We explore building generative neural network models of popular reinforcement learning environments. Our world model can be trained quickly in an unsupervised manner to learn a compressed spatial and temporal representation of the environment. By using features extracted from the world model as inputs to an agent, we can train a very compact and simple policy that can solve the required task. We can even train our agent entirely inside of its own dream environment generated by its world model, and transfer this policy back into the actual environment. Humans develop a mental model of the world based on what they are able to perceive with their limited senses.
Vandapel, M. The setup of our VizDoom experiment is largely the same as the Car Racing task, World models rd for a few key differences. Bellutta, R. In this work, we used evolution strategies ES to train our controller, as it offers many benefits. For instance, our VAE reproduced unimportant detailed brick tile patterns on the side walls in World models rd Doom environment, but failed to reproduce modele tiles on the road in the Car Racing environment. Ferguson, A. Sale Event. One way of understanding Porn fedilty predictive model inside of our brains is that it might not be about just predicting the future Worlf general, but predicting future sensory data given our current motor actions. Amidi, M.
Adult henti games. Can agents learn inside of their own dreams?
M is not able to transition to another mode in the mixture Workd Gaussian model where fireballs are formed and shot. Indigo East Indigo East Community. Explore a collection of the most striking and enigmatic landscapes available in Google Earth. To optimize the parameters of C, we chose the Covariance-Matrix Adaptation Evolution Strategy CMA-ES as our optimization algorithm since it is known to work well for solution spaces of up modwls a few thousand parameters. Each pixel is stored as three floating point values between 0 and 1 to represent each of the RGB channels. Many concepts first World models rd in the s for feed-forward neural networks FNNs and in the s for RNNs laid some of the groundwork for Learning to Think. Iterative training could allow the C--M rrd to develop a natural hierarchical way to learn. Leslie Braumann . NASA satellite imagery and astronaut photography reveal where an English alphabet can be found in the landforms of the Earth. This approach is very similar to previous work in the Unconditional Handwriting Generation section and also the decoder-only World models rd of SketchRNN. Deploying our policy learned inside mofels the dream RNN environment back into the World models rd VizDoom environment. Must qualify to be eligible for World Tour. After all, unsupervised learning cannot, by definition, know what will be useful for the task at hand. We find agents that perform well in higher temperature settings generally perform better in the Wordl setting.
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- We explore building generative neural network models of popular reinforcement learning environments.
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As a result of using M to generate a virtual environment for our agent, we are also giving the controller access to all of the hidden states of M. Learning a model of the dynamics from a compressed latent space enable RL algorithms to be much more data-efficient. This has been demonstrated not only in early work when compute was a million times more expensive than today but also in recent studies on several competitive VizDoom environments. Each convolution and deconvolution layer uses a stride of 2. The world's most detailed globe. In this section, we describe how we can train the Agent model described earlier to solve a car racing task.
World models rd. Can agents learn inside of their own dreams?
O.S. Engines - The World Models
We explore building generative neural network models of popular reinforcement learning environments. Our world model can be trained quickly in an unsupervised manner to learn a compressed spatial and temporal representation of the environment. By using features extracted from the world model as inputs to an agent, we can train a very compact and simple policy that can solve the required task.
We can even train our agent entirely inside of its own dream environment generated by its world model, and transfer this policy back into the actual environment. Humans develop a mental model of the world based on what they are able to perceive with their limited senses.
The decisions and actions we make are based on this internal model. Jay Wright Forrester, the father of system dynamics, described a mental model as:. Nobody in his head imagines all the world, government or country.
He has only selected concepts, and relationships between them, and uses those to represent the real system. To handle the vast amount of information that flows through our daily lives, our brain learns an abstract representation of both spatial and temporal aspects of this information.
We are able to observe a scene and remember an abstract description thereof. One way of understanding the predictive model inside of our brains is that it might not be about just predicting the future in general, but predicting future sensory data given our current motor actions. We are able to instinctively act on this predictive model and perform fast reflexive behaviours when we face danger , without the need to consciously plan out a course of action.
Take baseball for example. A baseball batter has milliseconds to decide how they should swing the bat -- shorter than the time it takes for visual signals from our eyes to reach our brain. The reason we are able to hit a mph fastball is due to our ability to instinctively predict when and where the ball will go.
