6784159
Randomized registers and iterative algorithms
Abstract.We present three different specifications of a read-write register that may occasionally return out-of-date values - namely, a (basic) random register, a P-random register, and a monotone random register. We show that these specifications are implemented by the probabilistic quorum algorithm of Malkhi, Reiter, Wool, and Wright, and we illustrate how to program with such registers in the framework of Bertsekas, using the notation of Üresin and Dubois. Consequently, existing iterative algorithms for a significant class of problems (including solving systems of linear equations, finding shortest paths, constraint satisfaction, and transitive closure) will converge with high probability if executed in a system in which the shared data is implemented with registers satisfying the new specifications. Furthermore, the algorithms in this framework will inherit positive attributes concerning load and fault-tolerance from the underlying register implementation. The expected convergence time for iterative algorithms using the monotone implementation is analyzed and shown experimentally to improve on that of the original implementation. The message complexity for iterative algorithms using the monotone probabilistic quorum implementation is shown to improve on that of non-probabilistic implementations in a quantifiable situation.
9646078
Parallel hashing algorithms on BSP and QSM models
Summary form only given. We study two parallel computing models - the bulk synchronous parallel (BSP) and the queued shared memory (QSM) - as alternatives to the PRAM model to provide more accurate performance predictions and analyses, and compares the two models in detail. As a case study, we consider a simple hashing problem, design the two versions - the message passing version and the shared memory version - of the algorithm, and compare their run time analytically. The message passing version of the algorithm is implemented and the experiments are performed to display the accuracy and the limitations of the predicted performance analysis.
8052541
Applications of probabilistic quorums to iterative algorithms
Presents a definition of a read-write register that sometimes returns out-of-date values, shows that the definition is implemented by the probabilistic quorum algorithm of D. Malkhi et al. (1997), and shows how to program with such registers using the framework of A. U/spl uml/resin and M. Dubois (1990). Consequently, existing iterative algorithms for an interesting class of problems (including finding shortest paths, constraint satisfaction and transitive closure) converge with high probability if executed in a system in which the shared data is implemented with registers satisfying the new definition. Furthermore, the algorithms in this framework inherit positive attributes concerning load and availability from the underlying register implementation. A monotone version of the new register definition is specified and implemented; it can provide improved expected convergence time and message complexity for iterative algorithms.
34762416
Generalized system for relaxed cocoercive variational inequalities in Hilbert spaces
Abstract The approximate solvability of a generalized system for relaxed cocoercive nonlinear variational inequality in Hilbert spaces is studied, based on the convergence of projection methods. The results presented in this paper extend and improve the main results of [R.U. Verma, Generalized system for relaxed cocoercive variational inequalities and its projection methods, J. Optim. Theory Appl. 121 (1) (2004) 203–210; R.U. Verma, Generalized class of partial relaxed monotonicity and its connections, Adv. Nonlinear Var. Inequal. 7 (2) (2004) 155–164; R.U. Verma, General convergence analysis for two-step projection methods and applications to variational problems, Appl. Math. Lett. 18 (11) (2005) 1286–1292; N.H. Xiu, J.Z. Zhang, Local convergence analysis of projection type algorithms: Unified approach, J. Optim. Theory Appl. 115 (2002) 211–230; H. Nie, Z. Liu, K.H. Kim, S.M. Kang, A system of nonlinear variational inequalities involving strongly monotone and pseudocontractive mappings, Adv. Nonlinear Var. Inequal. 6 (2) (2003) 91–99].
30313812
A flexible agent system for change adaptation in supply chains
The importance of supply chain management is increasing with globalization and the advancement of electronic business. Supply chains are dynamic due to frequent changes in suppliers, customers, and products. However, information systems for supply chains are not flexible enough to adapt to the changes, requiring high cost and time for re-implementation and re-customization. This paper suggests a flexible agent system for supply chains that can adapt to the changes in transactions introduced by new products or new trading partners. The flexible agent system consists of an interpretable conversation policy model, a procedure for exchanging new conversation policies, and a mechanism for actual transactions with newly acquired conversation policies. By using the flexible agent system, formation of supply chains becomes more robust to the dynamic changes. To show how the approach can be realized, a PC supply chain application is illustrated with a prototype agent platform.
5211893
The Growth of Broadband and Electronic Commerce in South Korea: Contributing Factors
From 1998 through 2001, South Korea witnessed a remarkable diffusion in broadband Internet connections. Using published and other data, this paper explores the actions and factors contributing to this diffusion from three viewpoints: government, private sector, and social. We suggest that the matching of demand and supply is the most important factor in the fast diffusion of broadband in Korea. In particular, fierce infrastructure competition led to quality services at a low fixed price. Online gaming exhibits some of the characteristics of a "killer application"; there are also some social and cultural drivers of demand. We then consider the impact that this rapid diffusion has had on electronic commerce. We produce conclusions of value to policymakers.
15007668
Wakeup scheduling in wireless sensor networks
A large number of ractical sensing and actuating applications require immediate notification of rare but urgent events and also fast delivery of time sensitive actuation commands. In this a er,we consider the design of efficient wakeup scheduling schemes for energy constrained sensor nodes that adhere to the bidirectional end-to-end delay constraints posed by such applications. We evaluate several existing scheduling schemes and propose novel scheduling methods that outperform existing ones.We also resent a new family of wakeu methods,called multi-parent schemes, which take a cross-layer a roach where multiple routes for transfer of messages and wakeup schedules for various nodes are crafted in synergy to increase longevity while reducing message delivery latencies. We analyze the power-delay and lifetime-latency tradeoffs for several wakeup methods and show that our proposed techniques significantly improve the performance and allow for much longer network lifetime while satisfying the latency constraints.
19026342
Eager writeback - a technique for improving bandwidth utilization
Modern high-performance processors utilize multi-level cache structures to help tolerate the increasing latency of main memory. Most of these caches employ either a writeback or a write-through strategy to deal with store operations. Write-through caches propagate data to more distant memory levels at the time each store occurs, which requires a very large bandwidth between the memory hierarchy levels. Writeback caches can significantly reduce the bandwidth requirements between caches and memory by marking cache lines as dirty when stores are processed and writing those lines to the memory system only when that dirty line is evicted. Unfortunately, for applications that experience significant numbers of cache misses due to streaming data, writeback cache designs can degrade overall system performance by clustering bus activity when dirty lines contend with data being fetched into the cache. In this paper we present a new technique called Eager Writeback, which re-distributes and balances memory traffic by writing and "cleaning" dirty cache lines prior to their eviction. Eager Writeback can be viewed as a compromise between write-through and writeback policies, in which dirty lines are written later than write-through, but prior to writeback. We will show that this approach can reduce the large number of writes seen in a write-through design, while avoiding the performance degradation caused by clustering bus traffic in a writeback approach.