ppxscal/embedding_network huggingface dataset:
Inexact SQP Interior Point Methods and Large Scale Optimal Control Problems
Authors: F. Leibfritz, E. W. Sachs
Venue: SIAM Journal on Control and Optimization (1999)

Optimal control problems with partial differential equations lead to large scale nonlinear optimization problems with constraints. An efficient solver which takes into account the structure and also the size of the problem is an inexact sequential quadratic programming method where the quadratic problems are solved iteratively. Based on a reformulation as a mixed nonlinear complementarity problem we give a measure of when to terminate the iterative quadratic program solver. For the latter we use an interior point algorithm. Under standard assumptions, local linear, superlinear, and quadratic convergence can be proved. The numerical application is an optimal control problem from nonlinear heat conduction.
Design and Implementation of an SNMPv2 Management System for MS-DOS&ndash;Novell NetWare and Unix-TCP&ndash;IP
Authors: Ahmed G. H. Patel, Stephen B. J. Morris
Venue: International Journal of Network Management (1997)

SNMPv2 management tools for networks based on Novell NetWare and TCP&ndash;IP facilitate management of individual network workstations which allows a very detailed description of the network operation to be constructed. Using this, management can then be achieved across both the full range of NetWare workstation software versions and Unix&hyphen;TCP&sol;IP nodes. &copy; 1997 John Wiley Sons, Ltd.
Experience with an automatically assessed course
Authors: John English, Phil Siviter
Venue: ACM SIGCSE Bulletin (2000)

This paper describes our experiences of developing and running an introductory module for first year Computing undergraduates. The 'Supporting Technologies' module is intended to equip students with basic computing skills that they will need for the rest of their course. A novel feature of the work discussed here is that several different automated assessment tools and techniques are integrated into a common framework sharing a common results database. This allows a wide range of different assessment formats within the same module framework.
Constructing Approximate Shortest Path Maps in Three Dimensions
Authors: Sariel Har-Peled
Venue: SIAM Journal on Computing (1999)

We present a new technique for constructing a data structure that approximates shortest path maps in $\Re^d$. By applying this technique, we get the following two results on approximate shortest path maps in $\Re^3$.(i) Given a polyhedral surface or a convex polytope $\P$ with n edges in $\Re^3$, a source point s on $\P$, and a real parameter $0 t on $\P$, one can compute, in $O(\log{(n/\eps)})$ time, a distance $\Delta_{\P,s}(t)$, such that $d_{\P,s}(t) \leq \Delta_{\P,s}(t) \leq (1 + \eps)d_{\P,s}(t)$, where $d_{\P,s}(t)$ is the length of a shortest path between s and t on $\P$. The map can be computed in $O(n^2 \log{n} + (n/\eps) \log{(1/\eps)} \log{(n/\eps)})$ time, for the case of a polyhedral surface, and in $O((n/\eps^3) \log ( 1/\eps ) + (n/\eps^{1.5}) \log{(1/\eps)} \log{n})$ time if $\P$ is a convex polytope. (ii) Given a set of polyhedral obstacles $\O$ with a total of n edges in $\Re^3$, a source point {\it s} in $\Re^3 {\rm \setminus \inter} \cup\scriptstyle{_{O \in \O}} O$, and a real parameter $0
Mathematical Morphology Based on Linear Combined MetricSpaces on Z2 (Part I): Fast Distance Transforms
Authors: J. L. Díaz De León S., J. H. Sossa-Azuela
Venue: Journal of Mathematical Imaging and Vision (2000)

Mathematical Morphology (MM) is a general method for image processing based on set theory. The two basic morphological operators are dilation and erosion. From these, several non linear filters have been developed usually with polynomial complexity, and this because the two basic operators depend strongly on the definition of the structural element. Most efforts to improve the algorithm's speed for each operator are based on structural element decomposition and/or efficient codification.A new framework and a theoretical basis toward the construction of fast morphological operators (of zero complexity) for an infinite (countable) family of regular metric spaces are presented in work. The framework is completely defined by the three axioms of metric. The theoretical basis here developed points out properties of some metric spaces and relationships between metric spaces in the same family, just in terms of the properties of the four basic metrics stated in this work. Concepts such as bounds, neighborhoods and contours are also related by the same framework.The presented results, are general in the sense that they cover the most commonly used metrics such as the chamfer, the city block and the chess board metrics. Generalizations and new results related with distances and distance transforms, which in turn are used to develop the morphologic operations in constant time, in contrast with the polynomial time algorithms are also given.
On the Optimal Value of the Spectral Abscissa for a System of Linear Oscillators
Authors: Pedro Freitas, Peter Lancaster
Venue: SIAM Journal on Matrix Analysis and Applications (1999)

