45853491
Testing Finite-State Machines: State Identification and Verification
We study the complexity of two fundamental problems in the testing of finite-state machines. 1) Distinguishing sequences (state identification). We show that it is PSPACE-complete to determine whether a finite-state machine has a preset distinguishing sequence. There are machines that have distinguishing sequences, but only of exponential length. We give a polynomial time algorithm that determines whether a finite-state machine has an adaptive distinguishing sequence. (The previous classical algorithms take exponential time.) Furthermore, if there is an adaptive distinguishing sequence, then we give an efficient algorithm that constructs such a sequence of length at most n(n/spl minus/1)/2 (which is the best possible), where n is the number of states. 2) Unique input output sequences (state verification). It is PSPACE-complete to determine whether a state of a machine has a unique input output sequence. There are machines whose states have unique input output sequences but only of exponential length. >
206832588
Optimization problems from feature testing of communication protocols
In feature testing of communication protocols, we want to construct a minimal number of tests with a desirable fault coverage. We model the protocols by extended finite state machines and reduce the test generation process to optimization problems on graphs. We study efficient algorithms and their complexity. We report experimental results on real systems, including Personal HandyPhone System, a 5ESS based ISDN wireless system, and 5ESS Intelligent Network Application Protocol.
46374921
A Formal Specification of the ATM ABR Rate Control Scheme
Abstract Formal specifications are indispensable for computer-aided validation, verification, and testing of communication protocols. However, a large number of practical protocols, including those for ATM, have only informal English specifications. A formal specification helps in achieving a consistent interpretation and thus increases the likelihood of interoperable implementations. As a case study, we consider an important protocol — ATM's Available Bit Rate (ABR) service specification. The ABR source/destination policies have been specified using an English description in the main body of the ATM Forum's draft Traffic Management specification, from which it is hard to conduct a formal analysis. It must be noted however that considerable energy has been spent in providing a reasonably precise specification, while allowing for appropriate implementation latitude. However, an English description still has the potential for different interpretations, which may lead to discrepancy in different vendors' implementations and cause serious problems in interoperability of the communication entities made by different manufacturers. We model the ABR protocols by parameterized communicating extended finite state machines with timers, which is often called a transition system. The protocol is formally specified by the specification of the transitions of the system. We also provide insights gained in the derivation of the formal specification. Furthermore, we introduce a scheduler, involved in transmitting queued cells at the allowed cell rate to meet the minimal requirements from the source/destination protocols. We present the transitions for the source/destination/scheduler machines primarily for transmitting in-rate cells.
206418940
Residual Analysis for Feature Detection
It is shown that in a very simple form residual analysis achieves results that are at least as good as if not better than those obtained by other techniques. There are many ways for extensions of the method. For example, moving average filters of regularization can be used to obtain the residual images. Also, the strength of the correlation, measured by D/sub rr/(O), can be used to eliminate noise, weak edges, etc. A more ambitious extension is by considering smoothing filters that leave invariant the function representing the reflectance from smooth surfaces. >
11856887
Approximation of linear functionals on a banach space with a Gaussian measure
Abstract We study approximation of linear functionals on separable Banach spaces equipped with a Gaussian measure. We study optimal information and optimal algorithms in average case, probabilistic, and asymptotic settings, for a general error criterion. We prove that adaptive information is not more powerful than nonadaptive information and that μ-spline algorithms, which are linear, are optimal in all three settings. Some of these results hold for approximation of linear operators. We specialize our results to the space of functions with continuous r th derivatives, equipped with a Wiener measure. In particular, we show that the natural splines of degree 2 r + I yield the optimal algorithms. We apply the general results to the problem of integration.
19220261
Path protection and blocking probability minimization in optical networks
We study the problem of shared path protection in optical networks from the viewpoint of blocking probability minimization. Unlike the worst-case approach common in other studies, which typically deals with one failure at a time and requires recomputation of the protection paths after every failure, our framework assumes a fixed path protection strategy for every connection that does not change in response to failures in other connections, which is more realistic for networks with high failure rates. We study backup-path strategy configurations that minimize the blocking probability and derive various properties. We show that configurations which do not have partial overlaps among connections backup paths are optimal in a rather general sense. We discuss the minmax optimal configuration properties and present an efficient algorithm for finding it in a case of special interest, while showing it to be NP-hard in general. In addition, we discuss the properties of the game resulting if each connection chooses its backup path selfishly; we show it to belong to the class of potential games, well-studied in the game theory literature, and derive several further properties resulting from its specific structure.
