SOFTWARE—PRACTICE AND EXPERIENCE Softw. Pract. Exper. 2004; 00:1–7 Prepared using speauth.cls [Version: 2002/09/23 v2.2] JiST: An efficient approach to simulation using virtual machines † Rimon Barr, 1 Zygmunt J. Haas, 2 and Robbert van Renesse 1 1 Department of Computer Science, Cornell University, Ithaca, NY 14853 2 Department of Electrical Engineering, Cornell University, Ithaca, NY 14853 E-mail: rimon@acm.org, haas@ece.cornell.edu, and rvr@cs.cornell.edu SUMMARY Discrete event simulators are important scientific tools and their efficient design and execution is the subject of much research. In this paper, we propose a new approach for constructing simulators that leverages virtual machines and combines advantages from the traditional systems-based and language-based simulator designs. We introduce JiST, a Java-based simulation system that executes discrete event simulations both efficiently and transparently by embedding simulation semantics directly into the Java execution model. The system provides standard benefits that the modern Java runtime affords. In addition, JiST is efficient, out-performing existing highly optimized simulation runtimes. As a case study, we illustrate the practicality of the JiST framework by applying it to the construction of SWANS, a scalable wireless ad hoc network simulator. We simulate million node wireless networks, which represents two orders of magnitude increase in scale over what existing simulators can achieve on equivalent hardware and at the same level of detail. key words: discrete event simulation, simulation languages, Java, wireless networks, aspect-oriented programming † As of this writing, the JiST and SWANS software distributions and documentation are available online [1]. Contract/grant sponsor: This work has been supported in part by the DoD Multidisciplinary University Research Initiative (MURI) program administered by the Office of Naval Research under the grant number N00014-00-1-0564 and by the DoD Multidisciplinary University Research Initiative (MURI) program administered by the Air Force Office of Scientific Research under the grant number F49620-02-1-0233. Copyright c  2004 John Wiley & Sons, Ltd.