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2,594 | 2 | Title: Can Recurrent Neural Networks Learn Natural Language Grammars? W&Z recurrent neural networks are able to
Abstract: Recurrent neural networks are complex parametric dynamic systems that can exhibit a wide range of different behavior. We consider the task of grammatical inference with recurrent neural networks. Specifically, we consider the task of classifying natural language sentences as grammatical or ungrammatical can a recurrent neural network be made to exhibit the same kind of discriminatory power which is provided by the Principles and Parameters linguistic framework, or Government and Binding theory? We attempt to train a network, without the bifurcation into learned vs. innate components assumed by Chomsky, to produce the same judgments as native speakers on sharply grammatical/ungrammatical data. We consider how a recurrent neural network could possess linguistic capability, and investigate the properties of Elman, Narendra & Parthasarathy (N&P) and Williams & Zipser (W&Z) recurrent networks, and Frasconi-Gori-Soda (FGS) locally recurrent networks in this setting. We show that both | [
411,
2306
] | Train |
2,595 | 2 | Title: TO IMPROVE FORECASTING
Abstract: Working Paper IS-97-007, Leonard N. Stern School of Business, New York University. In: Journal of Computational Intelligence in Finance 6 (1998) 14-23. (Special Issue on "Improving Generalization of Nonlinear Financial Forecasting Models".) http://www.stern.nyu.edu/~aweigend/Research/Papers/InteractionLayer Abstract. Predictive models for financial data are often based on a large number of plausible inputs that are potentially nonlinearly combined to yield the conditional expectation of a target, such as a daily return of an asset. This paper introduces a new architecture for this task: On the output side, we predict dynamical variables such as first derivatives and curvatures on different time spans. These are subsequently combined in an interaction output layer to form several estimates of the variable of interest. Those estimates are then averaged to yield the final prediction. Independently from this idea, on the input side, we propose a new internal preprocessing layer connected with a diagonal matrix of positive weights to a layer of squashing functions. These weights adapt for each input individually and learn to squash outliers in the input. We apply these two ideas to the real world example of the daily predictions of the German stock index DAX (Deutscher Aktien Index), and compare the results to a network with a single output. The new six layer architecture is more stable in training due to two facts: (1) More information is flowing back from the outputs to the input in the backward pass; (2) The constraint of predicting first and second derivatives focuses the learning on the relevant variables for the dynamics. The architectures are compared from both the training perspective (squared errors, robust errors), and from the trading perspective (annualized returns, percent correct, Sharpe ratio). | [
1315,
2452,
2562
] | Train |
2,596 | 3 | Title: Regression shrinkage and selection via the lasso
Abstract: We propose a new method for estimation in linear models. The "lasso" minimizes the residual sum of squares subject to the sum of the absolute value of the coefficients being less than a constant. Because of the nature of this constraint it tends to produce some coefficients that are exactly zero and hence gives interpretable models. Our simulation studies suggest that the lasso enjoys some of the favourable properties of both subset selection and ridge regression. It produces interpretable models like subset selection and exhibits the stability of ridge regression. There is also an interesting relationship with recent work in adaptive function estimation by Donoho and Johnstone. The lasso idea is quite general and can be applied in a variety of statistical models: extensions to generalized regression models and tree-based models are briefly described. | [
2669,
2680,
2686
] | Train |
2,597 | 0 | Title: Improved Heterogeneous Distance Functions
Abstract: Instance-based learning techniques typically handle continuous and linear input values well, but often do not handle nominal input attributes appropriately. The Value Difference Metric (VDM) was designed to find reasonable distance values between nominal attribute values, but it largely ignores continuous attributes, requiring discretization to map continuous values into nominal values. This paper proposes three new heterogeneous distance functions, called the Heterogeneous Value Difference Metric (HVDM), the Interpolated Value Difference Metric (IVDM), and the Windowed Value Difference Metric (WVDM). These new distance functions are designed to handle applications with nominal attributes, continuous attributes, or both. In experiments on 48 applications the new distance metrics achieve higher classification accuracy on average than three previous distance functions on those datasets that have both nominal and continuous attributes. | [
1698,
2256
] | Test |
2,598 | 1 | Title: Duplication of Coding Segments in Genetic Programming
Abstract: Research into the utility of non-coding segments, or introns, in genetic-based encodings has shown that they expedite the evolution of solutions in domains by protecting building blocks against destructive crossover. We consider a genetic programming system where non-coding segments can be removed, and the resultant chromosomes returned into the population. This parsimonious repair leads to premature convergence, since as we remove the naturally occurring non-coding segments, we strip away their protective backup feature. We then duplicate the coding segments in the repaired chromosomes, and place the modified chromosomes into the population. The duplication method significantly improves the learning rate in the domain we have considered. We also show that this method can be applied to other domains. | [
854,
956,
1230,
1232,
1631,
2330
] | Train |
2,599 | 2 | Title: Recognizing Handwritten Digit Strings Using Modular Spatio-temporal Connectionist Networks
Abstract: Research into the utility of non-coding segments, or introns, in genetic-based encodings has shown that they expedite the evolution of solutions in domains by protecting building blocks against destructive crossover. We consider a genetic programming system where non-coding segments can be removed, and the resultant chromosomes returned into the population. This parsimonious repair leads to premature convergence, since as we remove the naturally occurring non-coding segments, we strip away their protective backup feature. We then duplicate the coding segments in the repaired chromosomes, and place the modified chromosomes into the population. The duplication method significantly improves the learning rate in the domain we have considered. We also show that this method can be applied to other domains. | [
2162
] | Test |
2,600 | 1 | Title: Evolution of Iteration in Genetic Programming D a v d A The solution to many
Abstract: This paper introduces the new operation of restricted iteration creation that automatically Genetic programming extends Holland's genetic algorithm to the task of automatic programming. Early work on genetic programming demonstrated that it is possible to evolve a sequence of work-performing steps in a single result-producing branch (that is, a one-part "main" program). The book Genetic Programming: On the Programming of Computers by Means of Natural Selection (Koza 1992) describes an extension of Holland's genetic algorithm in which the genetic population consists of computer programs (that is, compositions of primitive functions and terminals). See also Koza and Rice (1992). In the most basic form of genetic programming (where only a single result-producing branch is evolved), genetic programming demonstrated the capability to discover a sequence (as to both its length and its content) of work-performing steps that is sufficient to produce a satisfactory solution to several problems, including many problems that have been used over the years as benchmarks in machine learning and artificial intelligence. Before applying genetic programming to a problem, the user must perform five major preparatory steps, namely identifying the terminals (inputs) of the to-be-evolved programs, identifying the primitive functions (operations) contained in the to-be-evolved programs, creating the fitness measure for evaluating how well a given program does at solving the problem at hand, choosing certain control parameters (notably population size and number of generations to be run), and determining the termination criterion and method of result designation (typically the best-so-far individual from the populations produced during the run). creates a restricted iteration-performing | [
163,
523,
1409,
2220
] | Train |
2,601 | 2 | Title: Stability and Chaos in an Inertial Two Neuron System in Statistical Mechanics and Complex Systems
Abstract: Inertia is added to a continuous-time, Hopfield [1], effective neuron system. We explore the effects on the stability of the fixed points of the system. A two neuron system with one or two inertial terms added is shown to exhibit chaos. The chaos is confirmed by Lyapunov exponents, power spectra, and phase space plots. Key words: chaos, Hopfield model, effective neurons, Lyapunov exponent, inertia. | [
2631
] | Train |
2,602 | 5 | Title: A Method for Partial-Memory Incremental Learning and its Application to Computer Intrusion Detection Machine Learning
Abstract: This paper describes a partial-memory incremental learning method based on the AQ15c inductive learning system. The method maintains a representative set of past training examples that are used together with new examples to appropriately modify the currently held hypotheses. Incremental learning is evoked by feedback from the environment or from the user. Such a method is useful in applications involving intelligent agents acting in a changing environment, active vision, and dynamic knowledge-bases. For this study, the method is applied to the problem of computer intrusion detection in which symbolic profiles are learned for a computer systems users. In the experiments, the proposed method yielded significant gains in terms of learning time and memory requirements at the expense of slightly lower predictive accuracy and higher concept complexity, when compared to batch learning, in which all examples are given at once. | [
2070
] | Train |
2,603 | 2 | Title: Pointer Adaptation and Pruning of Min-Max Fuzzy Inference and Estimation
Abstract: This paper describes a partial-memory incremental learning method based on the AQ15c inductive learning system. The method maintains a representative set of past training examples that are used together with new examples to appropriately modify the currently held hypotheses. Incremental learning is evoked by feedback from the environment or from the user. Such a method is useful in applications involving intelligent agents acting in a changing environment, active vision, and dynamic knowledge-bases. For this study, the method is applied to the problem of computer intrusion detection in which symbolic profiles are learned for a computer systems users. In the experiments, the proposed method yielded significant gains in terms of learning time and memory requirements at the expense of slightly lower predictive accuracy and higher concept complexity, when compared to batch learning, in which all examples are given at once. | [
1756
] | Train |
2,604 | 1 | Title: Empirical studies of the genetic algorithm with non-coding segments
Abstract: The genetic algorithm (GA) is a problem solving method that is modelled after the process of natural selection. We are interested in studying a specific aspect of the GA: the effect of non-coding segments on GA performance. Non-coding segments are segments of bits in an individual that provide no contribution, positive or negative, to the fitness of that individual. Previous research on non-coding segments suggests that including these structures in the GA may improve GA performance. Understanding when and why this improvement occurs will help us to use the GA to its full potential. In this article, we discuss our hypotheses on non-coding segments and describe the results of our experiments. The experiments may be separated into two categories: testing our program on problems from previous related studies, and testing new hypotheses on the effect of non-coding segments. | [
163,
168,
1631,
2330
] | Train |
2,605 | 0 | Title: Case-based Acquisition of User Preferences for Solution Improvement in Ill-Structured Domains
Abstract: 1 We have developed an approach to acquire complicated user optimization criteria and use them to guide | [
951,
986,
1401,
2502
] | Train |
2,606 | 2 | Title: Computational modeling of spatial attention
Abstract: 1 We have developed an approach to acquire complicated user optimization criteria and use them to guide | [
527,
2337,
2459,
2611,
2662
] | Validation |
2,607 | 0 | Title: Concept Learning and Flexible Weighting
Abstract: We previously introduced an exemplar model, named GCM-ISW, that exploits a highly flexible weighting scheme. Our simulations showed that it records faster learning rates and higher asymptotic accuracies on several artificial categorization tasks than models with more limited abilities to warp input spaces. This paper extends our previous work; it describes experimental results that suggest human subjects also invoke such highly flexible schemes. In particular, our model provides significantly better fits than models with less flexibility, and we hypothesize that humans selectively weight attributes depending on an item's location in the input space. We need more flexible models Many theories of human concept learning posit that concepts are represented by prototypes (Reed, 1972) or exemplars (Medin & Schaffer, 1978). Prototype models represent concepts by the "best example" or "central tendency" of the concept. 1 A new item belongs in a category C if it is relatively similar to C's prototype. Prototype models are relatively inflexible; they discard a great deal of information that people use during concept learning (e.g., the number of exemplars in a concept (Homa & Cultice, 1984), the variability of features (Fried & Holyoak, 1984), correlations between features (Medin et al., 1982), and the particular exemplars used (Whittlesea, 1987)). of concept learning | [
1987,
2074,
2310,
2369
] | Test |
2,608 | 2 | Title: Testing the Generalized Linear Model Null Hypothesis versus `Smooth' Alternatives 1
