Learning Graphical Models
Should we Reload Time Series Classification Performance Evaluation ? (a position paper)
Gay, Dominique, Lemaire, Vincent
Since the introduction and the public availability of the \textsc{ucr} time series benchmark data sets, numerous Time Series Classification (TSC) methods has been designed, evaluated and compared to each others. We suggest a critical view of TSC performance evaluation protocols put in place in recent TSC literature. The main goal of this `position' paper is to stimulate discussion and reflexion about performance evaluation in TSC literature.
Lifted Weight Learning of Markov Logic Networks Revisited
Kuzelka, Ondrej, Kungurtsev, Vyacheslav
In this paper, we complete the work of [14] by answering We study lifted weight learning of Markov whether maximum-likelihood learning of MLNs logic networks. We show that there is an algorithm can be done in time polynomial in the size of the domain for maximum-likelihood learning of for 2-variable MLNs. We give a positive answer 2-variable Markov logic networks which runs to this question (Theorem 11), under consideration of in time polynomial in the domain size. Our the dependence of the runtime bounds on how extreme results are based on existing lifted-inference the statistics of the training data are. To arrive at this algorithms and recent algorithmic results on positive result, we need to combine results from three computing maximum entropy distributions.
Explicit-risk-aware Path Planning with Reward Maximization
Xiao, Xuesu, Dufek, Jan, Murphy, Robin
This paper develops a path planner that minimizes risk (e.g. motion execution) while maximizing accumulated reward (e.g., quality of sensor viewpoint) motivated by visual assistance or tracking scenarios in unstructured or confined environments. In these scenarios, the robot should maintain the best viewpoint as it moves to the goal. However, in unstructured or confined environments, some paths may increase the risk of collision; therefore there is a tradeoff between risk and reward. Conventional state-dependent risk or probabilistic uncertainty modeling do not consider path-level risk or is difficult to acquire. This risk-reward planner explicitly represents risk as a function of motion plans, i.e., paths. Without manual assignment of the negative impact to the planner caused by risk, this planner takes in a pre-established viewpoint quality map and plans target location and path leading to it simultaneously, in order to maximize overall reward along the entire path while minimizing risk. Exact and approximate algorithms are presented, whose solution is further demonstrated on a physical tethered aerial vehicle. Other than the visual assistance problem, the proposed framework also provides a new planning paradigm to address minimum-risk planning under dynamical risk and absence of substructure optimality and to balance the trade-off between reward and risk.
Pixel-Attentive Policy Gradient for Multi-Fingered Grasping in Cluttered Scenes
Wu, Bohan, Akinola, Iretiayo, Allen, Peter K.
Recent advances in on-policy reinforcement learning (RL) methods enabled learning agents in virtual environments to master complex tasks with high-dimensional and continuous observation and action spaces. However, leveraging this family of algorithms in multi-fingered robotic grasping remains a challenge due to large sim-to-real fidelity gaps and the high sample complexity of on-policy RL algorithms. This work aims to bridge these gaps by first reinforcement-learning a multi-fingered robotic grasping policy in simulation that operates in the pixel space of the input: a single depth image. Using a mapping from pixel space to Cartesian space according to the depth map, this method transfers to the real world with high fidelity and introduces a novel attention mechanism that substantially improves grasp success rate in cluttered environments. Finally, the direct-generative nature of this method allows learning of multi-fingered grasps that have flexible end-effector positions, orientations and rotations, as well as all degrees of freedom of the hand.
The Variational Predictive Natural Gradient
Variational inference requires choosing an approximating Variational inference transforms posterior inference family. The variational family plus the model together define into parametric optimization thereby enabling the variational objective. The variational objective can the use of latent variable models where be optimized with stochastic gradients for a broad range of otherwise impractical. However, variational inference models (Kingma & Welling, 2014; Ranganath et al., 2014; can be finicky when different variational Rezende et al., 2014). When the posterior has correlations, parameters control variables that are strongly correlated dimensions of the optimization problem become tied, i.e., under the model. Traditional natural gradients there is curvature. One way to correct for curvature in optimization based on the variational approximation fail to is to use natural gradients (Amari, 1998; Ollivier correct for correlations when the approximation et al., 2011; Thomas et al., 2016) . Natural gradients for is not the true posterior. To address this, we construct variational inference (Hoffman et al., 2013) adjust for the a new natural gradient called the variational non-Euclidean nature of probability distributions.
