ppxscal/embedding_network huggingface dataset:
Simulation of transportation systems
Authors: Paul T. Fishburn, Javad Golkar, Kevin M. Taaffe
Venue: Proceedings of the 27th conference on Winter simulation (1995)

This tutorial describes the benefits of using simulation to evaluate the performance of transportation facilities and systems. The authors present specific examples in which simulation analysis has been applied to the transportation industry.
Augmented Binary Hypercube: A New Architecture for Processor Management
Authors: Hari Lalgudi, Ian F. Akyildiz, Sudhakar Yalamanchili
Venue: IEEE Transactions on Computers (1996)

Augmented Binary Hypercube (AH) architecture consists of the binary hypercube processor nodes (PNs) and a hierarchy of management nodes (MNs). Several distributed algorithms maintain subcube information at the MNs to realize fault tolerant, fragmentation free processor allocation and load balancing. For efficient implementation of AH, we map MNs onto PNs, define and prove infeasibility of ideal mappings. We propose easily implementable non-optimal mappings, having negligible overheads on performance. Extensive simulation studies and performance analysis conclude that these algorithms realize significantly better average job completion time and higher processor utilization, as compared to the best sequential allocation schemes and parallel implementation of Free List [7]. AH algorithms can be tuned or adapt to the job and system characteristics, and resource management traffic.
Linear Operators on Matrices: Preserving Spectrum and Displacement Structure
Authors: Kenneth R. Driessel, Wasin So
Venue: SIAM Journal on Matrix Analysis and Applications (1995)

In this paper we characterize those linear operators on general matrices that preserve singular values and displacement rank. We also characterize those linear operators on Hermitian matrices that preserve eigenvalues and displacement inertia.
An Optimal Algorithm for Computing Visibility in the Plane
Authors: Paul J. Heffernan, Joseph S. B. Mitchell
Venue: SIAM Journal on Computing (1995)

The authors give an algorithm to compute the visibility polygon from a point among a set of $h$ pairwise-disjoint polygonal obstacles with a total of $n$ vertices. Our algorithm uses $O(n)$ space and runs in optimal time $\Theta(n+h\log h)$, improving the previous upper bound of $O(n\log n)$. A direct consequence of the algorithm is an $O(n+h\log h)$ time algorithm for computing the convex hull of $h$ disjoint simple polygons.
Freeing the essence of a computation
Authors: Kenneth R. Anderson
Venue: ACM SIGPLAN Lisp Pointers (1995)

In theory, abstraction is important, but in practice, so is performance. Thus, there is a struggle between an abstract description of an algorithm and its efficient implementation. This struggle can be mediated by using an interpreter or a compiler. An interpreter takes a program that is a high level abstract description of an algorithm and applies it to some data. Don't think of an interpreter as slow. An interpreter is important enough to software that it is often implemented in hardware. A compiler takes the program and produces another program, perhaps in another language. The resulting program is applied to some data by another interpreter.
A Distributed System-Level Diagnosis Algorithm for Arbitrary Network Topologies
Authors: Sampath Rangarajan, Anton T. Dahbura, Eric A. Ziegler
Venue: IEEE Transactions on Computers (1995)

In this paper, a distributed algorithm is described for detecting and diagnosing faulty processors in an arbitrary network. Fault-free processors perform simple periodic tests on one another; when a fault is detected or a newly-repaired processor joins the network, this new information is disseminated $\mbi{in}$$\mbi{parallel}$ throughout the network. It is formally proven that the algorithm is correct, and it is also shown that the algorithm is optimal in terms of the time required for all of the fault-free processors in the network to learn of a new event. Simulation results are given for arbitrary network topologies.Index Terms¿Computer fault diagnosis, computer fault tolerance, computer networks, distributed computing, system-level fault diagnosis, distributed algorithm, fault detection.
Modeling psycho-social attributes in conflict, extended
Authors: Dean S. Hartley,  III
Venue: Proceedings of the 27th conference on Winter simulation (1995)

