ppxscal/embedding_network huggingface dataset:
Nomadic computing&mdash;an opportunity
Authors: Leonard Kleinrock
Venue: ACM SIGCOMM Computer Communication Review (1995)

We are in the midst of some truly revolutionary changes in the field of computer-communications, and these offer opportunities and challenges to the research community. One of these changes has to do with nomadic computing and communications. Nomadicity refers to the system support needed to provide a rich set of capabilities and services to the nomad as he moves from place to place in a transparent and convenient form. This new paradigm is already manifesting itself as users travel to many different locations with laptops, PDA's, cellular telephones, pagers, etc. In this paper we discuss some of the open issues that must be addressed as we bring about the system support necessary for nomadicity. In addition, we present some of the considerations with which one must be concerned in the area of wireless communications, which forms one (and only one) component of nomadicity.
A simulation modeler's view of a carousel
Authors: Edward J. Williams, Kevin A. Fosso
Venue: Proceedings of the 27th conference on Winter simulation (1995)

We describe the concept of a carousel as seen from the business-process and the system-modeler viewpoints, compare and contrast various algorithms for picking from a carousel, and discuss the simulation modeling logic of one such algorithm in detail. The results and conclusions from simulations of two carousel systems are presented. First, we present an introductory overview of a simulation study motivating a detailed examination of carousels. Next, we define a carousel and present an overview of the picking operation relative to a carousel. We then describe four algorithms for picking and discuss in detail the representation of these algorithms within simulation models, followed by a presentation of results from such simulations. In conclusion, we summarize carousel-configuration and picking algorithm conclusions.
An algorithm for the multiplication of symmetric polynomials
Authors: John S. Garavelli
Venue: ACM Transactions on Mathematical Software (TOMS) (1988)

Although the cycle index polynomial for a permutation group can often be easily determined, expansion of the figure counting series in a Po&acute;lya enumeration presents computational difficulties for object sets with higher degrees of symmetry and more than modest size. An algorithm that does not require algebraic symbol manipulation is derived for multiplying symmetric polynomials represented by partitions. Because the repetitive identification and collection of common terms are eliminated and storage requirements reduced, this algorithm is useful in rapidly expanding the figure counting series in such Po&acute;lya enumeration problems as the counting of chemical isomers.
The University of California CD-ROM Information System
Authors: Deane Merrill, Nathan Parker, Fredric Gey, Chris Stuber
Venue: Communications of the ACM (1995)

The University of California CD-ROM Information System replaces the equivalent of 260,000 books of published federal statistics with a CD-ROM-based online information system. The size of this database is currently 270 CD-ROMs (135GB). It contains 1990 U.S. census data (approximately 3,000 items of socio-economic and demographic information, including race-ethnicity, employment, income, educational level, and poverty) for every block and census tract in the U.S., as well as U.S. foreign trade data by commodity from every city in the U.S. to every country in the world. It also contains the digitized map outline boundary data for city blocks for the entire U.S. (census TIGER files).
Computer simulation: achieving credible experimental results in virtual environments
Authors: Richard E. Nance, C. Michael Overstreet
Venue: ACM SIGSIM Simulation Digest (1995)

"Computer simulation" is a broadly used term that can take on different meanings depending often on the disciplinary context. Within statistics the term is applied to repetitive sampling, described in more specific terms as "Monte Carlo simulation." Those working with computational solutions of numerical systems, typically modeling fluid flow or ballistics, use the term in place of the more specific "continuous simulation." While those modeling queueing or inventory problems in computer science, operations research or management science, use the term in place of the more accurate descriptor "discrete event simulation." This third substitution has become more prevalent; because the problem domains addressed have emerged as the most prominent. That is not to say that no meaningful work is on-going in the other disciplinary areas; rather the other two identified more readily with disciplinary areas, have profited from their ready recognition as belonging to statistics or applied mathematics.
Message passing versus distributed shared memory on networks of workstations
Authors: Honghui Lu, Sandhya Dwarkadas, Alan L. Cox, Willy Zwaenepoel
Venue: Proceedings of the 1995 ACM/IEEE conference on Supercomputing (CDROM) (1995)

