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 Statistical Learning


Alternative Function Approximation Parameterizations for Solving Games: An Analysis of $f$-Regression Counterfactual Regret Minimization

arXiv.org Artificial Intelligence

Function approximation is a powerful approach for structuring large decision problems that has facilitated great achievements in the areas of reinforcement learning and game playing. Regression counterfactual regret minimization (RCFR) is a flexible and simple algorithm for approximately solving imperfect information games with policies parameterized by a normalized rectified linear unit (ReLU). In contrast, the more conventional softmax parameterization is standard in the field of reinforcement learning and has a regret bound with a better dependence on the number of actions in the tabular case. We derive approximation error-aware regret bounds for $(\Phi, f)$-regret matching, which applies to a general class of link functions and regret objectives. These bounds recover a tighter bound for RCFR and provides a theoretical justification for RCFR implementations with alternative policy parameterizations ($f$-RCFR), including softmax. We provide exploitability bounds for $f$-RCFR with the polynomial and exponential link functions in zero-sum imperfect information games, and examine empirically how the link function interacts with the severity of the approximation to determine exploitability performance in practice. Although a ReLU parameterized policy is typically the best choice, a softmax parameterization can perform as well or better in settings that require aggressive approximation.


Reinforcement Learning Upside Down: Don't Predict Rewards -- Just Map Them to Actions

arXiv.org Artificial Intelligence

We transform reinforcement learning (RL) into a form of supervised learning (SL) by turning traditional RL on its head, calling this Upside Down RL (UDRL). Standard RL predicts rewards, while UDRL instead uses rewards as task-defining inputs, together with representations of time horizons and other computable functions of historic and desired future data. UDRL learns to interpret these input observations as commands, mapping them to actions (or action probabilities) through SL on past (possibly accidental) experience. UDRL generalizes to achieve high rewards or other goals, through input commands such as: get lots of reward within at most so much time! A separate paper [61] on first experiments with UDRL shows that even a pilot version of UDRL can outperform traditional baseline algorithms on certain challenging RL problems. We also introduce a related simple but general approach for teaching a robot to imitate humans. First videotape humans imitating the robot's current behaviors, then let the robot learn through SL to map the videos (as input commands) to these behaviors, then let it generalize and imitate videos of humans executing previously unknown behavior. This Imitate-Imitator concept may actually explain why biological evolution has resulted in parents who imitate the babbling of their babies.


Tensorflow 2.0: Solving Classification and Regression Problems

#artificialintelligence

By the end of the 50th epoch, we have training accuracy of 100% while validation accuracy of 98.56%, which is impressive. Let's finally evaluate the performance of our classification model on the test set: Our model achieves an accuracy of 97.39% on the test set. Though it is slightly less than the training accuracy of 100%, it is still very good given the fact that we randomly chose the number of layers and the nodes. You can add more layers to the model with more nodes and see if you can get better results on the validation and test sets. In regression problem, the goal is to predict a continuous value. In this section, you will see how to solve a regression problem with TensorFlow 2.0 The dataset for this problem can be downloaded freely from this link.


Calculate Similarity -- the most relevant Metrics in a Nutshell

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Many data science techniques are based on measuring similarity and dissimilarity between objects. For example, K-Nearest-Neighbors uses similarity to classify new data objects. In Unsupervised Learning, K-Means is a clustering method which uses Euclidean distance to compute the distance between the cluster centroids and it's assigned data points. Recommendation engines use neighborhood based collaborative filtering methods which identify an individual's neighbor based on the similarity/dissimilarity to the other users. In this blog post I will take a look at the most relevant similarity metrics in practice. Measuring similarity between objects can be performed in a number of ways.


NLP Picks Bestsellers – A Lesson in Using NLP for Hidden Feature Extraction

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Summary: 99% of our application of NLP has to do with chatbots or translation. This is a very interesting story about expanding the bounds of NLP and feature creation to predict bestselling novels. The authors created over 20,000 NLP features, about 2,700 of which proved to be predictive with a 90% accuracy rate in predicting NYT bestsellers. It's a pretty rare individual who hasn't had a personal experience with NLP (Natural Language Processing). About 99% of those experiences are in the form of chatbots or translators, either text or speech in, and text or speech out. This has proved to be one of the hottest and most economically valuable applications of deep learning but it's not the whole story.


GIFTCOURSE: Get Exclusive Deal on Data Science 2020 Bundle Course

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Machine learning model for predicting medium writer earnings

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On October 22, 2019, Medium unveiled a new model for calculating writer's earnings. According to this new model, earnings will be calculated based on the reading time of Medium members. You may find out more about the new model from this article: Improving how we calculate writer earnings. The new model took effect as of October 28, 2019. In a previous article (Medium Partner Program's New Model for Calculating Writer's Earnings -- Linear Regression Analysis), I had written about a model for writer earnings under the new Partner Program model.


r/MachineLearning - [D] The gradient descent renaissance

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The field of machine learning underwent massive changes in the 2010's. At the beginning, the field saw diverse approaches applied to a variety of topics and data structures. Then Alexnet blew away the competition for the Imagenet challenge with his CNN, and the field was forever changed. However, there was a warming up phase. Caffe's first release was in 2013.


benedekrozemberczki/ClusterGCN

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Graph convolutional network (GCN) has been successfully applied to many graph-based applications; however, training a large-scale GCN remains challenging. Current SGD-based algorithms suffer from either a high computational cost that exponentially grows with number of GCN layers, or a large space requirement for keeping the entire graph and the embedding of each node in memory. In this paper, we propose Cluster-GCN, a novel GCN algorithm that is suitable for SGD-based training by exploiting the graph clustering structure. Cluster-GCN works as the following: at each step, it samples a block of nodes that associate with a dense subgraph identified by a graph clustering algorithm, and restricts the neighborhood search within this subgraph. This simple but effective strategy leads to significantly improved memory and computational efficiency while being able to achieve comparable test accuracy with previous algorithms.


Choosing the Right Clustering Algorithm for your Dataset - KDnuggets

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Data clustering is an essential step in the arrangement of a correct and throughout data model. To fulfill an analysis, the volume of information should be sorted out according to the commonalities. The main question is, what commonality parameter provides the best results – and what is implicated under "the best" definition at all. This article should be useful for the beginning data scientists, or for experts who want to refresh their memories on the topic. It includes the most widespread clustering algorithms, as well as their insightful review.