We consider the linear system of differential equations Au''(t)+Bu'(t) +Cu(t)=0, where A,B, and C are n x n real symmetric matrices, and study the problem of, given A and C, finding B which optimizes the asymptotic rate of decay of solutions of this equation. The optimal value for this rate of decay is found and we show that it is attained within this class of matrices. We then study some of the properties of optimal matrices. In particular, we show that the solution is not unique in general and that optimal matrices do not have to be positive definite. A sufficient condition for all optimal matrices to be positive definite is given and some examples are discussed.
Improving on-line assessment: an investigation of existing marking methodologies
Authors: Jon A. Preston, Russell Shackelford
Venue: ACM SIGCSE Bulletin (1999)

We are in the process of developing an on-line marking system for use in our large-scale CS1 and CS2 courses. To better accommodate the needs of our numerous raters, we investigated their current methodologies in marking students' work; this paper presents our findings from recording "think out loud" marking sessions and surveys. A prototype for an on-line assessment software tool is described; this tool allows markers to view students' work at various degrees of detail ranging from complete, low-level to "meta-level." We believe such a system is beneficial for improving the marking process in large-scale and distance classes.
Edge Residuals Dominate A Posteriori Error Estimates for Low Order Finite Element Methods
Authors: Carsten Carstensen, Rüdiger Verfürth
Venue: SIAM Journal on Numerical Analysis (1999)

We prove that, up to higher order perturbation terms, edge residuals yield global upper and local lower bounds on the error of linear finite element methods both in H1- and L2-norms. We present two proofs: one uses the standard L2-projection and the other relies on a new, weighted Clément-type interpolation operator.
Remark on Algorithm 751
Authors: Robert J. Renka
Venue: ACM Transactions on Mathematical Software (TOMS) (1999)

The triangulation package TRIPACK has been revised to run more efficiently and to eliminate some potential errors. Also, a portable triangulation plotting routine was added.
Stability Implications of Bendixson's Criterion
Authors: C. Connell McCluskey, James S. Muldowney
Venue: SIAM Review (1998)

This note presents a proof that the omega limit set of a solution to a planar system satisfying the Bendixson criterion is either empty or is a single equilibrium. The proof involves elementary techniques which should be accessible to senior undergraduates and graduate students.
Improved Approximation Guarantees for Packing and Covering Integer Programs
Authors: Aravind Srinivasan
Venue: SIAM Journal on Computing (1999)

Several important NP-hard combinatorial optimization problems can be posed as packing/covering integer programs; the randomized rounding technique of Raghavan and Thompson is a powerful tool with which to approximate them well. We present one elementary unifying property of all these integer linear programs and use the FKG correlation inequality to derive an improved analysis of randomized rounding on them. This yields a pessimistic estimator, thus presenting deterministic polynomial-time algorithms for them with approximation guarantees that are significantly better than those known.
Finding replicated Web collections
Authors: Junghoo Cho, Narayanan Shivakumar, Hector Garcia-Molina
Venue: ACM SIGMOD Record (2000)

Many web documents (such as JAVA FAQs) are being replicated on the Internet. Often entire document collections (such as hyperlinked Linux manuals) are being replicated many times. In this paper, we make the case for identifying replicated documents and collections to improve web crawlers, archivers, and ranking functions used in search engines. The paper describes how to efficiently identify replicated documents and hyperlinked document collections. The challenge is to identify these replicas from an input data set of several tens of millions of web pages and several hundreds of gigabytes of textual data. We also present two real-life case studies where we used replication information to improve a crawler and a search engine. We report these results for a data set of 25 million web pages (about 150 gigabytes of HTML data) crawled from the web.
A Stable and Efficient Algorithm for the Indefinite Linear Least-Squares Problem
Authors: S. Chandrasekaran, M. Gu, A. H. Sayed
Venue: SIAM Journal on Matrix Analysis and Applications (1999)

