The proceedings contain 44 papers. The topics discussed include: a topological characterization of weakness;efficient dependency tracking for relevant events in shared-memory systems;building scalable and robust peer-...
详细信息
The proceedings contain 44 papers. The topics discussed include: a topological characterization of weakness;efficient dependency tracking for relevant events in shared-memory systems;building scalable and robust peer-to-peer overlay networks for broadcasting using network coding;skip webs: efficient distributed data structures for multi-dimensional data sets;brief announcement: an incentive-compatible capacity assignment algorithm for bulk data distribution using P2P;brief announcement: broadcast in radio networks in the presence of Byzantine adversaries;feedback control for router congestion resolution;toward a theory of transactional contention managers;and adaptive routing with stale information.
In this paper, we initiate the study of the approximability of the facility location problem in a distributed setting. In particular, we explore a trade-off between the amount of communication and the resulting approx...
详细信息
ISBN:
(纸本)9781581139945
In this paper, we initiate the study of the approximability of the facility location problem in a distributed setting. In particular, we explore a trade-off between the amount of communication and the resulting approximation ratio. We give a distributed algorithm that, for every constant k, achieves an O(√k(mp)1/√klog (m + n)) approximation in O(k] communication rounds where message size is bounded to O(log n) bits. The number of facilities and clients are m and n, respectively, and ρ is a coefficient that depends on the cost values of the instance. Our technique is based on a distributed primal-dual approach for approximating a linear program, that does not form a covering or packing program. Copyright 2005 acm.
We present a scheme for evenly partitioning the key space in distributed hash tables among the participating nodes. The scheme is based on the multiple random choices paradigm [3, 19], and handles both node joins and ...
详细信息
ISBN:
(纸本)9781581139945
We present a scheme for evenly partitioning the key space in distributed hash tables among the participating nodes. The scheme is based on the multiple random choices paradigm [3, 19], and handles both node joins and leaves. It achieves, with high probability, a ratio of at most 4 between the loads of the most and least burdened nodes, in the face or arbitrary node arrivals and departures. Each join or leave operation incurs message cost that is, with high probability, O(log2 n), where n is the number of nodes, and causes the relocation of keys from at most one node (for joins) or three nodes (for leaves). A version of our scheme is suitable for heterogeneous systems, where the capacities of nodes to serve keys can vary widely. Copyright 2005 acm.
We investigate issues related to the probe complexity of quorum systems and their implementation in a dynamic environment. Our contribution is twofold. The first regards the algorithmic complexity of finding a quorum ...
详细信息
ISBN:
(纸本)9781581137088
We investigate issues related to the probe complexity of quorum systems and their implementation in a dynamic environment. Our contribution is twofold. The first regards the algorithmic complexity of finding a quorum in case of random failures. We show a tradeoff between the load of a quorum system and its probe complexity for non adaptive algorithms. We analyze the algorithmic probe complexity of the Paths quorum system suggested by Naor and Wool in [29], and present two optimal algorithms. The first is a non adaptive algorithm that matches our lower bound. The second is an adaptive algorithm with a probe complexity that is linear in the cardinality of the smallest quorum set. We supply a constant degree network in which these algorithms could be executed efficiently. Thus the Paths quorum system is shown to have good balance between many measures of quality. Our second contribution is presenting Dynamic Paths-a suggestion for a dynamic and scalable quorum system, which can operate in an environment where elements join and leave the system. The quorum system could be viewed as a dynamic adaptation of the Paths system, and therefore has low load high availability and good probe complexity. We show that it scales gracefully as the number of elements grows.
We are interested in the relation between weak and strong temporal operators. We would like to find a characterization that shows what it means for an operator to be the weak or strong version of another operator, or ...
详细信息
ISBN:
(纸本)9781581139945
We are interested in the relation between weak and strong temporal operators. We would like to find a characterization that shows what it means for an operator to be the weak or strong version of another operator, or more generally for a formula to be a weak or strong version of another formula. We show that the weak version of a formula is not the same as Alpern and Schneider's safety component. By working over an extended alphabet, we show that their topological characterization of safety can be adapted to obtain a topological characterization of weakness. We study the resulting topology and the relations between weak and strong formulas. Finally, we apply the method to show the internal consistency of a logic containing both weak and strong versions of regular expressions. Copyright 2005 acm.
Many large-scale networks such as ad hoc and sensor networks, peer-to-peer networks, or the Internet have the property that the number of independent nodes does not grow arbitrarily when looking at neighborhoods of in...
详细信息
ISBN:
(纸本)9781581139945
Many large-scale networks such as ad hoc and sensor networks, peer-to-peer networks, or the Internet have the property that the number of independent nodes does not grow arbitrarily when looking at neighborhoods of increasing size. Due to this bounded "volume growth," one could expect that distributed algorithms are able to solve many problems more efficiently than on general graphs. The goal of this paper is to help understanding the distributed complexity of problems on "bounded growth" graphs. We show that on the widely used unit disk graph, covering and packing linear programs can be approximated by constant factors in constant time. For a more general network model which is based on the assumption that nodes are in a metric space of constant doubling dimension, we show that in o(log*n) rounds it is possible to construct a (O(1), O(1))-network decomposition. This results in asymptotically optimal O(log*n) time algorithms for many important problems. Copyright 2005 acm.
