Three-Head Neural Network Architecture for Alphazero Learning
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Elements of DSAI: Game Tree Search, Learning Architectures
Introduction Games Game Search Evaluation Fns AlphaGo/Zero Summary Quiz References Elements of DSAI AlphaGo Part 2: Game Tree Search, Learning Architectures Search & Learn: A Recipe for AI Action Decisions J¨orgHoffmann Winter Term 2019/20 Hoffmann Elements of DSAI Game Tree Search, Learning Architectures 1/49 Introduction Games Game Search Evaluation Fns AlphaGo/Zero Summary Quiz References Competitive Agents? Quote AI Introduction: \Single agent vs. multi-agent: One agent or several? Competitive or collaborative?" ! Single agent! Several koalas, several gorillas trying to beat these up. BUT there is only a single acting entity { one player decides which moves to take (who gets into the boat). Hoffmann Elements of DSAI Game Tree Search, Learning Architectures 3/49 Introduction Games Game Search Evaluation Fns AlphaGo/Zero Summary Quiz References Competitive Agents! Quote AI Introduction: \Single agent vs. multi-agent: One agent or several? Competitive or collaborative?" ! Multi-agent competitive! TWO players deciding which moves to take. Conflicting interests. Hoffmann Elements of DSAI Game Tree Search, Learning Architectures 4/49 Introduction Games Game Search Evaluation Fns AlphaGo/Zero Summary Quiz References Agenda: Game Search, AlphaGo Architecture Games: What is that? ! Game categories, game solutions. Game Search: How to solve a game? ! Searching the game tree. Evaluation Functions: How to evaluate a game position? ! Heuristic functions for games. AlphaGo: How does it work? ! Overview of AlphaGo architecture, and changes in Alpha(Go) Zero. Hoffmann Elements of DSAI Game Tree Search, Learning Architectures 5/49 Introduction Games Game Search Evaluation Fns AlphaGo/Zero Summary Quiz References Positioning in the DSAI Phase Model Hoffmann Elements of DSAI Game Tree Search, Learning Architectures 6/49 Introduction Games Game Search Evaluation Fns AlphaGo/Zero Summary Quiz References Which Games? ! No chance element. -
Artificial Intelligence in Health Care: the Hope, the Hype, the Promise, the Peril
Artificial Intelligence in Health Care: The Hope, the Hype, the Promise, the Peril Michael Matheny, Sonoo Thadaney Israni, Mahnoor Ahmed, and Danielle Whicher, Editors WASHINGTON, DC NAM.EDU PREPUBLICATION COPY - Uncorrected Proofs NATIONAL ACADEMY OF MEDICINE • 500 Fifth Street, NW • WASHINGTON, DC 20001 NOTICE: This publication has undergone peer review according to procedures established by the National Academy of Medicine (NAM). Publication by the NAM worthy of public attention, but does not constitute endorsement of conclusions and recommendationssignifies that it is the by productthe NAM. of The a carefully views presented considered in processthis publication and is a contributionare those of individual contributors and do not represent formal consensus positions of the authors’ organizations; the NAM; or the National Academies of Sciences, Engineering, and Medicine. Library of Congress Cataloging-in-Publication Data to Come Copyright 2019 by the National Academy of Sciences. All rights reserved. Printed in the United States of America. Suggested citation: Matheny, M., S. Thadaney Israni, M. Ahmed, and D. Whicher, Editors. 2019. Artificial Intelligence in Health Care: The Hope, the Hype, the Promise, the Peril. NAM Special Publication. Washington, DC: National Academy of Medicine. PREPUBLICATION COPY - Uncorrected Proofs “Knowing is not enough; we must apply. Willing is not enough; we must do.” --GOETHE PREPUBLICATION COPY - Uncorrected Proofs ABOUT THE NATIONAL ACADEMY OF MEDICINE The National Academy of Medicine is one of three Academies constituting the Nation- al Academies of Sciences, Engineering, and Medicine (the National Academies). The Na- tional Academies provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. -
Game Changer