We develop an algorithm for the solution of indefinite least-squares problems. Such problems arise in robust estimation, filtering, and control, and numerically stable solutions have been lacking. The algorithm developed herein involves the QR factorization of the coefficient matrix and is provably numerically stable.
The effect of communication modality on cooperation in online environments
Authors: Carlos Jensen, Shelly D. Farnham, Steven M. Drucker, Peter Kollock
Venue: Proceedings of the SIGCHI conference on Human factors in computing systems (2000)

One of the most robust findings in the sociological literature is the positive effect of communication on cooperation and trust. When individuals are able to communicate, cooperation increases significantly. How does the choice of communication modality influence this effect? We adapt the social dilemma research paradigm to quantitatively analyze different modes of communication. Using this method, we compare four forms of communication: no communication, text-chat, text-to-speech, and voice. We found statistically significant differences between different forms of communication, with the voice condition resulting in the highest levels of cooperation. Our results highlight the importance of striving towards the use of more immediate forms of communication in online environments, especially where trust and cooperation are essential. In addition, our research demonstrates the applicability of the social dilemma paradigm in testing the extent to which communication modalities promote the development of trust and cooperation.
AMVA techniques for high service time variability
Authors: Derek L. Eager, Daniel J. Sorin, Mary K. Vernon
Venue: Proceedings of the 2000 ACM SIGMETRICS international conference on Measurement and modeling of computer systems (2000)

Motivated by experience gained during the validation of a recent Approximate Mean Value Analysis (AMVA) model of modern shared memory architectures, this paper re-examines the &ldquo;standard&rdquo; AMVA approximation for non-exponential FCFS queues. We find that this approximation is often inaccurate for FCFS queues with high service time variability. For such queues, we propose and evaluate: (1) AMVA estimates of the mean residual service time at an arrival instant that are much more accurate than the standard AMVA estimate, (2) a new AMVA technique that provides a much more accurate estimate of mean center residence time than the standard AMVA estimate, and (3) a new AMVA technique for computing the mean residence time at a &ldquo;downstream&rdquo; queue which has a more bursty arrival process than is assumed in the standard AMVA equations. Together, these new techniques increase the range of applications to which AMVA may be fruitfully applied, so that for example, the memory system architecture of shared memory systems with complex modern processors can be analyzed with these computationally efficient methods.
WALRUS: a similarity retrieval algorithm for image databases
Authors: Apostol Natsev, Rajeev Rastogi, Kyuseok Shim
Venue: ACM SIGMOD Record (1999)

Traditional approaches for content-based image querying typically compute a single signature for each image based on color histograms, texture, wavelet tranforms etc., and return as the query result, images whose signatures are closest to the signature of the query image. Therefore, most traditional methods break down when images contain similar objects that are scaled differently or at different locations, or only certain regions of the image match. In this paper, we propose WALRUS (WAveLet-based Retrieval of User-specified Scenes), a novel similarity retrieval algorithm that is robust to scaling and translation of objects within an image. WALRUS employs a novel similarity model in which each image is first decomposed into its regions, and the similarity measure between a pair of images is then defined to be the fraction of the area of the two images covered by matching regions from the images. In order to extract regions for an image, WALRUS considers sliding windows of varying sizes and then clusters them based on the proximity of their signatures. An efficient dynamic programming algorithm is used to compute wavelet-based signatures for the sliding windows. Experimental results on real-life data sets corroborate the effectiveness of WALRUS's similarity model that performs similarity matching at a region rather than an image granularity.
Nonlinear Modeling of Scattered Multivariate Data and Its Application to Shape Change
Authors: Bernard Chalmond, Stéphane C. Girard
Venue: IEEE Transactions on Pattern Analysis and Machine Intelligence (1999)

