深度强化学习之Deep Q Learning

深度强化学习之Deep Q Learning

本文主要讲解:Deep Q Network 下面我们简称为 DQN。DQN采用深度神经网络来表示Q函数,通常也称为Deep Q Learning 。

DQN是在论文《Playing Atari with Deep Reinforcement Learning》中提出的。这篇论文主要讲解如何用深度强化学习来玩Astair游戏。

首先,先来简单介绍一下Astair游戏中的breakout游戏的游戏规则:
“打砖块”
游戏开始时,画面今显示8排砖块,每隔两排,砖块的颜色就不同。由下至上的颜色排序为黄色、绿色、橙色和红色。游戏开始后,玩家必须控制一块平台左右移动以反弹一个球。当那个球碰到砖块时,砖块就会消失,而球就会反弹。3当玩家未能用平台反弹球的话,那么玩家就输掉了那个回合。当玩家连续输掉3次后,玩家就会输掉整个游戏。

DQN要解决的问题是:如何从原始的游戏画面出发,通过强化学习自动学出玩游戏的方法。

Q-Learning算法是以Q(状态,动作)来表示函数。在这个过程中Q函数实际上Q函数是用一张表格来表示的。表格的每一行表示一种状态,每一列表示一种动作。

在这里插入图片描述
Q-Learning算法的缺点:状态与状态之间是相互独立的,没有联系。例如:在Astair游戏中,再用“表格”来表示Q函数就有点不合适了。原因在于Astair游戏画面为210×160的