Geo-political decisions can be critical determinants of success in war and peace. These decisions are based on assumed psychological and sociological responses to the decisions by the various individuals and groups in the decision environment. For example, mental models are used in deciding whether to display our naval "presence" in a foreign port or whether a discussion on the golf course would be more effective. However, in constructing consistent policies over long periods of time that involve the conflicting interests of many countries, the complexities often overwhelm simple models. A computer implementation, combining and extending the simple models, might be useful; but its design is a hard problem. This paper presents a philosophical framework for modeling psycho-social attributes at the theater level and develops some of the necessary structure.
Relaxed Minimax Control
Authors: E. N. Barron, R. Jensen
Venue: SIAM Journal on Control and Optimization (1995)

The relaxation of the optimal control problem with cost functional which is the supremum in time of some function $h(t,x,z)$ is determined. The trajectory is convexified in the usual way but the cost functional is convexified in a nonobvious manner. Thus, if the original value function is $V(t,x)=\inf \zeta \in z\left\| {h(s,\xi (s), \zeta (s))} \right\|L\infty [t,T]\cr$, then the relaxed value function is $$\hat V(t,x)=\mathop {\inf}\limits_{\mu \in \hat z\left| {t,T} \right|}\left\| {\left\| {h(s,\hat \xi (s),z)} \right\|L^\infty ({\rm Z};\mu (s))} \right\|L^\infty \left| {t,T} \right|\cr$$ where the inner norm is the essential sup of $h$ over $z\in {\rm Z}\cr$ with respect to the measure $\mu (s)\cr$. We prove that $V$ and ${\hat V}$ coincide.
On Bang-Bang Constrained Solutions of a Control System
Authors: Raphael Cerf, Carlo Mariconda
Venue: SIAM Journal on Control and Optimization (1995)

Given $\varphi_{1},\varphi_{2}\in L^1([0,T])$ and a function $x\in W^{2,1}([0,T])$ solving the control problem $(P)x"+a_{1} (t)x'+a_{0}(t)\in [\varphi_{1}(t),\varphi_{2}(t)]$ a.e., $x(0)=x_{0},x(T)=x_{1},x'(0)= v_{0},x'(T)=v_{1}$, there exists a bang-bang solution $y$ to (P) satisfying $y\le x$; moreover there exists a finite union of intervals $E$ such that $y"+a_{1}y+a_{0}y=\varphi_{1}\chi_{E}+\varphi_{2}\chi_{[0,T]\E}$. The reachable set of bang-bang constrained solutions is convex: an application to the calculus of variations.
Algorithm 649: A package for computing trigonometric Fourier coefficients based on Lyness's algorithm
Authors: G. Giunta, A. Murli
Venue: ACM Transactions on Mathematical Software (TOMS) (1987)

We present a package that allows the computation of the trigonometric Fourier coefficients of a smooth function. The function can be provided as a subprogram or as a data list of function values at equally spaced points.The computational cost of the algorithm does not depend on the required number of Fourier coefficients. Numerical results of comparative tests with a standard integrator for oscillatory functions are also reported.
Matrix Transformation is Complete for the Average Case
Authors: Andreas Blass, Yuri Gurevich
Venue: SIAM Journal on Computing (1995)

In the theory of worst case complexity, NP completeness is used to establish that, for all practical purposes, the given NP problem is not decidable in polynomial time. In the theory of average case complexity, average case completeness is supposed to play the role of NP completeness. However, the average case reduction theory is still at an early stage, and only a few average case complete problems are known. We present the first algebraic problem complete for the average case under a natural probability distribution. The problem is this: Given a unimodular matrix $X$ of integers, a set $S$ of linear transformations of such unimodular matrices and a natural number $n$, decide if there is a product of $\leq n$ (not necessarily different) members of $S$ that takes $X$ to the identity matrix.
Parallel evaluation of multi-join queries
Authors: Annita N. Wilschut, Jan Flokstra, Peter M. G. Apers
Venue: Proceedings of the 1995 ACM SIGMOD international conference on Management of data (1995)

