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46
Automated testdata generation for exception conditions
 Software  Practice and Experience
, 2000
"... This paper presents a technique for automatically generating testdata to test exceptions. The approach is based on the application of a dynamic global optimization based search for the required testdata. The authors ’ work has focused on testdata generation for safetycritical systems. Such syste ..."
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Cited by 39 (5 self)
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This paper presents a technique for automatically generating testdata to test exceptions. The approach is based on the application of a dynamic global optimization based search for the required testdata. The authors ’ work has focused on testdata generation for safetycritical systems. Such systems must be free from anomalous and uncontrolled behaviour. Typically, it is easier to prove the absence of any exceptions than proving that the exception handling is safe. A process for integrating automated testing with exception freeness proofs is presented as a way forward for tackling the special needs of safety critical systems. The results of a number of simple casestudies are presented and show the technique to be effective. The major result shows the application of the technique to a commercial aircraft engine controller system as part of a proof of exception freeness. This illustrates how automated testing can be effectively integrated into a formal safetycritical process to reduce costs and add value. Copyright © 2000 John Wiley & Sons, Ltd. KEY WORDS: testdata generation; verification; exception conditions
Optimization of Array Accesses by Collective Loop Transformations
, 1990
"... In this paper, we investigate the problem of optimizing array accesses across a collection of loops. We demonstrate that a good solution to such a problem should be based on an optimization scheme, called collective loop transformations, that considers all loops simultaneously. In particular, loop r ..."
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Cited by 37 (2 self)
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In this paper, we investigate the problem of optimizing array accesses across a collection of loops. We demonstrate that a good solution to such a problem should be based on an optimization scheme, called collective loop transformations, that considers all loops simultaneously. In particular, loop reversal, loop interchange and loop fusion are performed collectively on a set of loop nests. The main impact of these transformations is an optimization called array contraction, that saves space and time by converting an array variable into a scalar variable or a buffer containing a small number of scalar variables. This optimization is applicable to generalpurpose highperformance architectures. For a multiprocessor architecture, array contraction is performed by executing the producer and consumer loops on separate processors, and by using a smaller buffer for the array communication. For a uniprocessor architecture, array contraction is performed by fusing the producer and consumer loop...
A Survey of Spacecraft Formation Flying Guidance and
 Control (Part II): Control,” Proceedings of the American Control Conference
, 2004
"... AbstructFormation flying is defined as a set of more than one spacecraft whose states are coupled through a common control law. This paper provides a comprehensive survey of spacecraft formation flying control (FFC), which encompasses design techniques and stability results for these coupledstate ..."
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Cited by 25 (2 self)
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AbstructFormation flying is defined as a set of more than one spacecraft whose states are coupled through a common control law. This paper provides a comprehensive survey of spacecraft formation flying control (FFC), which encompasses design techniques and stability results for these coupledstate control laws. We divide the FFC literature into five FFC architectures: (i) MultipleInput MultipleOutput, in which the formation is treated as a single multipleinput, multipleoutput plant, (ii) Leader/Follower, in which individual spacecraft controllers are connected hierarchically, (iii) Virtual Structure, in which spacecraft are treated as rigid bodies embedded in an overall virtual rigid body, (iv) Cyclic, in which individual spacecraft controllers are connected nonhierarchically, and (v) Behavioral, in which multiple controllers for achieving different (and possibly competing) objectives are combined. This survey significantly extends an overview of the FFC literature provided by Lawton, which discussed the L/F, Virtual Structure and Behavioral architectures. We also include a brief history of the formation flying literature, and discuss connections between spacecraft FFC and other multivehicle control problems in the robotics, UAV, underwater vehicle and Automated Highway System literatures. I.
Determining Task Optimal Modular Robot Assembly Configurations
 in Proceedings of the 1995 IEEE International Conference on Robotics and Automation
, 1995
"... . A "modular" robotic system consists of standardized joint and link units that can be assembled into a number of different kinematic configurations in order to meet different task requirements. Given a predetermined set of modules, this paper considers the problem of finding an "optimal" module as ..."
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Cited by 24 (4 self)
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. A "modular" robotic system consists of standardized joint and link units that can be assembled into a number of different kinematic configurations in order to meet different task requirements. Given a predetermined set of modules, this paper considers the problem of finding an "optimal" module assembly configuration for a specific task. We formulate the solution as a discrete optimization procedure. The formulation is based on an assembly incidence matrix representation of a modular assembly configuration and a general taskoriented objective function that can incorporate many realistic task criteria. Genetic algorithms (GA) are employed to solve this optimization problem, and a canonical method to represent a modular assembly in terms of genetic strings is introduced. An example involving a 3DOF manipulator configuration is presented to demonstrate the feasibility of this approach. 1. Introduction A modular reconfigurable robotic system is a collection of various subassemblies,...
On Achieving Optimized Capacity Utilization in Application Overlay Networks with Multiple Competing Sessions
 Sessions, 16th annual ACM symposium on parallelism in algorithms and architectures (SPAA ’04
, 2004
"... In this paper, we examine the problem of largevolume data dissemination via overlay networks. A natural way to maximize the throughput of an overlay multicast session is to split the traffic and feed them into multiple trees. While in singletree solutions, bandwidth of leaf nodes may remain larg ..."