Matthew Sadler and Natasha Regan Game Changer AlphaZero’s Groundbreaking Chess Strategies and the Promise of AI New In Chess 2019 Contents Explanation of symbols 6 Foreword by Garry Kasparov �������������������������������������������������������������������������������� 7 Introduction by Demis Hassabis 11 Preface 16 Introduction ������������������������������������������������������������������������������������������������������������ 19 Part I AlphaZero’s history . 23 Chapter 1 A quick tour of computer chess competition 24 Chapter 2 ZeroZeroZero ������������������������������������������������������������������������������ 33 Chapter 3 Demis Hassabis, DeepMind and AI 54 Part II Inside the box . 67 Chapter 4 How AlphaZero thinks 68 Chapter 5 AlphaZero’s style – meeting in the middle 87 Part III Themes in AlphaZero’s play . 131 Chapter 6 Introduction to our selected AlphaZero themes 132 Chapter 7 Piece mobility: outposts 137 Chapter 8 Piece mobility: activity 168 Chapter 9 Attacking the king: the march of the rook’s pawn 208 Chapter 10 Attacking the king: colour complexes 235 Chapter 11 Attacking the king: sacrifices for time, space and damage 276 Chapter 12 Attacking the king: opposite-side castling 299 Chapter 13 Attacking the king: defence 321 Part IV AlphaZero’s -
AI Computer Wraps up 4-1 Victory Against Human Champion Nature Reports from Alphago's Victory in Seoul
The Go Files: AI computer wraps up 4-1 victory against human champion Nature reports from AlphaGo's victory in Seoul. Tanguy Chouard 15 March 2016 SEOUL, SOUTH KOREA Google DeepMind Lee Sedol, who has lost 4-1 to AlphaGo. Tanguy Chouard, an editor with Nature, saw Google-DeepMind’s AI system AlphaGo defeat a human professional for the first time last year at the ancient board game Go. This week, he is watching top professional Lee Sedol take on AlphaGo, in Seoul, for a $1 million prize. It’s all over at the Four Seasons Hotel in Seoul, where this morning AlphaGo wrapped up a 4-1 victory over Lee Sedol — incidentally, earning itself and its creators an honorary '9-dan professional' degree from the Korean Baduk Association. After winning the first three games, Google-DeepMind's computer looked impregnable. But the last two games may have revealed some weaknesses in its makeup. Game four totally changed the Go world’s view on AlphaGo’s dominance because it made it clear that the computer can 'bug' — or at least play very poor moves when on the losing side. It was obvious that Lee felt under much less pressure than in game three. And he adopted a different style, one based on taking large amounts of territory early on rather than immediately going for ‘street fighting’ such as making threats to capture stones. This style – called ‘amashi’ – seems to have paid off, because on move 78, Lee produced a play that somehow slipped under AlphaGo’s radar. David Silver, a scientist at DeepMind who's been leading the development of AlphaGo, said the program estimated its probability as 1 in 10,000. -
Reinforcement Learning (1) Key Concepts & Algorithms
Winter 2020 CSC 594 Topics in AI: Advanced Deep Learning 5. Deep Reinforcement Learning (1) Key Concepts & Algorithms (Most content adapted from OpenAI ‘Spinning Up’) 1 Noriko Tomuro Reinforcement Learning (RL) • Reinforcement Learning (RL) is a type of Machine Learning where an agent learns to achieve a goal by interacting with the environment -- trial and error. • RL is one of three basic machine learning paradigms, alongside supervised learning and unsupervised learning. • The purpose of RL is to learn an optimal policy that maximizes the return for the sequences of agent’s actions (i.e., optimal policy). https://en.wikipedia.org/wiki/Reinforcement_learning 2 • RL have recently enjoyed a wide variety of successes, e.g. – Robot controlling in simulation as well as in the real world Strategy games such as • AlphaGO (by Google DeepMind) • Atari games https://en.wikipedia.org/wiki/Reinforcement_learning 3 Deep Reinforcement Learning (DRL) • A policy is essentially a function, which maps the agent’s each action to the expected return or reward. Deep Reinforcement Learning (DRL) uses deep neural networks for the function (and other components). https://spinningup.openai.com/en/latest/spinningup/rl_intro.html 4 5 Some Key Concepts and Terminology 1. States and Observations – A state s is a complete description of the state of the world. For now, we can think of states belonging in the environment. – An observation o is a partial description of a state, which may omit information. – A state could be fully or partially observable to the agent. If partial, the agent forms an internal state (or state estimation). https://spinningup.openai.com/en/latest/spinningup/rl_intro.html 6 • States and Observations (cont.) – In deep RL, we almost always represent states and observations by a real-valued vector, matrix, or higher-order tensor. -