Scikit-learn Tutorial: Machine Learning in Python
Scikit-learn is a free machine learning library for Python. It features various algorithms like support vector machine, random forests, and k-neighbours, and it also supports Python numerical and scientific libraries like NumPy and SciPy. In this tutorial we will learn how to easily apply Machine Learning with the help of the scikit-learn library, which was created to make doing machine learning in Python easier and more robust. To do this, we'll be using the Sales_Win_Loss data set from IBM's Watson repository. We will import the data set using pandas, explore the data using pandas methods like head(), tail(), dtypes(), and then try our hand at using plotting techniques from Seaborn to visualize our data. Then we'll dive into scikit-learn and use preprocessing.LabelEncoder() in scikit-learn to process the data, and train_test_split() to split the data set into test and train samples. We will also use a cheat sheet to help us decide which algorithms to use for the data set. Finally we will use three different algorithms (Naive-Bayes, LinearSVC, K-Neighbors Classifier) to make predictions and compare their performance using methods like accuracy_score() provided by the scikit-learn library. We will also visualize the performance score of different models using scikit-learn and Yellowbrick visualization. If you need to brush up on these topics, check out these pandas and data visualization blog posts. For this tutorial, we will use the Sales-Win-Loss data set available on the IBM Watson website.
On Convergence Rate of the Gaussian Belief Propagation Algorithm for Markov Networks
Gaussian Belief Propagation (BP) algorithm is one of the most important distributed algorithms in signal processing and statistical learning involving Markov networks. It is well known that the algorithm correctly computes marginal density functions from a high dimensional joint density function over a Markov network in a finite number of iterations when the underlying Gaussian graph is acyclic. It is also known more recently that the algorithm produces correct marginal means asymptotically for cyclic Gaussian graphs under the condition of walk summability. This paper extends this convergence result further by showing that the convergence is exponential under the walk summability condition, and provides a simple bound for the convergence rate.
Scaling up budgeted reinforcement learning
Carrara, Nicolas, Leurent, Edouard, Laroche, Romain, Urvoy, Tanguy, Maillard, Odalric-Ambrym, Pietquin, Olivier
Can we learn a control policy able to adapt its behaviour in real time so as to take any desired amount of risk? The general Reinforcement Learning framework solely aims at optimising a total reward in expectation, which may not be desirable in critical applications. In stark contrast, the Budgeted Markov Decision Process (BMDP) framework is a formalism in which the notion of risk is implemented as a hard constraint on a failure signal. Existing algorithms solving BMDPs rely on strong assumptions and have so far only been applied to toy-examples. In this work, we relax some of these assumptions and demonstrate the scalability of our approach on two practical problems: a spoken dialogue system and an autonomous driving task. On both examples, we reach similar performances as Lagrangian Relaxation methods with a significant improvement in sample and memory efficiency.
Learning multimodal representations for sample-efficient recognition of human actions
Vasco, Miguel, Melo, Francisco S., de Matos, David Martins, Paiva, Ana, Inamura, Tetsunari
Humans interact in rich and diverse ways with the environment. However, the representation of such behavior by artificial agents is often limited. In this work we present \textit{motion concepts}, a novel multimodal representation of human actions in a household environment. A motion concept encompasses a probabilistic description of the kinematics of the action along with its contextual background, namely the location and the objects held during the performance. Furthermore, we present Online Motion Concept Learning (OMCL), a new algorithm which learns novel motion concepts from action demonstrations and recognizes previously learned motion concepts. The algorithm is evaluated on a virtual-reality household environment with the presence of a human avatar. OMCL outperforms standard motion recognition algorithms on an one-shot recognition task, attesting to its potential for sample-efficient recognition of human actions.
Attack Graph Obfuscation
Puzis, Rami, Polad, Hadar, Shapira, Bracha
Before executing an attack, adversaries usually explore the victim's network in an attempt to infer the network topology and identify vulnerabilities in the victim's servers and personal computers. Falsifying the information collected by the adversary post penetration may significantly slower lateral movement and increase the amount of noise generated within the victim's network. We investigate the effect of fake vulnerabilities within a real enterprise network on the attacker performance. We use the attack graphs to model the path of an attacker making its way towards a target in a given network. We use combinatorial optimization in order to find the optimal assignments of fake vulnerabilities. We demonstrate the feasibility of our deception-based defense by presenting results of experiments with a large scale real network. We show that adding fake vulnerabilities forces the adversary to invest a significant amount of effort, in terms of time and exploitability cost.