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37
Theory and applications of Robust Optimization
, 2007
"... In this paper we survey the primary research, both theoretical and applied, in the field of Robust Optimization (RO). Our focus will be on the computational attractiveness of RO approaches, as well as the modeling power and broad applicability of the methodology. In addition to surveying the most pr ..."
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Cited by 25 (5 self)
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In this paper we survey the primary research, both theoretical and applied, in the field of Robust Optimization (RO). Our focus will be on the computational attractiveness of RO approaches, as well as the modeling power and broad applicability of the methodology. In addition to surveying the most prominent theoretical results of RO over the past decade, we will also present some recent results linking RO to adaptable models for multistage decisionmaking problems. Finally, we will highlight successful applications of RO across a wide spectrum of domains, including, but not limited to, finance, statistics, learning, and engineering.
Robustness and regularization of support vector machines
, 1485
"... We consider regularized support vector machines (SVMs) and show that they are precisely equivalent to a new robust optimization formulation. We show that this equivalence of robust optimization and regularization has implications for both algorithms, and analysis. In terms of algorithms, the equival ..."
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Cited by 21 (4 self)
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We consider regularized support vector machines (SVMs) and show that they are precisely equivalent to a new robust optimization formulation. We show that this equivalence of robust optimization and regularization has implications for both algorithms, and analysis. In terms of algorithms, the equivalence suggests more general SVMlike algorithms for classification that explicitly build in protection to noise, and at the same time control overfitting. On the analysis front, the equivalence of robustness and regularization provides a robust optimization interpretation for the success of regularized SVMs. We use this new robustness interpretation of SVMs to give a new proof of consistency of (kernelized) SVMs, thus establishing robustness as the reason regularized SVMs generalize well.
The Interplay of Optimization and Machine Learning Research
 Journal of Machine Learning Research
, 2006
"... The fields of machine learning and mathematical programming are increasingly intertwined. Optimization problems lie at the heart of most machine learning approaches. The Special Topic on Machine Learning and Large Scale Optimization examines this interplay. Machine learning researchers have embra ..."
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Cited by 17 (1 self)
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The fields of machine learning and mathematical programming are increasingly intertwined. Optimization problems lie at the heart of most machine learning approaches. The Special Topic on Machine Learning and Large Scale Optimization examines this interplay. Machine learning researchers have embraced the advances in mathematical programming allowing new types of models to be pursued. The special topic includes models using quadratic, linear, secondorder cone, semidefinite, and semiinfinite programs. We observe that the qualities of good optimization algorithms from the machine learning and optimization perspectives can be quite different. Mathematical programming puts a premium on accuracy, speed, and robustness. Since generalization is the bottom line in machine learning and training is normally done offline, accuracy and small speed improvements are of little concern in machine learning. Machine learning prefers simpler algorithms that work in reasonable computational time for specific classes of problems. Reducing machine learning problems to wellexplored mathematical programming classes with robust general purpose optimization codes allows machine learning researchers to rapidly develop new techniques.
Ellipsoidal kernel machines
 In Proceedings of the Artificial Intelligence and Statistics
, 2007
"... A novel technique is proposed for improving the standard VapnikChervonenkis (VC) dimension estimate for the Support Vector Machine (SVM) framework. The improved VC estimates are based on geometric arguments. By considering bounding ellipsoids instead of the usual bounding hyperspheres and assuming ..."
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Cited by 14 (3 self)
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A novel technique is proposed for improving the standard VapnikChervonenkis (VC) dimension estimate for the Support Vector Machine (SVM) framework. The improved VC estimates are based on geometric arguments. By considering bounding ellipsoids instead of the usual bounding hyperspheres and assuming gaptolerant classifiers, a linear classifier with a given margin is shown to shatter fewer points than previously estimated. This improved VC estimation method directly motivates a different estimator for the parameters of a linear classifier. Surprisingly, only VCbased arguments are needed to justify this modification to the SVM. The resulting technique is implemented using Semidefinite Programming (SDP) and is solvable in polynomial time. The new linear classifier also ensures certain invariances to affine transformations on the data which a standard SVM does not provide. We demonstrate that the technique can be kernelized via extensions to Hilbert spaces. Promising experimental results are shown on several standardized datasets. 1
Robust Regression and Lasso
"... We consider robust leastsquares regression with featurewise disturbance. We show that this formulation leads to tractable convex optimization problems, and we exhibit a particular uncertainty set for which the robust problem is equivalent to ℓ1 regularized regression (Lasso). This provides an inte ..."