Discrete Sequential Prediction of Continu
Under review as a conference paper at ICLR 2018 DISCRETE SEQUENTIAL PREDICTION OF CONTINU- OUS ACTIONS FOR DEEP RL Anonymous authors Paper under double-blind review ABSTRACT It has long been assumed that high dimensional continuous control problems cannot be solved effectively by discretizing individual dimensions of the action space due to the exponentially large number of bins over which policies would have to be learned. In this paper, we draw inspiration from the recent success of sequence-to-sequence models for structured prediction problems to develop policies over discretized spaces. Central to this method is the realization that com- plex functions over high dimensional spaces can be modeled by neural networks that predict one dimension at a time. Specifically, we show how Q-values and policies over continuous spaces can be modeled using a next step prediction model over discretized dimensions. With this parameterization, it is possible to both leverage the compositional structure of action spaces during learning, as well as compute maxima over action spaces (approximately). On a simple example task we demonstrate empirically that our method can perform global search, which effectively gets around the local optimization issues that plague DDPG. We apply the technique to off-policy (Q-learning) methods and show that our method can achieve the state-of-the-art for off-policy methods on several continuous control tasks. 1 INTRODUCTION Reinforcement learning has long been considered as a general framework applicable to a broad range of problems. However, the approaches used to tackle discrete and continuous action spaces have been fundamentally different. In discrete domains, algorithms such as Q-learning leverage backups through Bellman equations and dynamic programming to solve problems effectively. -
Bridging Imagination and Reality for Model-Based Deep Reinforcement Learning
Bridging Imagination and Reality for Model-Based Deep Reinforcement Learning Guangxiang Zhu⇤ Minghao Zhang⇤ IIIS School of Software Tsinghua University Tsinghua University [email protected] [email protected] Honglak Lee Chongjie Zhang EECS IIIS University of Michigan Tsinghua University [email protected] [email protected] Abstract Sample efficiency has been one of the major challenges for deep reinforcement learning. Recently, model-based reinforcement learning has been proposed to address this challenge by performing planning on imaginary trajectories with a learned world model. However, world model learning may suffer from overfitting to training trajectories, and thus model-based value estimation and policy search will be prone to be sucked in an inferior local policy. In this paper, we propose a novel model-based reinforcement learning algorithm, called BrIdging Reality and Dream (BIRD). It maximizes the mutual information between imaginary and real trajectories so that the policy improvement learned from imaginary trajectories can be easily generalized to real trajectories. We demonstrate that our approach improves sample efficiency of model-based planning, and achieves state-of-the-art performance on challenging visual control benchmarks. 1 Introduction Reinforcement learning (RL) is proposed as a general-purpose learning framework for artificial intelligence problems, and has led to tremendous progress in a variety of domains [1, 2, 3, 4]. Model- free RL adopts a trail-and-error paradigm, which directly learns a mapping function from observations to values or actions through interactions with environments. It has achieved remarkable performance in certain video games and continuous control tasks because of its simplicity and minimal assumptions about environments. -
OLIVAW: Mastering Othello with Neither Humans Nor a Penny Antonio Norelli, Alessandro Panconesi Dept
