ppxscal/embedding_network huggingface dataset:
Using path control variates in activity network simulation
Authors: Sekhar Venkatraman, James R. Wilson
Venue: Proceedings of the 17th conference on Winter simulation (1985)

In the simulation of a stochastic activity network (SAN), the usual objective is to obtain point and confidence-interval estimators of the mean completion time for the network. This paper presents a new procedure for using path control variates to improve the efficiency of such estimators. Because each path control is the duration of an associated path in the network, the vector of selected path controls has both a known mean and a known covariance matrix. All of this information is incorporated into point- and interval-estimation procedures for both normal and nonnormal responses. To evaluate the performance of these procedures experimentally, we compare actual versus predicted reductions in point-estimator variance and confidence-interval half-length for a set of SANs in which the following characteristics are systematically varied: (a) the size of the network (number of nodes and activities); (b) the topology of the network; (c) the relative dominance (criticality index) of the critical path; and (d) the percentage of activities with exponentially distributed durations. The experimental results indicate that large variance reductions can be achieved with these estimation procedures in a wide variety of networks.
High-level microprogramming: an optimizing C compiler for a processing element of a CAD accelerator
Authors: Paul Kenyon, Prathima Agrawal, Sharad Seth
Venue: Proceedings of the 23rd annual workshop and symposium on Microprogramming and microarchitecture (1990)

The development of a high-level language compiler for a micro-programmable processing element (PE) in the MARS multicomputer is described. MARS, an MIMD message passing machine, was designed to speed up VLSI CAD and similar other non-numerical applications. The need for support of a high-level language at the PE level of a multicomputer is considered, and the choice of C as an appropriate programming language is justified. Special features found in VLSI processors are examined along with compiler support for them. Conventional retargetable compiler techniques are shown to be inadequate for the highly concurrent micro-programmable PE. These techniques must be extended for microcode generation. The design of the MARS compiler is outlined. Performance data is provided to evaluate the benefit of various compiler optimizations, and to compare compiler generated microcode to hand generated microcode in terms of space and time performance
CALIN: a user interface based on a simple natural language
Authors: P. Bosc, M. Courant, S. Robin
Venue: Proceedings of the 9th annual international ACM SIGIR conference on Research and development in information retrieval (1986)

In the framework of an application dealing with classified advertisement matching, a dedicated user interface has been designed and implemented. Its major originality relies on the user's language which is neither an artificial one, nor the usual natural language, but in fact the ad language. Beyond the language itself, the interface provides some facilities such as paraphrasing or explanations when needed. An expert system approach has been adopted and the interface is built up from the knowledge given by experts. They are in charge of describing what are acceptable ads, from both syntax and semantics points of view &hellip; Although designed in the context of ad matching, that interface may interestingly be adapted to other retrieving systems. We especially think that an adlike language is well-suited to ask questions since it is based on natural simple expressions. A given sentence involves terms that stand for elementary conditions applying to instances of a logical object contained inside the information system. This approach defines a complete interface, involving both a language and aiding capabilities. Moreover, the query language, although less powerful, represents a compromise between artificial languages and the usual natural language, with respect to ergonomics and analysis complexity.
The Quadric Reference Surface: Theory and Applications
Authors: Amnon Shashua, Sebastian Toelg
Venue: International Journal of Computer Vision (1997)

The conceptual component of this work is about &ldquo;reference surfaces&rdquo; which are the analogous to reference frames often used for shape representation purposes. The theoretical component of this work involves the question of whether one can find a unique (and simple) mapping that aligns two arbitrary perspective views of an opaque textured quadric surface in 3D, given (i) few corresponding points in the two views, or (ii) the outline conic of the surface in one view (only) and few corresponding points in the two views. The practical component of this work is concerned with applying the theoretical results as tools for the task of achieving full correspondence between views of arbitrary objects.
Learning from Multiple Sources of Inaccurate Data
Authors: Ganesh Baliga, Sanjay Jain, Arun Sharma
Venue: SIAM Journal on Computing (1997)