The message passing programs are executed with the Parallel Virtual Machine (PVM) library and the shared memory programs are executed using TreadMarks. The programs are Water and Barnes-Hut from the SPLASH benchmark suite; 3-D FFT, Integer Sort (IS) and Embarrassingly Parallel (EP) from the NAS benchmarks; ILINK, a widely used genetic linkage analysis program; and Successive Over-Relaxation (SOR), Traveling Salesman (TSP), and Quicksort (QSORT). Two different input data sets were used for Water (Water-288 and Water-1728), IS (IS-Small and IS-Large), and SOR (SOR-Zero and SOR-NonZero). Our execution environment is a set of eight HP735 workstations connected by a 100Mbits per second FDDI network. For Water-1728, EP, ILINK, SOR-Zero, and SOR-NonZero, the performance of TreadMarks is within 10%of PVM. For IS-Small, Water-288, Barnes-Hut, 3-D FFT, TSP, and QSORT, differences are on the order of 10%to 30%. Finally, for IS-Large, PVM performs two times better than TreadMarks. More messages and more data are sent in TreadMarks, explaining the performance differences. This extra communication is caused by 1) the separation of synchronization and data transfer, 2) extra messages to request updates for data by the invalidate protocol used in TreadMarks, 3) false sharing, and 4) diff accumulation for migratory data in TreadMarks.
Designing programs that check their work
Authors: Manuel Blum, Sampath Kannan
Venue: Journal of the ACM (JACM) (1995)

A program correctness checker is an algorithm for checking the output of a computation. That is, given a program and an instance on which the program is run, the checker certifies whether the output of the program on that instance is correct. This paper defines the concept of a program checker. It designs program checkers for a few specific and carefully chosen problems in the class FP of functions computable in polynomial time. Problems in FP for which checkers are presented in this paper include Sorting, Matrix Rank and GCD. It also applies methods of modern cryptography, especially the idea of a probabilistic interactive proof, to the design of program checkers for group theoretic computations.Two structural theorems are proven here. One is a characterization of problems that can be checked. The other theorem establishes equivalence classes of problems such that whenever one problem in a class is checkable, all problems in the class are checkable.
A theory of using history for equational systems with applications
Authors: Rakesh M. Verma
Venue: Journal of the ACM (JACM) (1995)

Implementation of programming language interpreters, proving theorem of the form A=B, implementation of abstract data types, and program optimization are all problems that can be reduced to the problem of finding a normal form for an expression with respect to a finite set of equations. In 1980, Chew proposed an elegant congruence closure based simplifier (CCNS) for computing with regular systems, which stores the history of it computations in a compact data structure. In 1990, Verma and Ramakrishnan showed that it can also be used for noetherian systems with no overlaps.In this paper, we develop a general theory of using CCNS for computing normal forms and present several applications. Our results are more powerful and widely applicable than earlier work. We present an independent set of postulates and prove that CCNS can be used for any system that satisfies them. (This proof is based on the notion of strong closure). We then show that CCNS can be used for consistent convergent systems and for various kinds of priority rewrite systems. This is the first time that the applicability of CCNS has been shown for priority systems. Finally, we present a new and simpler translation scheme for converting convergent systems into effectively nonoverlapping convergent priority systems. Such a translation scheme has been proposed earlier, but we show that it is incorrect.Because CCNS requires some strong properties of the given system, our demonstration of its wide applicability is both difficult and surprising. The tension between demands imposed by CCNS and our efforts to satisfy them gives our work much general significance. Our results are partly achieved through the idea of effectively simulating &ldquo;bad&rdquo; systems by almost-equivalent &ldquo;good&rdquo; ones, partly through our theory that substantially weakens the demands, and partly through the design of a powerful and unifying reduction proof method.
Approximations to Solutions to Systems of Linear Inequalities
Authors: Osman Guler, Alan J. Hoffman, Uriel G. Rothblum
Venue: SIAM Journal on Matrix Analysis and Applications (1995)