1 OLIVAW: Mastering Othello with neither Humans nor a Penny Antonio Norelli, Alessandro Panconesi Dept. of Computer Science, Universita` La Sapienza, Rome, Italy Abstract—We introduce OLIVAW, an AI Othello player adopt- of companies. Another aspect of the same problem is the ing the design principles of the famous AlphaGo series. The main amount of training needed. AlphaGo Zero required 4.9 million motivation behind OLIVAW was to attain exceptional competence games played during self-play. While to attain the level of in a non-trivial board game at a tiny fraction of the cost of its illustrious predecessors. In this paper, we show how the grandmaster for games like Starcraft II and Dota 2 the training AlphaGo Zero’s paradigm can be successfully applied to the required 200 years and more than 10,000 years of gameplay, popular game of Othello using only commodity hardware and respectively [7], [8]. free cloud services. While being simpler than Chess or Go, Thus one of the major problems to emerge in the wake Othello maintains a considerable search space and difficulty of these breakthroughs is whether comparable results can be in evaluating board positions. To achieve this result, OLIVAW implements some improvements inspired by recent works to attained at a much lower cost– computational and financial– accelerate the standard AlphaGo Zero learning process. The and with just commodity hardware. In this paper we take main modification implies doubling the positions collected per a small step in this direction, by showing that AlphaGo game during the training phase, by including also positions not Zero’s successful paradigm can be replicated for the game played but largely explored by the agent. -
Improving the Gating Mechanism of Recurrent
Under review as a conference paper at ICLR 2020 IMPROVING THE GATING MECHANISM OF RECURRENT NEURAL NETWORKS Anonymous authors Paper under double-blind review ABSTRACT Gating mechanisms are widely used in neural network models, where they allow gradients to backpropagate more easily through depth or time. However, their satura- tion property introduces problems of its own. For example, in recurrent models these gates need to have outputs near 1 to propagate information over long time-delays, which requires them to operate in their saturation regime and hinders gradient-based learning of the gate mechanism. We address this problem by deriving two synergistic modifications to the standard gating mechanism that are easy to implement, introduce no additional hyperparameters, and improve learnability of the gates when they are close to saturation. We show how these changes are related to and improve on alternative recently proposed gating mechanisms such as chrono-initialization and Ordered Neurons. Empirically, our simple gating mechanisms robustly improve the performance of recurrent models on a range of applications, including synthetic memorization tasks, sequential image classification, language modeling, and reinforcement learning, particularly when long-term dependencies are involved. 1 INTRODUCTION Recurrent neural networks (RNNs) have become a standard machine learning tool for learning from sequential data. However, RNNs are prone to the vanishing gradient problem, which occurs when the gradients of the recurrent weights become vanishingly small as they get backpropagated through time (Hochreiter et al., 2001). A common approach to alleviate the vanishing gradient problem is to use gating mechanisms, leading to models such as the long short term memory (Hochreiter & Schmidhuber, 1997, LSTM) and gated recurrent units (Chung et al., 2014, GRUs). -
Monte-Carlo Tree Search As Regularized Policy Optimization
Monte-Carlo tree search as regularized policy optimization Jean-Bastien Grill * 1 Florent Altche´ * 1 Yunhao Tang * 1 2 Thomas Hubert 3 Michal Valko 1 Ioannis Antonoglou 3 Remi´ Munos 1 Abstract AlphaZero employs an alternative handcrafted heuristic to achieve super-human performance on board games (Silver The combination of Monte-Carlo tree search et al., 2016). Recent MCTS-based MuZero (Schrittwieser (MCTS) with deep reinforcement learning has et al., 2019) has also led to state-of-the-art results in the led to significant advances in artificial intelli- Atari benchmarks (Bellemare et al., 2013). gence. However, AlphaZero, the current state- of-the-art MCTS algorithm, still relies on hand- Our main contribution is connecting MCTS algorithms, crafted heuristics that are only partially under- in particular the highly-successful AlphaZero, with MPO, stood. In this paper, we show that AlphaZero’s a state-of-the-art model-free policy-optimization algo- search heuristics, along with other common ones rithm (Abdolmaleki et al., 2018). Specifically, we show that such as UCT, are an approximation to the solu- the empirical visit distribution of actions in AlphaZero’s tion of a specific regularized policy optimization search procedure approximates the solution of a regularized problem. With this insight, we propose a variant policy-optimization objective. With this insight, our second of AlphaZero which uses the exact solution to contribution a modified version of AlphaZero that comes this policy optimization problem, and show exper- significant performance gains over the original algorithm, imentally that it reliably outperforms the original especially in cases where AlphaZero has been observed to algorithm in multiple domains. -
