ppxscal/embedding_network huggingface dataset:
Automatic Generation of Path Covers Based on the Control Flow Analysis of Computer Programs
Authors: Antonia Bertolino, Martina Marré
Venue: IEEE Transactions on Software Engineering (1994)

Branch testing a program involves generating a set of paths that will cover every arc in the program flowgraph, called a path cover, and finding a set of program inputs that will execute every path in the path cover. This paper presents a generalized algorithm that finds a path cover for a given program flowgraph. The analysis is conducted on a reduced flowgraph, called a ddgraph, and uses graph theoretic principles differently than previous approaches. In particular, the relations of dominance and implication which form two trees of the arcs of the ddgraph are exploited. These relations make it possible to identify a subset of ddgraph arcs, called unconstrained arcs, having the property that a set of paths exercising all the unconstrained arcs also cover all the arcs in the ddgraph. In fact, the algorithm has been designed to cover all the unconstrained arcs of a given ddgraph: the paths are derived one at a time, each path covering at least one as yet uncovered unconstrained arc. The greatest merits of the algorithm are its simplicity and its flexibility. It consists in just visiting recursively in combination the dominator and the implied trees, and is flexible in the sense that it can derive a path cover to satisfy different requirements, according to the strategy adopted for the selection of the unconstrained arc to be covered at each recursive iteration. This feature of the algorithm can be employed to address the problem of infeasible paths, by adopting the most suitable selection strategy for the problem at hand. Embedding of the algorithm into a software analysis and testing tool is recommended.
Set-associative cache simulation using generalized binomial trees
Authors: Rabin A. Sugumar, Santosh G. Abraham
Venue: ACM Transactions on Computer Systems (TOCS) (1995)

Set-associative caches are widely used in CPU memory hierarchies, I/O subsystems, and file systems to reduce average access times. This article proposes an efficient simulation technique for simulating a group of set-associative caches in a single pass through the address trace, where all caches have the same line size but varying associativities and varying number of sets. The article also introduces a generalization of the ordinary binomial tree and presents a representation of caches in this class using the Generalized Binomial Tree (gbt). The tree representation permits efficient search and update of the caches. Theoretically, the new algorithm, GBF_LS, based on the gbt structure, always takes fewer comparisons than the two earlier algorithms for the same class of caches: all-associativity and generalized forest simulation. Experimentally, the new algorithm shows performance gains in the range of 1.2 to 3.8 over the earlier algorithms on address traces of the SPEC benchmarks. A related algorithm for simulating multiple alternative direct-mapped caches with fixed cache size, but varying line size, is also presented.
Query evaluation in deductive databases with alternating fixpoint semantics
Authors: Weidong Chen
Venue: ACM Transactions on Database Systems (TODS) (1995)

First-order formulas allow natural descriptions of queries and rules. Van Gelder's alternating fixpoint semantics extends the well-founded semantics of normal logic programs to general logic programs with arbitrary first-order formulas in rule bodies. However, an implementation of general logic programs through the standard translation into normal logic programs does not preserve the alternating fixpoint semantics. This paper presents a direct method for goal-oriented query evaluation of general logic programs. Every general logic program is first transformed into a normal form where the body of each rule is either an existential conjunction of literals or a universal disjunction of literals. Techniques of memoing and loop checking are incorporated so that termination and polynomial-time data complexity are guaranteed for deductive databases (or function-free programs). Results of the soundness and search space completeness are established.
An introduction to SLX
Authors: James O. Henriksen
Venue: Proceedings of the 27th conference on Winter simulation (1995)

This paper provides introduction to SLX (Henriksen, 1993) for readers who are already familiar with simulation. Comparisons with GPSS/H (Banks, Carson and Sy, 1989; Henriksen and Crain, 1989; Schriber, 1991; and Smith, Brunner and Crain, 1992) are used to provide a frame of reference for describing SLX features. The goal of the SLX project is to produce a simulation system which provides a multiplicity of layers, ranging from the SLX kernel, at the bottom, all the way up to layers which provide graphical model building "without programming." In this paper, only the "lower" layers of SLX are described. Accordingly, this paper will perhaps be of greater interest to simulation software package developers than to end users of simulation software. Six key concepts which underlie the SLX kernel are presented, and SLX's extensibility mechanisms, which facilitate the construction of higher layers from lower layers, are illustrated.
Downdating the Singular Value Decomposition
Authors: Ming Gu, Stanley C. Eisenstat
Venue: SIAM Journal on Matrix Analysis and Applications (1995)