Most theoretical models of inductive inference make the idealized assumption that the data available to a learner is from a single and accurate source. The subject of inaccuracies in data emanating from a single source has been addressed by several authors. The present paper argues in favor of a more realistic learning model in which data emanates from multiple sources, some or all of which may be inaccurate. Three kinds of inaccuracies are considered: spurious data (modeled as noisy texts), missing data (modeled as incomplete texts), and a mixture of spurious and missing data (modeled as imperfect texts).Motivated by the above argument, the present paper introduces and theoretically analyzes a number of inference criteria in which a learning machine is fed data from multiple sources, some of which may be infected with inaccuracies. The learning situation modeled is the identification in the limit of programs from graphs of computable functions. The main parameters of the investigation are: the kind of inaccuracy, the total number of data sources, the number of faulty data sources which produce data within an acceptable bound, and the bound on the number of errors allowed in the final hypothesis learned by the machine.Sufficient conditions are determined under which, for the same kind of inaccuracy, for the same bound on the number of errors in the final hypothesis, and for the same bound on the number of inaccuracies, learning from multiple texts, some of which may be inaccurate, is equivalent to learning from a single inaccurate text. The general problem of determining when learning from multiple inaccurate texts is a restriction over learning from a single inaccurate text turns out to be combinatorially very complex. Significant partial results are provided for this problem. Several results are also provided about conditions under which the detrimental effects of multiple texts can be overcome by either allowing more errors in the final hypothesis or by reducing the number of inaccuracies in the texts.It is also shown that the usual hierarchies resulting from allowing extra errors in the final program (results in increased learning power) and allowing extra inaccuracies in the texts (results in decreased learning power) hold.Finally, it is demonstrated that in the context of learning from multiple inaccurate texts, spurious data is better than missing data, which in turn is better than a mixture of spurious and missing data.
Application of Ada on a distributed missile control system
Authors: D. Wengelin, L. Asplund
Venue: Proceedings of the conference on TRI-ADA '90 (1990)

A system for distributing a single Ada program to a network of loosely coupled computers is described. The system is applied to the distribution of a missile control system. We have found that implementing the entire Ada semantics for distributed systems is difficult, but that a pragmatic approach can give reasonable semantics. Our approach is based on source code transformation of the single Ada program into multiple Ada programs. These programs are then compiled with a standard compiler. The units of distribution are tasks and task types, subprograms, and variables. Restrictions are implied by the task termination semantics, the exception propagation between nodes, and the synchronization of tasks at activation.
A discretionary access control model with temporal authorizations
Authors: Elisa Bertino, Claudio Bettini, Pierangela Samarati
Venue: Proceedings of the 1994 workshop on New security paradigms (1994)

Conventional authorization models enforcing discretionary policies are based on authorizations which specify, for each user or group of users in the system, the accesses he is allowed to execute on objects. We propose a new authorization model which allows to associate with each authorization temporal constraints which restrict the validity of the authorization. Moreover, in our model we allow the specification of temporal dependencies among authorizations. Temporal dependencies allow the derivation of new authorizations on the basis of the presence or of the absence of other authorizations in given time intervals. In the paper we present the main characteristics of our model and illustrate some research issues we are currently investigating.
Quantitative Analysis of MR Brain Image Sequences by Adaptive Self-Organizing Finite Mixtures
Authors: Yue Wang, Tülay Adali, Chi-Ming Lau, Sun-Yuan Kung
Venue: Journal of VLSI Signal Processing Systems (1998)

This paper presents an adaptive structure self-organizing finite mixture network for quantification of magnetic resonance (MR) brain image sequences. We present justification for the use of standard finite normal mixture model for MR images and formulate image quantification as a distribution learning problem. The finite mixture network parameters are updated such that the relative entropy between the true and estimated distributions is minimized. The new learning scheme achieves flexible classifier boundaries by forming winner-takes-in probability splits of the data allowing the data to contribute simultaneously to multiple regions. Hence, the result is unbiased and satisfies the asymptotic optimality properties of maximum likelihood. To achieve a fully automatic quantification procedure that can adapt to different slices in the MR image sequence, we utilize an information theoretic criterion that we have introduced recently, the minimum conditional bias/variance (MCBV) criterion. MCBV allows us to determine the suitable number of mixture components to represent the characteristics of each image in the sequence. We present examples to show that the new method yields very efficient and accurate performance compared to expectation-maximization, K-means, and competitive learning procedures.
The hit-and-run sampler: a globally reaching Markov chain sampler for generating arbitrary multivariate distributions
Authors: Robert L. Smith
Venue: Proceedings of the 28th conference on Winter simulation (1996)

The problem of efficiently generating general multivariate densities via a Monte Carlo procedure has experienced dramatic progress in recent years through the device of a Markov chain sampler. This procedure produces a sequence of random deviates corresponding to a random walk over the support of the target distribution. Under certain regularity conditions, the corresponding Markov chain converges in distribution to the target distribution. Thus the sample of points so generated can serve as a statistical sample of points drawn from the target distribution. A random walk that can globally reach across the support of the distribution in one step is called a Hit-and-Run sampler. Hit-and-Run Markov chain samplers offer the promise of faster convergence to the target distribution than conventional small step random walks. Applications to optimization are considered.
Real-time computing with lock-free shared objects
Authors: James H. Anderson, Srikanth Ramamurthy, Kevin Jeffay
Venue: ACM Transactions on Computer Systems (TOCS) (1997)

