The paper is devoted to two problems: (1) reinforcement of SVM algorithms, and (2) justification of memorization mechanisms for generalization.
Statistical theory of learning considers methods of constructing approximations that converge to the desired function with increasing number of observations. This theory studies mechanisms that provide convergence in the space of functions in L2 norm, i.e., it studies the so-called strong mode of convergence. However, in Hilbert space, along with the convergence in the space of functions, there also exists the so-called weak mode of convergence, i.e., convergence in the space of functionals. Under some conditions, this weak mode of convergence also implies the convergence of approximations to the desired function in L2 norm, although such convergence is based on other mechanisms. The paper discusses new learning methods which use both modes of convergence (weak and strong) simultaneously. Such methods allow one to execute the following: (1) select an admissible subset of functions (i.e., the set of appropriate approximation functions), and (2) find the desired approximation in this admissible subset. Since only two modes of convergence exist in Hilbert space, we call the theory that uses both modes the complete statistical theory of learning. Along with general reasoning, we describe new learning algorithms referred to as Learning Using Statistical Invariants (LUSI). LUSI algorithms were developed for sets of functions belonging to Reproducing Kernel Hilbert Space (RKHS); they include the modified SVM method (LUSI-SVM method). Also, the paper presents a LUSI modification of Neural Networks (LUSI-NN). LUSI methods require fewer training examples that standard approaches for achieving the same performance. In conclusion, the paper discusses the general (philosophical) framework of a new learning paradigm that includes the concept of intelligence.
In this paper, we present a method for automatic recognition of isolated Marathi handwritten numerals in which Zernike moments and Fourier Descriptors are used as features. After preprocessing the numeral image, Zernike moment and the Fourier Descriptor features of the numeral are extracted. These features are then fed in the k-NN classifier for classification. The proposed method is experimented on a database of 12690 samples of Marathi handwritten numeral. We have obtained recognition accuracy of 96. 58% using k-NN classifier.
This paper introduces a new learning paradigm, called Learning Using Statistical Invariants (LUSI), which is different from the classical one. In a classical paradigm, the learning machine constructs a classification rule that minimizes the probability of expected error; it is data-driven model of learning. In the LUSI paradigm, in order to construct the desired classification function, a learning machine computes statistical invariants that are specific for the problem, and then minimizes the expected error in a way that preserves these invariants; it is thus both data- and invariant-driven learning. From a mathematical point of view, methods of the classical paradigm employ mechanisms of strong convergence of approximations to the desired function, whereas methods of the new paradigm employ both strong and weak convergence mechanisms. This can significantly increase the rate of convergence.
Existing mathematical model of learning requires using training data find in a given subset of admissible function the function that minimizes the expected loss. In the paper this setting is called Second selection problem. Mathematical model of learning in this paper along with Second selection problem requires to solve the so-called First selection problem where using training data one first selects from wide set of function in Hilbert space an admissible subset of functions that include the desired function and second selects in this admissible subset a good approximation to the desired function. Existence of two selection problems reflects fundamental property of Hilbert space, existence of two different concepts of convergence of functions: weak convergence (that leads to solution of the First selection problem) and strong convergence (that leads to solution of the Second selection problem). In the paper we describe simultaneous solution of both selection problems for functions that belong to Reproducing Kernel Hilbert space. The solution is obtained in closed form.
The paper considers general machine learning models, where knowledge transfer is positioned as the main method to improve their convergence properties. Previous research was focused on mechanisms of knowledge transfer in the context of SVM framework; the paper shows that this mechanism is applicable to neural network framework as well. The paper describes several general approaches for knowledge transfer in both SVM and ANN frameworks and illustrates algorithmic implementations and performance of one of these approaches for several synthetic examples.
This article describes a method for constructing a special rule (we call it synergy rule) that uses as its input information the outputs (scores) of several monotonic rules which solve the same pattern recognition problem. As an example of scores of such monotonic rules we consider here scores of SVM classifiers.In order to construct the optimal synergy rule, we estimate the conditional probability function based on the direct problem setting, which requires solving a Fredholm integral equation. Generally, solving a Fredholm equation is an ill-posed problem. However, in our model, we look for the solution of the equation in the set of monotonic and bounded functions, which makes the problem well-posed. This allows us to solve the equation accurately even with training data sets of limited size.In order to construct a monotonic solution, we use the set of functions that belong to Reproducing Kernel Hilbert Space (RKHS) associated with the INK-spline kernel (splines with In finite Numbers of Knots) of degree zero. The paper provides details of the methods for finding multidimensional conditional probability in a set of monotonic functions to obtain the corresponding synergy rules. We demonstrate effectiveness of such rules for1) solving standard pattern recognition problems,2) constructing multi-class classification rules,3) constructing a method for knowledge transfer from multiple intelligent teachers in the LUPI paradigm.