In this paper we consider a result of Hoffman [J. Res. Nat. Bur. Stand., 49 (1952) pp. 263-265] about approximate solutions to systems of linear inequalities. We obtain a new representation for a corresponding Lipschitz bound via singular values. We also provide geometric representations of these bounds via extreme points. The latter have been developed independently by Bergthaller and Singer [Linear Algebra Appl., 169 (1992), pp. 111-129] and Li [Linear Algebra Appl., 187 (1993), pp. 15-40], but, our proofs are simpler. We obtain a particularly simple proof of Hoffman's existence result which relies only on linear programming duality.
A Scalable Scheduling Scheme for Functional Parallelism on Distributed Memory Multiprocessor Systems
Authors: Santosh Pande, Dharma P. Agrawal, Jon Mauney
Venue: IEEE Transactions on Parallel and Distributed Systems (1995)

We attempt a new variant of the scheduling problem by investigating the scalability of the schedule length with the required number of processors, by performing scheduling partially at compile time and partially at run time. Assuming infinite number of processors, the compile time schedule is found using a new concept of the threshold of a task that quantifies a trade-off between the schedule-length and the degree of parallelism. The schedule is found to minimize either the schedule length or the number of required processors and it satisfies: A feasibility condition which guarantees that the schedule delay of a task from its earliest start time is below the threshold, andAn optimality condition which uses a merit function to decide the best task¿processor match for a set of tasks competing for a given processor.At run time, the tasks are merged producing a schedule for a smaller number of available processors. This allows the program to be scaled down to the processors actually available at run time. Usefulness of this scheduling heuristic has been demonstrated by incorporating the scheduler in the compiler backend for targeting Sisal (Streams and Iterations in a Single Assignment Language) on iPSC/860.Index Terms¿Compile time scheduling, dataflow graphs, distributed memory multiprocessors, functional parallelism, runtime scheduling, scaling, schedule length.
Short Random Walks on Graphs
Authors: Greg Barnes, Uriel Feige
Venue: SIAM Journal on Discrete Mathematics (1996)

The short-term behavior of random walks on graphs is studied, in particular, the rate at which a random walk discovers new vertices and edges. A conjecture by Linial that the expected time to find $\cal N$ distinct vertices is $O({\cal N}^{3})$ is proved. In addition, upper bounds of $O({\cal M}^{2})$ on the expected time to traverse $\cal M$ edges and of $O(\cal M \cal N)$ on the expected time to either visit $\cal N$ vertices or traverse $\cal M$ edges (whichever comes first) are proved.
The INGRES Tutorial as a tool in teaching database theory (or, I can't believe it's not training)
Authors: Don Goelman
Venue: Proceedings of the twenty-seventh SIGCSE technical symposium on Computer science education (1996)

The course in database principles is an example of a course in the computer science curriculum in which a balance is sought between theory and applications. With some exceptions, most computer science majors at the author's university prefer material which is oriented towards what they view as practical applications. At best, they tolerate the theoretical component of their courses. In particular, many who enroll in the database course hope to acquire expertise in particular software. One of the course projects has managed to finesse this prejudice by hiding some theoretical ideas in the benign cloak of an application.
An integrated approach to logical design of relational database schemes
Authors: Catriel Beeri, Michael Kifer
Venue: ACM Transactions on Database Systems (TODS) (1986)

We propose a new approach to the design of relational database schemes. The main features of the approach are the following: A combination of the traditional decomposition and synthesis approaches, thus allowing the use of both functional and multivalued dependencies. Separation of structural dependencies relevant for the design process from integrity constraints, that is, constraints that do not bear any structural information about the data and which should therefore be discarded at the design stage. This separation is supported by a simple syntactic test filtering out nonstructural dependencies. Automatic correction of schemes which lack certain desirable properties.
The use of variance reduction techniques in the estimation of simulation metamodels
Authors: Joan M. Donohue
Venue: Proceedings of the 27th conference on Winter simulation (1995)