Deadlock detection scheduling is an important, yet oftoverlooked problem that can significantly affect the overall performance of deadlock handling. An excessive initiation of deadlock detection increases overall mess...
详细信息
ISBN:
(纸本)1581139942
Deadlock detection scheduling is an important, yet oftoverlooked problem that can significantly affect the overall performance of deadlock handling. An excessive initiation of deadlock detection increases overall message usage, resulting in degraded system performance in the absence of deadlocks;while a deficient initiation of deadlock detection increases the deadlock persistence time, resulting in an increased deadlock resolution cost in the presence of dead-locks. Such a performance tradeoff, however, is generally missing in literature. In this paper we study the impact of deadlock detection scheduling on the system performance, and show that there exists an optimal deadlock detection frequency that yields the minimum long-run mean average cost associated with the message complexity of deadlock detection and resolution algorithms, and the rate of deadlock formation, λ. Based on the up-to-date deadlock detection and resolution algorithms, we show that the asymptotically optimal frequency of deadlock detection scheduling that minimizes the message overhead is O((λn)1/3), when the total number of processes n is sufficiently large. Furthermore, we show that in general fully distributed (uncoordinated) deadlock detection scheduling can not be performed as efficiently as centralized (coordinated) deadlock detection scheduling. Copyright 2005 acm.
In recent years, the rapid growth of peer-to-peer (P2P) networks has provided a new paradigm for content distribution. To improve the efficiency of a P2P system, it is important to provide incentives for the peers to ...
详细信息
ISBN:
(纸本)9781581139945
In recent years, the rapid growth of peer-to-peer (P2P) networks has provided a new paradigm for content distribution. To improve the efficiency of a P2P system, it is important to provide incentives for the peers to participate and contribute their resources. In this work, we address the incentive provisioning problem for distribution of large-volume content in P2P networks, and present a "seeing-is-believing" incentive-compatible mechanism in which a peer will decide how much resources will be assigned to which neighbors based on what it has experienced. The protocol applies a utility-based resource-trading concept where peers will maximize their contributions for a fair or better return, and we show that by adopting this protocol, the system will achieve Cournot Equlibrium. Our protocol is light-weight, completely decentralized, and cheat-proof.
In a concurrent system with N processes, vector clocks of size N are used for tracking dependencies between the events. Using vectors of size N leads to scalability problems. Moreover, association of components with p...
详细信息
ISBN:
(纸本)9781581139945
In a concurrent system with N processes, vector clocks of size N are used for tracking dependencies between the events. Using vectors of size N leads to scalability problems. Moreover, association of components with processes makes vector clocks cumbersome and inefficient for systems with a dynamic number of processes. We present a class of logical clock algorithms, called chain clock, for tracking dependencies between relevant events based on generalizing a process to any chain in the computation poset. Chain clocks are generally able to track dependencies using fewer than N components and also adapt automatically to systems with dynamic number of processes. We compared the performance of Dynamic Chain Clock (DCC) with vector clock for multithreaded programs in Java. With 1% of total events being relevant events, DCC requires 10 times fewer components than vector clock and the times-tamp traces are smaller by a factor of 100. Although DCC requires shared data structures, it is still 10 times faster than vector clock in our experiments. Copyright 2005 acm.
This paper addresses the problem of locally verifying global properties. Several natural questions are studied, such as "how expensive is local verification?" and more specifically "how expensive is loc...
详细信息
ISBN:
(纸本)9781581139945
This paper addresses the problem of locally verifying global properties. Several natural questions are studied, such as "how expensive is local verification?" and more specifically "how expensive is local verification compared to computation?" A suitable model is introduced in which these questions are studied in terms of the number of bits a node needs to communicate. In particular, it is shown that the cost of verification is sometimes rather high, even higher than the number of bits needed for a computation. On the other hand, approaches are presented for the efficient construction of schemes, and upper and lower bounds are established on the cost of schemes for multiple basic problems. The paper also studies the role and cost of unique identities in terms of impossibility and complexity. Previous studies on related questions deal with distributed algorithms that simultaneously compute a configuration and verify that this configuration has a certain desired property. It turns out that this combined approach enables verification to be less costly, since the configuration is typically generated so as to be easily verifiable. In contrast, our approach separates the configuration design from the verification. That is, it first generates the desired configuration without bothering with the need to verify, and then handles the task of constructing a suitable verification scheme. Our approach thus allows for a more modular design of algorithms, and has the potential to aid in verifying properties even when the original design of the structures for maintaining them was done without verification in mind. Copyright 2005 acm.
暂无评论