Value Targets in Off-Policy Alphazero: a New Greedy Backup
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
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. -
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 -
Improving Model-Based Reinforcement Learning with Internal State Representations Through Self-Supervision
1 Improving Model-Based Reinforcement Learning with Internal State Representations through Self-Supervision Julien Scholz, Cornelius Weber, Muhammad Burhan Hafez and Stefan Wermter Knowledge Technology, Department of Informatics, University of Hamburg, Germany [email protected], fweber, hafez, [email protected] Abstract—Using a model of the environment, reinforcement the design decisions made for MuZero, namely, how uncon- learning agents can plan their future moves and achieve super- strained its learning process is. After explaining all necessary human performance in board games like Chess, Shogi, and Go, fundamentals, we propose two individual augmentations to while remaining relatively sample-efficient. As demonstrated by the MuZero Algorithm, the environment model can even be the algorithm that work fully unsupervised in an attempt to learned dynamically, generalizing the agent to many more tasks improve its performance and make it more reliable. After- while at the same time achieving state-of-the-art performance. ward, we evaluate our proposals by benchmarking the regular Notably, MuZero uses internal state representations derived from MuZero algorithm against the newly augmented creation. real environment states for its predictions. In this paper, we bind the model’s predicted internal state representation to the environ- II. BACKGROUND ment state via two additional terms: a reconstruction model loss and a simpler consistency loss, both of which work independently A. MuZero Algorithm and unsupervised, acting as constraints to stabilize the learning process. Our experiments show that this new integration of The MuZero algorithm [1] is a model-based reinforcement reconstruction model loss and simpler consistency loss provide a learning algorithm that builds upon the success of its prede- significant performance increase in OpenAI Gym environments. -
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. -
ELF: an Extensive, Lightweight and Flexible Research Platform for Real-Time Strategy Games
ELF: An Extensive, Lightweight and Flexible Research Platform for Real-time Strategy Games Yuandong Tian1 Qucheng Gong1 Wenling Shang2 Yuxin Wu1 C. Lawrence Zitnick1 1Facebook AI Research 2Oculus 1fyuandong, qucheng, yuxinwu, [email protected] [email protected] Abstract In this paper, we propose ELF, an Extensive, Lightweight and Flexible platform for fundamental reinforcement learning research. Using ELF, we implement a highly customizable real-time strategy (RTS) engine with three game environ- ments (Mini-RTS, Capture the Flag and Tower Defense). Mini-RTS, as a minia- ture version of StarCraft, captures key game dynamics and runs at 40K frame- per-second (FPS) per core on a laptop. When coupled with modern reinforcement learning methods, the system can train a full-game bot against built-in AIs end- to-end in one day with 6 CPUs and 1 GPU. In addition, our platform is flexible in terms of environment-agent communication topologies, choices of RL methods, changes in game parameters, and can host existing C/C++-based game environ- ments like ALE [4]. Using ELF, we thoroughly explore training parameters and show that a network with Leaky ReLU [17] and Batch Normalization [11] cou- pled with long-horizon training and progressive curriculum beats the rule-based built-in AI more than 70% of the time in the full game of Mini-RTS. Strong per- formance is also achieved on the other two games. In game replays, we show our agents learn interesting strategies. ELF, along with its RL platform, is open sourced at https://github.com/facebookresearch/ELF. 1 Introduction Game environments are commonly used for research in Reinforcement Learning (RL), i.e. -
Survey on Reinforcement Learning for Language Processing
Survey on reinforcement learning for language processing V´ıctorUc-Cetina1, Nicol´asNavarro-Guerrero2, Anabel Martin-Gonzalez1, Cornelius Weber3, Stefan Wermter3 1 Universidad Aut´onomade Yucat´an- fuccetina, [email protected] 2 Aarhus University - [email protected] 3 Universit¨atHamburg - fweber, [email protected] February 2021 Abstract In recent years some researchers have explored the use of reinforcement learning (RL) algorithms as key components in the solution of various natural language process- ing tasks. For instance, some of these algorithms leveraging deep neural learning have found their way into conversational systems. This paper reviews the state of the art of RL methods for their possible use for different problems of natural language processing, focusing