14664253
A Bit-Width Optimization Methodology for Polynomial-Based Function Evaluation
We present an automated bit-width optimization methodology for polynomial-based hardware function evaluation. Due to the analytical nature of the approach, overflow protection and precision accurate to one unit in the last place (ulp) can be guaranteed. A range analysis technique based on computing the root of the derivative of a signal is utilized to determine the minimal number of integer bits. Fractional bit requirements are established using an analytical error expression derived from the functions that occur along the data path. Global fractional bit optimization across multiple computation stages is performed using simulated annealing and circuit area estimation functions
41830429
An Optimal Algorithm for Roundness Determination on Convex Polygons
Abstract In tolerancing, the Out-Of-Roundness factor determines the relative circularity of planar shapes. The measurement of concern in this work is the Minimum Radial Separation, as recommended by the American National Standards Institute (ANSI). Here we show that the algorithm given in Le and Lee [6] runs in θ ( n 2 ) time even for convex polygons. Furthermore, we present an optimal O ( n ) time algorithm to compute the Minimum Radial Separation of convex polygons, which represents not only a factor n improvement over the previously best known algorithm, but also a factor of log n improvement over Le and Lee's conjectured complexity for the problem.
12459424
The Min-Max Voronoi Diagram of Polygons and Applications in VLSI Manufacturing
We study the min-max Voronoi diagram of a set S of polygonal objects, a generalization of Voronoi diagrams based on the maximum distance between a point and a polygon. We show that the min-max Voronoi diagram is equivalent to the Voronoi diagram under the Hausdorff distance function. We investigate the combinatorial properties of this diagram and give improved combinatorial bounds and algorithms. As a byproduct we introduce the min-max hull which relates to the min-max Voronoi diagram in the way a convex hull relates to the ordinary Voronoi diagram.
17062756
Toward alternative measures for ranking venues: a case of database research community
Ranking of publication venues is often closely related with important issues such as evaluating the contributions of individual scholars/research groups, or subscription decision making. The development of large-scale digital libraries and the availability of various meta data provide the possibility of building new measures more efficiently and accurately. In this work, we propose two novel measures for ranking the impacts of academic venues an easy-to-implement seed-based measure that does not use citation analysis, and a realistic browsing-based measure that takes an article reader's behavior into account. Both measures are computationally efficient yet mimic the results of the widely accepted Impact Factor. In particular, our proposal exploits the fact that: (1)in most disciplines, there are "top" venues that most people agree on; and (2) articles that appeared in good venues are more likely to be viewed by readers. Our proposed measures are extensively evaluated on a test case of the Database research community using two real bibliography data sets - ACM and DBLP. Finally, ranks of venues by our proposed measures are compared against the Impact Factor using the Spearman's rank correlation coefficient, and their positive rank order relationship is proved with a statistical significance test.
15124242
Solving the all-pair shortest path query problem on interval and circular-arc graphs
In this paper, we study the following all-pair shortest path query problem: Given the interval model of an unweighted interval graph of n vertices, build a data structure such that each query on the shortest path (or its length) between any pair of vertices of the graph can be processed eeciently (both sequentially and in parallel). We show that, after sorting the input intervals by their endpoints, a data structure can be constructed sequentially in O(n) time and O(n) space; using this data structure, each query on the length of the shortest path between any two intervals can be answered in O(1) time, and each query on the actual shortest path can be answered in O(k) time, where k is the number of intervals on that path. Furthermore, this data structure can be constructed optimally in parallel, in O(log n) time using O(n= log n) CREW PRAM processors; each query on the actual shortest path can be answered in O(1) time using k processors. Our techniques can be extended to solving the all-pair shortest path query problem on circular-arc graphs, both sequentially and in parallel, in the same complexity bounds. As an immediate consequence of our results, we improve by a factor of n the space complexity of the previously best known sequential all-pair shortest path algorithm for unweighted interval graphs.