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Cited by 8 (4 self)
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We consider robust leastsquares regression with featurewise disturbance. We show that this formulation leads to tractable convex optimization problems, and we exhibit a particular uncertainty set for which the robust problem is equivalent to ℓ1 regularized regression (Lasso). This provides an interpretation of Lasso from a robust optimization perspective. We generalize this robust formulation to consider more general uncertainty sets, which all lead to tractable convex optimization problems. Therefore, we provide a new methodology for designing regression algorithms, which generalize known formulations. The advantage is that robustness to disturbance is a physical property that can be exploited: in addition to obtaining new formulations, we use it directly to show sparsity properties of Lasso, as well as to prove a general consistency result for robust regression problems, including Lasso, from a unified robustness perspective. 1
Maximum Relative Margin and DataDependent regularization
 JOURNAL OF MACHINE LEARNING RESEARCH
"... Leading classification methods such as support vector machines (SVMs) and their counterparts achieve strong generalization performance by maximizing the margin of separation between data classes. While the maximum margin approach has achieved promising performance, this article identifies its sensit ..."
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Cited by 6 (1 self)
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Leading classification methods such as support vector machines (SVMs) and their counterparts achieve strong generalization performance by maximizing the margin of separation between data classes. While the maximum margin approach has achieved promising performance, this article identifies its sensitivity to affine transformations of the data and to directions with large data spread. Maximum margin solutions may be misled by the spread of data and preferentially separate classes along large spread directions. This article corrects these weaknesses by measuring margin not in the absolute sense but rather only relative to the spread of data in any projection direction. Maximum relative margin corresponds to a datadependent regularization on the classification function while maximum absolute margin corresponds to an ℓ2 norm constraint on the classification function. Interestingly, the proposed improvements only require simple extensions to existing maximum margin formulations and preserve the computational efficiency of SVMs. Through the maximization of relative margin, surprising performance gains are achieved on realworld problems such as digit, image histogram, and text classification. In addition, risk bounds are derived for the new formulation based on Rademacher averages.
Learning Algorithms for Link Prediction Based on Chance Constraints
"... In this paper, we consider the link prediction problem, where we are given a partial snapshot of a network at some time and the goal is to predict the additional links formed at a later time. The accuracy of current prediction methods is quite low due to the extreme class skew and the large number ..."
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Cited by 5 (0 self)
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In this paper, we consider the link prediction problem, where we are given a partial snapshot of a network at some time and the goal is to predict the additional links formed at a later time. The accuracy of current prediction methods is quite low due to the extreme class skew and the large number of potential links. Here, we describe learning algorithms based on chance constrained programs and show that they exhibit all the properties needed for a good link predictor, namely, they allow preferential bias to positive or negative class; handle skewness in the data; and scale to large networks. Our experimental results on three realworld domains—coauthorship networks, biological networks and citation networks—show significant performance improvement over baseline algorithms. We conclude by briefly describing some promising future directions based on this work.
ChanceConstrained Programs for Link Prediction
"... In this paper, we consider the link prediction problem, where we are given a partial snapshot of a network at some time and the goal is to predict additional links at a later time. The accuracy of the current prediction methods is quite low due to the extreme class skew and the large number of poten ..."
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Cited by 3 (0 self)
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In this paper, we consider the link prediction problem, where we are given a partial snapshot of a network at some time and the goal is to predict additional links at a later time. The accuracy of the current prediction methods is quite low due to the extreme class skew and the large number of potential links. In this paper, we describe learning algorithms based on chance constrained programs and show that they exhibit all the properties needed for a good link predictor, namely, allow preferential bias to positive or negative class; handle skewness in the data; and scale to large networks. Our experimental results on three realworld coauthorship networks show significant improvement in prediction accuracy over baseline algorithms. 1
Learning from Incomplete Data with Infinite Imputations
"... We address the problem of learning decision functions from training data in which some attribute values are unobserved. This problem can arise, for instance, when training data is aggregated from multiple sources, and some sources record only a subset of attributes. We derive a generic joint optimiz ..."
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Cited by 3 (0 self)
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We address the problem of learning decision functions from training data in which some attribute values are unobserved. This problem can arise, for instance, when training data is aggregated from multiple sources, and some sources record only a subset of attributes. We derive a generic joint optimization problem in which the distribution governing the missing values is a free parameter. We show that the optimal solution concentrates the density mass on finitely many imputations, and provide a corresponding algorithm for learning from incomplete data. We report on empirical results on benchmark data, and on the email spam application that motivates our work. 1.