We are given a set of points in a space of high dimension. For instance, this set may represent many visual appearances of an object, a face, or a hand. We address the problem of approximating this set by a manifold in order to have a compact representation of the object appearance. When the scattering of this set is approximately an ellipsoid, then the problem has a well-known solution given by Principal Components Analysis (PCA). However, in some situations like object displacement learning or face learning, this linear technique may be ill-adapted and nonlinear approximation has to be introduced. The method we propose can be seen as a Non Linear PCA (NLPCA), the main difficulty being that the data are not ordered. We propose an index which favors the choice of axes preserving the closest point neighborhoods. These axes determine an order for visiting all the points when smoothing. Finally, a new criterion, called "generalization error," is introduced to determine the smoothing rate, that is, the knot number for the spline fitting. Experimental results conclude this paper: The method is tested on artificial data and on two data bases used in visual learning.
Solving Ill-Conditioned and Singular Linear Systems: A Tutorial on Regularization
Authors: Arnold Neumaier
Venue: SIAM Review (1998)

It is shown that the basic regularization procedures for finding meaningful approximate solutions of ill-conditioned or singular linear systems can be phrased and analyzed in terms of classical linear algebra that can be taught in any numerical analysis course. Apart from rewriting many known results in a more elementary form, we also derive a new two-parameter family of merit functions for the determination of the regularization parameter. The traditional merit functions from generalized cross validation (GCV) and generalized maximum likelihood (GML) are recovered as special cases.
On the Effects of Downstream Entry
Authors: Alfred A. Marcus, Mary L. Nichols, Rajeev K. Tyagi
Venue: Management Science (1999)

We study the effects of entry in a downstream market where firms (e.g., Compaq and IBM; CVS and Safeway) buy an input (e.g., microprocessor, grocery items) from an upstream supplier (e.g., Intel, Procter & Gamble) and sell their output to consumers. We show demand conditions where, contrary to conventional wisdom, entry of a new downstream firm lowers the downstream-market output and increases the consumer price. Thus consumers may be better off with fewer sellers in such markets. We also show that this entry may cause the profit of each incumbent downstream firm to: (i) remain unchanged; (ii) decrease; or (iii) even increase. Also, for a class of widely used demand conditions, the supplier's optimal price is shown invariant to the entry/exit of its downstream buyer firms. We classify all possible effects of downstream entry in terms of fundamental market demand conditions.
Constraining Plane Configurations in Computer-Aided Design: Combinatorics of Directions and Lengths
Authors: Brigitte Servatius, Walter Whiteley
Venue: SIAM Journal on Discrete Mathematics (1999)

Configurations of points in the plane constrained by directions only or by lengths alone lead to equivalent theories known as parallel drawings and infinitesimal rigidity of plane frameworks. We combine these two theories by introducing a new matroid on the edge set of the complete graph with doubled edges to describe the combinatorial properties of direction-length designs.
Evaluating the use of a geographic digital library in undergraduate classrooms: ADEPT
Authors: Gregory H. Leazer, Anne J. Gilliland-Swetland, Christine L. Borgman
Venue: Proceedings of the fifth ACM conference on Digital libraries (2000)

The evaluation plan for the Alexandria Digital Earth Prototype (ADEPT) centers on two investigations: a study of classroom use of the system by faculty and students and lab-based usability studies. The classroom-based study is primarily an investigation of the digital library's impact on student learning, using multiple research methods. The five-year work plan includes investigations of the use of ADEPT in non-geography classes.
Interactive 3D sound hyperstories for blind children
Authors: Maruricio Lumbreras, Jaime Sánchez
Venue: Proceedings of the SIGCHI conference on Human factors in computing systems: the CHI is the limit (1999)

Interactive software is currently used for learning and entertainment purposes. This type of software is not very common among blind children because most computer games and electronic toys do not have appropriate interfaces to be accessible without visual cues. This study introduces the idea of interactive hyperstories carried out in a 3D acoustic virtual world for blind children. We have conceptualized a model to design hyperstories. Through AudioDoom we have an application that enables testing cognitive tasks with blind children. The main research question underlying this work explores how audio- based entertainment and spatial sound navigable experiences can create cognitive spatial structures in the minds of blind children. AudioDoom presents first person experiences through exploration of interactive virtual worlds by using only 3D aural representations of the space.
A Low Overhead Logging Scheme for Fast Recovery in Distributed Shared Memory Systems
Authors: Taesoon Park, Heon Y. Yeom
Venue: The Journal of Supercomputing (2000)

