Distributed algorithm

About: Distributed algorithm is a research topic. Over the lifetime, 20416 publications have been published within this topic receiving 548109 citations.

On Synchronous Robotic Networks—Part I: Models, Tasks, and Complexity

Abstract: This paper proposes a formal model for a network of robotic agents that move and communicate. Building on concepts from distributed computation, robotics, and control theory, we define notions of robotic network, control and communication law, coordination task, and time and communication complexity. We illustrate our model and compute the proposed complexity measures in the example of a network of locally connected agents on a circle that agree upon a direction of motion and pursue their immediate neighbors.

Tree-Based Broadcasting in Multihop Radio Networks

Abstract: This paper considers the issue of broadcasting protocols in multihop radio networks. The objective of a broadcasting protocol is to deliver the broadcasted message to all network nodes. To efficiently achieve this objective the broad- casting protocol in this paper utilizes two basic properties of the multihop radio network. One is the broadcast nature of the radio which allows every single trasmission to reach all nodes that are in line of sight and within range of the transmitting node. The other, spatial reuse of the radio channel, which due to the multihop nature of the network allows multiple simultaneous transmissions to be received correctly. The proposed protocol incorporates these properties to obtain a collision free forwarding of the broadcasted message on a tree. Centralized and distributed algorithms for the tree construction are presented. The obtained trees are unique in incorporating radio oriented time ordering as part of their definition. In this way multiple copies of one or more broadcasted messages can be transmitted simultaneously without collision, requiring only a small number of message transmissions. Consequently, the protocol not only guarantees that the broadcasted message reaches all network nodes in bounded time, but also ensures that the broadcasting activity will use only limited channel bandwidth and node memory. The proposed broadcast protocol thus possesses the advantages of TDM solutions while allowing the channel bandwidth to be shared, concurrently with the broadcast, with other transmission activities as dictated, for instance, by data link protocols. Some NP-completeness proofs are also given.

The BG distributed simulation algorithm

Abstract: We present a shared memory algorithm that allows a set of f+1 processes to wait-free “simulate” a larger system of n processes, that may also exhibit up to f stopping failures.

Optimization based rate control for multirate multicast sessions

Abstract: Multirate multicasting, where the receivers of a multicast group can receive service at different rates, is an efficient mode of data delivery for many real-time applications. We address the problem of achieving rates that maximize the total receiver utility for multirate multicast sessions. This problem not only takes into account the heterogeneity in user requirements, but also provides a unified framework for diverse fairness objectives. We propose two algorithms and prove that they converge to the optimal rates for this problem. The algorithms are distributed and scalable, and do not require the network to know the receiver utilities. We discuss how these algorithms can be implemented in a real network, and also demonstrate their convergence through simulation experiments.

Replicated distributed programs

Abstract: This dissertation presents a new software architecture for fault-tolerant distributed programs. This new architecture allows replication to be added transparently and flexibly to existing programs. Tuning the availability of a replicated program becomes a programming-in-the-large problem that a programmer need address only after the individual modules have been written and verified. The increasing reliance that people place on computer systems makes it essential that those systems remain available. The low cost of computer hardware and the high cost of computer software make replicated distributed programs an attractive solution to the problem of providing fault-tolerant operation. A troupe is a set of replicas of a module, executing on machines that have independent failure modes. Troupes are the building blocks of replicated distributed programs and the key to achieving high availability. Individual members of a troupe do not communicate among themselves, and are unaware of one another''s existence; this property is what distinguishes troupes from other software architectures for fault tolerance. Replicated procedure call is introduced to handle the many- to-many pattern of communication between troupes. Replicated procedure cal is an elegant and powerful way of expressing many distributed algorithms. The semantics of replicated procedure call can be summarized as exactly-once execution at all replicas. An implementation of troupes and replicated procedure call is described. Experiments were conducted to measure the performance of this implementation; an analysis of the results of these experiments is presented. The problem of concurrency control for troupes is examined, and algorithms for replicated atomic transactions are presented as a solution. Binding and reconfiguration mechanisms for replicated distributed programs are described, and the problem of when to replace failed troupe members is analyzed. Several issues relating to programming languages and environments for reliable distributed applications are discussed. Integration of the replication mechanisms into current programming languages is accomplished by means of stub compilers. Four stub compilers are examined, and some lessons learned form them are presented. A language for specifying troupe configurations is described, and the design of a configuration manager, a programming-in-the-large tool for configuring replicated distributed programs, is presented.