Abstract: We previously introduced an exemplar model, named GCM-ISW, that exploits a highly flexible weighting scheme. Our simulations showed that it records faster learning rates and higher asymptotic accuracies on several artificial categorization tasks than models with more limited abilities to warp input spaces. This paper extends our previous work; it describes experimental results that suggest human subjects also invoke such highly flexible schemes. In particular, our model provides significantly better fits than models with less flexibility, and we hypothesize that humans selectively weight attributes depending on an item's location in the input space. We need more flexible models Many theories of human concept learning posit that concepts are represented by prototypes (Reed, 1972) or exemplars (Medin & Schaffer, 1978). Prototype models represent concepts by the "best example" or "central tendency" of the concept. 1 A new item belongs in a category C if it is relatively similar to C's prototype. Prototype models are relatively inflexible; they discard a great deal of information that people use during concept learning (e.g., the number of exemplars in a concept (Homa & Cultice, 1984), the variability of features (Fried & Holyoak, 1984), correlations between features (Medin et al., 1982), and the particular exemplars used (Whittlesea, 1987)). of concept learning | [
519,
2549
] | Train |
2,609 | 5 | Title: ILP with Noise and Fixed Example Size: A Bayesian Approach
Abstract: Current inductive logic programming systems are limited in their handling of noise, as they employ a greedy covering approach to constructing the hypothesis one clause at a time. This approach also causes difficulty in learning recursive predicates. Additionally, many current systems have an implicit expectation that the cardinality of the positive and negative examples reflect the "proportion" of the concept to the instance space. A framework for learning from noisy data and fixed example size is presented. A Bayesian heuristic for finding the most probable hypothesis in this general framework is derived. This approach evaluates a hypothesis as a whole rather than one clause at a time. The heuristic, which has nice theoretical properties, is incorporated in an ILP system, Lime. Experimental results show that Lime handles noise better than FOIL and PROGOL. It is able to learn recursive definitions from noisy data on which other systems do not perform well. Lime is also capable of learning from only positive data and also from only negative data. | [
344,
2079,
2080
] | Train |
2,610 | 2 | Title: Lending Direction to Neural Networks
Abstract: We present a general formulation for a network of stochastic directional units. This formulation is an extension of the Boltzmann machine in which the units are not binary, but take on values on a cyclic range, between 0 and 2 radians. This measure is appropriate to many domains, representing cyclic or angular values, e.g., wind direction, days of the week, phases of the moon. The state of each unit in a Directional-Unit Boltzmann Machine (DUBM) is described by a complex variable, where the phase component specifies a direction; the weights are also complex variables. We associate a quadratic energy function, and corresponding probability, with each DUBM configuration. The conditional distribution of a unit's stochastic state is a circular version of the Gaussian probability distribution, known as the von Mises distribution. In a mean-field approximation to a stochastic dubm, the phase component of a unit's state represents its mean direction, and the magnitude component specifies the degree of certainty associated with this direction. This combination of a value and a certainty provides additional representational power in a unit. We present a proof that the settling dynamics for a mean-field DUBM cause convergence to a free energy minimum. Finally, we describe a learning algorithm and simulations that demonstrate a mean-field DUBM's ability to learn interesting mappings. fl To appear in: Neural Networks. | [
2337
] | Train |
2,611 | 2 | Title: The end of the line for a brain-damaged model of unilateral neglect
Abstract: For over a century, it has been known that damage to the right hemisphere of the brain can cause patients to be unaware of the contralesional side of space. This condition, known as unilateral neglect, represents a collection of clinically related spatial disorders characterized by the failure in free vision to respond, explore, or orient to stimuli predominantly located on the side of space opposite the damaged hemisphere. Recent studies using the simple task of line bisection, a conventional diagnostic test, have proved surprisingly revealing with respect to the spatial and attentional impairments involved in neglect. In line bisection, the patient is asked to mark the midpoint of a thin horizontal line on a sheet of paper. Neglect patients generally transect far to the right of the center. Extensive studies of line bisection have been conducted, manipulating|among other factors|line length, orientation, and position. We have simulated the pattern of results using an existing computational model of visual perception and selective attention called morsel (Mozer, 1991). morsel has already been used to model data in a related disorder, neglect dyslexia (Mozer & Behrmann, 1990). In this earlier work, morsel was "lesioned" in accordance with the damage we suppose to have occurred in the brains of | [
1763,
2606
] | Train |
2,612 | 2 | Title: Models of Parallel Adaptive Logic
Abstract: This paper overviews a proposed architecture for adaptive parallel logic referred to as ASOCS (Adaptive Self-Organizing Concurrent System). The ASOCS approach is based on an adaptive network composed of many simple computing elements which operate in a parallel asynchronous fashion. Problem specification is given to the system by presenting if-then rules in the form of boolean conjunctions. Rules are added incrementally and the system adapts to the changing rule-base. Adaptation and data processing form two separate phases of operation. During processing the system acts as a parallel hardware circuit. The adaptation process is distributed amongst the computing elements and efficiently exploits parallelism. Adaptation is done in a self-organizing fashion and takes place in time linear with the depth of the network. This paper summarizes the overall ASOCS concept and overviews three specific architectures. | [
26,
724,
1903,
2625
] | Test |
2,613 | 1 | Title: Genetic Algorithms for Automated Tuning of Fuzzy Controllers: A Transportation Application
Abstract: We describe the design and tuning of a controller for enforcing compliance with a prescribed velocity profile for a rail-based transportation system. This requires following a trajectory, rather than fixed set-points (as in automobiles). We synthesize a fuzzy controller for tracking the velocity profile, while providing a smooth ride and staying within the prescribed speed limits. We use a genetic algorithm to tune the fuzzy controller's performance by adjusting its parameters (the scaling factors and the membership functions) in a sequential order of significance. We show that this approach results in a controller that is superior to the manually designed one, and with only modest computational effort. This makes it possible to customize automated tuning to a variety of different configurations of the route, the terrain, the power configuration, and the cargo. | [
1756
] | Test |
2,614 | 0 | Title: PRONOUNCING NAMES BY A COMBINATION OF RULE-BASED AND CASE-BASED REASONING
Abstract: We describe the design and tuning of a controller for enforcing compliance with a prescribed velocity profile for a rail-based transportation system. This requires following a trajectory, rather than fixed set-points (as in automobiles). We synthesize a fuzzy controller for tracking the velocity profile, while providing a smooth ride and staying within the prescribed speed limits. We use a genetic algorithm to tune the fuzzy controller's performance by adjusting its parameters (the scaling factors and the membership functions) in a sequential order of significance. We show that this approach results in a controller that is superior to the manually designed one, and with only modest computational effort. This makes it possible to customize automated tuning to a variety of different configurations of the route, the terrain, the power configuration, and the cargo. | [
986,
1644,
2484,
2616
] | Validation |
2,615 | 2 | Title: A Patient-Adaptive Neural Network ECG Patient Monitoring Algorithm
Abstract: The patient-adaptive classifier was compared with a well-established baseline algorithm on six major databases, consisting of over 3 million heartbeats. When trained on an initial 77 records and tested on an additional 382 records, the patient-adaptive algorithm was found to reduce the number of Vn errors on one channel by a factor of 5, and the number of Nv errors by a factor of 10. We conclude that patient adaptation provides a significant advance in classifying normal vs. ventricular beats for ECG Patient Monitoring. | [
1647,
2074,
2084
] | Train |
2,616 | 0 | Title: A comparison of Anapron with seven other name-pronunciation systems
Abstract: This paper presents an experiment comparing a new name-pronunciation system, Anapron, with seven existing systems: three state-of-the-art commercial systems (from Bellcore, Bell Labs, and DEC), two variants of a machine-learning system (NETtalk), and two humans. Anapron works by combining rule-based and case-based reasoning. It is based on the idea that it is much easier to improve a rule-based system by adding case-based reasoning to it than by tuning the rules to deal with every exception. In the experiment described here, Anapron used a set of rules adapted from MITalk and elementary foreign-language textbooks, and a case library of 5000 names. With these components | which required relatively little knowledge engineering | Anapron was found to perform almost at the level of the commercial systems, and significantly better than the two versions of NETtalk. This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories of Cambridge, Massachusetts; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Research Laboratories. All rights reserved. | [
986,
1644,
2484,
2614
] | Train |
2,617 | 5 | Title: Predicting Ordinal Classes in ILP
Abstract: This paper is devoted to the problem of learning to predict ordinal (i.e., ordered discrete) classes in an ILP setting. We start with a relational regression algorithm named SRT (Structural Regression Trees) and study various ways of transforming it into a first-order learner for ordinal classification tasks. Combinations of these algorithm variants with several data preprocessing methods are compared on two ILP benchmark data sets to verify the relative strengths and weaknesses of the strategies and to study the trade-off between optimal categorical classification accuracy (hit rate) and minimum distance-based error. Preliminary results indicate that this is a promising avenue towards algorithms that combine aspects of classification and regression in relational learning. | [
228,
344,
1275,
1428,
2091
] | Validation |
2,618 | 6 | Title: Mistake-Driven Learning in Text Categorization
Abstract: Learning problems in the text processing domain often map the text to a space whose dimensions are the measured features of the text, e.g., its words. Three characteristic properties of this domain are (a) very high dimensionality, (b) both the learned concepts and the instances reside very sparsely in the feature space, and (c) a high variation in the number of active features in an instance. In this work we study three mistake-driven learning algorithms for a typical task of this nature - text categorization. We argue that these algorithms which categorize documents by learning a linear separator in the feature space have a few properties that make them ideal for this domain. We then show that a quantum leap in performance is achieved when we further modify the algorithms to better address some of the specific characteristics of the domain. In particular, we demonstrate (1) how variation in document length can be tolerated by either normalizing feature weights or by using negative weights, (2) the positive effect of applying a threshold range in training, (3) alternatives in considering feature frequency, and (4) the benefits of discarding features while training. Overall, we present an algorithm, a variation of Littlestone's Winnow, which performs significantly better than any other algorithm tested on this task using a similar feature set. | [
453,
1269,
2509
] | Train |
2,619 | 2 | Title: An Efficient Implementation of Sigmoidal Neural Nets in Temporal Coding with Noisy Spiking Neurons
Abstract: We show that networks of relatively realistic mathematical models for biological neurons can in principle simulate arbitrary feedforward sigmoidal neural nets in a way which has previously not been considered. This new approach is based on temporal coding by single spikes (respectively by the timing of synchronous firing in pools of neurons), rather than on the traditional interpretation of analog variables in terms of firing rates. The resulting new simulation is substantially faster and hence more consistent with experimental results about the maximal speed of information processing in cortical neural systems. As a consequence we can show that networks of noisy spiking neurons are "universal approximators" in the sense that they can approximate with regard to temporal coding any given continuous function of several variables. This result holds for a fairly large class of schemes for coding analog variables by firing times of spiking neurons. Our new proposal for the possible organization of computations in networks of spiking neurons systems has some interesting consequences for the type of learning rules that would be needed to explain the self-organization of such networks. Finally, our fast and noise-robust implementation of sigmoidal neural nets via temporal coding points to possible new ways of implementing feedforward and recurrent sigmoidal neural nets with pulse stream VLSI. | [
328,
1774,
1968
] | Test |
2,620 | 3 | Title: Monte Carlo Approach to Bayesian Regression Modeling
Abstract: In the framework of a functional response model (i.e. a regression model, or a feedforward neural network) an estimator of a nonlinear response function is constructed from a set of functional units. The parameters defining these functional units are estimated using the Bayesian approach. A sample representing the Bayesian posterior distribution is obtained by applying the Markov chain Monte Carlo procedure, namely the combination of Gibbs and Metropolis-Hastings algorithms. The method is described for histogram, B-spline and radial basis function estimators of a response function. In general, the proposed approach is suitable for finding Bayes-optimal values of parameters in a complicated parameter space. We illustrate the method on numerical examples. | [
1972
] | Test |