This paper presents an efficient, writer-based logging scheme for recoverable distributed shared memory systems, in which logging of a data item is performed by its writer process, instead of every process that accesses the item logging it. Since the writer process maintains the log of data items, volatile storage can be used for logging. Only the readers' access information needs to be logged into the stable storage of the writer process to tolerate multiple failures. Moreover, to reduce the frequency of stable logging, only the data items accessed by multiple processes are logged with their access information when the items are invalidated, and also semantic-based optimization in logging is considered. Compared with the earlier schemes in which stable logging was performed whenever a new data item was accessed or written by a process, the size of the log and the logging frequency can be significantly reduced in the proposed scheme.
Optimal schedules for data-parallel cycle-stealing in networks of workstations (extended abstract)
Authors: Arnold L. Rosenberg
Venue: Proceedings of the twelfth annual ACM symposium on Parallel algorithms and architectures (2000)

We refine the model underlying our prior work on scheduling cycle-stealing opportunities in NOWs [5, 16], obtaining a model wherein the scheduling guidelines of [16] produce optimal schedules for every such opportunity. Although computing optimal schedules usually requires the use of general (often inefficient) function-optimizing methods, we show how to compute optimal schedules efficiently for the broad class of opportunities whose durations come from a concave probability distribution. Even when no such efficient computation of an optimal schedule is available, our refined model always suggests a natural notion of approximately optimal schedule, which may be efficiently computable. We illustrate such efficient approximability via the important class of cycle-stealing opportunities whose durations come from a heavy-tailed distribution. Such opportunities do not admit any optimal schedule&mdash;nor even a natural notion of approximately optimal schedule&mdash;within the model of [5, 16]. Within our refined model, though, we derive computationally simple schedules for heavy-tailed opportunities, which can be &ldquo;tuned&rdquo; to have expected work-output that is arbitrarily close to optimal.
Reduction Techniques for Instance-BasedLearning Algorithms
Authors: D. Randall Wilson, Tony R. Martinez
Venue: Machine Learning (2000)

Instance-based learning algorithms are often faced with the problem of deciding which instances to store for use during generalization. Storing too many instances can result in large memory requirements and slow execution speed, and can cause an oversensitivity to noise. This paper has two main purposes. First, it provides a survey of existing algorithms used to reduce storage requirements in instance-based learning algorithms and other exemplar-based algorithms. Second, it proposes six additional reduction algorithms called DROP1&ndash;DROP5 and DEL (three of which were first described in Wilson Martinez, 1997c, as RT1&ndash;RT3) that can be used to remove instances from the concept description. These algorithms and 10 algorithms from the survey are compared on 31 classification tasks. Of those algorithms that provide substantial storage reduction, the DROP algorithms have the highest average generalization accuracy in these experiments, especially in the presence of uniform class noise.
Thiele Rational Interpolation for the Numerical Computation of the Reversible Randles&ndash;Sevcik Function in Electrochemistry
Authors: Frank G. Lether
Venue: Journal of Scientific Computing (1999)

This paper uses Thiele rational interpolation to derive a simple method for computing the Randles&ndash;Sevcik function &pi;1/2&chi;(x), with relative error at most 1.9 &times; 10&minus;5 for &minus;&infin; < x < &infin;. We develop a piecewise approximation method for the numerical computation of &pi;1/2&chi;(x) on the union (&minus;&infin;, &minus;10) &cup; &lsqb;&minus;10, 10&rsqb; &cup; (10, &infin;). This approximation is particularly convenient to employ in electrochemical applications where four significant digits of accuracy are usually sufficient. Although this paper is primarily concerned with the approximation of the Randles&ndash;Sevcik function, some examples are included that illustrate how Thiele rational interpolation can be employed to generate useful approximations to other functions of interest in scientific work.