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3rd Scandinavian Workshop on Algorithm Theory, SWAT 1992

作者： Freivalds, Rūsiņšg Smith, Carl H. Institute of Mathematics and Computer Science University of Latvia Ralņa bulvāris 29 Riga226250 Latvia Department of Computer Science and Institute for Advanced Computer Studies The University of Maryland College ParkMD20742 United States

ISBN: (纸本)9783540557067

The traditional model of learning in the limit is restricted so as to allow the learning machines only a fixed, finite amount of memory to store input and other data. A class of recursive functions is presented that cannot be learned deterministically by any such machine, but can be learned by a memory limited probabilistic leaning machine with probability 1. © Springer-Verlag Berlin Heidelberg 1992.

关键词： Recursive functions

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Learning Visual Coordinate Transformations with Competition

Learning Visual Coordinate Transformations with Competition

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1992 International Joint Conference on Neural Networks, IJCNN 1992

作者： Cho, Sungzoon Reggia, James A. Dept. of Computer Science University of Maryland College ParkMD20742 United States The Institute for Advanced Computer Studies The Department of Neurology The University of Maayland United States

ISBN: (纸本)0780305590

As the angle of gaze changes, so does the retinal location of the visual image of a stationary object. Since the object is correctly perceived as stationary, the retinotopic coordinates of the object have been transformed into craniotopic coordinates somehow using eye position information. Neurons in area 7a of posterior parietal cortex in macaque monkeys are thought to contribute to this transformation, and previous studies have shown that neural networks trained to perform this task develop properties similar to those of area 7a neurons. We trained networks on this task using competitive backpropagation learning to see if this new learning method would reproduce previous results and to assess topographic map formation. The trained networks generalized well to previously unseen patterns. As with other learning methods, the hidden units developed large retinal receptive fields, planar spatial gain fields, and eye position dependent spatial tuning like the neurons in area 7a. In addition, this study demonstrates for the first time that networks with fixed lateral connections in the hidden layer produced a topographic structure where adjacent units tended to be tuned to the same area in head-centered space. This coarse coding mechanism could be used as a mechanism for an eye position independent spatial coding. Also, this study shows that competitive backpropagation learning is capable of training networks to learn continuous valued functions as well as binary ones. © 1992 IEEE.

关键词： Neurons

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APPROXIMATION ALGORITHMS FOR GRAPH AUGMENTATION 19th

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19TH INTERNATIONAL COLLOQUIUM ON AUTOMATA, LANGUAGES, AND PROGRAMMING ( ICALP 92 )

作者： KHULLER, S THURIMELLA, R Institute for Advanced Computer Studies (UMIACS) University of Maryland at College Park College Park 20742 MD United States Department of Mathematics and Computer Science University of Denver Denver 80208 CO United States

We study the problem of increasing the connectivity1 of a graph at an optimal cost. Since the general problem is NP-hard, we focus on efficient approximation schemes that come within a constant factor from the optimal... 详细信息

ISBN: (纸本)3540557199

We study the problem of increasing the connectivity¹ of a graph at an optimal cost. Since the general problem is NP-hard, we focus on efficient approximation schemes that come within a constant factor from the optimal. Previous algorithms either do not take edge costs into consideration, or run slower than our algorithm. Our algorithm takes as input an undirected graph G_o= (V, E₀) on n vertices, that is not necessarily connected, and a set Feasible of m weighted edges on V, and outputs a subset Aug of edges which when added to Go make it 2-connected. The weight of Aug, when Go is initially connected, is no more than twice the weight of the least weight subset of edges of Feasible that increases the connectivity to 2. The running time of our algorithm is O(m+n log n). We also study the problem of increasing the edge connectivity of any graph G, to k, within a factor of 2 (for any k > 0). The running time of this algorithm is O(nk log n(m + n log n)). We observe that when k is odd we can use different techniques to obtain an approximation factor of 2 for increasing edge connectivity from k to (k+1) in O(kn²) time. © Springer-Verlag Berlin Heidelberg 1992.

关键词： Undirected graphs

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Semantics of disjunctive deductive databases 4th

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4th International Conference on Database Theory, ICDT 1992

作者： Fernándaz, José Alberto Minker, Jack Department of Computer Science University of Maryland College ParkMD20742 United States Institute for Advanced Computer Studies University of Maryland College ParkMD20742 United States

ISBN: (纸本)9783540560395

A review is presented of work on disjunctive deductive databases. The semantic approach to disjunctive deductive databases as developed by Fernándaz and Minker is explored. The method is applied to stratified and stable model semantics for disjunctive deductive databases. The semantics for updating a subclass of disjunctive deductive databases is described. © 1992, Springer-Verlag. All rights reserved.

关键词： Semantics

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A simple assertional proof system for real-time systems

A simple assertional proof system for real-time systems

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1992 Real-Time Systems Symposium, RTSS 1992

作者： Shankar, A. Udaya Department of Computer Science University of Maryland College Park MD 20742 United States Institute for Advanced Computer Studies University of Maryland College Park MD 20742 United States

ISBN: (纸本)0818631953

We present a simple proof system for a real-time system model similar to that of timed I/O automata. By introducing state variables indicating the last event occurrence time and event deadline time, we can express real-time properties in terms of traditional safety and progress assertions (e.g. invariant, unless, and leads-to) which are interpreted in the standard way. As a result, we can prove them using traditional proof rules (with weak fairness assumptions being replaced by finite upper bound timing assumptions). Unlike other approaches, we do not use a "current time" variable. The proof system is illustrated on a real-time mutual exclusion algorithm. We have also applied it to examples from the timed I/O automata literature. © 1992 IEEE.