primarily on conversational systems, mainly due to their growing relevance. We provide detailed descriptions of the problems as well as discussions of why RL is well-suited to solve them. Also, we analyze the advantages and limitations of these methods. Finally, we elaborate on promising research directions in natural language processing that might benefit from reinforcement learning. Keywords| reinforcement learning, natural language processing, conversational systems, pars- ing, translation, text generation 1 Introduction Machine learning algorithms have been very successful to solve problems in the natural language pro- arXiv:2104.05565v1 [cs.CL] 12 Apr 2021 cessing (NLP) domain for many years, especially supervised and unsupervised methods. However, this is not the case with reinforcement learning (RL), which is somewhat surprising since in other domains, reinforcement learning methods have experienced an increased level of success with some impressive results, for instance in board games such as AlphaGo Zero [106]. -
Improved Policy Networks for Computer Go
Improved Policy Networks for Computer Go Tristan Cazenave Universite´ Paris-Dauphine, PSL Research University, CNRS, LAMSADE, PARIS, FRANCE Abstract. Golois uses residual policy networks to play Go. Two improvements to these residual policy networks are proposed and tested. The first one is to use three output planes. The second one is to add Spatial Batch Normalization. 1 Introduction Deep Learning for the game of Go with convolutional neural networks has been ad- dressed by [2]. It has been further improved using larger networks [7, 10]. AlphaGo [9] combines Monte Carlo Tree Search with a policy and a value network. Residual Networks improve the training of very deep networks [4]. These networks can gain accuracy from considerably increased depth. On the ImageNet dataset a 152 layers networks achieves 3.57% error. It won the 1st place on the ILSVRC 2015 classifi- cation task. The principle of residual nets is to add the input of the layer to the output of each layer. With this simple modification training is faster and enables deeper networks. Residual networks were recently successfully adapted to computer Go [1]. As a follow up to this paper, we propose improvements to residual networks for computer Go. The second section details different proposed improvements to policy networks for computer Go, the third section gives experimental results, and the last section con- cludes. 2 Proposed Improvements We propose two improvements for policy networks. The first improvement is to use multiple output planes as in DarkForest. The second improvement is to use Spatial Batch Normalization. 2.1 Multiple Output Planes In DarkForest [10] training with multiple output planes containing the next three moves to play has been shown to improve the level of play of a usual policy network with 13 layers. -
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. -
Unsupervised State Representation Learning in Atari
Unsupervised State Representation Learning in Atari Ankesh Anand⇤ Evan Racah⇤ Sherjil Ozair⇤ Mila, Université de Montréal Mila, Université de Montréal Mila, Université de Montréal Microsoft Research Yoshua Bengio Marc-Alexandre Côté R Devon Hjelm Mila, Université de Montréal Microsoft Research Microsoft Research Mila, Université de Montréal Abstract State representation learning, or the ability to capture latent generative factors of an environment, is crucial for building intelligent agents that can perform a wide variety of tasks. Learning such representations without supervision from rewards is a challenging open problem. We introduce a method that learns state representations by maximizing mutual information across spatially and tem- porally distinct features of a neural encoder of the observations. We also in- troduce a new benchmark based on Atari 2600 games where we evaluate rep- resentations based on how well they capture the ground truth state variables. We believe this new framework for evaluating representation learning models will be crucial for future representation learning research. Finally, we com- pare our technique with other state-of-the-art generative and contrastive repre- sentation learning methods. The code associated with this work is available at https://github.com/mila-iqia/atari-representation-learning 1 Introduction The ability to perceive and represent visual sensory data into useful and concise descriptions is con- sidered a fundamental cognitive capability in humans [1, 2], and thus crucial for building intelligent agents [3]. Representations that concisely capture the true state of the environment should empower agents to effectively transfer knowledge across different tasks in the environment, and enable learning with fewer interactions [4]. -
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.