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Parallel and Distributed Systems, IEEE Transactions on

Issue 1 • Date Jan 1994

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Displaying Results 1 - 11 of 11
  • An optimal strategy for comparing file copies

    Page(s): 87 - 93
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (732 KB)  

    We study the problem of identifying corrupted pages between two remotely located copies of a file in a distributed system. An efficient deterministic algorithm is presented to identify up to any given number of differing pages. The algorithm requires a single exchange of messages and is based on the structure of the Reed-Solomon code. In order to identify up to f corrupted pages, 2f signatures are transmitted. The algorithm requires less communication costs than previously proposed solutions. In fact, we prove that our algorithm is optimal, in the sense that no other algorithm is guaranteed to identify with probability 1 the corrupted pages by exchanging less information View full abstract»

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  • Reaching approximate agreement with mixed-mode faults

    Page(s): 53 - 63
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    In a fault-tolerant distributed system, different non-faulty processes may arrive at different values for a given system parameter. To resolve this disagreement, processes must exchange and vote upon their respective local values. Faulty processes may attempt to inhibit agreement by acting in a malicious or “Byzantine” manner. Approximate agreement defines one form of agreement in which the voted values obtained by the non-faulty processes need not be identical. Instead, they need only agree to within a predefined tolerance. Approximate agreement can be achieved by a sequence of convergent voting rounds, in which the range of values held by non-faulty processes is reduced in each round. Historically, each new convergent voting algorithm has been accompanied by ad-hoc proofs of its convergence rate and fault-tolerance, using an overly conservative fault model in which all faults exhibit worst-case Byzantine behavior. This paper presents a general method to quickly determine convergence rate and fault-tolerance for any member of a broad family of convergent voting algorithms. This method is developed under a realistic mixed-mode fault model comprised of asymmetric, symmetric, and benign fault modes. These results are employed to more accurately analyze the properties of several existing voting algorithms, to derive a sub-family of optimal mixed-mode voting algorithms, and to quickly determine the properties of proposed new voting algorithms View full abstract»

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  • The hierarchical hypercube: a new interconnection topology for massively parallel systems

    Page(s): 17 - 30
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1056 KB)  

    Interconnection networks play a crucial role in the performance of parallel systems. This paper introduces a new interconnection topology that is called the hierarchical hypercube (HHC). This topology is suitable for massively parallel systems with thousands of processors. An appealing property of this network is the low number of connections per processor, which enhances the VLSI design and fabrication of the system. Other alluring features include symmetry and logarithmic diameter, which imply easy and fast algorithms for communication. Moreover, the HHC is scalable; that is it can embed HHC's of lower dimensions. The paper presents two algorithms for data communication in the HHC. The first algorithm is for one-to-one transfer, and the second is for one-to-all broadcasting. Both algorithms take O(log2 k), where k is the total number of processors in the system. A wide class of problems, the divide & conquer class (D&Q), is shown to be easily and efficiently solvable on the HHC topology. Parallel algorithms are provided to describe how a D&Q problem can be solved efficiently on an HHC structure. The solution of a D&Q problem instance having up to k inputs requires a time complexity of O(log2 k) View full abstract»

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  • Access graphs: a model for investigating memory consistency

    Page(s): 39 - 52
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    Computer architectures supporting shared memory continue to increase in complexity as designers seek to improve memory performance. This is especially true of proposals for massively parallel systems with distributed, yet shared, memory. The need to maintain a reasonably simple memory model for programmers, in spite of enhancements like caches and access pipelining, is responsible for many of the complications. We develop a novel graph model, access graphs, for visualizing processor/memory interaction. Access graphs symbolically represent the causal relationships between load, store, and synchronization events. The focus is on two classes of access graphs: pseudo and real. A pseudo access graph describes an execution in terms of abstract events familiar to the programmer. If the pseudo access graph is acyclic, then memory consistency is preserved during the execution. A real access graph describes an execution in terms of physical events known to the hardware designer. A real access graph must be acyclic since hardware cannot violate causality. Memory consistency can be verified for a given computer system by proving that for any acyclic real access graph describing a program's execution on that computer, an acyclic pseudo access graph can be derived describing the same execution View full abstract»

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  • The impact of pipelined channels on k-ary n-cube networks

    Page(s): 2 - 16
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    In a pipelined-channel interconnection network, multiple bits may be simultaneously in flight on a single wire. This allows the cycle time of the network to be independent of the wire lengths, significantly affecting the network design trade-offs. This paper investigates the design and performance of pipelined channel k-ary n-cube networks, with particular emphasis on the choice of dimensionality and radix. Networks are investigated under the constant link width, constant node size and constant bisection constraints. We find that the optimal dimensionality of pipelined-channel networks is higher than that of nonpipelined-channel networks, with the difference being greater under looser wiring constraints. Their radix should remain roughly constant as network size is grown, decreasing slightly for some unidirectional tori and increasing slightly for some bidirectional meshes. Pipelined-channel networks are shown to provide lower latency and higher bandwidth than their nonpipelined-channel counterparts, especially for high-dimensional networks. The paper also investigates the effects of switching overhead and message lengths, indicating where results agree with and differ from previous results obtained for nonpipelined-channel networks View full abstract»