2,621 | 2 | Title: Information Processing in Primate Retinal Cone Pathways: A Model
Abstract: In the framework of a functional response model (i.e. a regression model, or a feedforward neural network) an estimator of a nonlinear response function is constructed from a set of functional units. The parameters defining these functional units are estimated using the Bayesian approach. A sample representing the Bayesian posterior distribution is obtained by applying the Markov chain Monte Carlo procedure, namely the combination of Gibbs and Metropolis-Hastings algorithms. The method is described for histogram, B-spline and radial basis function estimators of a response function. In general, the proposed approach is suitable for finding Bayes-optimal values of parameters in a complicated parameter space. We illustrate the method on numerical examples. | [
2105
] | Train |
2,622 | 0 | Title: Feature Selection by Means of a Feature Weighting Approach
Abstract: Selecting a set of features which is optimal for a given classification task is one of the central problems in machine learning. We address the problem using the flexible and robust filter technique EUBAFES. EUBAFES is based on a feature weighting approach which computes binary feature weights and therefore a solution in the feature selection sense and also gives detailed information about feature relevance by continuous weights. Moreover the user gets not only one but several potentially optimal feature subsets which is important for filter-based feature selection algorithms since it gives the flexibility to use even complex classifiers by the application of a combined filter/wrapper approach. We applied EUBAFES on a number of artificial and real world data sets and used radial basis function networks to examine the impact of the feature subsets to classifier accuracy and complexity. | [
2033
] | Train |
2,623 | 6 | Title: Theoretical Models of Learning to Learn Editor:
Abstract: A Machine can only learn if it is biased in some way. Typically the bias is supplied by hand, for example through the choice of an appropriate set of features. However, if the learning machine is embedded within an environment of related tasks, then it can learn its own bias by learning sufficiently many tasks from the environment [4, 6]. In this paper two models of bias learning (or equivalently, learning to learn) are introduced and the main theoretical results presented. The first model is a PAC-type model based on empirical process theory, while the second is a hierarchical Bayes model. | [
2113
] | Test |
2,624 | 1 | Title: A Comparison between Cellular Encoding and Direct Encoding for Genetic Neural Networks
Abstract: This paper compares the efficiency of two encoding schemes for Artificial Neural Networks optimized by evolutionary algorithms. Direct Encoding encodes the weights for an a priori fixed neural network architecture. Cellular Encoding encodes both weights and the architecture of the neural network. In previous studies, Direct Encoding and Cellular Encoding have been used to create neural networks for balancing 1 and 2 poles attached to a cart on a fixed track. The poles are balanced by a controller that pushes the cart to the left or the right. In some cases velocity information about the pole and cart is provided as an input; in other cases the network must learn to balance a single pole without velocity information. A careful study of the behavior of these systems suggests that it is possible to balance a single pole with velocity information as an input and without learning to compute the velocity. A new fitness function is introduced that forces the neural network to compute the velocity. By using this new fitness function and tuning the syntactic constraints used with cellular encoding, we achieve a tenfold speedup over our previous study and solve a more difficult problem: balancing two poles when no information about the velocity is provided as input. | [
1204,
1878,
1931,
2277,
2317,
2429,
2702
] | Train |
2,625 | 2 | Title: Digital Neural Networks
Abstract: Demands for applications requiring massive parallelism in symbolic environments have given rebirth to research in models labeled as neura l networks. These models are made up of many simple nodes which are highly interconnected such that computation takes place as data flows amongst the nodes of the network. To present, most models have proposed nodes based on simple analog functions, where inputs are multiplied by weights and summed, the total then optionally being transformed by an arbitrary function at the node. Learning in these systems is accomplished by adjusting the weights on the input lines. This paper discusses the use of digital (boolean) nodes as a primitive building block in connectionist systems. Digital nodes naturally engender new paradigms and mechanisms for learning and processing in connectionist networks. The digital nodes are used as the basic building block of a class of models called ASOCS (Adaptive Self-Organizing Concurrent Systems). These models combine massive parallelism with the ability to adapt in a self-organizing fashion. Basic features of standard neural network learning algorithms and those proposed using digital nodes are compared and contrasted. The latter mechanisms can lead to vastly improved efficiency for many applications. | [
2612
] | Validation |
2,626 | 0 | Title: Focusing Construction and Selection of Abductive Hypotheses
Abstract: Many abductive understanding systems explain novel situations by a chaining process that is neutral to explainer needs beyond generating some plausible explanation for the event being explained. This paper examines the relationship of standard models of abductive understanding to the case-based explanation model. In case-based explanation, construction and selection of abductive hypotheses are focused by specific explanations of prior episodes and by goal-based criteria reflecting current information needs. The case-based method is inspired by observations of human explanation of anomalous events during everyday understanding, and this paper focuses on the method's contributions to the problems of building good explanations in everyday domains. We identify five central issues, compare how those issues are addressed in traditional and case-based explanation models, and discuss motivations for using the case-based approach to facilitate generation of plausible and useful explanations in domains that are complex and imperfectly un derstood. | [
1843,
2399,
2656
] | Test |
2,627 | 6 | Title: Probability Estimation via Error-Correcting Output Coding
Abstract: Previous research has shown that a technique called error-correcting output coding (ECOC) can dramatically improve the classification accuracy of supervised learning algorithms that learn to classify data points into one of k 2 classes. In this paper, we will extend the technique so that ECOC can also provide class probability information. ECOC is a method of converting k-class supervised learning problem into a large number L of two-class supervised learning problems and then combining the results of these L evaluations. The underlying two-class supervised learning algorithms are assumed to provide L probability estimates. The problem of computing class probabilities is formulated as an over-constrained system of L linear equations. Least squares methods are applied to solve these equations. Accuracy and reliability of the probability estimates are demonstrated. | [
2423
] | Train |
2,628 | 4 | Title: Generalizing in TD() learning
Abstract: Previous research has shown that a technique called error-correcting output coding (ECOC) can dramatically improve the classification accuracy of supervised learning algorithms that learn to classify data points into one of k 2 classes. In this paper, we will extend the technique so that ECOC can also provide class probability information. ECOC is a method of converting k-class supervised learning problem into a large number L of two-class supervised learning problems and then combining the results of these L evaluations. The underlying two-class supervised learning algorithms are assumed to provide L probability estimates. The problem of computing class probabilities is formulated as an over-constrained system of L linear equations. Least squares methods are applied to solve these equations. Accuracy and reliability of the probability estimates are demonstrated. | [
565,
738,
2629
] | Train |
2,629 | 4 | Title: Towards a Reactive Critic
Abstract: In this paper we propose a reactive critic, that is able to respond to changing situations. We will explain why this is usefull in reinforcement learning, where the critic is used to improve the control strategy. We take a problem for which we can derive the solution analytically. This enables us to investigate the relation between the parameters and the resulting approximations of the critic. We will also demonstrate how the reactive critic reponds to changing situations. | [
565,
738,
2536,
2628
] | Validation |
2,630 | 1 | Title: Simulating Quadratic Dynamical Systems is PSPACE-complete (preliminary version)
Abstract: Quadratic Dynamical Systems (QDS), whose definition extends that of Markov chains, are used to model phenomena in a variety of fields like statistical physics and natural evolution. Such systems also play a role in genetic algorithms, a widely-used class of heuristics that are notoriously hard to analyze. Recently Rabinovich et al. took an important step in the study of QDS's by showing, under some technical assumptions, that such systems converge to a stationary distribution (similar theorems for Markov Chains are well-known). We show, however, that the following sampling problem for QDS's is PSPACE-hard: Given an initial distribution, produce a random sample from the t'th generation. The hardness result continues to hold for very restricted classes of QDS's with very simple initial distributions, thus suggesting that QDS's are intrinsically more complicated than Markov chains. | [
1826
] | Train |
2,631 | 2 | Title: Nonlinear Resonance in Neuron Dynamics in Statistical Mechanics and Complex Systems
Abstract: Hubler's technique using aperiodic forces to drive nonlinear oscillators to resonance is analyzed. The oscillators being examined are effective neurons that model Hopfield neural networks. The method is shown to be valid under several different circumstances. It is verified through analysis of the power spectrum, force, resonance, and energy transfer of the system. | [
2601
] | Validation |
2,632 | 2 | Title: The Role of Activity in Synaptic Competition at the Neuromuscular Junction
Abstract: An extended version of the dual constraint model of motor end-plate morphogenesis is presented that includes activity dependent and independent competition. It is supported by a wide range of recent neurophysiological evidence that indicates a strong relationship between synaptic efficacy and survival. The computational model is justified at the molecular level and its predictions match the developmental and regenerative behaviour of real synapses. | [
2584
] | Train |
2,633 | 6 | Title: Learning Using Group Representations (Extended Abstract)
Abstract: We consider the problem of learning functions over a fixed distribution. An algorithm by Kushilevitz and Mansour [7] learns any boolean function over f0; 1g n in time polynomial in the L 1 -norm of the Fourier transform of the function. We show that the KM-algorithm is a special case of a more general class of learning algorithms. This is achieved by extending their ideas using representations of finite groups. We introduce some new classes of functions which can be learned using this generalized KM algorithm. | [
2011,
2182
] | Validation |
2,634 | 3 | Title: Bayesian Model Averaging
Abstract: Standard statistical practice ignores model uncertainty. Data analysts typically select a model from some class of models and then proceed as if the selected model had generated the data. This approach ignores the uncertainty in model selection, leading to over-confident inferences and decisions that are more risky than one thinks they are. Bayesian model averaging (BMA) provides a coherent mechanism for accounting for this model uncertainty. Several methods for implementing BMA have recently emerged. We discuss these methods and present a number of examples. In these examples, BMA provides improved out-of-sample predictive performance. We also provide a catalogue of currently available BMA software. | [
1197,
1876
] | Train |
2,635 | 0 | Title: Utilising Explanation to Assist the Refinement of Knowledge-Based Systems
Abstract: Standard statistical practice ignores model uncertainty. Data analysts typically select a model from some class of models and then proceed as if the selected model had generated the data. This approach ignores the uncertainty in model selection, leading to over-confident inferences and decisions that are more risky than one thinks they are. Bayesian model averaging (BMA) provides a coherent mechanism for accounting for this model uncertainty. Several methods for implementing BMA have recently emerged. We discuss these methods and present a number of examples. In these examples, BMA provides improved out-of-sample predictive performance. We also provide a catalogue of currently available BMA software. | [
136,
2231
] | Train |
2,636 | 5 | Title: EMERALD: An Integrated System of Machine Learning and Discovery Programs to Support AI Education and
Abstract: With the rapid expansion of machine learning methods and applications, there is a strong need for computer-based interactive tools that support education in this area. The EMERALD system was developed to provide hands-on experience and an interactive demonstration of several machine learning and discovery capabilities for students in AI and cognitive science, and for AI professionals. The current version of EMERALD integrates five programs that exhibit different types of machine learning and discovery: learning rules from examples, determining structural descriptions of object classes, inventing conceptual clusterings of entities, predicting sequences of objects, and discovering equations characterizing collections of quantitative and qualitative data. EMERALD extensively uses color graphic capabilities, voice synthesis, and a natural language representation of the knowledge acquired by the learning programs. Each program is presented as a "learning robot," which has its own "personality," expressed by its icon, its voice, the comments it generates during the learning process, and the results of learning presented as natural language text and/or voice output. Users learn about the capabilities of each "robot" both by being challenged to perform some learning tasks themselves, and by creating their own similar tasks to challenge the "robot." EMERALD is an extension of ILLIAN, an initial, much smaller version that toured eight major US Museums of Science, and was seen by over half a million visitors. EMERALD's architecture allows it to incorporate new programs and new capabilities. The system runs on SUN workstations, and is available to universities and educational institutions. | [
