ppxscal/embedding_network huggingface dataset:
The EAN X.500 Directory Service
Authors: Barry B Gerald Neufeld, Stickings Duncan
Venue:  (1991)

The OSI directory system manages a distributed directory information database of named objects, defining a hierarchical relationship between the objects. An object consists of a set of attributes as determined by a particular class. Attributes are tuples that include a type and one or more values. The directory database is partitioned among a set of directory system agents. The directory service is provided by a collection of agents and incorporates distributed algorithms for name resolution and search, resulting in a network transparent service. The objects can represent many real-world entities. The service is intended to serve a very large and diverse user community. This paper describes experiences gained in implementing the directory service. It also points out a number of areas in the current OSI directory design that require further work and then describes how the EAN directory system has addressed these difficulties.
From theory to practice: an evolutionary algorithm for the antenna placement problem
Authors: Jörg Zimmermann, Robin Höns, Heinz Mühlenbein
Venue: Advances in evolutionary computing: theory and applications (2003)

We give a short introduction to the results of our theoretical analysis of evolutionary algorithms. These results are used to design an algorithm for a large real-world problem: the placement of antennas for mobile radio networks. Our model for the antenna placement problem (APP) addresses cover, traffic demand, interference, different parameterized antenna types, and the geometrical structure of cells. The resulting optimization problem is constrained and multi-objective. The evolutionary algorithm derived from our theoretical analysis is capable of dealing with more than 700 candidate sites in the working area. The results show that the APP is tractable. The automatically generated designs enable experts to focus their efforts on the difficult parts of a network design problem.
Theory and Operation of the Warwick Multiprocessor Scheduling (MS) System
Authors: S. C. Perry, J. S. Harper, D. J. Kerbyson, G. R. Nudd
Venue:  (1999)

This paper is concerned with the application of performance prediction techniques to the optimisation of parallel systems, and, in particular, the use of these techniques on-the-fly for optimising performance at run-time. In contrast to other performance tools, performance prediction results are made available very rapidly, which allows their use in real-time environments. When applied to program optimisation, this allows consideration of run-time variables such as input data and resource availability that are not, in general, available during the traditional (ahead-of-time) performance tuning stage. The main contribution of this work is the application of predictive performance data to the scheduling of a number of parallel tasks across a large heterogeneous distributed computing system. This is achieved through use of just-in-time performance prediction coupled with iterative heuristic algorithms for optimisation of the meta-schedule. The paper describes the main theoretical considerations for development of such a scheduling system, and then describes a prototype implementation, the MS scheduling system, together with some results obtained from this system when operated over a medium-sized (campus-wide) distributed computing network.
Order Preserving Minimal Perfect Hash Functions and Information Retrieval
Authors: Edward A. Fox, Qi Chen, Amjad M. Daoud
Venue:  (1991)

Rapid access to information is essential for a wide variety of retrieval systems and applications. Hashing has long been used when the fastest possible direct search is desired, but is generally not appropriate when sequential or range searches are also required. This paper describes a hashing method, developed for collections that are relatively static, that supports both direct and sequential access. The algorithms described give hash functions that are optimal in terms of time and hash table space utilization, and that preserve any a priori ordering desired. Furthermore, the resulting order preserving minimal perfect hash functions (OPMPHFs) can be found using time and space that are linear in the number of keys involved and so are close to optimal.
Light-Driven Global Illumination with a Wavelet Representation of Light Transport
Authors: Robert R. Lewis, Alain Fournier
Venue:  (1995)

We describe the basis of the work he have currently under way to implement a new rendering algorithm called "light-driven global illumination". This algorithm is a departure from conventional raytracing and radiosity renderers which addresses a number of deficiencies intrinsic to those approaches.
On-line Parallel Tomography
Authors: Shava Smallen
Venue:  (2001)