Variance reduction techniques can be useful strategies for improving the estimates of simulation metamodel coefficients. Depending upon the goals of the experimenter, the type of metamodel being estimated, and the characteristics of the system being simulated, an appropriate variance reduction technique can be applied. This paper provides a review of recent research that investigates the application of variance reduction techniques in the simulation metamodeling context. One strategy, Schruben and Margolin's (1978) assignment rule, which utilizes a combination of antithetic and common random number streams, is found to be a particularly useful variance reduction technique for the estimation of simulation metamodels.
A Fast, Efficient Parallel-Acting Method of Generating Functions Defined by Power Series, Including Logarithm, Exponential, and Sine, Cosine
Authors: David M. Mandelbaum, Stefanie G. Mandelbaum
Venue: IEEE Transactions on Parallel and Distributed Systems (1996)

A fundamental parallel procedure of implementing certain algorithms is by means of trees and arrays, [1]. A method of generating any function defined by a power series in a fast, efficient parallel-acting manner using trees and arrays is described. The power series considered can be written as f(Y) = a0 + a1Y + a2Y2 + ... where Y = v1x + v2x2 + ... + vkxk, vi = (0, 1), is a binary fraction when x = ½. The power series must be expanded into individual terms cxi. These terms are then transformed into weighted binary terms. Two methods are given to obtain all the individual terms (including coefficients) associated with each power of x. The hardware required for implementation is a tree similar to a Wallace or Dadda tree used for parallel multiplication of two binary numbers. Despite the multiplicity of terms required, Boolean logic methods reduce the tree dimensions in many cases so that the total tree required is smaller than an existing multiplier tree. In that case, Schwarz and Flynn, [13], [15], have shown that the required tree can be superimposed on the existing multiplier tree in a multiplexed manner with relatively little increase in hardware. The generation of the logarithmic function is described in detail. Comparisons with other methods are made for the case of 11 bit accuracy of the logarithm. Using a figure of merit of latency times area (number of transistors), estimates show that the superposition scheme gives the best (smallest) figure of merit. For 11 bit accuracy, the superposition scheme requires only about 480 additional gates to be superimposed upon a 41 bit or larger multiplier, and the speed of operation is that of the multiplier.
Structures for manipulating proposed updates in object-oriented databases
Authors: Michael Doherty, Richard Hull, Mohammed Rupawalla
Venue: ACM SIGMOD Record (1996)

Support for virtual states and deltas between them is useful for a variety of database applications, including hypothetical database access, version management, simulation, and active databases. The Heraclitus paradigm elevates delta values to be "first-class citizens" in database programming languages, so that they can be explicitly created, accessed and manipulated.A fundamental issue concerns the trade-off between the "accuracy" or "robustness" of a form of delta representation, and the ease of access and manipulation of that form. At one end of the spectrum, code-blocks could be used to represent delta values, resulting in a more accurate capture of the intended meaning of a proposed update, at the cost of more expensive access and manipulation. In the context of object-oriented databases, another point on the spectrum is "attribute-granularity" deltas which store the net changes to each modified attribute value of modified objects.This paper introduces a comprehensive framework for specifying a broad array of forms for representing deltas for complex value types (tuple, set, bag, list, o-set and dictionary). In general, the granularity of such deltas can be arbitrarily deep within the complex value structure. Applications of this framework in connection with hypothetical access to, and "merging" of, proposed updates are discussed.
Building the business using process simulation
Authors: Anil Swami
Venue: Proceedings of the 27th conference on Winter simulation (1995)

The paper looks at how process simulation can provide managers with a powerful means to make better decisions in building the business through reengineering initiatives. An illustrative simulation model is used to demonstrate the powerful application of process simulation in reengineering. The model shows the order to delivery process (or order management) of a computer hardware manufacturer in the current state and in the future state after reengineering. Using key performance metrics managers can evaluate the benefits of various scenarios with the goal of building the business (increase throughput, increase revenue, etc.).
The computation of optical flow
Authors: S. S. Beauchemin, J. L. Barron
Venue: ACM Computing Surveys (CSUR) (1995)

