9086045
The distributed program reliability analysis on star topologies
We show that computing distributed program reliability on the star distributed computing system is NP-hard. We develop a polynomially solvable case to compute distributed program reliability when some additional file distribution is restricted on the star topology. We also propose a polynomial time algorithm for computing distributed program reliability with an approximate solution when the star topology is not satisfied with the additional file distribution.
45057698
The distributed program reliability analysis on star topologies
Abstract A distributed computing system consists of processing elements, communication links, memory units, data files, and programs. These resources are interconnected via a communication network and controlled by a distributed operating system. The distributed program reliability in a distributed computing system is the probability that a program which runs on multiple processing elements and needs to retrieve data files from other processing elements will be executed successfully. This reliability varies according to (1) the topology of the distributed computing system, (2) the reliability of the communication edges, (3) the data files and programs distribution among processing elements, and (4) the data files required to execute a program. In this paper, we show that computing the distributed program reliability on the star distributed computing systems is NP-hard. We also develop an efficiently solvable case to compute distributed program reliability when some additional file distribution is restricted on the star topology. Scope and purpose Recent advances in VLSI circuitry have a tremendous impact on the price-performance revolution in microelectronics. This development has led to an increased use of workstations connected in the form of a powerful distributed computing system. Potential benefits offered by such distributed computing systems include better cost performance, enhanced fault tolerance, increased system throughput, and efficient sharing of resources. Distributed program reliability is an important measure that should be examined for designing a high fault-tolerance distributed computing system. This reliability varies according to (1) the topology of the distributed computing system, (2) the reliability of the communication edges, (3) the data files and programs distribution among processing elements, and (4) the data files required to execute a program. This article is concerned with the analysis of distributed program reliability on star distributed computing systems.
5909240
The Computational Complexity of the Reliability Problem on Distributed Systems
Abstract The reliability of a distributed program in a distributed computing system is the probability that a program which runs on multiple processing elements and needs to communicate with other processing elements for remote data files will be executed successfully. This reliability varies according to 1. (1) the topology of the distributed computing system 2. (2) the reliability of the communication links 3. (3) the data files and program distribution among processing elements and 4. (4) the data files required to execute a program. This paper shows that solving this reliability problem is NP-hard even when the distributed computing system is restricted to a series-parallel, a 2-tree, a tree, or a star structure.
205481590
Fast and simple algorithms to count the number of vertex covers in an interval graph
This study provides the following fast and simple algorithms for an interval graph: (1) an algorithm for counting the number of vertex covers, and (2) an algorithm for counting the number of minimal vertex covers.
50312
The distributed program reliability analysis on ring-type topologies
Abstract Distributed computing system (DCS) has become very popular for its high fault-tolerance, potential for parallel processing, and better reliability performance. One of the important issues in the design of the DCS is the reliability performance. Distributed program reliability (DPR) is addressed to obtain this reliability measure. In this paper, we propose a polynomial-time algorithm for computing the DPR of ring topology and show that solving the DPR problem on a ring of trees topology is NP-hard. Scope and purpose The widespread use of distributed computing system is due to the price–performance revolution in microelectronics, the development of cost-effective and efficient communication subsets, the development of resource sharing software, and the increased user demands for communication, economical sharing of resources, and productivity. This article is concerned with the analysis of distributed program reliability on a ring-distributed computing system. The distributed program reliability is a useful measure for reliability evaluation of distributed computing system. The distributed program reliability analyses also give a good index for designing a high-reliability-performance-distributed computing system.
14607261
Efficient and accurate interference detection for polynomial deformation
We present efficient and accurate algorithms for interference detection among objects undergoing polynomial deformation. The scope of our algorithms include physically-based models undergoing dynamic simulation subject to non-penetration constraints, variational models, deformable models used in soft object animation, geometric models including polygonal meshes, parametric surfaces such as Bezier patches and B-splines, and solid models defined by such surfaces. Our algorithms use axis aligned bounding boxes and convex hulls of the objects to identify the object pairs in close vicinity. They use subdivision, convex hull properties and linear programming to perform surface intersection tests and loop intersection tests. Frame-to-frame coherence is utilized to achieve incremental computations. The resulting algorithms have been implemented and work well in practice. In particular we are able to compute all contacts accurately and at interactive speeds for flexible bodies undergoing second-order polynomial deformations.