479,
2300
] | Train |
2,637 | 1 | Title: A Computational Environment for Exhaust Nozzle Design
Abstract: The Nozzle Design Associate (NDA) is a computational environment for the design of jet engine exhaust nozzles for supersonic aircraft. NDA may be used either to design new aircraft or to design new nozzles that adapt existing aircraft so they may be reutilized for new missions. NDA was developed in a collaboration between computer scientists at Rut-gers University and exhaust nozzle designers at General Electric Aircraft Engines and General Electric Corporate Research and Development. The NDA project has two principal goals: to provide a useful engineering tool for exhaust nozzle design, and to explore fundamental research issues that arise in the application of automated design optimization methods to realistic engineering problems. | [
2652
] | Train |
2,638 | 1 | Title: An Evolutionary Heuristic for the Minimum Vertex Cover Problem
Abstract: The Nozzle Design Associate (NDA) is a computational environment for the design of jet engine exhaust nozzles for supersonic aircraft. NDA may be used either to design new aircraft or to design new nozzles that adapt existing aircraft so they may be reutilized for new missions. NDA was developed in a collaboration between computer scientists at Rut-gers University and exhaust nozzle designers at General Electric Aircraft Engines and General Electric Corporate Research and Development. The NDA project has two principal goals: to provide a useful engineering tool for exhaust nozzle design, and to explore fundamental research issues that arise in the application of automated design optimization methods to realistic engineering problems. | [
163,
2202
] | Train |
2,639 | 2 | Title: New Modes of Generalization in Perceptual Learning
Abstract: The learning of many visual perceptual tasks, such as motion discrimination, has been shown to be specific to the practiced stimulus, and new stimuli require re-learning from scratch [1-6]. This specificity, found in so many different tasks, supports the hypothesis that perceptual learning takes place in early visual cortical areas. In contrast, using a novel paradigm in motion discrimination where learning has been shown to be specific, we found generalization: We trained subjects to discriminate the directions of moving dots, and verified that learning does not transfer from the trained direction to a new one. However, by tracking the subjects' performance across time in the new direction, we found that their rate of learning doubled. Moreover, after mastering the task with an easy stimulus, subjects who had practiced briefly to discriminate the easy stimulus in a new direction generalized to a difficult stimulus in that direction. This generalization demanded both the mastering and the brief practice. Thus learning in motion discrimination always generalizes to new stimuli. Learning is manifested in various forms: acceleration of learning rate, indirect transfer, or direct transfer [7, 8]. These results challenge existing theories of perceptual learning, and suggest a more complex picture in which learning takes place at multiple levels. Learning in biological systems is of great importance. But while cognitive learning (or "problem solving") is abrupt and generalizes to analogous problems, we appear to acquire our perceptual skills gradually and specifically: human subjects cannot generalize a perceptual discrimination skill to solve similar problems with different attributes. For example, in a discrimination task as described in Fig. 1, a subject who is trained to discriminate motion directions between 43:5 ffi and 46:5 ffi cannot use this skill to discriminate 133:5 ffi from 136:5 ffi . 1 Such specificity supports the hypothesis that perceptual learning embodies neuronal modifications in the brain's stimulus-specific cortical areas (e.g., visual area MT) [1-6]. In contrast to previous results of specificity, we will show, in three experiments, that learning in motion discrimination always generalizes. (1) When the task is easy, it generalizes to all directions after training in | [
2117
] | Train |
2,640 | 5 | Title: Learning Evolving Concepts Using Partial-Memory Approach Machine Learning and Inference Laboratory
Abstract: This paper addresses the problem of learning evolving concepts, that is, concepts whose meaning gradually evolves in time. Solving this problem is important to many applications, for example, building intelligent agents for helping users in Internet search, active vision, automatically updating knowledge-bases, or acquiring profiles of users of telecommunication networks. Requirements for a learning architecture supporting such applications include the ability to incrementally modify concept definitions to accommodate new information, fast learning and recognition rates, low memory needs, and the understandability of computer-created concept descriptions. To address these requirements, we propose a learning architecture based on Variable-Valued Logic, the Star Methodology, and the AQ algorithm. The method uses a partial-memory approach, which means that in each step of learning, the system remembers the current concept descriptions and specially selected representative examples from the past experience. The developed method has been experimentally applied to the problem of computer system intrusion detection. The results show significant advantages of the method in learning speed and memory requirements with only slight decreases in predictive accuracy and concept simplicity when compared to traditional batch-style learning in which all training examples are provided at once. | [
2070
] | Train |
2,641 | 1 | Title: Toward Simulated Evolution of Machine-Language Iteration
Abstract: We use a simulated evolution search (genetic programming) for the automatic synthesis of small iterative machine-language programs. For an integer register machine with an addition instruction as its sole arithmetic operator, we show that genetic programming can produce exact and general multiplication routines by synthesizing the necessary iterative control structures from primitive machine-language instructions. Our program representation is a virtual register machine that admits arbitrary control flow. Our evolution strategy furthermore does not artificially restrict the synthesis of any control structure; we only place an upper bound on program evaluation time. A program's fitness is the distance between the output produced by a test case and the desired output (multiplication). The test cases exhaustively cover multiplication over a finite subset of the natural numbers (N 10 ); yet the derived solutions constitute general multiplication for the positive integers. For this problem, simulated evolution with a two-point crossover operator examines significantly fewer individuals in finding a solution than random search. Introduction of a small rate of mutation fur ther increases the number of solutions. | [
380,
1745
] | Validation |
2,642 | 2 | Title: Learning to Play Games From Experience: An Application of Artificial Neural Networks and Temporal Difference Learning
Abstract: We use a simulated evolution search (genetic programming) for the automatic synthesis of small iterative machine-language programs. For an integer register machine with an addition instruction as its sole arithmetic operator, we show that genetic programming can produce exact and general multiplication routines by synthesizing the necessary iterative control structures from primitive machine-language instructions. Our program representation is a virtual register machine that admits arbitrary control flow. Our evolution strategy furthermore does not artificially restrict the synthesis of any control structure; we only place an upper bound on program evaluation time. A program's fitness is the distance between the output produced by a test case and the desired output (multiplication). The test cases exhaustively cover multiplication over a finite subset of the natural numbers (N 10 ); yet the derived solutions constitute general multiplication for the positive integers. For this problem, simulated evolution with a two-point crossover operator examines significantly fewer individuals in finding a solution than random search. Introduction of a small rate of mutation fur ther increases the number of solutions. | [
523,
565,
2368
] | Validation |
2,643 | 1 | Title: GP-Music: An Interactive Genetic Programming System for Music Generation with Automated Fitness Raters
Abstract: Technical Report CSRP-98-13 Abstract In this paper we present the GP-Music System, an interactive system which allows users to evolve short musical sequences using interactive genetic programming, and its extensions aimed at making the system fully automated. The basic GP-system works by using a genetic programming algorithm, a small set of functions for creating musical sequences, and a user interface which allows the user to rate individual sequences. With this user interactive technique it was possible to generate pleasant tunes over runs of 20 individuals over 10 generations. As the user is the bottleneck in interactive systems, the system takes rating data from a users run and uses it to train a neural network based automatic rater, or auto rater, which can replace the user in bigger runs. Using this auto rater we were able to make runs of up to 50 generations with 500 individuals per generation. The best of run pieces generated by the auto raters were pleasant but were not, in general, as nice as those generated in user interactive runs. | [
2470,
2646
] | Train |
2,644 | 6 | Title: Bayesian Induction of Features in Temporal Domains
Abstract: Most concept induction algorithms process concept instances described in terms of properties that remain constant over time. In temporal domains, instances are best described in terms of properties whose values vary with time. Data engineering is called upon in temporal domains to transform the raw data into an appropriate form for concept induction. I investigate a method for inducing features suitable for classifying finite, univariate, time series that are governed by unknown deterministic processes contaminated by noise. In a supervised setting, I induce piecewise polynomials of appropriate complexity to characterize the data in each class, using Bayesian model induction principles. In this study, I evaluate the proposed method empirically in a semi-deterministic domain: the waveform classification problem, originally presented in the CART book. I compared the classification accuracy of the proposed algorithm to the accuracy attained by C4.5 under various noise levels. Feature induction improved the classification accuracy in noisy situations, but degraded it when there was no noise. The results demonstrate the value of the proposed method in the presence of noise, and reveal a weakness shared by all classifiers using generative rather than discriminative models: sensitivity to model inaccuracies. | [
2134
] | Train |
2,645 | 0 | Title: CBR on Semi-structured Documents: The ExperienceBook and the FAllQ Project
Abstract: In this article, we present a case-based approach on flexible query answering systems in two different application areas: The ExperienceBook supports technical diagnosis in the field of system administration. In the FAllQ project we use our CBR system for document retrieval in an industrial setting. The objective of these systems is to manage knowledge stored in less structured documents. The internal case memory is implemented as a Case Retrieval Net. This allows to handle large case bases with an efficient retrieval process. In order to provide multi user access we chose the client server model combined with a web interface. | [
1854,
2482
] | Train |
2,646 | 1 | Title: Automated Fitness Raters for the GP-Music System
Abstract: | [
2470,
2643
] | Train |
2,647 | 4 | Title: Using Local Trajectory Optimizers To Speed Up Global Optimization In Dynamic Programming
Abstract: Dynamic programming provides a methodology to develop planners and controllers for nonlinear systems. However, general dynamic programming is computationally intractable. We have developed procedures that allow more complex planning and control problems to be solved. We use second order local trajectory optimization to generate locally optimal plans and local models of the value function and its derivatives. We maintain global consistency of the local models of the value function, guaranteeing that our locally optimal plans are actually globally optimal, up to the resolution of our search procedures. | [
2430,
2658
] | Test |
2,648 | 2 | Title: The Task Rehearsal Method of Sequential Learning
Abstract: An hypothesis of functional transfer of task knowledge is presented that requires the development of a measure of task relatedness and a method of sequential learning. The task rehearsal method (TRM) is introduced to address the issues of sequential learning, namely retention and transfer of knowledge. TRM is a knowledge based inductive learning system that uses functional domain knowledge as a source of inductive bias. The representations of successfully learned tasks are stored within domain knowledge. Virtual examples generated by domain knowledge are rehearsed in parallel with the each new task using either the standard multiple task learning (MTL) or the MTL neural network methods. The results of experiments conducted on a synthetic domain of seven tasks demonstrate the method's ability to retain and transfer task knowledge. TRM is shown to be effective in developing hypothesis for tasks that suffer from impoverished training sets. Difficulties encountered during sequential learning over the diverse domain reinforce the need for a more robust measure of task relatedness. | [
1889
] | Test |
2,649 | 5 | Title: Limits of Control Flow on Parallelism
Abstract: This paper discusses three techniques useful in relaxing the constraints imposed by control flow on parallelism: control dependence analysis, executing multiple flows of control simultaneously, and speculative execution. We evaluate these techniques by using trace simulations to find the limits of parallelism for machines that employ different combinations of these techniques. We have three major results. First, local regions of code have limited parallelism, and control dependence analysis is useful in extracting global parallelism from different parts of a program. Second, a superscalar processor is fundamentally limited because it cannot execute independent regions of code concurrently. Higher performance can be obtained with machines, such as multiprocessors and dataflow machines, that can simultaneously follow multiple flows of control. Finally, without speculative execution to allow instructions to execute before their control dependences are resolved, only modest amounts of parallelism can be obtained for programs with complex control flow. | [