In-Datacenter Performance Analysis of a Tensor Processing Unit
In-Datacenter Performance Analysis of a Tensor Processing Unit Presented by Josh Fried Background: Machine Learning Neural Networks: ● Multi Layer Perceptrons ● Recurrent Neural Networks (mostly LSTMs) ● Convolutional Neural Networks Synapse - each edge, has a weight Neuron - each node, sums weights and uses non-linear activation function over sum Propagating inputs through a layer of the NN is a matrix multiplication followed by an activation Background: Machine Learning Two phases: ● Training (offline) ○ relaxed deadlines ○ large batches to amortize costs of loading weights from DRAM ○ well suited to GPUs ○ Usually uses floating points ● Inference (online) ○ strict deadlines: 7-10ms at Google for some workloads ■ limited possibility for batching because of deadlines ○ Facebook uses CPUs for inference (last class) ○ Can use lower precision integers (faster/smaller/more efficient) ML Workloads @ Google 90% of ML workload time at Google spent on MLPs and LSTMs, despite broader focus on CNNs RankBrain (search) Inception (image classification), Google Translate AlphaGo (and others) Background: Hardware Trends End of Moore’s Law & Dennard Scaling ● Moore - transistor density is doubling every two years ● Dennard - power stays proportional to chip area as transistors shrink Machine Learning causing a huge growth in demand for compute ● 2006: Excess CPU capacity in datacenters is enough ● 2013: Projected 3 minutes per-day per-user of speech recognition ○ will require doubling datacenter compute capacity! Google’s Answer: Custom ASIC Goal: Build a chip that improves cost-performance for NN inference What are the main costs? Capital Costs Operational Costs (power bill!) TPU (V1) Design Goals Short design-deployment cycle: ~15 months! Plugs in to PCIe slot on existing servers Accelerates matrix multiplication operations Uses 8-bit integer operations instead of floating point How does the TPU work? CISC instructions, issued by host. -
Quantum Reinforcement Learning During Human Decision-Making
ARTICLES https://doi.org/10.1038/s41562-019-0804-2 Quantum reinforcement learning during human decision-making Ji-An Li 1,2, Daoyi Dong 3, Zhengde Wei1,4, Ying Liu5, Yu Pan6, Franco Nori 7,8 and Xiaochu Zhang 1,9,10,11* Classical reinforcement learning (CRL) has been widely applied in neuroscience and psychology; however, quantum reinforce- ment learning (QRL), which shows superior performance in computer simulations, has never been empirically tested on human decision-making. Moreover, all current successful quantum models for human cognition lack connections to neuroscience. Here we studied whether QRL can properly explain value-based decision-making. We compared 2 QRL and 12 CRL models by using behavioural and functional magnetic resonance imaging data from healthy and cigarette-smoking subjects performing the Iowa Gambling Task. In all groups, the QRL models performed well when compared with the best CRL models and further revealed the representation of quantum-like internal-state-related variables in the medial frontal gyrus in both healthy subjects and smok- ers, suggesting that value-based decision-making can be illustrated by QRL at both the behavioural and neural levels. riginating from early behavioural psychology, reinforce- explained well by quantum probability theory9–16. For example, one ment learning is now a widely used approach in the fields work showed the superiority of a quantum random walk model over Oof machine learning1 and decision psychology2. It typi- classical Markov random walk models for a modified random-dot cally formalizes how one agent (a computer or animal) should take motion direction discrimination task and revealed quantum-like actions in unknown probabilistic environments to maximize its aspects of perceptual decisions12.