16920752
Runlength Limited Codes for Single Error-Detection and Single Error-Correction with Mixed Type Errors
Runlength limited (RLL) codes are used in magnetic recording. The error patterns that occur with peak detection magnetic recording systems when using a runlength-limited code consist of both symmetric errors and shift errors. We refer to shift errors and symmetric errors collectively as mixed type errors. A method of providing error control for mixed type errors that occur in a runlength limited code comprised of (d, k) constrained sequences is examined. The coding scheme is to choose parity blocks to insert in the constrained information sequence. The parity blocks are chosen to satisfy the constraints and to provide some error control. The cases of single error-detection and single error-correction are investigated, where the single error is allowed to be a shift error or a symmetric error. Bounds are discussed on the possible lengths for the parity blocks. It is shown that the single error-detection codes are the best possible in terms of the length of the parity blocks.
5692452
k-server optimal task scheduling problem with convex cost function
We consider a class of k-server optimal task scheduling problems partitioning and scheduling N tasks with various real-time constrains and work loads on k servers with convex task processing cost function so as to minimize the total task processing cost while still guaranteeing satisfaction of all time constraints. This class has broad expressing power for practical scheduling problems in several areas such as real-time multimedia wireless transmission , CPU energy conservation, and warehouse order processing management, et. al. Our formulation is quite general such that most previous works can be readily reduced to a special case of the presented k-server optimal task scheduling problem. We show that, when k = 1, optimal solution can be obtained in computational complexity of O(N) and the corresponding optimal scheduling problem is equivalent to finding the shortest 2D Euclidean distance between two vertices inside a well-defined 2D polygon. However, when k 2, the optimal scheduling problem can be demonstrated to be NP-hard by reducing it to a well-known NP-complete bin-packing problem. Therefore, we conclude no polynomial time algorithm exists for a general k-server optimal task scheduling problem. We then construct approximation algorithms to solve the presented k-server problem in a practical way and illustrate its performance by simulation results and analysis.
16198203
On Semantics of Reactive Rule-Based Systems
In this paper we address special issues which arise when the rule-based programming paradigm is emlployed in development of reactive real-time systems. We begin by presenting a rule-based language which has emerged while developing intelligent cruise control systems. We describe a naive operational semantics based on an an implemented inference engine, and explain why the semantics is not appropriate in safety-critical real-time contexts. We then deene a number of correct-ness criteria ensuring termination, consistency and determinism, based on a formal declarative semantics. However, the declarative semantics is non-constructive. In order to be able to build an implementation satisfying the correctness criteria, two alternative approaches are proposed. Both approaches build upon static checks of a rule-based program. In the rst approach some correctness criteria are met by accepting only stratiied programs after the static checks. In the second approach we accept programs which are correct with respect to a constructive semantics. For both approaches we present the analysis methods and soundness results with respect to the desired declarative semantics. Abstract In this paper we address special issues which arise when the rule-based programming paradigm is emlployed in development of reactive real-time systems. We begin by presenting a rule-based language which has emerged while developing intelligent cruise control systems. We describe a naive operational semantics based on an an implemented inference engine, and explain why the semantics is not appropriate in safety-critical real-time contexts. We then deene a number of correct-ness criteria ensuring termination, consistency and determinism, based on a formal declarative semantics. However, the declarative semantics is non-constructive. In order to be able to build an implementation satisfying the correctness criteria, two alternative approaches are proposed. Both approaches build upon static checks of a rule-based program. In the rst approach some correctness criteria are met by accepting only stratiied programs after the static checks. In the second approach we accept programs which are correct with respect to a constructive semantics. For both approaches we present the analysis methods and soundness results with respect to the desired declarative semantics.
2903221
Algorithms for clique-independent sets on subclasses of circular-arc graphs
A circular-arc graph is the intersection graph of arcs on a circle. A Helly circular-arc graph is a circular-arc graph admitting a model whose arcs satisfy the Helly property. A clique-independent set of a graph is a set of pairwise disjoint cliques of the graph. It is NP-hard to compute the maximum cardinality of a clique-independent set for a general graph. In the present paper, we propose polynomial time algorithms for finding the maximum cardinality and weight of a clique-independent set of a 3K2-free CA graph. Also, we apply the algorithms to the special case of an HCA graph. The complexity of the proposed algorithm for the cardinality problem in HCA graphs is O(n). This represents an improvement over the existing algorithm by Guruswami and Pandu Rangan, whose complexity is O(n2). These algorithms suppose that an HCA model of the graph is given.