This article considers the use of lock-free shared objects within hard real-time systems. As the name suggests, lock-free shared objects are distinguished by the fact that they are accessed without locking. As such, they do not give rise to priority inversions, a key advantage over conventional, lock-based object-sharing approaches. Despite this advantage, it is not immediately apparent that lock-free shared objects can be employed if tasks must adhere to strict timing constraints. In particular, lock-free object implementations permit concurrent operations to interfere with each other, and repeated interferences can cause a given operation to take an arbitrarily long time to complete. The main contribution of this article is to show that such interferences can be bounded by judicious scheduling. This work pertains to periodic, hard real-time tasks that share lock-free objects on a uniprocessor. In the first part of the article, scheduling conditions are derived for such tasks, for both static and dynamic priority schemes. Based on these conditions, it is formally shown that lock-free shared objects often incur less overhead than object implementations based on wait-free algorithms or lock-based schemes. In the last part of the article, this conclusion is validated experimentally through work involving a real-time desktop videoconferencing system.
Students' attitudes toward computers: validation of a computer attitude scale for 16--19 education
Authors: Neil Selwyn
Venue: Computers Education (1997)

There is a strong need for both educators and researchers to be aware of students' attitudes toward using and interacting with computers in 16-19 education (i.e. year levels 12-14)--but as yet little work has been carried out in this area. This article therefore describes the development of an instrument for measuring the attitudes toward computers of students aged 16-19 years. Initial item selection produced a pilot scale consisting of 49 items which was administered to 266 students. Subsequent factor analysis revealed four structurally independent attitude constructs and justified retention of 21 of the original items. The revised scale was then administered to 87 Year 12-14 students for formal validation. The full instrument was found to have both a high internal reliability coefficient (0.90) and test-retest reliability (0.93), and significant construct validity (P<0.001).
Geometric Information Criterion for Model Selection
Authors: Kenichi Kanatani
Venue: International Journal of Computer Vision (1998)

In building a 3-D model of the environment from image and sensor data, one must fit to the data an appropriate class of models, which can be regarded as a parametrized manifold, or geometric model, defined in the data space. In this paper, we present a statistical framework for detecting degeneracies of a geometric model by evaluating its predictive capability in terms of the expected residual and derive the geometric AIC. We show that it allows us to detect singularities in a structure-from-motion analysis without introducing any empirically adjustable thresholds. We illustrate our approach by simulation examples. We also discuss the application potential of this theory for a wide range of computer vision and robotics problems.
TETE: an intelligent knowledge testing engine (poster)
Authors: Adam Wojciechowski, Jerzy R. Nawrocki, Karolina Kups, Michal Kosiedowski
Venue: ACM SIGCSE Bulletin (1998)

There were two actions which resulted in the project named TETE - An Intelligent Knowledge Testing Engine". The first one was launched by Polish Ministry of Education which aimed at starting "teleteaching" (a kind of Open University) in Poland. Poznan University of Technology was proposed to start distant courses in the field of Informatics (see [3]). The other stimulant for the project was the ECDL project. In 1996 CEPIS (Council of European Professional Informatics Societies) has decided to promote a Finnish idea of Computer Driving Licence and named it "European Computer Driving Licence" (ECDL). ECDL is a set of examinations - the same across Europe - which defines a certain standard of knowledge and skills necessary for effective usage of computers. In 1997 the authors started work on a computer system which would be used in distant education courses on ECDL. We focused our work on intelligent kernel for computer-aided learning system. Important feature of the system is the ability to work on-line as well as a standalone system for knowledge presentation and self-assessment. Structure of the TETE kernel allows to use it with wide variety of courses. TETE uses a web browser (e.g. Netscape) as a presentation tool and it consists of the following modules: bull; a progress database keeping track of the student's behaviour (e.g. student's answers, time between subsequent lessons and test sessions, forgetting curve etc.) which defines student's perception profile bull; an intelligent question selection and scheduling engine making decision on the basis of the progress data and description of available knowledge units and test questions; bull; student's time manager bull; progress reporter bull; smart pre-loader of web pages
Reconstruction and Decomposition Algorithms for Biorthogonal Multiwavelets
Authors: Charles A. Micchelli, Yuesheng Xu
Venue: Multidimensional Systems and Signal Processing (1997)

We construct biorthogonal multiwavelets (abbreviated to wavelets) in a weighted Hilbert space L^2(E,\rho) where E is a compact subset in \bR^d. A recursive formula for biorthogonal wavelet construction is presented. The construction of the initial wavelets is reformulated as the solution of a certain matrix completion problem. A general solution of the matrix completion problem is identified and expressed conveniently in terms of any given particular solution. Several particular solutions are proposed. Reconstruction and decomposition algorithms are developed for the biorthogonal wavelets. Special results for the univariate case E=[0,1] are obtained.
Memory allocation for long-running server applications
Authors: Per-Åke Larson, Murali Krishnan
Venue: Proceedings of the 1st international symposium on Memory management (1998)