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Cited by 18 (3 self)
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In this paper, we examine the problem of largevolume data dissemination via overlay networks. A natural way to maximize the throughput of an overlay multicast session is to split the traffic and feed them into multiple trees. While in singletree solutions, bandwidth of leaf nodes may remain largely underutilized, multitree solutions increase the chances for a node to contribute its bandwidth by being a relaying node in at least one of the trees. We study the following problems: (1) What is the maximum capacity multitree solutions can exploit from overlay networks? (2) When multiple sessions compete within the same network, what is the relationship of two contradictory goals: achieving fairness and maximizing overall throughput? (3) What is the impact of IP routing in achieving at constraining the optimal performance of overlay multicast? We extend the multicommodity flow model to the case of overlay data dissemination, where each commodity is associated with an overlay session, rather than the traditional sourcedestination pair. We first prove that the problem is solvable in polynomial time, then propose an #approximation algorithm, assuming that each commodity can be split in arbitrary ways. The solution to this problem establishes the theoretical upper bound of overall throughput that any multitree solution could reach. We then study the same problem with the restriction that each commodity can only be split and fed into a limited number of trees. A randomized rounding algorithm and an online treeconstruction algorithm are presented. All these algorithms are evaluated by extensive simulations.
Optimal Hierarchical Decomposition Synthesis Using Integer Programming
 PROCEEDINGS OF 22TH ASME DESIGN AUTOMATION CONFERENCE
, 1996
"... Decomposition synthesis in optimal design is the process of creating an optimal design model by selecting objectives and constraints so that it can be directly partitioned into an appropriate decomposed form. Such synthesis results are not unique since there may be many partitions that satisfy the d ..."
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Cited by 14 (10 self)
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Decomposition synthesis in optimal design is the process of creating an optimal design model by selecting objectives and constraints so that it can be directly partitioned into an appropriate decomposed form. Such synthesis results are not unique since there may be many partitions that satisfy the decomposition requirements. Introducing suitable criteria an optimal decomposition synthesis process can be defined in a manner analogous to optimal partitioning formulations. The article presents an integer programming formulation and solution techniques for synthesizing hierarchically decomposed optimal design problems. Examples for designing a pressure vessel, an automotive caliper disc brake and a speed reducer are presented. The application of the integer programming formulation in the decomposition synthesis of large systems is illustrated using an automotive powertrain design problem.
Statistical Analysis of Financial Networks
, 2005
"... Massive datasets arise in a broad spectrum of scientific, engineering and commercial applications. In many practically important cases, a massive dataset can be represented as a very large graph with certain attributes associated with its vertices and edges. Studying the structure of this graph is e ..."
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Cited by 13 (0 self)
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Massive datasets arise in a broad spectrum of scientific, engineering and commercial applications. In many practically important cases, a massive dataset can be represented as a very large graph with certain attributes associated with its vertices and edges. Studying the structure of this graph is essential for understanding the structural properties of the application it represents. Wellknown examples of applying this approach are the Internet graph, the Web graph, and the Call graph. It turns out that the degree distributions of al these graphs can be described by the powerlaw model. Here we consider another important application  a network representation of the stock market. Stock markets generate huge amounts of data, which can be used for constructing the market graph reflecting the market behavior. We conduct the statistical analysis of this graph and show that it also folliws the powerlaw model. Moreover, we detect cliques and independent sets in this graph. These special formations have a clear practical interpretation, and their analysis allows one to apply a new data mining technique of classifying financial instruments based on stock prices data, which provides a deeper insight into the internal structure of the stock market.
On the Intractability of Permuting a Block Code to Minimize Trellis Complexity
 IEEE Trans. Inform. Theory
"... An important problem in the theory and application of block code trellises is to find a coordinate permutation of a given code to minimize the trellis complexity. In this paper we show that the problem of finding a coordinate permutation that minimizes the number of vertices at a given depth in the ..."
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Cited by 12 (0 self)
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An important problem in the theory and application of block code trellises is to find a coordinate permutation of a given code to minimize the trellis complexity. In this paper we show that the problem of finding a coordinate permutation that minimizes the number of vertices at a given depth in the minimal trellis for a binary linear block code is NPcomplete. Keywords: permutation trellis complexity, NPcompleteness. I. Introduction Although the codes obtained by permuting the coordinates of a linear block code are equivalent, it is well known that the minimal trellises for these equivalent codes in general are not equivalent [17]; in particular, different coordinate permutations may yield trellises with different state complexity profiles. As J. L. Massey pointed out some time ago [2]: "the art of trellis decoding of a linear code [is] that of rearranging the order of digits in the code word to obtain a nonsystematic code for which [the trellis complexity] is as small as possibl...
A Heuristic for Ordering a Linear Block Code to Minimize Trellis State Complexity
 IN PROC. 32ND ANNUAL ALLERTON CONF. ON COMMUNICATION, CONTROL, AND COMPUTING, ALLERTON PARK, ILLINOIS
, 1994
"... An important problem in the theory and application of block code trellises is to find a coordinate permutation for a given code that minimizes the trellis state complexity. In this paper we show that the problem of minimizing a given component of the state complexity profile is NPcomplete. We descr ..."
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Cited by 10 (3 self)
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An important problem in the theory and application of block code trellises is to find a coordinate permutation for a given code that minimizes the trellis state complexity. In this paper we show that the problem of minimizing a given component of the state complexity profile is NPcomplete. We describe an algorithm, though not guaranteed to find an optimal coordinate ordering, uses a heuristic descent technique to find "good" solutions to the problem. We have applied this algorithm to various codes, and our results are tabulated.