A number of execution strategies for parallel evaluation of multi-join queries have been proposed in the literature; their performance was evaluated by simulation. In this paper we give a comparative performance evaluation of four execution strategies by implementing all of them on the same parallel database system, PRISMA/DB. Experiments have been done up to 80 processors. The basic strategy is to first determine an execution schedule with minimum total cost and then parallelize this schedule with one of the four execution strategies. These strategies, coming from the literature, are named: Sequential Parallel, Synchronous Execution, Segmented Right-Deep, and Full Parallel. Based on the experiments clear guidelines are given when to use which strategy.
Displacement Structures of Covariance Matrices,Lossless Systems, and Numerical Algorithm Design
Authors: Phillip A. Regalia, Francois Desbouvries
Venue: SIAM Journal on Matrix Analysis and Applications (1995)

Low displacement rank theory underlies many fast algorithms designed for structured covariance matrices. Some of these have gained notoriety for their numerical instability problems, particularly fast least-squares algorithms. Recent studies have shown that instability is not inherent to fast algorithms, but rather comes from the violation of backward consistency constraints. This paper thus details the connection between covariance matrices of a given displacement inertia and lossless rational matrices, as well as the role of this connection in numerically consistent algorithms. This basic connection allows displacement structures to be parametrized via a sequence of rotation angles obtained from a lossless system. The utility of this approach is that, irrespective of errors in the rotation parameter set, they remain consistent with a positive definite matrix of a prescribed displacement inertia. This property in turn may be rephrased as meaningful forms of backward consistency in numerical algorithms. The rotation parameters then take the form of Givens or Jacobi angles applied to data, in contrast to classical approaches which directly manipulate dyadic decompositions of the displacement structure. The concepts are illustrated in popular signal processing applications. In particular, these connections lend clear insight into the stable computation of reflection coefficients of Toeplitz systems, and also serve to resolve the numerical instability problem of fast least-squares algorithms.
An incremental algorithm for satisfying hierarchies of multiway dataflow constraints
Authors: Brad Vander Zanden
Venue: ACM Transactions on Programming Languages and Systems (TOPLAS) (1996)

One-way dataflow constraints have gained popularity in many types of interactive systems because of their simplicity, efficiency, and manageability. Although it is widely acknowledged that multiway dataflow constraint could make it easier to specify certain relationships in these applications, concerns about their predictability and efficiency have impeded their acceptance. Constraint hierarchies have been developed to address the predictability problem, and incremental algorithms have been developed to address the efficiency problem. However, existing incremental alogrithms for satisfying constraint hierarchies encounter two difficulties : (1) they are incapable of guaranteeing an acylic solution if a constraint hierarchy has one or more cyclic solutions and (2) they require worst-case exponential time to satisfy systems of multioutput constriants. This article surmounts these difficulties by presenting an incremental algorithm called QuickPlan that satisfies in worst-case O(N2) time any hierarchy of multiway, multiout-put dataflow constraint that has at least one acyclic solution, where N is the number of constraints. With benchmarks and real problems that can be solved efficiently using exisitng algorithms, its performance is competitive or superior. With benchmarks and real problems that cannot be solved using exisitng algorithms or that cannot be solved efficiently, QuickPlan finds solutions and does so efficiently, typically in O(N) time or less. QuickPlan is based on the strategy of propagation of degrees of freedom. The only restriction it imposes is that every constraint method must use all of the variables in the constraint as either an input or an output variable. This requirement is met in every constraint-based, interactive application that we have developed or seen.
UNICORN: misuse detection for UNICOS
Authors: Gary G. Christoph, Kathleen A. Jackson, Michael C. Neuman, Christine L. B. Siciliano, Dennis D. Simmonds, Cathy A. Stallings, Joseph L. Thompson
Venue: Proceedings of the 1995 ACM/IEEE conference on Supercomputing (CDROM) (1995)

An effective method for detecting computer misuse is the automatic auditing and analysis of on-line user activity. This activity is reflected in the system audit record, by changes in the vulnerability posture of the system configuration, and in other evidence found through active testing of the system. In 1989 we started developing an automatic misuse detection system for the Integrated Computing Network (ICN) at Los Alamos National Laboratory. Since 1990 this system has been operational, monitoring a variety of network systems and services. We call it the Network Anomaly Detection and Intrusion Reporter, or NADIR. During the last year and a half, we expanded NADIR to include processing of audit and activity records for the Cray UNICOS operating system. This new component is called the UNICOS Real-time NADIR, or UNICORN. UNICORN summarizes user activity and system configuration information in statistical profiles. In near real-time, it can compare current activity to historical profiles and test activity against expert rules that express our security policy and define improper or suspicious behavior. It reports suspicious behavior to security auditors and provides tools to aid in follow-up investigations. UNICORN is currently operational on four Crays in Los Alamos' main computing network, the ICN.
Las Vegas algorithms for linear and integer programming when the dimension is small
Authors: Kenneth L. Clarkson
Venue: Journal of the ACM (JACM) (1995)