Let $A$ be a matrix with known singular values and left and/or right singular vectors, and let $A'$ be the matrix obtained by deleting a row from $A$. We present efficient and stable algorithms for computing the singular values and left and/or right singular vectors of $A'$. We also show that the problem of computing the singular values of $A'$ is well conditioned when the left singular vectors of $A$ are given, but can be ill conditioned when they are not. Our algorithms reduce the problem to computing the eigendecomposition or singular value decomposition of a matrix that has a simple structure, and solve the reduced problem via finding the roots of a secular equation. Previous algorithms of this type can be unstable and always solve the ill-conditioned problem.
A note concerning proof processor animation with SIMAN
Authors: Roger McHaney, Doug White
Venue: ACM SIGSIM Simulation Digest (1995)

The purpose of this note is to clarify statements made about Proof Animation's built-in drawing tool and its potential to recreate complex systems' layouts. The article, Proof Processor Animation With SIMAN (McHaney and White, 1994), was in no way meant to disparage Proof Animation or its capabilities. Several references to difficulty in development of a 'high-quality' animation layout failed to mention the development for this project was undertaken using the student edition of Proof. The student edition has been provided by Wolverine Software Corporation as an educational and instructional tool. It is in no way intended to facilitate complicated development efforts. In order to make the student edition of Proof more affordable, several features found in the full version have been left out. These include (Wolverine Software Corporation, 1992, p. 11):1) Animation Trace File Limited to 1250 Lines2) Layout Files Larger than 12500 Bytes Cannot Be Read3) Execution Stops after 2 Minutes
Extracting RTL models from transistor netlists
Authors: K. J. Singh, P. A. Subrahmanyam
Venue: Proceedings of the 1995 IEEE/ACM international conference on Computer-aided design (1995)

This paper addresses the problem of deriving a register-transfer level (RTL) model from a transistor-level circuit. Using existing techniques, the transistor-level circuit is converted into a relation that describes the evolution of the signals in the circuit with respect to the simulator clock. This simulation relation is then manipulated to derive the stable behavior of the circuit. Given this stable behavior and information about the clocking scheme, we determine if the circuit is combinational, asynchronous or synchronous. For combinational and synchronous circuits we derive an equivalent register-transfer level model. This development enables full-custom circuit designers to use tools that were till now available only to designers working at the gate-level. The algorithm has been successfully used to characterize several custom designs, as well as the entire AT&T standard-cell library.
Optimal register assignment to loops for embedded code generation
Authors: David J. Kolson, Alexandru Nicolau, Nikil Dutt, Ken Kennedy
Venue: ACM Transactions on Design Automation of Electronic Systems (TODAES) (1996)

One of the challenging tasks in code generation for embedded systems is register assignment. When more live variables than registers exist, some variables will necessarily be accessed from data memory. Because loops are typically executed many times and are often time-critical, good register assignment in loops is exceedingly important as accessing data memory can degrade performance. The issue of finding an optimal register assignment to loops has been open for some time. In this article, we present a technique for optimal (i.e., spill minimizing) register assignment to loops. First we present a technique for register assignment to architecture styles that are characterized by a consolidated register file. Then we extend the technique to include architecture styles that are characterized by distributed memories and/or a combination of general- and special-purpose registers. Experimental results demonstrate that although the optimal algorithm may be computationally prohibitive, heuristic versions obtain results with performance better than that of an existing graph coloring approach.
Maiden voyage
Authors: Hal Berghel
Venue: Communications of the ACM (1995)

Welcome to the first installment of Digital Village. This new column will be a reliable source of information on modern digital network technologies, particularly from the client side, and the use of those technologies for the betterment of society. In an attempt to provide information on cyberspace and its tools, we hope to be useful to readers in maintaining currency and perspective.
HPC undergraduate curriculum development at SDSU using SDSC resources
Authors: Kris Stewart
Venue: Proceedings of the 1995 ACM/IEEE conference on Supercomputing (CDROM) (1995)

Results from the development and teaching of a senior-level undergraduate multidisciplinary course in high performance computing are presented. Having been taught four times, there are several "Lesson Learned" presented in this paper. Help from the technical staff at the San Diego Supercomputer Center and support from the National Science Foundation has been instrumental in the evolution of this course. The work of faculty at other universities has influenced the author's courses and is gratefully acknowledged. A subsequent sophomore level course was developed at SDSU and has become part of a voluntary, cooperative program, Undergraduate Computational Science and Engineering.
Performance analysis of redundant-path networks for multiprocessor systems
Authors: Krishnan Padmanabhan, Duncan H. Lawrie
Venue: ACM Transactions on Computer Systems (TOCS) (1985)

Performance of a class of multistage interconnection networks employing redundant paths is investigated. Redundant path networks provide significant tolerance to faults at minimal costs; in this paper improvements in performance and very graceful degradation are also shown to result from the availability of redundant paths. A Markov model is introduced for the operation of these networks in the circuit-switched mode and is solved numerically to obtain the performance measures of interest. The structure of the networks that provide maximal performance is also characterized.
Some Properties of Fully Semimonotone, $Q_0$-Matrices
Authors: G. S. R. Murthy, T. Parthasarathy
Venue: SIAM Journal on Matrix Analysis and Applications (1995)