Two-dimensional image motion is the projection of the three-dimensional motion of objects, relative to a visual sensor, onto its image plane. Sequences of time-orderedimages allow the estimation of projected two-dimensional image motion as either instantaneous image velocities or discrete image displacements. These are usually called the optical flow field or the image velocity field. Provided that optical flow is a reliable approximation to two-dimensional image motion, it may then be used to recover the three-dimensional motion of the visual sensor (to within a scale factor) and the three-dimensional surface structure (shape or relative depth) through assumptions concerning the structure of the optical flow field, the three-dimensional environment, and the motion of the sensor. Optical flow may also be used to perform motion detection, object segmentation, time-to-collision and focus of expansion calculations, motion compensated encoding, and stereo disparity measurement. We investigate the computation of optical flow in this survey: widely known methods for estimating optical flow are classified and examined by scrutinizing the hypothesis and assumptions they use. The survey concludes with a discussion of current research issues.
Can we trust in HDLC?
Authors: D. Fiorini, M. Chiani, V. Tralli, C. Salati
Venue: ACM SIGCOMM Computer Communication Review (1994)

in spite of the theoretical error detecting capability of its CRC, the actual degree of data integrity provided by HDLC is quite low.The paper gives a quantitative assessment of HDLC's deficiencies and of their reasons, paying particular attention to actual applications of the HDLC family of standards.Finally, we look at some strategies that have been suggested to allow the use of HDLC in the most demanding applications.
Such easy-to-use systems!: How organizations shape the design and use of online help systems
Authors: Lisa M. Covi, Mark S. Ackerman
Venue: Proceedings of conference on Organizational computing systems (1995)

Despite the pervasiveness and proliferation of computerized systems, people still get stuck when they are trying to use them. Because organizations are heavily invested in their systems, they seek efficient and effective means to allocate necessary resources to make systems usable. Online help systems attempt to provide such targeted assistance in a variety of modes. This paper will review several online help systems, highlighting the organizational issues inherent in online help by focusing on the organizational arrangements that contextualize the design and use of these systems.
Multivariate Decision Trees
Authors: Carla E. Brodley, Paul E. Utgoff
Venue: Machine Learning (1995)

Unlike a univariate decision tree, a multivariate decision tree is not restricted to splits of the instance space that are orthogonal to the features' axes. This article addresses several issues for constructing multivariate decision trees: representing a multivariate test, including symbolic and numeric features, learning the coefficients of a multivariate test, selecting the features to include in a test, and pruning of multivariate decision trees. We present several new methods for forming multivariate decision trees and compare them with several well-known methods. We compare the different methods across a variety of learning tasks, in order to assess each method's ability to find concise, accurate decision trees. The results demonstrate that some multivariate methods are in general more effective than others (in the context of our experimental assumptions). In addition, the experiments confirm that allowing multivariate tests generally improves the accuracy of the resulting decision tree over a univariate tree.
Pairing heaps: experiments and analysis
Authors: John T. Stasko, Jeffrey Scott Vitter
Venue: Communications of the ACM (1987)

The pairing heap has recently been introduced as a new data structure for priority queues. Pairing heaps are extremely simple to implement and seem to be very efficient in practice, but they are difficult to analyze theoretically, and open problems remain. It has been conjectured that they achieve the same amortized time bounds as Fibonacci heaps, namely, O(log n) time for delete and delete_min and O(1) for all other operations, where n is the size of the priority queue at the time of the operation. We provide empirical evidence that supports this conjecture. The most promising algorithm in our simulations is a new variant of the twopass method, called auxiliary twopass. We prove that, assuming no decrease_key operations are performed, it achieves the same amortized time bounds as Fibonacci heaps.