249,
735,
1956,
2106,
2436
] | Validation |
2,650 | 5 | Title: Learning Search-Control Heuristics for Logic Programs: Applications to Speedup Learning and Language Acquisition
Abstract: This paper presents a general framework, learning search-control heuristics for logic programs, which can be used to improve both the efficiency and accuracy of knowledge-based systems expressed as definite-clause logic programs. The approach combines techniques of explanation-based learning and recent advances in inductive logic programming to learn clause-selection heuristics that guide program execution. Two specific applications of this framework are detailed: dynamic optimization of Prolog programs (improving efficiency) and natural language acquisition (improving accuracy). In the area of program optimization, a prototype system, Dolphin is able to transform some intractable specifications into polynomial-time algorithms, and outperforms competing approaches in several benchmark speedup domains. A prototype language acquisition system, Chill is also described. It is capable of automatically acquiring semantic grammars, which uniformly incorprate syntactic and semantic constraints to parse sentences into case-role representations. Initial experiments show that this approach is able to construct accurate parsers which generalize well to novel sentences and significantly outperform previous approaches to learning case-role mapping based on connectionist techniques. Planned extensions of the general framework and the specific applications as well as plans for further evaluation are also discussed. | [
204,
2215
] | Test |
2,651 | 6 | Title: Relative Loss Bounds for Multidimensional Regression Problems
Abstract: We study on-line generalized linear regression with multidimensional outputs, i.e., neural networks with multiple output nodes but no hidden nodes. We allow at the final layer transfer functions such as the softmax function that need to consider the linear activations to all the output neurons. We also use a parameterization function which transforms parameter vectors maintained by the algorithm into the actual weights. The on-line algorithm we consider updates the parameters in an additive manner, analogous to the delta rule, but because the actual weights are obtained via the possibly nonlinear parameterization function they may behave in a very different manner. Our approach is based on applying the notion of a matching loss function in two different contexts. First, we measure the loss of the algorithm in terms of the loss that matches the transfer function used to produce the outputs. Second, the loss function that matches the parameterization function can be used both as a measure of distance between models in motivating the update rule of the algorithm and as a potential function in analyzing its relative performance compared to an arbitrary fixed model. As a result, we have a unified treatment that generalizes earlier results for the gradient descent and exponentiated gradient algorithms to multidimensional outputs, including multiclass logistic regression. | [
1062,
2059
] | Train |
2,652 | 0 | Title: Knowledge-Based Re-engineering of Legacy Programs for Robustness in Automated Design
Abstract: Systems for automated design optimization of complex real-world objects can, in principle, be constructed by combining domain-independent numerical routines with existing domain-specific analysis and simulation programs. Unfortunately, such legacy analysis codes are frequently unsuitable for use in automated design. They may crash for large classes of input, be numerically unstable or locally non-smooth, or be highly sensitive to control parameters. To be useful, analysis programs must be modified to reduce or eliminate only the undesired behaviors, without altering the desired computation. To do this by direct modification of the programs is labor-intensive, and necessitates costly revalidation. We have implemented a high-level language and run-time environment that allow failure-handling strategies to be incorporated into existing Fortran and C analysis programs while preserving their computational integrity. Our approach relies on globally managing the execution of these programs at the level of discretely callable functions so that the computation is only affected when problems are detected. Problem handling procedures are constructed from a knowledge base of generic problem management strategies. We show that our approach is effective in improving analysis program robustness and design optimization performance in the domain of conceptual design of jet engine nozzles. | [
240,
2308,
2637
] | Train |
2,653 | 6 | Title: On the Sample Complexity of Weakly Learning
Abstract: In this paper, we study the sample complexity of weak learning. That is, we ask how much data must be collected from an unknown distribution in order to extract a small but significant advantage in prediction. We show that it is important to distinguish between those learning algorithms that output deterministic hypotheses and those that output randomized hypotheses. We prove that in the weak learning model, any algorithm using deterministic hypotheses to weakly learn a class of Vapnik-Chervonenkis dimension d(n) requires ( d(n)) examples. In contrast, when randomized hypotheses are allowed, we show that fi(1) examples suffice in some cases. We then show that there exists an efficient algorithm using deterministic hypotheses that weakly learns against any distribution on a set of size d(n) with only O(d(n) 2=3 ) examples. Thus for the class of symmetric Boolean functions over n variables, where the strong learning sample complexity is fi(n), the sample complexity for weak learning using deterministic hypotheses is ( n) and O(n 2=3 ), and the sample complexity for weak learning using randomized hypotheses is fi(1). Next we prove the existence of classes for which the distribution-free sample size required to obtain a slight advantage in prediction over random guessing is essentially equal to that required to obtain arbitrary accuracy. Finally, for a class of small circuits, namely all parity functions of subsets of n Boolean variables, we prove a weak learning sample complexity of fi(n). This bound holds even if the weak learning algorithm is allowed to replace random sampling with membership queries, and the target distribution is uniform on f0; 1g n . p | [
456,
672,
1363,
2028
] | Train |
2,654 | 3 | Title: On the Sample Complexity of Weakly Learning
Abstract: Convergence Results for the EM Approach to Abstract The Expectation-Maximization (EM) algorithm is an iterative approach to maximum likelihood parameter estimation. Jordan and Jacobs (1993) recently proposed an EM algorithm for the mixture of experts architecture of Jacobs, Jordan, Nowlan and Hinton (1991) and the hierarchical mixture of experts architecture of Jordan and Jacobs (1992). They showed empirically that the EM algorithm for these architectures yields significantly faster convergence than gradient ascent. In the current paper we provide a theoretical analysis of this algorithm. We show that the algorithm can be regarded as a variable metric algorithm with its searching direction having a positive projection on the gradient of the log likelihood. We also analyze the convergence of the algorithm and provide an explicit expression for the convergence rate. In addition, we describe an acceleration technique that yields a significant speedup in simulation experiments. This report describes research done at the Dept. of Brain and Cognitive Sciences, the Center for Biological and Computational Learning, and the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for CBCL is provided in part by a grant from the NSF (ASC-9217041). Support for the laboratory's artificial intelligence research is provided in part by the Advanced Research Projects Agency of the Dept. of Defense. The authors were supported by a grant from the McDonnell-Pew Foundation, by a grant from ATR Human Information Processing Research Laboratories, by a grant from Siemens Corporation, by by grant IRI-9013991 from the National Science Foundation, by grant N00014-90-J-1942 from the Office of Naval Research, and by NSF grant ECS-9216531 to support an Initiative in Intelligent Control at MIT. Michael I. Jordan is a NSF Presidential Young Investigator. | [
74,
2421
] | Train |
2,655 | 4 | Title: Associative Reinforcement Learning: A Generate and Test Algorithm
Abstract: An agent that must learn to act in the world by trial and error faces the reinforcement learning problem, which is quite different from standard concept learning. Although good algorithms exist for this problem in the general case, they are often quite inefficient and do not exhibit generalization. One strategy is to find restricted classes of action policies that can be learned more efficiently. This paper pursues that strategy by developing an algorithm that performans an on-line search through the space of action mappings, expressed as Boolean formulae. The algorithm is compared with existing methods in empirical trials and is shown to have very good performance. | [
1975
] | Train |
2,656 | 0 | Title: ADAPtER: an Integrated Diagnostic System Combining Case-Based and Abductive Reasoning
Abstract: The aim of this paper is to describe the ADAPtER system, a diagnostic architecture combining case-based reasoning with abductive reasoning and exploiting the adaptation of the solution of old episodes, in order to focus the reasoning process. Domain knowledge is represented via a logical model and basic mechanisms, based on abductive reasoning with consistency constraints, have been defined for solving complex diagnostic problems involving multiple faults. The model-based component has been supplemented with a case memory and adaptation mechanisms have been developed, in order to make the diagnostic system able to exploit past experience in solving new cases. A heuristic function is proposed, able to rank the solutions associated to retrieved cases with respect to the adaptation effort needed to transform such solutions into possible solutions for the current case. We will discuss some preliminary experiments showing the validity of the above heuristic and the convenience of solving a new case by adapting a retrieved solution rather than solving the new problem from scratch. | [
799,
1699,
2626
] | Train |
2,657 | 6 | Title: Learning Complex Boolean Functions: Algorithms and Applications
Abstract: The most commonly used neural network models are not well suited to direct digital implementations because each node needs to perform a large number of operations between floating point values. Fortunately, the ability to learn from examples and to generalize is not restricted to networks of this type. Indeed, networks where each node implements a simple Boolean function (Boolean networks) can be designed in such a way as to exhibit similar properties. Two algorithms that generate Boolean networks from examples are presented. The results show that these algorithms generalize very well in a class of problems that accept compact Boolean network descriptions. The techniques described are general and can be applied to tasks that are not known to have that characteristic. Two examples of applications are presented: image reconstruction and hand-written character recognition. | [
1161,
2423
] | Validation |
2,658 | 0 | Title: Control Systems Magazine, 14, 1, pp.57-71. Robot Juggling: An Implementation of Memory-based Learning
Abstract: This paper explores issues involved in implementing robot learning for a challenging dynamic task, using a case study from robot juggling. We use a memory-based local model - ing approach (locally weighted regression) to represent a learned model of the task to be performed. Statistical tests are given to examine the uncertainty of a model, to optimize its pre diction quality, and to deal with noisy and corrupted data. We develop an exploration algorithm that explicitly deals with prediction accuracy requirements dur ing explo - ration. Using all these ingredients in combination with methods from optimal control, our robot achieves fast real - time learning of the task within 40 to 100 trials. * Address of both authors: Massachusetts Institute of Technology, The Artificial Intelligence Laboratory & The Department of Brain and Cognitive Sciences, 545 Technology Square, Cambride, MA 02139, USA. Email: ss-chaal@ai.mit.edu, cga@ai.mit.edu. Support was provided by the Air Force Office of Sci entific Research and by Siemens Cor pora tion. Support for the first author was provided by the Ger man Scholar ship Foundation and the Alexander von Hum boldt Founda tion. Support for the second author was provided by a Na tional Sci ence Foundation Pre sidential Young Investigator Award. We thank Gideon Stein for im ple ment ing the first version of LWR on the i860 microprocessor, and Gerrie van Zyl for build ing the devil stick robot and implementing the first version of devil stick learning. | [
427,
477,
566,
691,
843,
1559,
1860,
2647
] | Train |
2,659 | 1 | Title: Adaptation of Genetic Algorithms for Engineering Design Optimization
Abstract: Genetic algorithms have been extensively used in different domains as a means of doing global optimization in a simple yet reliable manner. However, in some realistic engineering design optimization domains it was observed that a simple classical implementation of the GA based on binary encoding and bit mutation and crossover was sometimes inefficient and unable to reach the global optimum. Using floating point representation alone does not eliminate the problem. In this paper we describe a way of augmenting the GA with new operators and strategies that take advantage of the structure and properties of such engineering design domains. Empirical results (initially in the domain of conceptual design of supersonic transport aircraft and the domain of high performance supersonic missile inlet design) demonstrate that the newly formulated GA can be significantly better than the classical GA in terms of efficiency and reliability. http://www.cs.rutgers.edu/~shehata/papers.html | [
163,
743,
2030,
2316
] | Train |
2,660 | 3 | Title: Discovering Structure in Continuous Variables Using Bayesian Networks
Abstract: We study Bayesian networks for continuous variables using nonlinear conditional density estimators. We demonstrate that useful structures can be extracted from a data set in a self-organized way and we present sampling techniques for belief update based on | [
558,
577,
1933
] | Validation |
2,661 | 3 | Title: Minimax Risk over l p -Balls for l q -error Key Words. Minimax Decision Theory.