Distillation (Hinton et al., 2015) and privileged information (Vapnik & Izmailov, 2015) are two techniques that enable machines to learn from other machines. This paper unifies these two techniques into generalized distillation, a framework to learn from multiple machines and data representations. We provide theoretical and causal insight about the inner workings of generalized distillation, extend it to unsupervised, semisupervised and multitask learning scenarios, and illustrate its efficacy on a variety of numerical simulations on both synthetic and real-world data.
The paper considers several topics on learning with privileged information: (1) general machine learning models, where privileged information is positioned as the main mechanism to improve their convergence properties, (2) existing and novel approaches to leverage that privileged information, (3) algorithmic realization of one of these (namely, knowledge transfer) approaches, and its performance characteristics, illustrated on simple synthetic examples.
This paper presents direct settings and rigorous solutions of the main Statistical Inference problems. It shows that rigorous solutions require solving multidimensional Fredholm integral equations of the first kind in the situation where not only the right-hand side of the equation is an approximation, but the operator in the equation is also de fined approximately. Using Stefanuyk-Vapnik theory for solving such ill-posed operator equations, constructive methods of empirical inference are introduced. These methods are based on a new concept called V-matrix. This matrix captures geometric properties of the observation data that are ignored by classical statistical methods.
We introduce a constructive setting for the problem of density ratio estimation through the solution of a multidimensional integral equation. In this equation, not only its right hand side is approximately known, but also the integral operator is approximately defined. We show that this ill-posed problem has a rigorous solution and obtain the solution in a closed form. The key element of this solution is the novel V -matrix, which captures the geometry of the observed samples. We compare our method with previously proposed ones, using both synthetic and real data. Our experimental results demonstrate the good potential of the new approach.
This paper describes a new paradigm of machine learning, in which Intelligent Teacher is involved. During training stage, Intelligent Teacher provides Student with information that contains, along with classification of each example, additional privileged information (for example, explanation) of this example. The paper describes two mechanisms that can be used for significantly accelerating the speed of Student's learning using privileged information: (1) correction of Student's concepts of similarity between examples, and (2) direct Teacher-Student knowledge transfer.
This paper presents direct settings and rigorous solutions of Statistical Inference problems. It shows that rigorous solutions require solving ill-posed Fredholm integral equations of the first kind in the situation where not only the right-hand side of the equation is an approximation, but the operator in the equation is also defined approximately. Using Stefanuyk-Vapnik theory for solving such operator equations, constructive methods of empirical inference are introduced. These methods are based on a new concept called V -matrix. This matrix captures geometric properties of the observation data that are ignored by classical statistical methods.
Radial basis function (RBF) kernels for SVM have been routinely used in a wide range of classification problems, delivering consistently good performance for those problems where the kernel computations are numerically feasible (high-dimensional problems typically use linear kernels). One of the drawbacks of RBF kernels is the necessity of selecting the proper value of the hyperparameter γ in addition to the standard SVM penalty parameter C - this process can lead to overfitting. Another (more obscure) drawback of RBF is its inherent non-optimality as an approximation function. In order to address these issues, we propose to extend the concept of polynomial splines (designed explicitly for approximation purposes) to multidimensional normalized splines with infinite number of knots and use the resulting hyperparameter-free kernel SVMs instead of RBF kernel SVMs. We tested our approach for a number of standard classification datasets used in the literature. The results suggest that new kernels deliver mostly better classification performance than RBF kernel (for problems of moderately large dimensions), but allow faster computation (if measured on large cross-validation grids), with less chance of overfitting.
There is rapidly accumulating evidence that the application of machine learning classification to neuroimaging measurements may be valuable for the development of diagnostic and prognostic prediction tools in psychiatry. However, current methods do not produce a measure of the reliability of the predictions. Knowing the risk of the error associated with a given prediction is essential for the development of neuroimaging-based clinical tools. We propose a general probabilistic classification method to produce measures of confidence for magnetic resonance imaging (MRI) data. We describe the application of transductive conformal predictor (TCP) to MRI images. TCP generates the most likely prediction and a valid measure of confidence, as well as the set of all possible predictions for a given confidence level. We present the theoretical motivation for TCP, and we have applied TCP to structural and functional MRI data in patients and healthy controls to investigate diagnostic and prognostic prediction in depression. We verify that TCP predictions are as accurate as those obtained with more standard machine learning methods, such as support vector machine, while providing the additional benefit of a valid measure of confidence for each prediction.
Dmitry Pechyony合作论文数Microsoft in Cambridge4
Volodya Vovk合作论文数Department of Computer Science3
Alex Gammerman合作论文数CLRC2