Prior work on dynamic memory allocation has largely neglected long-running server applications, for example, web servers and mail servers. Their requirements differ from those of one-shot applications like compilers or text editors. We investigated how to build an allocator that is not only fast and memory efficient but also scales well on SMP machines. We found that it is not sufficient to focus on reducing lock contention - higher speedups require a reduction in cache misses and bus traffic. We then designed and prototyped a new allocator, called LKmalloc, targeted for both traditional applications and server applications. LKmalloc uses several subheaps, each one with a separate set of free lists and memory arena. A thread always allocates from the same subheap but can free a block belonging to any subheap. A thread is assigned to a subheap by hashing on its thread ID. WC compared its performance with several other allocators on a server-like, simulated workload and found that it indeed scales well and is quite fast hut memory more efficiently.
OMP: a RISC-based multiprocessor using orthogonal-access memories and multiple spanning buses
Authors: K. Hwang, M. Dubois, D. K. Panda, S. Rao, S. Shang, A. Uresin, W. Mao, H. Nair, M. Lytwyn, F. Hsieh, J. Liu, S. Mehrotra, C. M. Cheng
Venue: Proceedings of the 4th international conference on Supercomputing (1990)

This paper presents the architectural design and RISC based implementation of a prototype supercomputer, namely the Orthogonal MultiProcessor (OMP). The OMP system is constructed with 16 Intel 1860 RISC microprocessors and 256 parallel memory modules, which are 2-D interleaved and orthogonally accessed using custom-designed spanning buses. The architectural design has been validated by a CSIM-based multiprocessor simulator. The design choices are based on worst-case delay analysis and simulation validation. The current OMP prototype chooses a 2-dimensional memory architecture, mainly for image processing, computer vision, and neural network simulation applications. The 16-processor OMP prototype is targeted to achieve a peak performance of 400 RISC integer MIPS or a maximum of 640 Mflops. This paper presents the architectural design of the OMP prototype at system and PC board levels. We are presently entering the fabrication stage of all the PC boards. The system is expected to become operational in late 1991 and benchmarking results will be available in 1992. Only hardware design features are reported here. Software and simulation results are reported elsewhere.
Quasi Lumpability, Lower-Bounding Coupling Matrices, and Nearly Completely Decomposable Markov Chains
Authors: Tugrul Dayar, William J. Stewart
Venue: SIAM Journal on Matrix Analysis and Applications (1997)

In this paper, it is shown that nearly completely decomposable (NCD) Markov chains are quasi-lumpable. The state space partition is the natural one, and the technique may be used to compute lower and upper bounds on the stationary probability of each NCD block. In doing so, a lower-bounding nonnegative coupling matrix is employed. The nature of the stationary probability bounds is closely related to the structure of this lower-bounding matrix. Irreducible lower-bounding matrices give tighter bounds compared with bounds obtained using reducible lower-bounding matrices. It is also noticed that the quasi-lumped chain of an NCD Markov chain is an ill-conditioned matrix and the bounds obtained generally will not be tight. However, under some circumstances, it is possible to compute the stationary probabilities of some NCD blocks exactly.
Adaptive source rate control for real-time wireless video transmission
Authors: Hang Liu, Magda El Zarki
Venue: Mobile Networks and Applications (1998)

Hybrid ARQ schemes can yield much better throughput and reliability than static FEC schemes for the transmission of data over time-varying wireless channels. However these schemes result in extra delay. They adapt to the varying channel conditions by retransmitting erroneous packets, this causes variable effective data rates for current PCS networks because the channel bandwidth is constant. Hybrid ARQ schemes are currently being proposed as the error control schemes for real-time video transmission. An important issue is how to ensure low delay while taking advantage of the high throughput and reliability that these schemes provide for. In this paper we propose an adaptive source rate control (ASRC) scheme which can work together with the hybrid ARQ error control schemes to achieve efficient transmission of real-time video with low delay and high reliability. The ASRC scheme adjusts the source rate based on the channel conditions, the transport buffer occupancy and the delay constraints. It achieves good video quality by dynamically changing both the number of the forced update (intracoded) macroblocks and the quantization scale used in a frame. The number of the forced update macroblocks used in a frame is first adjusted according to the allocated source rate. This reduces the fluctuation of the quantization scale with the change in the channel conditions during encoding so that the uniformity of the video quality is improved. The simulation results show that the proposed ASRC scheme performs very well for both slow fading and fast fading channels.