关键词： Real time systems

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On the precise loop transfer recovery and transmission zeros 1

On the precise loop transfer recovery and transmission zeros

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1st IEEE Conference on Control Applications, CCA 1992

作者： O'Leary, Dianne P. Monanemi, Moghen M. Barlow, Jewel B. Computer Science Department Institute for Advanced Computer Studies University of Maryland College ParkMD20742 United States Aerospace Engineering Department University of Maryland College ParkMD20742 United States

ISBN: (纸本)0780300475

The purpose of this paper is to elaborate on our previous work concerned with obtaining precise loop transfer recovery using a reduced-order Luenberger observer. We now show that for a non-square system in which the number of sensors exceeds the number of actuators, precise loop transfer recovery will exist when the system does not possess transmission zeros. © 1992 IEEE.

关键词： Recovery

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RANDOMIZED RANGE-MAXIMA IN NEARLY-CONSTANT PARALLEL TIME 3rd

RANDOMIZED RANGE-MAXIMA IN NEARLY-CONSTANT PARALLEL TIME

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3RD INTERNATIONAL SYMP ON ALGORITHMS AND COMPUTATION ( ISAAC 92 )

作者： BERKMAN, O MATIAS, Y VISHKIN, U Dept. of Computing School of Physical Sciences and Engineering King’s College London Strand London WC2R 2LS United Kingdom Institute for Advanced Computer Studies University of Maryland College Park 20742 MD United States Department of Computer Science Tel Aviv University Israel

ISBN: (纸本)3540562796

Given an array of n input numbers, the mnge. mazima problem is to preprocess the data so that queries of the type “what is the maximum value in subarray [i..j]” can be answered quickly using one processor. We present a randomized preprocessing algorithm that runs in O(log* n) time with high probability, using all optimal number of processors on a CRCW PRAM;each query can be processed in constant time by one processor. We also present a randomized algorithm for a parallel comparison model. Using an optimal number of processors, the preprocessing algorithm runs in O(α(n)) time with high probability;each query can be processed in O(α(n)) time by one processor. (α(n) is the inverse of Ackermann function.) A constunt time query can be achieved by some slowdown in the performance of the preprocessing stage. © Springer-Verlag Berlin Heidelberg 1992.

关键词： Artificial intelligence

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LEADERS ELECTION WITHOUT CONFLICT-RESOLUTION RULE - FAST AND EFFICIENT RANDOMIZED SIMULATIONS AMONG CRCW PRAMS 1st

LEADERS ELECTION WITHOUT CONFLICT-RESOLUTION RULE - FAST AND...

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1ST LATIN AMERICAN SYMP ON THEORETICAL INFORMATICS ( LATIN 92 )

作者： GIL, J MATIAS, Y The University of British Columbia Department of Computer Science 6356 Agricultural Road Vancouver V6T 1Z2 BC Canada University of Maryland Institute for Advanced Computer Studies College Paxk 20742 MD United States Tel Aviv University Department of Computer Science Israel

ISBN: (纸本)3540552847

We study the problem of fast leaders election on Tolerant, a CRCW PRAM model which tolerates concurrent write but does not support symmetry breaking. The leaders election problem is related to the problem of simulating stronger CRCW models, which support leaders election by pre-defined conflict resolution rules. We give a randomized simulation of Maximum-a very strong CRCW PRAM-on Tolerant. The simulation is optimal, reliable, and runs in nearly doubly logarithmic time and linear space. This is the first simulation which is fast, optimal and space-efficient, and therefore grants true comparison of algorithms running on different CRCW PRAMs. Moreover, it implies that the memory to which concurrent read or concurrent write are assumed should never be more than linear-the rest of the memory can always be addressed under the EREW convention. The techniques presented in this paper tackle fundamental difficulties in the design of fast parallel algorithms. © Springer-Verlag Berlin Heidelberg 1992.

关键词： computers

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A robust distributed mutual exclusion algorithm 5th

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5th International Workshop on Distributed Algorithms, WDAG 1991

作者： Rangarajan, Sampath Tripathi, Satish K. Institute for Advanced Computer Studies University of Maryland College ParkMD20742 United States Department of Computer Science University of Maryland at College Park College ParkMD20742 United States

ISBN: (纸本)9783540552369

Correct operation of a distributed system with replicated resources requires that mutual exclusion be maintained among independent requests to these resources at different sites in the system. In this paper, we propose "asymptotically high resiliency" as a performance measure for fault-tolerant mutual exclusion algorithms for systems where sites can fail. We then present an efficient highly fault-tolerant algorithm for mutual exclusion. The algorithm is totally distributed in nature and is shown to have a message overhead of O(√ N log N) where N is the number of sites. The algorithm provides mutual exclusion with a resiliency (that is, probability that permission for a mutual exclusion request is obtained in spite of site failures) approaching 1 asymptotically with an increase in N. © Springer-Verlag Berlin Heidelberg 1992.

关键词： Fault tolerance

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Learning Programs with an Easy to Calculate Set of Errors

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Fundamenta Informaticae 1992年第3-4期16卷 355-370页

作者： Gasarch, William I. Sitaraman, Ramesh K. Smith, Carl H. Velauthapillai, Mahendran University of Maryland Department of Computer Science and the University of Maryland Institute for Advanced Computer Studies Princeton University Department of Computer Science Princeton USA Georgetown University Department of Computer Science Georgetown USA

Within the study of inductive inference a recurring theme has been to investigate the learning of programs that are not exactly correct. Previous work attempted to quantify the difference between the function to be learned and the one computed by the result of a learning process. In this paper we study a qualitative measure of approximate correctness of the result of attempting to learn a program for a given function. What we require is that the set of errors be somehow easy to describe.

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