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An MM Algorithm for Split Feasibility Problems

arXiv.org Machine Learning

The classical multi-set split feasibility problem seeks a point in the intersection of finitely many closed convex domain constraints, whose image under a linear mapping also lies in the intersection of finitely many closed convex range constraints. Split feasibility generalizes important inverse problems including convex feasibility, linear complementarity, and regression with constraint sets. When a feasible point does not exist, solution methods that proceed by minimizing a proximity function can be used to obtain optimal approximate solutions to the problem. We present an extension of the proximity function approach that generalizes the linear split feasibility problem to allow for non-linear mappings. Our algorithm is based on the principle of majorization-minimization, is amenable to quasi-Newton acceleration, and comes complete with convergence guarantees under mild assumptions. Furthermore, we show that the Euclidean norm appearing in the proximity function of the non-linear split feasibility problem can be replaced by arbitrary Bregman divergences. We explore several examples illustrating the merits of non-linear formulations over the linear case, with a focus on optimization for intensity-modulated radiation therapy.


Learning Bound for Parameter Transfer Learning

arXiv.org Machine Learning

We consider a transfer-learning problem by using the parameter transfer approach, where a suitable parameter of feature mapping is learned through one task and applied to another objective task. Then, we introduce the notion of the local stability and parameter transfer learnability of parametric feature mapping,and thereby derive a learning bound for parameter transfer algorithms. As an application of parameter transfer learning, we discuss the performance of sparse coding in self-taught learning. Although self-taught learning algorithms with plentiful unlabeled data often show excellent empirical performance, their theoretical analysis has not been studied. In this paper, we also provide the first theoretical learning bound for self-taught learning.


Accelerated Stochastic Subgradient Methods under Local Error Bound Condition

arXiv.org Machine Learning

In this paper, we propose two {\bf accelerated stochastic subgradient} methods for stochastic non-strongly convex optimization problems by leveraging a generic local error bound condition. The novelty of the proposed methods lies at smartly leveraging the recent historical solution to tackle the variance in the stochastic subgradient. The key idea of both methods is to iteratively solve the original problem approximately in a local region around a recent historical solution with size of the local region gradually decreasing as the solution approaches the optimal set. The difference of the two methods lies at how to construct the local region. The first method uses an explicit ball constraint and the second method uses an implicit regularization approach. For both methods, we establish the improved iteration complexity in a high probability for achieving an $\epsilon$-optimal solution. Besides the improved order of iteration complexity with a high probability, the proposed algorithms also enjoy a logarithmic dependence on the distance of the initial solution to the optimal set. We also consider applications in machine learning and demonstrate that the proposed algorithms enjoy faster convergence than the traditional stochastic subgradient method. For example, when applied to the $\ell_1$ regularized polyhedral loss minimization (e.g., hinge loss, absolute loss), the proposed stochastic methods have a logarithmic iteration complexity.


Triplet Probabilistic Embedding for Face Verification and Clustering

arXiv.org Machine Learning

Despite significant progress made over the past twenty five years, unconstrained face verification remains a challenging problem. This paper proposes an approach that couples a deep CNN-based approach with a low-dimensional discriminative embedding learned using triplet probability constraints to solve the unconstrained face verification problem. Aside from yielding performance improvements, this embedding provides significant advantages in terms of memory and for post-processing operations like subject specific clustering. Experiments on the challenging IJB-A dataset show that the proposed algorithm performs comparably or better than the state of the art methods in verification and identification metrics, while requiring much less training data and training time. The superior performance of the proposed method on the CFP dataset shows that the representation learned by our deep CNN is robust to extreme pose variation. Furthermore, we demonstrate the robustness of the deep features to challenges including age, pose, blur and clutter by performing simple clustering experiments on both IJB-A and LFW datasets.


Unknowable Manipulators: Social Network Curator Algorithms

arXiv.org Machine Learning

For a social networking service to acquire and retain users, it must find ways to keep them engaged. By accurately gauging their preferences, it is able to serve them with the subset of available content that maximises revenue for the site. Without the constraints of an appropriate regulatory framework, we argue that a sufficiently sophisticated curator algorithm tasked with performing this process may choose to explore curation strategies that are detrimental to users. In particular, we suggest that such an algorithm is capable of learning to manipulate its users, for several qualitative reasons: 1. Access to vast quantities of user data combined with ongoing breakthroughs in the field of machine learning are leading to powerful but uninterpretable strategies for decision making at scale. 2. The availability of an effective feedback mechanism for assessing the short and long term user responses to curation strategies. 3. Techniques from reinforcement learning have allowed machines to learn automated and highly successful strategies at an abstract level, often resulting in non-intuitive yet nonetheless highly appropriate action selection. In this work, we consider the form that these strategies for user manipulation might take and scrutinise the role that regulation should play in the design of such systems.


Towards Principled Methods for Training Generative Adversarial Networks

arXiv.org Machine Learning

The goal of this paper is not to introduce a single algorithm or method, but to make theoretical steps towards fully understanding the training dynamics of generative adversarial networks. In order to substantiate our theoretical analysis, we perform targeted experiments to verify our assumptions, illustrate our claims, and quantify the phenomena. This paper is divided into three sections. The first section introduces the problem at hand. The second section is dedicated to studying and proving rigorously the problems including instability and saturation that arize when training generative adversarial networks. The third section examines a practical and theoretically grounded direction towards solving these problems, while introducing new tools to study them.


Astronaut Gene Cernan, the last man to walk on the moon, dies at 82

Los Angeles Times

Former astronaut Gene Cernan, the last of only a dozen men to walk on the moon who returned to Earth with a message of "peace and hope for all mankind," has died. Cernan died Monday following ongoing heath issues, his family said in a statement released by NASA spokesman Bob Jacobs. NASA said Cernan was surrounded by his family. "Even at the age of 82, Gene was passionate about sharing his desire to see the continued human exploration of space and encouraged our nation's leaders and young people to not let him remain the last man to walk on the Moon," the family said. Cernan, commander of NASA's Apollo 17 mission, set foot on the lunar surface in December 1972 during his third space flight.


Artificial intelligence predicts when heart will fail - BBC News

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Artificial intelligence can predict when patients with a heart disorder will die, according to scientists. The software learned to analyse blood tests and scans of beating hearts to spot signs that the organ was about to fail. The team, from the UK's Medical Research Council, say the technology could save lives by finding patients that need more aggressive treatment. The results were published in the journal Radiology. The researchers, at the MRC London Institute of Medical Sciences, were investigating patients with pulmonary hypertension.


Heuritech โ€“ Artificial Intelligence for Webs Trends Tracking

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Our pioneering algorithm identifies items and people in both text or image. We trained it to adress fashion industry issues. Items, shapes, colors, textures, sentiment, peopleโ€ฆ Our cutting-edge solution searches in real time for your answers into all texts and images posted on social networks, blogs, forums and websites. An Ai-powered virtual assistant that can detect trends worldwide, to help you design and launch new collections or manage purchases, product range and stocks. Our powerful text & image recognition solution also provides you with automated products and catalogues tagging with direct benefits for your eCommerce platform: sales conversion increase, cost reduction, recommendation relevance and merchandising optimisation.


What is Machine Learning?

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Finally, If you would like to start building Machine Learning algorithms without coding, Microsoft's Azure Machine Learning cloud software offers an incredibly simple drag and drop interface to build models and expose them as Web Services.