# Deep Reinforcement Learning for Keras [![Build Status](https://api.travis-ci.org/matthiasplappert/keras-rl.svg?branch=master)](https://travis-ci.org/matthiasplappert/keras-rl) [![Documentation](https://readthedocs.org/projects/keras-rl/badge/)](http://keras-rl.readthedocs.io/) [![License](https://img.shields.io/github/license/mashape/apistatus.svg?maxAge=2592000)](https://github.com/matthiasplappert/keras-rl/blob/master/LICENSE) [![Join the chat at https://gitter.im/keras-rl/Lobby](https://badges.gitter.im/keras-rl/Lobby.svg)](https://gitter.im/keras-rl/Lobby) ## What is it? `keras-rl` implements some state-of-the art deep reinforcement learning algorithms in Python and seamlessly integrates with the deep learning library [Keras](http://keras.io). Just like Keras, it works with either [Theano](http://deeplearning.net/software/theano/) or [TensorFlow](https://www.tensorflow.org/), which means that you can train your algorithm efficiently either on CPU or GPU. Furthermore, `keras-rl` works with [OpenAI Gym](https://gym.openai.com/) out of the box. This means that evaluating and playing around with different algorithms is easy. Of course you can extend `keras-rl` according to your own needs. You can use built-in Keras callbacks and metrics or define your own. Even more so, it is easy to implement your own environments and even algorithms by simply extending some simple abstract classes. In a nutshell: `keras-rl` makes it really easy to run state-of-the-art deep reinforcement learning algorithms, uses Keras and thus Theano or TensorFlow and was built with OpenAI Gym in mind. ## What is included? As of today, the following algorithms have been implemented: - Deep Q Learning (DQN) [[1]](http://arxiv.org/abs/1312.5602), [[2]](http://home.uchicago.edu/~arij/journalclub/papers/2015_Mnih_et_al.pdf) - Double DQN [[3]](http://arxiv.org/abs/1509.06461) - Deep Deterministic Policy Gradient (DDPG) [[4]](http://arxiv.org/abs/1509.02971) - Continuous DQN (CDQN or NAF) [[6]](http://arxiv.org/abs/1603.00748) - Cross-Entropy Method (CEM) [[7]](http://learning.mpi-sws.org/mlss2016/slides/2016-MLSS-RL.pdf), [[8]](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.81.6579&rep=rep1&type=pdf) - Dueling network DQN (Dueling DQN) [[9]](https://arxiv.org/abs/1511.06581) - Deep SARSA [[10]](http://people.inf.elte.hu/lorincz/Files/RL_2006/SuttonBook.pdf) You can find more information on each agent in the [wiki](https://github.com/matthiasplappert/keras-rl/wiki/Agent-Overview). I'm currently working on the following algorithms, which can be found on the `experimental` branch: - Asynchronous Advantage Actor-Critic (A3C) [[5]](http://arxiv.org/abs/1602.01783) Notice that these are **only experimental** and might currently not even run. ## How do I install it and how do I get started? Installing `keras-rl` is easy. Just run the following commands and you should be good to go: ```bash pip install keras-rl ``` This will install `keras-rl` and all necessary dependencies. If you want to run the examples, you'll also have to install `gym` by OpenAI. Please refer to [their installation instructions](https://github.com/openai/gym#installation). It's quite easy and works nicely on Ubuntu and Mac OS X. You'll also need the `h5py` package to load and save model weights, which can be installed using the following command: ```bash pip install h5py ``` Once you have installed everything, you can try out a simple example: ```bash python examples/dqn_cartpole.py ``` This is a very simple example and it should converge relatively quickly, so it's a great way to get started! It also visualizes the game during training, so you can watch it learn. How cool is that? Unfortunately, the documentation of `keras-rl` is currently almost non-existent. However, you can find a couple of more examples that illustrate the usage of both DQN (for tasks with discrete actions) as well as for DDPG (for tasks with continuous actions). While these examples are not replacement for a proper documentation, they should be enough to get started quickly and to see the magic of reinforcement learning yourself. I also encourage you to play around with other environments (OpenAI Gym has plenty) and maybe even try to find better hyperparameters for the existing ones. If you have questions or problems, please file an issue or, even better, fix the problem yourself and submit a pull request! ## Do I have to train the models myself? Training times can be very long depending on the complexity of the environment. [This repo](https://github.com/matthiasplappert/keras-rl-weights) provides some weights that were obtained by running (at least some) of the examples that are included in `keras-rl`. You can load the weights using the `load_weights` method on the respective agents. ## Requirements - Python 2.7 - [Keras](http://keras.io) >= 1.0.7 That's it. However, if you want to run the examples, you'll also need the following dependencies: - [OpenAI Gym](https://github.com/openai/gym) - [h5py](https://pypi.python.org/pypi/h5py) `keras-rl` also works with [TensorFlow](https://www.tensorflow.org/). To find out how to use TensorFlow instead of [Theano](http://deeplearning.net/software/theano/), please refer to the [Keras documentation](http://keras.io/#switching-from-theano-to-tensorflow). ## Documentation We are currently in the process of getting a proper documentation going. [The latest version of the documentation is available online](http://keras-rl.readthedocs.org). All contributions to the documentation are greatly appreciated! ## Support You can ask questions and join the development discussion: - On the [Keras-RL Google group](https://groups.google.com/forum/#!forum/keras-rl-users). - On the [Keras-RL Gitter channel](https://gitter.im/keras-rl/Lobby). You can also post **bug reports and feature requests** (only!) in [Github issues](https://github.com/matthiasplappert/keras-rl/issues). ## Running the Tests To run the tests locally, you'll first have to install the following dependencies: ```bash pip install pytest pytest-xdist pep8 pytest-pep8 pytest-cov python-coveralls ``` You can then run all tests using this command: ```bash py.test tests/. ``` If you want to check if the files conform to the PEP8 style guidelines, run the following command: ```bash py.test --pep8 ``` ## Citing If you use `keras-rl` in your research, you can cite it as follows: ```bibtex @misc{plappert2016kerasrl, author = {Matthias Plappert}, title = {keras-rl}, year = {2016}, publisher = {GitHub}, journal = {GitHub repository}, howpublished = {\url{https://github.com/matthiasplappert/keras-rl}}, } ``` ## Acknowledgments The foundation for this library was developed during my work at the [High Performance Humanoid Technologies (H²T)](https://h2t.anthropomatik.kit.edu/) lab at the [Karlsruhe Institute of Technology (KIT)](https://kit.edu). It has since been adapted to become a general-purpose library. ## References 1. *Playing Atari with Deep Reinforcement Learning*, Mnih et al., 2013 2. *Human-level control through deep reinforcement learning*, Mnih et al., 2015 3. *Deep Reinforcement Learning with Double Q-learning*, van Hasselt et al., 2015 4. *Continuous control with deep reinforcement learning*, Lillicrap et al., 2015 5. *Asynchronous Methods for Deep Reinforcement Learning*, Mnih et al., 2016 6. *Continuous Deep Q-Learning with Model-based Acceleration*, Gu et al., 2016 7. *Learning Tetris Using the Noisy Cross-Entropy Method*, Szita et al., 2006 8. *Deep Reinforcement Learning (MLSS lecture notes)*, Schulman, 2016 9. *Dueling Network Architectures for Deep Reinforcement Learning*, Wang et al., 2016 10. *Reinforcement learning: An introduction*, Sutton and Barto, 2011 ## Todos - Documentation: Work on the documentation has begun but not everything is documented in code yet. Additionally, it would be super nice to have guides for each agents that describe the basic ideas behind it. - TRPO, priority-based memory, A3C, async DQN, ...
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