the best static value. Furthermore, the best algorithms performed as much as 12% better than the best static value.
Time Warp's optimistic scheduling requires the maintenance of simulation state history to support rollback in the event of causality violations. State history, and the ability to rollback the simulation, can provi...
ISBN:
(纸本)9780818679650
Time Warp's optimistic scheduling requires the maintenance of simulation state history to support rollback in the event of causality violations. State history, and the ability to rollback the simulation, can provide unique functionality for human-in-the-loop simulation environments. This paper investigates the use of Time Warp to output valid simulation state in a near real-time manner, re-execute portions of the simulation, and interactively probe simulation values to ascertain underlying causes of transient behavior.A shared-memory, multi-threaded interactive simulation architecture is presented and the additional state saving requirements imposed by interactivity are examined. The shortcomings of existing state saving schemes lead us to propose Multiplexed State Saving (MSS). By interleaving checkpointing and incremental state logs MSS provides bounded rollback costs and asynchronous access to prior simulation state. The interaction algorithms and MSS form a scalable, bounded cost component suitable for use in a real-time interactive Time Warp system.
Development of multiple robot systems which solve complex and dynamic problems in parallel and distributed manners is one of the key issues in robotics research. The multiple robot systems require robust methods to id...
详细信息
Development of multiple robot systems which solve complex and dynamic problems in parallel and distributed manners is one of the key issues in robotics research. The multiple robot systems require robust methods to identify robots for collaborative behaviors. This paper proposes a method using omnidirectional vision sensors for the identification between the robots. In addition to the several advantages of the omnidirectional vision sensor as a vision of a mobile robot, the omnidirectional vision sensor brings a significant benefit for realizing collaborative behaviors in multiple robot systems. After discussing on the algorithm, this paper shows several simulation results and real experimental results in a real environment.
We present, in this paper, a hybrid algorithm which makes use of Time Warp between clusters of LPs and a sequential algorithm within the cluster. Time Warp is, of course, traditionally implemented between individual L...
详细信息
ISBN:
(纸本)9780818671203
We present, in this paper, a hybrid algorithm which makes use of Time Warp between clusters of LPs and a sequential algorithm within the cluster. Time Warp is, of course, traditionally implemented between individual LPs. The algorithm was implemented in a digital logic simulator, and its performance compared to that of Time *** upon this platform we develop a family of three checkpointing algorithms, each of which occupies a different point in the spectrum of possible trade-offs between memory usage and execution time. The algorithms were implemented on several digital logic circuits and their speed, number of states saved and maximal memory consumption were compared to those of Time Warp. One of the algorithms saved between 35 and 50% of the maximal memory consumed by Time Warp (depending upon the number of processors used), while the other two decreased the maximal usage up to 30%. The latter two algorithms exhibited a speed comparable to Time Warp, while the first algorithm was 30-60% *** algorithms are also simpler to implement than optimal checkpointing algorithms.
暂无评论