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  • A comparative study of topological properties of hypercubes and star graphs

    Page(s): 31 - 38
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    Undertakes a comparative study of two important interconnection network topologies: the star graph and the hypercube, from the graph theory point of view. Topological properties are derived for the star graph and are compared with the corresponding properties of the hypercube. Among other results, the authors determine necessary and sufficient conditions for shortest path routing and characterize maximum-sized families of parallel paths between any two nodes of the star graph. These parallel paths are proven of minimum length within a small additive constant. They also define greedy and asymptotically balanced spanning trees to support broadcasting and personalized communication on the star graph. These results confirm the already claimed topological superiority of the star graph over the hypercube View full abstract»

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  • Highly reliable symmetric networks

    Page(s): 94 - 97
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    We generalize directed loop networks to loop-symmetric networks in which there are N nodes and in which each node has in-degree and out-degree k, subject to the condition that 2k does not exceed N. We show that by proper selection of links one can obtain generalized loop networks with optimal or close to optimal diameter and connectivity. The optimized diameter is less than k[N1k/], where [x] indicates the ceiling of x. We also show that these networks are rather compact in that the diameter is not more than twice the average distance. Roughly 1/2(k-1)N1k/ nodes can be removed such that the network of remaining nodes is still strongly connected, if all remaining nodes have at least one incoming and one outgoing link left View full abstract»

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  • Voting as the optimal static pessimistic scheme for managing replicated data

    Page(s): 64 - 73
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    This paper investigates the problem of finding an optimal static pessimistic replica control scheme. It has been widely accepted that coteries (proposed by Garcia-Molina and Barbara) provide the most general framework for such schemes. We demonstrate that voting schemes, a very small subset of static pessimistic schemes, are optimal for fully connected networks with negligible link failure rates, as well as for Ethernet systems. We also show that voting is not optimal for somewhat more general systems. We propose a modification of the algorithm of Z. Tong and R.Y. Kain (1988) for computing optimal voting in operation independent case, so that it runs in linear (rather than exponential) time. Finally, we propose the first efficient algorithm for computing the optimal vote assignment and appropriate thresholds for fully connected networks when relative frequencies of read and write operations are known. We also extend this result to Ethernet systems View full abstract»

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  • Evaluation of a parallel branch-and-bound algorithm on a class of multiprocessors

    Page(s): 74 - 86
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    We propose and evaluate a parallel “decomposite best-first” search branch-and-bound algorithm (dbs) for MIN-based multiprocessor systems. We start with a new probabilistic model to estimate the number of evaluated nodes for a serial best-first search branch-and-bound algorithm. This analysis is used in predicting the parallel algorithm speed-up. The proposed algorithm initially decomposes a problem into N subproblems, where N is the number of processors available in a multiprocessor. Afterwards, each processor executes the serial best-first search to find a local feasible solution. Local solutions are broadcasted through the network to compute the final solution. A conflict-free mapping scheme, known as the step-by-step spread, is used for subproblem distribution on the MIN. A speedup expression for the parallel algorithm is then derived using the serial best-first search node evaluation model. Our analysis considers both computation and communication overheads for providing realistic speed-up. Communication modeling is also extended for the parallel global best-first search technique. All the analytical results are validated via simulation. For large systems, when communication overhead is taken into consideration, it is observed that the parallel decomposite best-first search algorithm provides better speed-up compared to other reported schemes View full abstract»

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  • Aggressive transmissions of short messages over redundant paths

    Page(s): 102 - 109
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    Fault-tolerant computer systems have redundant paths connecting their components. Given these paths, it is possible to use aggressive techniques to reduce the average value and variability of the response time for short, critical messages. One technique is to send a copy of a packet over an alternate path before it is known whether the first copy failed or was delayed. A second technique is to split a single stream of packets over multiple paths. The authors analyze both approaches and show that they can provide significant improvements over conventional, conservative mechanisms View full abstract»

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  • Incomplete star: an incrementally scalable network based on the star graph

    Page(s): 97 - 102
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    Introduces a new interconnection network for massively parallel systems called the incomplete star graph. The authors describe unique ways of interconnecting and labeling the nodes and routing point-to-point communications within this network. In addition, they provide an analysis of a special class of incomplete star graph called C n-1 graph and obtain the diameter and average distance for this network. For the Cn-1 graph, an efficient broadcasting scheme is presented. Furthermore, it is proven that a Cn-1 with N nodes (i.e. N=m(n-1)!) is Hamiltonian if m=4 or m=3k, and k≠2 View full abstract»

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Aims & Scope

IEEE Transactions on Parallel and Distributed Systems (TPDS) is published monthly. It publishes a range of papers, comments on previously published papers, and survey articles that deal with the parallel and distributed systems research areas of current importance to our readers.

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Meet Our Editors

Editor-in-Chief
David Bader
College of Computing
Georgia Institute of Technology