Abstract: Consider estimating the mean vector from data N n (; 2 I) with l q norm loss, q 1, when is known to lie in an n-dimensional l p ball, p 2 (0; 1). For large n, the ratio of minimax linear risk to minimax risk can be arbitrarily large if p < q. Obvious exceptions aside, the limiting ratio equals 1 only if p = q = 2. Our arguments are mostly indirect, involving a reduction to a univariate Bayes minimax problem. When p < q, simple non-linear co-ordinatewise threshold rules are asymptotically minimax at small signal-to-noise ratios, and within a bounded factor of asymptotic minimaxity in general. Our results are basic to a theory of estimation in Besov spaces | [
1910,
2159,
2242,
2375,
2506
] | Train |
2,662 | 2 | Title: Efficient Visual Search: A Connectionist Solution
Abstract: Searching for objects in scenes is a natural task for people and has been extensively studied by psychologists. In this paper we examine this task from a connectionist perspective. Computational complexity arguments suggest that parallel feed-forward networks cannot perform this task efficiently. One difficulty is that, in order to distinguish the target from distractors, a combination of features must be associated with a single object. Often called the binding problem, this requirement presents a serious hurdle for connectionist models of visual processing when multiple objects are present. Psychophysical experiments suggest that people use covert visual attention to get around this problem. In this paper we describe a psychologically plausible system which uses a focus of attention mechanism to locate target objects. A strategy that combines top-down and bottom-up information is used to minimize search time. The behavior of the resulting system matches the reaction time behavior of people in several interesting tasks. | [
527,
1822,
2606
] | Train |
2,663 | 5 | Title: Inverting Implication with Small Training Sets
Abstract: We present an algorithm for inducing recursive clauses using inverse implication (rather than inverse resolution) as the underlying generalization method. Our approach applies to a class of logic programs similar to the class of primitive recursive functions. Induction is performed using a small number of positive examples that need not be along the same resolution path. Our algorithm, implemented in a system named CRUSTACEAN, locates matched lists of generating terms that determine the pattern of decomposition exhibited in the (target) recursive clause. Our theoretical analysis defines the class of logic programs for which our approach is complete, described in terms characteristic of other ILP approaches. Our current implementation is considerably faster than previously reported. We present evidence demonstrating that, given randomly selected inputs, increasing the number of positive examples increases accuracy and reduces the number of outputs. We relate our approach to similar recent work on inducing recursive clauses. | [
1781,
2229
] | Train |
2,664 | 1 | Title: Coevolving Communicative Behavior in a Linear Pursuer-Evader Game
Abstract: The pursuer-evader (PE) game is recognized as an important domain in which to study the coevolution of robust adaptive behavior and protean behavior (Miller and Cliff, 1994). Nevertheless, the potential of the game is largely unrealized due to methodological hurdles in coevolutionary simulation raised by PE; versions of the game that have optimal solutions (Isaacs, 1965) are closed-ended, while other formulations are opaque with respect to their solution space, for the lack of a rigorous metric of agent behavior. This inability to characterize behavior, in turn, obfuscates coevolutionary dynamics. We present a new formulation of PE that affords a rigorous measure of agent behavior and system dynamics. The game is moved from the two-dimensional plane to the one-dimensional bit-string; at each time step, the evader generates a bit that the pursuer must simultaneously predict. Because behavior is expressed as a time series, we can employ information theory to provide quantitative analysis of agent activity. Further, this version of PE opens vistas onto the communicative component of pursuit and evasion behavior, providing an open-ended serial communications channel and an open world (via coevolution). Results show that subtle changes to our game determine whether it is open-ended, and profoundly affect the viability of arms-race dynamics. | [
189,
415,
712,
2102
] | Train |
2,665 | 0 | Title: Parametric Design Problem Solving
Abstract: The aim of this paper is to understand what is involved in parametric design problem solving. In order to achieve this goal, in this paper i) we identify and detail the conceptual elements defining a parametric design task specification; ii) we illustrate how these elements are interpreted and operationalised during the design process; and iii) we formulate a generic model of parametric design problem solving. We then redescribe a number of problem solving methods in terms of the proposed generic model and we show that such a redescription enables us to provide a more precise account of the different competence behaviours expressed by the methods in Design is about constructing artifacts. This means that, broadly speaking, any design process is 'creative', in the sense that a design process produces a 'new solution', as opposed to selecting a solution from a predefined set. While recognizing the essential creative elements present in any design process, researchers, e.g. Gero (1990), restrict the use of the term 'creative design' to those design applications where the design elements of the target artifact cannot be selected from a predefined set. For instance, when designing a new car model it is normally the case that some design innovations are included, which were not present in previous car designs. In other words it is not (always) possible to characterise the process of designing a new car as one in which components are assembled and configured from a predefined set. Nevertheless, in a large number of real-world applications it is possible to assume that the target artifact is going to be designed in terms of predefined design elements. In such a scenario the design process consists of assembling and configuring these preexisting design elements in a way which satisfies the design requirements and constraints, and approximates some, typically cost-related, optimization criterion. This class of design tasks takes the name of configuration design (Stefik, 1995). In many cases, typically when the problem in hand does not exhibit complex spatial requirements and all possible solutions adhere to a common solution template, it is possible to simplify the configuration design problem even further, by modelling the target artifact as a set of parameters and characterizing design problem solving as the process of assigning values to parameters in accordance with the given design requirements, constraints, and optimization criterion. When this assumption is true for a particular task, we say that this is a parametric design task. The VT application (Marcus et al., 1988; Yost and Rothenfluh, 1996) provides a well-known example of a parametric design task. The aim of this paper is to understand what is involved in parametric design problem solving. In order to achieve this goal, in this paper i) we identify and detail the conceptual elements defining a parametric design task specification; ii) we illustrate how these elements are interpreted and operationalised during the design process; and iii) we produce a generic model of parametric design problem solving, characterised at the knowledge level, which generalizes from existing methods for parametric design. We then redescribe a number of problem solving methods in terms of the question. | [
2395
] | Test |
2,666 | 4 | Title: A Distributed Reinforcement Learning Scheme for Network Routing
Abstract: In this paper we describe a self-adjusting algorithm for packet routing in which a reinforcement learning method is embedded into each node of a network. Only local information is used at each node to keep accurate statistics on which routing policies lead to minimal routing times. In simple experiments involving a 36-node irregularly-connected network, this learning approach proves superior to routing based on precomputed shortest paths. | [
451,
2411,
2453
] | Train |
2,667 | 1 | Title: Biological metaphors and the design of modular artificial neural networks Master's thesis of
Abstract: In this paper we describe a self-adjusting algorithm for packet routing in which a reinforcement learning method is embedded into each node of a network. Only local information is used at each node to keep accurate statistics on which routing policies lead to minimal routing times. In simple experiments involving a 36-node irregularly-connected network, this learning approach proves superior to routing based on precomputed shortest paths. | [
163,
2295,
2381,
2429,
2504
] | Validation |
2,668 | 5 | Title: Efficient Instruction Scheduling Using Finite State Automata
Abstract: Modern compilers employ sophisticated instruction scheduling techniques to shorten the number of cycles taken to execute the instruction stream. In addition to correctness, the instruction scheduler must also ensure that hardware resources are not oversubscribed in any cycle. For a contemporary processor implementation with multiple pipelines and complex resource usage restrictions, this is not an easy task. The complexity involved in reasoning about such resource hazards is one of the primary factors that constrain the instruction scheduler from performing many aggressive transformations. For example, the ability to do code motion or instruction replacement in the middle of an already scheduled block would be a very powerful transformation if it could be performed efficiently. We extend a technique for detecting pipeline resource hazards based on finite state automata, to support the efficient implementation of such transformations that are essential for aggressive instruction scheduling beyond basic blocks. Although similar code transformations can be supported by other schemes such as reservation tables, our scheme is superior in terms of space and time. A global instruction scheduler that used these techniques was implemented in the KSR compiler. | [
2365
] | Train |
2,669 | 3 | Title: A proposal for variable selection in the Cox model
Abstract: We propose a new method for variable selection and estimation in Cox's proportional hazards model. Our proposal minimizes the log partial likelihood subject to the sum of the absolute values of the parameters being bounded by a constant. Because of the nature of this constraint it tends to produce some coefficients that are exactly zero and hence gives interpretable models. The method is a variation of the "lasso" proposal of Tibshirani (1994), designed for the linear regression context. Simulations indicate that the lasso can be more accurate than stepwise selection in this setting. | [
2596
] | Validation |
2,670 | 2 | Title: A proposal for variable selection in the Cox model
Abstract: GMD Report #633 Abstract Many of the current artificial neural network systems have serious limitations, concerning accessibility, flexibility, scaling and reliability. In order to go some way to removing these we suggest a reflective neural network architecture. In such an architecture, the modular structure is the most important element. The building-block elements are called "minos' modules. They perform self-observation and inform on the current level of development, or scope of expertise, within the module. A Pandemonium system integrates such submodules so that they work together to handle mapping tasks. Network complexity limitations are attacked in this way with the Pandemonium problem decomposition paradigm, and both static and dynamic unreliability of the whole Pandemonium system is effectively eliminated through the generation and interpretation of confidence and ambiguity measures at every moment during the development of the system. Two problem domains are used to test and demonstrate various aspects of our architecture. Reliability and quality measures are defined for systems that only answer part of the time. Our system achieves better quality values than single networks of larger size for a handwritten digit problem. When both second and third best answers are accepted, our system is left with only 5% error on the test set, 2.1% better than the best single net. It is also shown how the system can elegantly learn to handle garbage patterns. With the parity problem it is demonstrated how complexity of problems may be decomposed automatically by the system, through solving it with networks of size smaller than a single net is required to be. Even when the system does not find a solution to the parity problem, because networks of too small a size are used, the reliability remains around 99-100%. Our Pandemonium architecture gives more power and flexibility to the higher levels of a large hybrid system than a single net system can, offering useful information for higher-level feedback loops, through which reliability of answers may be intelligently traded for less reliable but important "intuitional" answers. In providing weighted alternatives and possible generalizations, this architecture gives the best possible service to the larger system of which it will form part. | [