This paper gives an algorithm for solving linear programming problems. For a problem with n constraints and d variables, the algorithm requires an expectedOd2n+lognOdd/2+O1+Od4nlogn arithmetic operations, asn&rarr;&infin;. The constant factors do not depend on d. Also, an algorithm is given for integer linear programming. Let 4 bound the number of bits required to specify the rational numbers defining an input constraint or the objective function vector. Let n and d be as before. Then, the algorithm requires expected O2ddn+8ddnl nnlnn +dod4 lnn operations on numbers with do14 bits, as n&rarr;&infin; , where the constant factors do not depend on d or4to other convex programming problems. For example, an algorithm for finding the smallest sphere enclosing a set of n points in Edhas the same time bound.
A Diagnosis Algorithm for Constant Degree Structures and Its Application to VLSI Circuit Testing
Authors: Kaiyuan Huang, Vinod K. Agarwal, Laurence LaForge, K. Thulasiraman
Venue: IEEE Transactions on Parallel and Distributed Systems (1995)

A simple diagnosis algorithm is presented for constant degree systems such as rectangular grids connected as tori. The algorithm determines the status of a unit according to the size of its faction, a cluster of units that call each other fault-free but outsiders faulty. Almost all units are correctly identified with this algorithm under a binomial failure distribution even when the probability of failure is rather high. The complexity of the algorithm is $O(n),$ where $n$ is the number of units in a constant degree system. The application of the algorithm to production testing of VLSI chips is also considered. With a test board that houses a large number of chips to be tested, all the chips can be tested in parallel in a way that they test each other and the test outcomes, not necessarily correct, are reported to a host system for analysis. The actual status of each chip is determined by using this new diagnosis algorithm. The above chip screening process can be repeated for higher accuracy. It is shown that no more than two steps are needed in most real situations. Compared with testing by test equipment that usually tests only one chip at a time, the saving of test time and the test equipment cost could be significant with our approach.Index Terms¿Probabilistic diagnosis, system level diagnosis, diagnosis algorithm, production testing, VLSI testing.
Log-based receiver-reliable multicast for distributed interactive simulation
Authors: Hugh W. Holbrook, Sandeep K. Singhal, David R. Cheriton
Venue: ACM SIGCOMM Computer Communication Review (1995)

Reliable multicast communication is important in large-scale distributed applications. For example, reliable multicast is used to transmit terrain and environmental updates in distributed simulations. To date, proposed protocols have not supported these applications' requirements, which include wide-area data distribution, low-latency packet loss detection and recovery, and minimal data and management over-head within fine-grained multicast groups, each containing a single data source.In this paper, we introduce the notion of Log-Based Receiver-reliable Multicast (LBRM) communication, and we describe and evaluate a collection of log-based receiver reliable multicast optimizations that provide an efficient, scalable protocol for high-performance simulation applications. We argue that these techniques provide value to a broader range of applications and that the receiver-reliable model is an appropriate one for communication in general.
Australian attitudes toward legal intervention into hacking
Authors: R. A. Coldwell
Venue: Communications of the ACM (1995)

The Australian public seems to have a characteristic response to computer crime. It is worth giving some anecdotal evidence to support this statement. During fieldwork [1-5], respondents were quizzed regarding their reasoning for their responses to the criminality of hacking. Some results are given here in response to the social attitudes of Australians towards reporting evidence of the enactment of computer crimes (see Table 1). This is in support of Thompson's [12, 13] and others' claims that relatively few computer crimes are, indeed, reported to the police in Australia (see also [9]).
Computing Solutions Uniquely Collapses the Polynomial Hierarchy
Authors: Lane A. Hemaspaandra, Ashish V. Naik, Mitsunori Ogihara, Alan L. Selman
Venue: SIAM Journal on Computing (1996)