Tomography is a computationally intensive process by which the three-dimensional structure of an object can be reconstructed from a series of two-dimensional projections. In this thesis, we address on-line execution of tomography to provide real-time feedback to users collecting data from an on-line instrument. Context for this work is provided by a powerful electron microscope located at the National Center for Microscopy and Imaging Research (NCMIR). Acquiring data from NCMIR''s microscope is a lengthy process and is susceptible to configuration errors. Thus, real-time tomography feedback will allow users to quickly NCMIR''s microscope is a lengthy process and is susceptible to configuration errors. Thus, real-time tomography feedback will allow users to quickly identify configuration problems and interact with the microscope in order to more efficiently acquire data from it. We present an implementation of on-line parallel tomography which allows for production runs in Computational Grid environments. Developing applications that leverage this type of platform is difficult because resources are heterogenous and dynamic. In our approach, on-line parallel tomography is designed to be tunable such that it can be configured to adapt to different resource availabilities. It is coupled with an user-directed, application-level scheduler which exploits the tunability of the application to determine a schedule for soft real-time execution. The scheduler utilizes user constraints, an application model, and dynamic resource load predictions to determine feasible run-time configurations. The configurations are displayed as choices to the user where each configuration involves trade-offs between resolution of the reconstruction, frequency of feedback, and cost of execution. Once an appropriate configuration is chosen by the user, the scheduler selects resources, allocates work, and executes the application.
Data representation in industrial systems
Authors: Claudia Raibulet, Claudio Demartini
Venue: Enterprise information systems IV (2003)

The specification and implementation of data related to heterogeneous resources are still actual problems in industrial systems in spite of the variety of data storage models and technologies available on the market today. And this is because industrial resources have associated proprietary specifications and implementations for their related data. The paper proposes two possible solutions to these problems. The first specifies a Distributed Repository Model that aims at providing a unified/common view of the heterogeneous resources in an industrial system. This approach makes use of the ISO 10303 standard. The second proposes the definition of an industrial-specific language that provides the syntax and the rules to create logical data models for industrial systems. It is based on the eXtensible Markup Language. Both approaches are independent of any implementation detail and/or storage-model architecture. A comparison of the two solutions is provided at the end of the paper.
``Coaxial Stereo \& Scale Based Matching''''
Authors: Katz Itzhak
Venue:  (1985)

The past decade has seen a growing interest in {\em computer stereo vision}: the recovery of the depth map of a scene from two-dimensional images. The main problem of computer stereo is in establishing correspondence between features or regions in two or more images. This is referred to as the {\em correspondence problem}. One way to reduce the difficulty of the above problem is to constrain the {\em camera modeling}. Conventional stereo systems use two or more cameras, which are positioned in space at a uniform distance from the scene. These systems use {\em epipolar geometry} for their camera modeling, in order to curb the search space to be one-dimensional --- along {\em epipolar lines}. Following Jain''s approach, this thesis exploits a non-conventional camera modeling: the cameras are positioned in space one behind the other, such that their optical axes are collinear (hence the name {\em coaxial stereo}), and their distance apart is known. This approach complies with a simple case of epipolar geometry which further reduces the magnitude of the correspondence problem. The displacement of the projection of a stationary point occurs along a {\em radial line}, and depends only on its spatial depth and the distance between the cameras. Thus, to simplify (significantly) the recovery of depth from {\em disparity}, complex logarithmic mapping is applied to the original images. The logarithmic part of the transformation introduces great distortion to the image''s resolution. Therefore, to minimize this distortion, it is applied to the features used in the matching process. The search for matching features is conducted along radial lines. Following Mokhtarian and Mackworth''s approach, a {\em scale-space} image is constructed for each radial line by smoothing its intensity profile with a {\em Gaussian filter} and finding {\em zero-crossings} in the second derivative at varying scale levels. Scale-space images of corresponding radial lines are then matched, based on a modified uniform cost algorithm. The matching algorithm is written with generality in mind. As a consequence, it can be easily adopted to other stereoscopic systems. Some new results on the structure of scale-space images of one dimensional functions are presented.
Inference of Syntax for Point Sets
Authors: Mike Alder
Venue:  (1994)