Stone [Ph. D. thesis, Dept. of Operations Research, Stanford University, Stanford, CA, 1981] proved that within the class of $Q_0$-matrices, the $U$-matrices are $P_0$-matrices and conjectured that the same must be true for fully semimonotone ($E^{f}_{0}$) matrices. In this paper we show that this conjecture is true for matrices of order up to $4 \times 4$ and partially resolve it for higher order matrices. This is done by establishing the result that if $A$ is in $E^{f}_{0} \cap Q_0$ and if every proper principal minor of $A$ is nonnegative, then $A$ is a $P_0$-matrix. Using this key result we settle the conjecture for a number of special cases of matrices of general order. These special cases include $E^{f}_0$-matrices which are either symmetric or nonnegative or copositive-plus or $Z$-matrices or $E$-matrices. Also the conjecture is established for $5 \times 5$ matrices with all diagonal entries positive. While trying to settle the conjecture, we obtained a number of results on $Q_0$-matrices. The main among these are characterizations of nonnegative $Q_0$-matrices and symmetric semimonotone $Q_0$-matrices; results providing sufficient conditions under which, principal submatrices of order $(n-1)$ of a $n \times n \ Q_0$-matrix are also in $Q__0$.
Texture Segmentation Using Fractal Dimension
Authors: B. B. Chaudhuri, Nirupam Sarkar
Venue: IEEE Transactions on Pattern Analysis and Machine Intelligence (1995)

This paper deals with the problem of recognizing and segmenting textures in images. For this purpose we employ a technique based on the fractal dimension (FD) and the multi-fractal concept. Six FD features are based on the original image, the above average/high gray level image, the below average/low gray level image, the horizontally smoothed image, the vertically smoothed image, and the multi-fractal dimension of order two. A modified box-counting approach is proposed to estimate the FD, in combination with feature smoothing in order to reduce spurious regions. To segment a scene into the desired number of classes, an unsupervised K-means like clustering approach is used. Mosaics of various natural textures from the Brodatz album as well as microphotographs of thin sections of natural rocks are considered, and the segmentation results to show the efficiency of the technique. Supervised techniques such as minimum-distance and k-nearest neighbor classification are also considered. The results are compared with other techniques.
Rich interaction in the digital library
Authors: Ramana Rao, Jan O. Pedersen, Marti A. Hearst, Jock D. Mackinlay, Stuart K. Card, Larry Masinter, Per-Kristian Halvorsen, George C. Robertson
Venue: Communications of the ACM (1995)

Effective information access involves rich interactions between users and information residing in diverse locations. Users seek and retrieve information from the sources&mdash;for example, file serves, databases, and digital libraries&mdash;and use various tools to browse, manipulate, reuse, and generally process the information. We have developed a number of techniques that support various aspects of the process of user/information interaction. These techniques can be considered attempts to increase the bandwidth and quality of the interactions between users and information in an information workspace&mdash;an environment designed to support information work (see Figure 1).
Modeling a hospital main cafeteria
Authors: William A. Stout,  Jr.
Venue: Proceedings of the 27th conference on Winter simulation (1995)

Taylor II version 2.0 is a PC based, menu-driven, discrete event simulation modeling software package featuring 2D/3D animation; a user programmable interface-Taylor Language Interface (TLI); graphics and paintbox (drawing) capabilities, distribution curve-fitting; and context-sensitive help. Add-on modules include advanced statistics, a run-time development kit, and shaded animation. When learning a new simulation language, it is helpful to have a frame of reference that delineates at least the minimum programming elements required to formulate a successful model. Unfortunately, this is not always the case. Often, examples in the documentation are presented out of the context of a completed model leaving it up to the simulation practitioner to assemble the various pieces. Concepts presented in sample programs included with the package may be difficult to follow and to place in the context of your specific program development effort. The purpose of the paper is to provide the new user with the basics of Taylor II by building a "hard-copy" application step by step. We illustrate the importance of the relationships between various individually presented menus to emphasize the linkage between menu choices and the construction of user-written functions. By providing an overview of the total application development cycle, the user gains perspective on how individual parts are integrated into a working model.
Interactive learning tool for statistical reasoning with uncertainty
Authors: Deborah A. Vastola, Ellen L. Walker
Venue: ACM SIGART Bulletin (1995)

We describe a tool which was developed as a Masters project to help students learn the concepts of reasoning with uncertainty. While the initial implementation has focused on Dempster-Shafer theory, the tool is designed so that it can be expanded to other models of uncertain reasoning. The tool uses interactive graphical representations, together with animation and color, to convey the principles of reasoning with uncertainty. It runs on the Unix platform under the X-window system and uses the SUIT toolkit [1].
The ATM physical layer
Authors: Sailes K. Rao, Mehdi Hatamian
Venue: ACM SIGCOMM Computer Communication Review (1995)

