13046770
Local leader election, signal strength aware flooding, and routeless routing
We have identified a fundamental operator in wireless networks that we named the local leader election in which the goal is to select a node in a spatially close neighborhood. We present a simple and efficient solution to the local leader election problem by making use of both: (i) implicit synchronization points, commonly observable by all nodes in the same neighborhood, and (ii) the prioritized backoff delay, dependent on the desired probability of each node becoming a leader. We then show that both flooding and routing are instances of the local leader election problem, so our general solution naturally applies. By relating the backoff delay to the signal strength of the received packet, we have designed a variant of flooding named signal strength aware flooding (SSAF) that can improve its efficiency. By using a different metric to derive the backoff delay, we have designed a new generation wireless routing protocol, that we named the routeless routing protocol that possesses several interesting properties.
2548796
Four types of lookback
We present a classification that groups lookback into four types: direct strong lookback, universal strong lookback, direct weak lookback, and universal weak lookback. They are defined in terms of absolute and dynamic impact times. We discuss relationships between lookback types by considering when rollbacks and/or antimessages are avoided. From different types of lookback, we also derive three optimization techniques for optimistic simulation and point out their advantages over lazy cancellation. Finally, we show that all four types of lookback exist in the PCS network simulation and can be exploited by either lookback-based or optimistic protocols.
7075872
Lookback:a new way of exploiting parallelism in discrete event simulation
Lookback is defined as the ability of a logical process to change its past locally (without involving other logical processes). Logical processes with lookback are able to process out-of-timestamp order events, enabling new synchronization protocols for the parallel discrete event simulation. Two of such protocols, LB-GVT (LookBack-Global Virtual Time) and LB-EIT (LookBack-Earliest Input Time), are presented and their performance on the Closed Queuing Network (CQN) simulation is discussed. We also discuss in detail the relation between lookahead and lookback. Finally, we demonstrate that lookback allows conservative simulations to circumvent the speedup limit imposed by the critical path.
15801995
Data space oriented scheduling in embedded systems
With the widespread use of embedded devices such as PDAs, printers, game machines, cellular telephones, achieving high performance demands an optimized operating system (OS) that can take full advantage of the underlying hardware components. This paper presents a locality conscious process scheduling strategy for embedded environments. The objective of our scheduling strategy is to maximize reuse in the data cache. It achieves this by restructuring the process codes based on data sharing patterns between processes.
206977606
Priority Based Overlay Multicast for Distributed Interactive Applications
Distributed Interactive Applications (DIAs) is different with other network-based applications, since the data should be delivered to the receiver node according to its priority. Among the existing overlay multicast protocols the "priority-based directed minimum spanning tree" (PST) is designed for DIAs. But in PST the available bandwidth (avail-bw) is used inefficiently and the system becomes unstable when its scale increases. This paper proposed a novel overlay multicast protocol named Priority Based Overlay Multicast (POM), which uses the entities’ priority, links’ delay and node’s avail-bw to build multicast tree. By using POM the nodes with high priority receive the data in short delay, while the nodes with low priority tolerate a long delay in order to balance the available bandwidth usage among the nodes. The simulation results show that POM uses the avail-bw efficiently and keeps the system stable when its scale increases. Keywords: DIAs; Priority; Available bandwidth.
9256979
Convergence of difference schemes with high resolution for conservation laws
We are concerned with the convergence of Lax-Wendroff type schemes with high resolution to the entropy solutions for conservation laws. These schemes include the original Lax-Wendroff scheme proposed by Lax and Wendroff in 1960 and its two step versions-the Richtmyer scheme and the MacCormack scheme. For the convex scalar conservation laws with algebraic growth flux functions, we prove the convergence of these schemes to the weak solutions satisfying appropriate entropy inequalities. The proof is based on detailed L P estimates of the approximate solutions, H -1 compactness estimates of the corresponding entropy dissipation measures, and some compensated compactness frameworks. Then these techniques are generalized to study the convergence problem for the nonconvex scalar case and the hyperbolic systems of conservation laws.
15396672
Maintaining System State Information in a Multiagent Environment for Effective Learning
One fundamental issue in multiagent reinforcement learning is how to deal with the limited local knowledge of an agent in order to achieve effective learning. In this paper, we argue that this issue can be more effectively solved if agents are equipped with a consistent global view. We achieve this by requiring agents to follow an interacting protocol. The properties of the protocol are derived and theoretically analyzed. A distributed protocol that satisfies these properties is presented. The experimental evaluations are conducted for a well-known test-case (i.e., pursuit game) in the context of two learning algorithms. The results show that the protocol is effective and the reinforcement learning algorithms using it perform much better. key words: multiagent system, system state, distributed protocol, token ring
14750422
Reducing power with performance constraints for parallel sparse applications
Sparse and irregular computations constitute a large fraction of applications in the data-intensive scientific domain. While every effort is made to balance the computational workload in such computations across parallel processors, achieving sustained near machine-peak performance with close-to-ideal load balanced computation-to-processor mapping is inherently difficult. As a result, most of the time, the loads assigned to parallel processors can exhibit significant variations. While there have been numerous past efforts that study this imbalance from the performance viewpoint, to our knowledge, no prior study has considered exploiting the imbalance for reducing power consumption during execution. Power consumption in large-scale clusters of workstations is becoming a critical issue as noted by several recent research papers from both industry and academia. Focusing on sparse matrix computations in which underlying parallel computations and data dependencies can be represented by trees, this paper proposes schemes that save power through voltage/frequency scaling. Our goal is to reduce overall energy consumption by scaling the voltages/frequencies of those processors that are not in the critical path; i.e., our approach is oriented towards saving power without incurring performance penalties.