This is the final version of the Vlieland paper which appears in draft as TR93-08. It describes in a low key manner, using lots of English and some pictures the ideas behind the inference of a hierarchical grammar of a certain type. This is sketched for understanding of some simple images. To be read before the other Vlieland papers.
Massively Parallel Simulations with Application to Queueing Networks
Authors: Jain J. Wang, Marc Abrams
Venue:  (1995)

This paper investigates two parallel simulation methodologies, multiple replication and parallel regenerative simulation. Problems of applying these methodologies to massively parallel simulations are identified. Two approaches (MR-PI and PR) are proposed to overcome some of these problems. The MR-PI approach, based on multiple replication simulation, uses a pilot simulation to reduce the initial transient bias by starting the simulation from a state that is representative of the steady-state conditions. The PR approach allows approximate regeneration by using substate matching for models that do no regenerate frequently. Empirical results suggest that the proposed approaches can produce very accurate results.
Effects of adding perturbations to phenotypic parameters in genetic algorithms for searching robust solutions
Authors: Shigeyoshi Tsutsui, Ashish Ghosh
Venue: Advances in evolutionary computing: theory and applications (2003)

We have proposed a scheme that extends the application of GAs to domains that require detection of robust solutions. We called this technique GAs/RS3 - GAs with a robust solution searching scheme. In the GAs/RS3, a perturbation is added to the phenotypic feature once for evaluation of an individual, thereby reducing the chance of selecting sharp peaks. We refer to this method as a single-evaluation model (SEM). In this chapter, we introduce a natural variant of this method, a multi-evaluation-model (MEM), where perturbations are given more than once for evaluation of the individual, and we offer comparative studies on their convergence property. The results showed that for the GAs/RS with SEM the population converges to robust solutions faster than with the MEM, and as the number of evaluations increases, the convergence speed decreases. We may conclude that the GAs/RS3 with the SEM is more efficient than with the MEM. We also introduced a variation of the MEM, i.e., multievaluation model keeping the worst value (MEM-W), and provided a mathematical analysis.
Lower Bounds for Union-Split-Find Related Problems on Random Access Machines
Authors: Per Bro Miltersen
Venue:  (1993)

We prove =(Clog logn ) lower bounds on the random access machine complexity of several dynamic, partially dynamic and static data structure problems, including the union-split-find problem, dynamic prefix problems and one-dimensional range query problems. The proof techniques include a general technique using perfect hashing for reducing static data structure problems (with a restriction of the size of the structure) into partially dynamic data structure problems (with no such restriction), thus providing a way to transfer lower bounds. We use a generalization of a method due to Ajtai for proving the lower bounds on the static problems, but describe the proof in terms of communication complexity, revealing a striking similarity to the proof used by Karchmer and Wigderson for proving lower bounds on the monotone circuit depth of connectivity.
Probabilistic Evaluation of Common Functions On Rings of Known Size
Authors: Karl Abrahamson, Andrew Adler, Lisa Higham, David G. Kirkpatrick
Venue:  (1988)

In [5]. Duris and Galil prove an $ \Omega (n \log n)$ lower bound for the average number of messages required by any deterministic algorithm which elects a leader on an asynchronous ring with distinct identifiers where ring size $n$ is known and is a power of 2. Their results imply the same lower bound for the expected complexity of any randomized leader election algorithm for an anonymous ring of known size 2^{k}$. If their new techniques are used to achieve the randomized result directly, the resulting proof is significantly simpler than the original deterministic one. This simplicity facilitates extension of the result in two directions; namely, for arbitrary known ring size, and for algorithms that permit error with probability at most $\epsilon $. Specifically, we prove that the expected message complexity of any probabilistic algorithm that selects a leader with probability at least $1 - \epsilon $ on an anonymous ring of known size $n$, is $\Omega (n \min(\log n, \log \log(l / \epsilon ))) $. A number of common function evaluation problems (including AND, OR, PARITY, and SUM) on rings of known size, are shown to inherit this complexity bound and that the bound is tight to within a constant factor.
UNIVERSAL COVERS OF EDGE-LABELED DIGRAPHS:ISOMORPHISM TO DEPTH n - 1 IMPLIES ISOMORPHISM TO ALL DEPTHS
Authors: N. Norris
Venue:  (1990)