In this article, we present an overview of the physical layer specification of the emerging Asynchronous Transfer Mode (ATM) networks. These specifications concern the complete details of how to ship 53-byte ATM cells from Point A to Point B over a physical medium on a Local Area Network (WAN). While the task of defining the interfaces and line coding of the transceivers over different physical media is ongoing, the primary underlying theme has been the leveraging of existing standards and practices to the maximum extent possible.
On the Approximation of Shortest Common Supersequencesand Longest Common Subsequences
Authors: Tao Jiang, Ming Li
Venue: SIAM Journal on Computing (1995)

The problems of finding shortest common supersequences (SCS) and longest common subsequences (LCS) are two well-known {\bf NP}-hard problems that have applications in many areas including computational molecular biology, data compression, robot motion planning and scheduling, text editing, etc. A lot of fruitless effort has been spent in searching for good approximation algorithms for these problems. In this paper, we show that these problems are inherently hard to approximate in the worst case. In particular, we prove that (i) SCS does not have a polynomial time linear approximation algorithm, unless {\bf P} = {\bf NP}; (ii) There exists a constant $\delta > 0$ such that, if SCS has a polynomial time approximation algorithm with ratio $\log^{\delta} n$, where $n$ is the number of input sequences, then {\bf NP} is contained in {\bf DTIME}$(2^{\polylog n})$; (iii) There exists a constant $\delta > 0$ such that, if LCS has a polynomial time approximation algorithm with performance ratio $n^{\delta}$, then {\bf P} = {\bf NP}. The proofs utilize the recent results of Arora et al. [Proc. 23rd IEEE Symposium on Foundations of Computer Science, 1992, pp. 14-23] on the complexity of approximation problems. In the second part of the paper, we introduce a new method for analyzing the average-case performance of algorithms for sequences, based on Kolmogorov complexity. Despite the above nonapproximability results, we show that near optimal solutions for both SCS and LCS can be found on the average. More precisely, consider a fixed alphabet $\Sigma$ and suppose that the input sequences are generated randomly according to the uniform probability distribution and are of the same length $n$. Moreover, assume that the number of input sequences is polynomial in $n$. Then, there are simple greedy algorithms which approximate SCS and LCS with expected additive errors $O(n^{0.707})$ and $O(n^{\frac{1}{2}+\epsilon})$ for any $\epsilon > 0$, respectively. Incidentally, our analyses also provide tight upper and lower bounds on the expected LCS and SCS lengths for a set of random sequences, solving a generalization of another well-known open question on the expected LCS length for two random sequences [K. Alexander, The rate of convergence of the mean length of the longest common subsequence, 1992, manuscript],[V. Chvatal and D. Sankoff, J. Appl. Probab., 12 (1975), pp. 306-315], [D. Sankoff and J. Kruskall, eds., Time Warps, String Edits, and Macromolecules: The Theory and Practice of Sequence Comparison, Addison-Wesley, Reading, MA, 1983].
Creating reference architectures: an example from avionics
Authors: Don Batory, Lou Coglianese, Mark Goodwin, Steve Shafer
Venue: ACM SIGSOFT Software Engineering Notes (1995)

ADAGE is a project to define and build a domain-specific software architecture (DSSA) environment for assisting the development of avionics software. A central concept of DSSA is the use of software system generators to implement component-based models of software synthesis in the target domain [SEI90].In this paper, we present the ADAGE component-based model (or reference architecture) for avionics software synthesis. We explain the modeling procedures used, review our initial goals, show how component reuse is achieved, and examine what we were (and were not) able to accomplish. The contributions of our paper are the avionics reference architecture and the lessons that we learned; both may be beneficial to others in future modeling efforts.
A hierarchical simulation environment for mobile wireless networks
Authors: R. Bagrodia, M. Gerla, L. Kleinrock, J. Short, T.-C. Tsai
Venue: Proceedings of the 27th conference on Winter simulation (1995)

A hierarchical simulator has been designed for multimedia communication protocols in a wireless mobile environment. The hierarchical approach integrates performance evaluation of protocols with their implementation. The approach supports scalability studies of the protocols in an efficient manner using coarse grain models that abstract implementation details of the protocol and its execution environment by a few key parameters. Fine grain, low level models that capture implementation details are used for detailed evaluation of small networks and for automatic implementation on radio platforms. The design, evaluation, and implementation cycle is closed by feeding the measurements from the implementation back into the model to improve its accuracy. The paper describes the use of the environment in the evaluation and implementation of a cluster based multihop protocol for multimedia traffic.