FELT: A Far Future Event List Structure Optimized for Calendar Queues

Abstract

Calendar queues (CQ) are often employed in discrete event simulators to store pending events. They can achieve O(1) access time as long as the CQ resizes often enough to ensure that events are not skewed but evenly distributed in the queue structure. However, a resize operation would involve creating a new CQ structure and then moving each item from the old CQ to the new CQ before discarding the old CQ. Hence, such resizes can be costly if the size of the queue is very large. This article proposes a new secondary queuing structure that complements the primary CQ structure. Known as FELT (far future event leaf tree), the secondary FELT structure is a lazy queue (i.e., semisorted) structure that manages events that are considered to be too far away to be considered in the primary CQ structure. The FELT structure is shown to be far superior than the dynamic lazy calendar queue. Downloaded from 1. By overhead costs, we mean the queue maintenance costs that are above the basic enqueue and dequeue costs. . His research interests include very high-speed digital communications, array signal processing, provision of quality of service for handoffs in wireless cellular networks, and the development of high speed network simulators.

Priority-flood: An optimal depression-filling and watershed-labeling algorithm for digital elevation models

“…Calendar queues [Brown, 1988] have higher overhead, but this becomes negligible for large problems and they are well suited to the monotonically-increasing priorities exhibited by Priority-Flood. Calendar queues may be improved through delayed sorting [Rönngren et al, 1991;Steinman, 1994Steinman, , 1996Rönngren and Ayani, 1997], choosing or adaptively determining appropriately sized bins Ahn, 1997, 1999;Tan and Thng, 2000;Hui and Thng, 2002;Siangsukone et al, 2003;Tang et al, 2005], reducing resize operations Thng, 2003, 2004], or leveraging statistical properties of the priority of newlyinserted elements [Yan and Eidenbenz, 2006]. However, with the efficiency of the calendar queue comes subtleties in programming and determining algorithmic correctness.…”