Edge-labeled digraphs have been used to model computer networks, and the universal covers of such graphs to describe what a processor in an anonymous network ``knows'''' about the network. If G is a connected edge-labeled directed graph with n vertices, write U^k_v for the universal cover of G, rooted at a vertex v and truncated at depth k . In this note we consider the smallest depth m for which isomorphism between U^m_v and U^m_w guarantees that U^k_v and U^k_w are isomorphic to all depths, k, for v, w vertices in the universal cover of G. We show that this m equals n - 1 . Isomorphism to a depth smaller than n - 1 does not insure isomorphism to all depths. Our result is an improvement over the previous result of n^2 due to Yamashita and Kameda. It applies immediately to graphs without edge-labels. The ACM Portal is published by the Association for Computing Machinery. Copyright © 2010 ACM, Inc. Terms of Usage Privacy Policy Code of Ethics Contact Us Useful downloads: Adobe Acrobat QuickTime Windows Media Player Real Player
Unsupervised Image Segmentation Combining Region and Boundary Estimation
Authors: Abhir Bhalerao, Roland Wilson
Venue:  (2000)

An integrated approach to image segmentation is presented that combines region and boundary information using maximum a posteriori estimation and decision theory. The algorithm employs iterative, decision-directed estimation performed on a novel multiresolution representation. The use of a multiresolution technique ensures both robustness in noise and efficiency of computation, while the model-based estimation and decision process is flexible and spatially local, thus avoiding assumptions about global homogeneity or size and number of regions. A comparative evaluation of the method against region-only and boundary-only methods is presented and is shown to produce accurate segmentations at quite low signal-to-noise ratios.
Characterisation Survey
Authors: M. J. Zemerly, E. Papaefstathiou
Venue:  (1993)

The performance of a computer system is affected by the characteristics of its various hardware and software subsystems. Hardware and software characterisation give the ability to change machine and programs parameters and observe their effects on the performance of the system without changing the existing hardware which can be time consuming and cost prohibitive. This report provides a survey of the techniques and tools used in the hardware and software characterisation of parallel systems.
NSTAT: A Model-based Real-time Network Intrusion Detection System
Authors: Richard A. Kemmerer
Venue:  (1998)

The Reliable Software Group at UCSB has developed a new approach to representing computer penetrations. This approach models penetrations as a series of state transitions described in terms of signature actions and state assertions. State transition representations are written to correspond to the states of an actual computer system, and they form the basis of a rule-based expert system for detecting penetrations. The system is called the State Transition Analysis Tool (STAT). On a network filesystem where the files are distributed on many hosts and where each host mounts directories from the others, actions on each host computer need to be audited. A natural extension of the STAT effort is to run the system on audit data collected by multiple hosts. This means an audit mechanism needs to be run on each host. However, running an implementation of STAT on each host would result in inefficient use of computer resources. In addition, the possibility of having cooperative attacks on different hosts would make detection difficult. Therefore, for the distributed version of STAT, called NSTAT, there is a single STAT process with a single, chronological audit trail. We are currently designing a client/server approach to the problem. The client side has two threads: a producer that reads and filters the audit trail and a consumer that sends it to the server. The server side merges the filtered information from the various clients and performs the analysis.
Report on RSNA 94
Authors: R. Chandrasekhar
Venue:  (1994)