Is there an NP function that, when given a satisfiable formula as input, outputs one satisfying assignment uniquely? That is, can a nondeterministic function cull just one satisfying assignment from a possibly exponentially large collection of assignments? We show that if there is such a nondeterministic function, then the polynomial hierarchy collapses to $\zppnp$ (and thus, in particular, to $\npnp$). As the existence of such a function is known to be equivalent to the statement ``every NP function has an NP refinement with unique outputs," our result provides the strongest evidence yet that NP functions cannot be refined. We prove our result via a result of independent interest. We say that a set $A$ is NPSV-selective (NPMV-selective) if there is a 2-ary partial NP function with unique values (a 2-ary partial NP function) that decides which of its inputs (if any) is ``more likely'' to belong to $A$; this is a nondeterministic analog of the recursion-theoretic notion of the semi-recursive sets and the extant complexity-theoretic notion of P-selectivity. Our hierarchy collapse result follows by combining %%foo the easy observation that every set in NP is NPMV-selective with the following result: If $A \in \np$ is NPSV-selective, then $A \in (\np\cap\conp)/\poly$. Relatedly, we prove that if $A \in \np$ is NPSV-selective, then $A$ is Low$_2$. We prove that the polynomial hierarchy collapses even further, namely to NP, if all coNP sets are NPMV-selective. This follows from a more general result we prove: Every self-reducible NPMV-selective set is in NP\@.
Aspect: detecting bugs with abstract dependences
Authors: Daniel Jackson
Venue: ACM Transactions on Software Engineering and Methodology (TOSEM) (1995)

Aspect is a static analysis technique for detecting bugs in imperative programs, consisting of an annotation language and a checking tool. Like a type declaration, an Aspect annotation of a procedure is a kind of declarative, partial specification that can be checked efficiently in a modular fashion. But instead of constraining the types of arguments and results, Aspect specifications assert dependences that should hold between inputs and outputs. The checker uses a simple dependence analysis to check code against annotations and can find bugs automatically that are not detectable by other static means, especially errors of omission, which are common, but resistant to type checking. This article explains the basic scheme and shows how it is elaborated to handle data abstraction and aliasing.
The direct cost of virtual function calls in C++
Authors: Karel Driesen, Urs Hölzle
Venue: ACM SIGPLAN Notices (1996)

We study the direct cost of virtual function calls in C++ programs, assuming the standard implementation using virtual function tables. We measure this overhead experimentally for a number of large benchmark programs, using a combination of executable inspection and processor simulation. Our results show that the C++ programs measured spend a median of 5.2% of their time and 3.7% of their instructions in dispatch code. For "all virtuals" versions of the programs, the median overhead rises to 13.7% (13% of the instructions). The "thunk" variant of the virtual function table implementation reduces the overhead by a median of 21% relative to the standard implementation. On future processors, these overheads are likely to increase moderately.
A model and compilation strategy for out-of-core data parallel programs
Authors: Rajesh Bordawekar, Alok Choudhary, Ken Kennedy, Charles Koelbel, Michael Paleczny
Venue: ACM SIGPLAN Notices (1995)

It is widely acknowledged in high-performance computing circles that parallel input/output needs substantial improvement in order to make scalable computers truly usable. We present a data storage model that allows processors independent access to their own data and a corresponding compilation strategy that integrates data-parallel computation with data distribution for out-of-core problems. Our results compare several communication methods and I/O optimizations using two out-of-core problems, Jacobi iteration and LU factorization.
The MG retrieval system: compressing for space and speed
Authors: Timothy C. Bell, Alistair Moffat, Ian H. Witten, Justin Zobel
Venue: Communications of the ACM (1995)

Recent advances in compression and indexing techniques have yielded a qualitative change in the feasibility of large-scale full-text retrieval.
A sequence of lab exercises for an introductory compiler construction course
Authors: Lawrence A. Coon
Venue: ACM SIGCSE Bulletin (1996)

A sequence of laboratory exercises for an introductory compiler construction course is described. The labs are based on four increasingly complex versions of an imperative language designed so that each version builds on the previous. The third version supports integer and character data types and arrays of integers and characters. The fourth version adds procedures, but has only integer data. The procedures do not nest, but direct recursion is supported.