253,
489,
1815
] | Train |
2,671 | 2 | Title: Rejection of Incorrect Answers from a Neural Net Classifier
Abstract: Frank Smieja Report number: 1993/2 | [
1815
] | Train |
2,672 | 2 | Title: REINFORCEMENT LEARNING FOR COORDINATED REACTIVE CONTROL
Abstract: The demands of rapid response and the complexity of many environments make it difficult to decompose, tune and coordinate reactive behaviors while ensuring consistency. Reinforcement learning networks can address the tuning problem, but do not address the problem of decomposition and coordination. We hypothesize that interacting reactions can often be decomposed into separate control tasks resident in separate networks and that the interaction can be coordinated through the tuning mechanism and a higher level controller. To explore these issues, we have implemented a reinforcement learning architecture as the reactive component of a two layer control system for a simulated race car. By varying the architecture, we test whether decomposing reactivity into separate controllers leads to superior overall performance and learning convergence in our domain. | [
465,
565,
636,
2409
] | Train |
2,673 | 1 | Title: A genetic prototype learner
Abstract: Supervised classification problems have received considerable attention from the machine learning community. We propose a novel genetic algorithm based prototype learning system, PLEASE, for this class of problems. Given a set of prototypes for each of the possible classes, the class of an input instance is determined by the prototype nearest to this instance. We assume ordinal attributes and prototypes are represented as sets of feature-value pairs. A genetic algorithm is used to evolve the number of prototypes per class and their positions on the input space as determined by corresponding feature-value pairs. Comparisons with C4.5 on a set of artificial problems of controlled complexity demonstrate the effectiveness of the pro posed system. | [
163,
638,
995,
1224,
2541
] | Test |
2,674 | 2 | Title: Comparing Methods for Refining Certainty-Factor Rule-Bases
Abstract: This paper compares two methods for refining uncertain knowledge bases using propositional certainty-factor rules. The first method, implemented in the Rapture system, employs neural-network training to refine the certainties of existing rules but uses a symbolic technique to add new rules. The second method, based on the one used in the Kbann system, initially adds a complete set of potential new rules with very low certainty and allows neural-network training to filter and adjust these rules. Experimental results indicate that the former method results in significantly faster training and produces much simpler refined rule bases with slightly greater accuracy. | [
159,
1352,
2066,
2543
] | Train |
2,675 | 6 | Title: CONSTRUCTING CONJUNCTIVE TESTS FOR DECISION TREES
Abstract: This paper discusses an approach of constructing new attributes based on decision trees and production rules. It can improve the concepts learned in the form of decision trees by simplifying them and improving their predictive accuracy. In addition, this approach can distinguish relevant primitive attributes from irrelevant primitive attributes. | [
1256,
1595,
1824,
1862,
1964
] | Test |
2,676 | 2 | Title: Models of perceptual learning in vernier hyperacuity
Abstract: Performance of human subjects in a wide variety of early visual processing tasks improves with practice. HyperBF networks (Poggio and Girosi, 1990) constitute a mathematically well-founded framework for understanding such improvement in performance, or perceptual learning, in the class of tasks known as visual hyperacuity. The present article concentrates on two issues raised by the recent psychophysical and computational findings reported in (Poggio et al., 1992b; Fahle and Edelman, 1992). First, we develop a biologically plausible extension of the HyperBF model that takes into account basic features of the functional architecture of early vision. Second, we explore various learning modes that can coexist within the HyperBF framework and focus on two unsupervised learning rules which may be involved in hyperacuity learning. Finally, we report results of psychophysical experiments that are consistent with the hypothesis that activity-dependent presynaptic amplification may be involved in perceptual learning in hyperacuity. | [
611,
1787,
2385
] | Test |
2,677 | 3 | Title: Mining and Model Simplicity: A Case Study in Diagnosis
Abstract: Proceedings of the 2nd International Conference on Knowledge Discovery and Data Mining (KDD), 1996. The official version of this paper has been published by the American Association for Artificial Intelligence (http://www.aaai.org) c fl 1996, American Association for Artificial Intelligence. All rights reserved. Abstract We describe the results of performing data mining on a challenging medical diagnosis domain, acute abdominal pain. This domain is well known to be difficult, yielding little more than 60% predictive accuracy for most human and machine diagnosticians. Moreover, many researchers argue that one of the simplest approaches, the naive Bayesian classifier, is optimal. By comparing the performance of the naive Bayesian classifier to its more general cousin, the Bayesian network classifier, and to selective Bayesian classifiers with just 10% of the total attributes, we show that the simplest models perform at least as well as the more complex models. We argue that simple models like the selective naive Bayesian classifier will perform as well as more complicated models for similarly complex domains with relatively small data sets, thereby calling into question the extra expense necessary to induce more complex models. | [
1339,
1582,
1909,
2017,
2338
] | Train |
2,678 | 2 | Title: Egocentric spatial representation in early vision
Abstract: Proceedings of the 2nd International Conference on Knowledge Discovery and Data Mining (KDD), 1996. The official version of this paper has been published by the American Association for Artificial Intelligence (http://www.aaai.org) c fl 1996, American Association for Artificial Intelligence. All rights reserved. Abstract We describe the results of performing data mining on a challenging medical diagnosis domain, acute abdominal pain. This domain is well known to be difficult, yielding little more than 60% predictive accuracy for most human and machine diagnosticians. Moreover, many researchers argue that one of the simplest approaches, the naive Bayesian classifier, is optimal. By comparing the performance of the naive Bayesian classifier to its more general cousin, the Bayesian network classifier, and to selective Bayesian classifiers with just 10% of the total attributes, we show that the simplest models perform at least as well as the more complex models. We argue that simple models like the selective naive Bayesian classifier will perform as well as more complicated models for similarly complex domains with relatively small data sets, thereby calling into question the extra expense necessary to induce more complex models. | [
2477,
2576
] | Validation |
2,679 | 3 | Title: STUDIES OF QUALITY MONITOR TIME SERIES: THE V.A. HOSPITAL SYSTEM build on foundational contributions in
Abstract: This report describes statistical research and development work on hospital quality monitor data sets from the nationwide VA hospital system. The project covers statistical analysis, exploration and modelling of data from several quality monitors, with the primary goals of: (a) understanding patterns of variability over time in hospital-level and monitor area specific quality monitor measures, and (b) understanding patterns of dependencies between sets of monitors. We present discussion of basic perspectives on data structure and preliminary data exploration for three monitors, followed by developments of several classes of formal models. We identify classes of hierarchical random effects time series models to be of relevance in mod-elling single or multiple monitor time series. We summarise basic model features and results of analyses of the three monitor data sets, in both single and multiple monitor frameworks, and present a variety of summary inferences in graphical displays. Our discussion includes summary conclusions related to the two key goals, discussions of questions of comparisons across hospitals, and some recommendations about further potential substantive and statistical investigations. | [
99,
2578
] | Train |
2,680 | 2 | Title: Least Absolute Shrinkage is Equivalent to Quadratic Penalization
Abstract: Adaptive ridge is a special form of ridge regression, balancing the quadratic penalization on each parameter of the model. This paper shows the equivalence between adaptive ridge and lasso (least absolute shrinkage and selection operator). This equivalence states that both procedures produce the same estimate. Least absolute shrinkage can thus be viewed as a particular quadratic penalization. From this observation, we derive an EM algorithm to compute the lasso solution. We finally present a series of applications of this type of algorithm in regres sion problems: kernel regression, additive modeling and neural net training. | [
101,
157,
2596
] | Train |
2,681 | 2 | Title: Regression with Input-dependent Noise: A Gaussian Process Treatment
Abstract: Technical Report NCRG/98/002, available from http://www.ncrg.aston.ac.uk/ To appear in Advances in Neural Information Processing Systems 10 eds. M. I. Jordan, M. J. Kearns and S. A. Solla. Lawrence Erlbaum (1998). Abstract Gaussian processes provide natural non-parametric prior distributions over regression functions. In this paper we consider regression problems where there is noise on the output, and the variance of the noise depends on the inputs. If we assume that the noise is a smooth function of the inputs, then it is natural to model the noise variance using a second Gaussian process, in addition to the Gaussian process governing the noise-free output value. We show that prior uncertainty about the parameters controlling both processes can be handled and that the posterior distribution of the noise rate can be sampled from using Markov chain Monte Carlo methods. Our results on a synthetic data set give a posterior noise variance that well-approximates the true variance. | [
78,
160,
1857
] | Validation |
2,682 | 3 | Title: Importance Sampling
Abstract: Technical Report No. 9805, Department of Statistics, University of Toronto Abstract. Simulated annealing | moving from a tractable distribution to a distribution of interest via a sequence of intermediate distributions | has traditionally been used as an inexact method of handling isolated modes in Markov chain samplers. Here, it is shown how one can use the Markov chain transitions for such an annealing sequence to define an importance sampler. The Markov chain aspect allows this method to perform acceptably even for high-dimensional problems, where finding good importance sampling distributions would otherwise be very difficult, while the use of importance weights ensures that the estimates found converge to the correct values as the number of annealing runs increases. This annealed importance sampling procedure resembles the second half of the previously-studied tempered transitions, and can be seen as a generalization of a recently-proposed variant of sequential importance sampling. It is also related to thermodynamic integration methods for estimating ratios of normalizing constants. Annealed importance sampling is most attractive when isolated modes are present, or when estimates of normalizing constants are required, but it may also be more generally useful, since its independent sampling allows one to bypass some of the problems of assessing convergence and autocorrelation in Markov chain samplers. | [
48,
2348
] | Train |
2,683 | 2 | Title: Introduction to Radial Basis Function Networks
Abstract: This document is an introduction to radial basis function (RBF) networks, a type of artificial neural network for application to problems of supervised learning (e.g. regression, classification and time series prediction). It is available in either PostScript or hyper-text 2 . | [