Abstract unavailable. The ACM Portal is published by the Association for Computing Machinery. Copyright © 2010 ACM, Inc. Terms of Usage Privacy Policy Code of Ethics Contact Us Useful downloads: Adobe Acrobat QuickTime Windows Media Player Real Player
Conservative Approximations of Hybrid Systems
Authors: Andrew K. Martin, Carl Seger
Venue:  (1994)

Systems that are modeled using both continuous and discrete mathematics are commonly called hybrid systems. Although much work has been done to develop frameworks in which both types of systems can be modeled at the same time, this is often a very difficult task. Verifying that desired properties hold in such hybrid models is even more daunting. In this paper we attack the problem from a different direction. First we make a distinction between two models of the system. A detailed model is developed as accurately as possible. Ultimately, one must trust in its correctness. An abstract model, which is typically less detailed, is actually used to verify properties of the system. The detailed model is typically defined in terms of both continuous and discrete mathematics, whereas the abstract one is typically discrete. We formally define the concept of conservative approximation, a relationship between models, that holds with respect to a translation between specification languages. We then progress by developing a theory that allows us to build a complicated detailed model by combining simple primitives. Simultaneously, we build a conservative approximation by similarly combining pre-defined parameterized approximations of those primitives.
The Hardness of Approximating Spanner Problems
Authors: M. Elkin, D. Peleg
Venue:  (1999)

This paper examines a number of variants of the sparse k-spanner problem, and presents hardness results concerning their approximability. In general, it is shown that unless NP = P, these problems admit no 2log1-e>sub<n>/sub<-ratio approximation, for any e < 0, for certain ranges of the stretch requirement k depending on the particular variant at hand. The problems studied differ by the types of edge weights and lengths used, and include also directed, augmentation and client-server variants of the problem.
Quantum Computing Applied to Optimization
Authors: Ge Yuzhen, Watson Layne T.
Venue:  (1999)

Optimization problems represent a class of problems that can be time consuming to solve and very complex. In this paper, a quantum algorithm for solving optimization problems is proposed. The algorithm utilizes the encoding scheme from genetic algorithms to encode the problem and then uses Grover''s unitary transformation to seek out a solution. The efficiency of the algorithm depends on the length of the chromosome or the coded variable. As a simple example the satisfiability problem, an NP-complete problem, is examined using the algorithm and the time complexity of solving this problem is greatly improved. The traveling salesman and minimum spanning tree problems are also briefly discussed.
Wave motion in infinite inhomogeneous waveguides
Authors: I. Špacapan, M. Premrov
Venue: Proceedings of the eighth international conference on The application of artificial intelligence to civil and structural engineering computing (2001)

The analysis of wave motion in infinite homogeneous waveguides, having a cross-section which is not simple, and/or having an irregular inclusion, is by the majority of the available methods a rather difficult task, especially when striving for exact results. On the contrary, the presented procedure, which is in frequency domain, is simple to apply. It yields exact results and a clear parametric insight into wave motion. Radiation conditions are satisfied exactly. The procedure uses FE modelling of the interesting section of the waveguide, and the decomposition of the wave motion into the distinct wavemodes with constant velocities by eigenvalue problem solution. The presented examples demonstrates the effectiveness of the procedure, while analytical results confirm its accuracy.
An Automatic Oxalate Needle Counting System for Optical Microscope Images
Authors: Anthnoy Zaknich
Venue:  (1994)

This report describes a PC based system for dinscriminating oxalate needles from hydrate particles in specially prepared optical microscope images. The oxalate needles are counted and sized. The system is able to function automatically with both normal and polarised light sources and with both white on black and black on white views. It is hoped that the introduction of this system to monitor the presence of oxalate needles in critical plant locations will provide a consistent and repeatable measure. The ACM Portal is published by the Association for Computing Machinery. Copyright © 2010 ACM, Inc. Terms of Usage Privacy Policy Code of Ethics Contact Us Useful downloads: Adobe Acrobat QuickTime Windows Media Player Real Player