427,
668,
687,
2044
] | Train |
2,684 | 2 | Title: INVERSION IN TIME
Abstract: Inversion of multilayer synchronous networks is a method which tries to answer questions like "What kind of input will give a desired output?" or "Is it possible to get a desired output (under special input/output constraints)?". We will describe two methods of inverting a connectionist network. Firstly, we extend inversion via backpropagation (Linden/Kindermann [4], Williams [11]) to recurrent (El-man [1], Jordan [3], Mozer [5], Williams/Zipser [10]), time-delayed (Waibel at al. [9]) and discrete versions of continuous networks (Pineda [7], Pearlmutter [6]). The result of inversion is an input vector. The corresponding output vector is equal to the target vector except a small remainder. The knowledge of those attractors may help to understand the function and the generalization qualities of connectionist systems of this kind. Secondly, we introduce a new inversion method for proving the non-existence of an input combination under special constraints, e.g. in a subspace of the input space. This method works by iterative exclusion of invalid activation values. It might be a helpful way to judge the properties of a trained network. We conclude with simulation results of three different tasks: XOR, morse signal decoding and handwritten digit recognition. | [
2523
] | Validation |
2,685 | 6 | Title: Learning under persistent drift
Abstract: In this paper we study learning algorithms for environments which are changing over time. Unlike most previous work, we are interested in the case where the changes might be rapid but their "direction" is relatively constant. We model this type of change by assuming that the target distribution is changing continuously at a constant rate from one extreme distribution to another. We show in this case how to use a simple weighting scheme to estimate the error of an hypothesis, and using this estimate, to minimize the error of the prediction. | [
2053,
2054
] | Test |
2,686 | 2 | Title: Penalisation multiple adaptative un nouvel algorithme de regression, la penalisation multiple adapta-tive. Cet algorithme represente
Abstract: Chaque parametre du modele est penalise individuellement. Le reglage de ces penalisations se fait automatiquement a partir de la definition d'un hyperparametre de regularisation globale. Cet hyperparametre, qui controle la complexite du regresseur, peut ^etre estime par des techniques de reechantillonnage. Nous montrons experimentalement les performances et la stabilite de la penalisation multiple adaptative dans le cadre de la regression lineaire. Nous avons choisi des problemes pour lesquels le probleme du controle de la complexite est particulierement crucial, comme dans le cadre plus general de l'estimation fonctionnelle. Les comparaisons avec les moindres carres regularises et la selection de variables nous permettent de deduire les conditions d'application de chaque algorithme de penalisation. Lors des simulations, nous testons egalement plusieurs techniques de reechantillonnage. Ces techniques sont utilisees pour selectionner la complexite optimale des estimateurs de la fonction de regression. Nous comparons les pertes occasionnees par chacune d'entre elles lors de la selection de modeles sous-optimaux. Nous regardons egalement si elles permettent de determiner l'estimateur de la fonction de regression minimisant l'erreur en generalisation parmi les differentes methodes de penalisation en competition. | [
101,
916,
2596
] | Train |
2,687 | 4 | Title: ALECSYS and the AutonoMouse: Learning to Control a Real Robot by Distributed Classifier Systems
Abstract: Chaque parametre du modele est penalise individuellement. Le reglage de ces penalisations se fait automatiquement a partir de la definition d'un hyperparametre de regularisation globale. Cet hyperparametre, qui controle la complexite du regresseur, peut ^etre estime par des techniques de reechantillonnage. Nous montrons experimentalement les performances et la stabilite de la penalisation multiple adaptative dans le cadre de la regression lineaire. Nous avons choisi des problemes pour lesquels le probleme du controle de la complexite est particulierement crucial, comme dans le cadre plus general de l'estimation fonctionnelle. Les comparaisons avec les moindres carres regularises et la selection de variables nous permettent de deduire les conditions d'application de chaque algorithme de penalisation. Lors des simulations, nous testons egalement plusieurs techniques de reechantillonnage. Ces techniques sont utilisees pour selectionner la complexite optimale des estimateurs de la fonction de regression. Nous comparons les pertes occasionnees par chacune d'entre elles lors de la selection de modeles sous-optimaux. Nous regardons egalement si elles permettent de determiner l'estimateur de la fonction de regression minimisant l'erreur en generalisation parmi les differentes methodes de penalisation en competition. | [
636,
764,
2174
] | Train |
2,688 | 1 | Title: An Adverse Interaction between the Crossover Operator and a Restriction on Tree Depth of Crossover
Abstract: The Crossover operator is common to most implementations of Genetic Programming (GP). Another, usually unavoidable, factor is some form of restriction on the size of trees in the GP population. This paper concentrates on the interaction between the Crossover operator and a restriction on tree depth demonstrated by the MAX problem, which involves returning the largest possible value for given function and terminal sets. | [
1784,
1839,
1840,
2216
] | Train |
2,689 | 6 | Title: Expected Mistake Bound Model for On-Line Reinforcement Learning
Abstract: We propose a model of efficient on-line reinforcement learning based on the expected mistake bound framework introduced by Haussler, Littlestone and Warmuth (1987). The measure of performance we use is the expected difference between the total reward received by the learning agent and that received by an agent behaving optimally from the start. We call this expected difference the cumulative mistake of the agent and we require that it "levels off" at a reasonably fast rate as the learning progresses. We show that this model is polynomially equivalent to the PAC model of off-line reinforcement learning introduced in (Fiechter, 1994). In particular we show how an off-line PAC reinforcement learning algorithm can be transformed into an efficient on-line algorithm in a simple and practical way. An immediate consequence of this result is that the PAC algorithm for the general finite state-space reinforcement learning problem described in (Fiechter, 1994) can be transformed into a polynomial on-line al gorithm with guaranteed performances. | [
1975,
2209
] | Test |
2,690 | 6 | Title: Robust Trainability of Single Neurons
Abstract: We propose a model of efficient on-line reinforcement learning based on the expected mistake bound framework introduced by Haussler, Littlestone and Warmuth (1987). The measure of performance we use is the expected difference between the total reward received by the learning agent and that received by an agent behaving optimally from the start. We call this expected difference the cumulative mistake of the agent and we require that it "levels off" at a reasonably fast rate as the learning progresses. We show that this model is polynomially equivalent to the PAC model of off-line reinforcement learning introduced in (Fiechter, 1994). In particular we show how an off-line PAC reinforcement learning algorithm can be transformed into an efficient on-line algorithm in a simple and practical way. An immediate consequence of this result is that the PAC algorithm for the general finite state-space reinforcement learning problem described in (Fiechter, 1994) can be transformed into a polynomial on-line al gorithm with guaranteed performances. | [
591,
2053
] | Train |
2,691 | 2 | Title: A map of the protein space An automatic hierarchical classification of all protein sequences
Abstract: We investigate the space of all protein sequences. We combine the standard measures of similarity (SW, FASTA, BLAST), to associate with each sequence an exhaustive list of neighboring sequences. These lists induce a (weighted directed) graph whose vertices are the sequences. The weight of an edge connecting two sequences represents their degree of similarity. This graph encodes much of the fundamental properties of the sequence space. We look for clusters of related proteins in this graph. These clusters correspond to strongly connected sets of vertices. Two main ideas underlie our work: i) Interesting homologies among proteins can be deduced by transitivity. ii) Transitivity should be applied restrictively in order to prevent unrelated proteins from clustering together. Our analysis starts from a very conservative classification, based on very significant similarities, that has many classes. Subsequently, classes are merged to include less significant similarities. Merging is performed via a novel two phase algorithm. First, the algorithm identifies groups of possibly related clusters (based on transitivity and strong connectivity) using local considerations, and merges them. Then, a global test is applied to identify nuclei of strong relationships within these groups of clusters, and the classification is refined accordingly. This process takes place at varying thresholds of statistical significance, where at each step the algorithm is applied on the classes of the previous classification, to obtain the next one, at the more permissive threshold. Consequently, a hierarchical organization of all proteins is obtained. The resulting classification splits the space of all protein sequences into well defined groups of proteins. The results show that the automatically induced sets of proteins are closely correlated with natural biological families and super families. The hierarchical organization reveals finer sub-families that make up known families of proteins as well as many interesting relations between protein families. The hierarchical organization proposed may be considered as the first map of the space of all protein sequences. An interactive web site including the results of our analysis has been constructed, and is now accessible through http://www.protomap.cs.huji.ac.il | [
1751
] | Test |
2,692 | 0 | Title: Multi-Strategy Learning and Theory Revision
Abstract: This paper presents the system WHY, which learns and updates a diagnostic knowledge base using domain knowledge and a set of examples. The a-priori knowledge consists of a causal model of the domain, stating the relationships among basic phenomena, and a body of phenomenological theory, describing the links between abstract concepts and their possible manifestations in the world. The phenomenological knowledge is used deductively, the causal model is used abductively and the examples are used inductively. The problems of imperfection and intractability of the theory are handled by allowing the system to make assumptions during its reasoning. In this way, robust knowledge can be learned with limited complexity and limited number of examples. The system works in a first order logic environment and has been applied in a real domain. | [
1370,
2038,
2172
] | Validation |
2,693 | 3 | Title: FROM METROPOLIS TO DIFFUSIONS: GIBBS STATES AND OPTIMAL SCALING
Abstract: This paper investigates the behaviour of the random walk Metropolis algorithm in high dimensional problems. Here we concentrate on the case where the components in the target density is a spatially homogeneous Gibbs distribution with finite range. The performance of the algorithm is strongly linked to the presence or absence of phase transition for the Gibbs distribution; the convergence time being approximately linear in dimension for problems where phase transition is not present. Related to this, there is an optimal way to scale the variance of the proposal distribution in order to maximise the speed of convergence of the algorithm. This turns out to involve scaling the variance of the proposal as the reciprocal of dimension (at least in the phase transition free case). Moreover the actual optimal scaling can be characterised in terms of the overall acceptance rate of the algorithm, the maximising value being 0:234, the value as predicted by studies on simpler classes of target density. The results are proved in the framework of a weak convergence result, which shows that the algorithm actually behaves like an infinite dimensional diffusion process in high dimensions. 1. Introduction and discussion of results | [
2025
] | Train |
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