For professional players, this all happens subconsciously. Their muscles reflexively swing the bat at the right time and location in line with their internal models' predictions. They can quickly act on their predictions of the future without the need to consciously roll out possible future scenarios to form a plan.
In many reinforcement learning RL problems , an artificial agent also benefits from having a good representation of past and present states, and a good predictive model of the future , preferably a powerful predictive model implemented on a general purpose computer such as a recurrent neural network RNN. Large RNNs are highly expressive models that can learn rich spatial and temporal representations of data. However, many model-free RL methods in the literature often only use small neural networks with few parameters.
The RL algorithm is often bottlenecked by the credit assignment problem In many RL problems, the feedback positive or negative reward is given at end of a sequence of steps. The credit assignment problem tackles the problem of figuring out which steps caused the resulting feedback--which steps should receive credit or blame for the final result?
Ideally, we would like to be able to efficiently train large RNN-based agents. The backpropagation algorithm can be used to train large neural networks efficiently. In principle, the procedure described in this article can take advantage of these larger networks if we wanted to use them.
We first train a large neural network to learn a model of the agent's world in an unsupervised manner, and then train the smaller controller model to learn to perform a task using this world model.
A small controller lets the training algorithm focus on the credit assignment problem on a small search space, while not sacrificing capacity and expressiveness via the larger world model. By training the agent through the lens of its world model, we show that it can learn a highly compact policy to perform its task.
In this article, we combine several key concepts from a series of papers from on RNN-based world models and controllers with more recent tools from probabilistic modelling, and present a simplified approach to test some of those key concepts in modern RL environments.
Experiments show that our approach can be used to solve a challenging race car navigation from pixels task that previously has not been solved using more traditional methods. Most existing model-based RL approaches learn a model of the RL environment, but still train on the actual environment. Here, we also explore fully replacing an actual RL environment with a generated one, training our agent's controller only inside of the environment generated by its own internal world model, and transfer this policy back into the actual environment.
To overcome the problem of an agent exploiting imperfections of the generated environments, we adjust a temperature parameter of internal world model to control the amount of uncertainty of the generated environments. We train an agent's controller inside of a noisier and more uncertain version of its generated environment, and demonstrate that this approach helps prevent our agent from taking advantage of the imperfections of its internal world model.
We will also discuss other related works in the model-based RL literature that share similar ideas of learning a dynamics model and training an agent using this model. We present a simple model inspired by our own cognitive system. In this model, our agent has a visual sensory component that compresses what it sees into a small representative code.
It also has a memory component that makes predictions about future codes based on historical information. Finally, our agent has a decision-making component that decides what actions to take based only on the representations created by its vision and memory components.
The environment provides our agent with a high dimensional input observation at each time step. This input is usually a 2D image frame that is part of a video sequence. The role of the V model is to learn an abstract, compressed representation of each observed input frame. This compressed representation can be used to reconstruct the original image. While it is the role of the V model to compress what the agent sees at each time frame, we also want to compress what happens over time.
For this purpose, the role of the M model is to predict the future. The M model serves as a predictive model of the future z z z vectors that V is expected to produce. Because many complex environments are stochastic in nature, we train our RNN to output a probability density function p z p z p z instead of a deterministic prediction of z z z.
The Controller C model is responsible for determining the course of actions to take in order to maximize the expected cumulative reward of the agent during a rollout of the environment. In our experiments, we deliberately make C as simple and small as possible, and trained separately from V and M, so that most of our agent's complexity resides in the world model V and M.
Below is the pseudocode for how our agent model is used in the OpenAI Gym environment. Running this function on a given controller C will return the cumulative reward during a rollout of the environment.
This minimal design for C also offers important practical benefits. Advances in deep learning provided us with the tools to train large, sophisticated models efficiently, provided we can define a well-behaved, differentiable loss function. Our V and M models are designed to be trained efficiently with the backpropagation algorithm using modern GPU accelerators, so we would like most of the model's complexity, and model parameters to reside in V and M. The number of parameters of C, a linear model, is minimal in comparison.
This choice allows us to explore more unconventional ways to train C -- for example, even using evolution strategies ES to tackle more challenging RL tasks where the credit assignment problem is difficult. To optimize the parameters of C, we chose the Covariance-Matrix Adaptation Evolution Strategy CMA-ES as our optimization algorithm since it is known to work well for solution spaces of up to a few thousand parameters.
We evolve parameters of C on a single machine with multiple CPU cores running multiple rollouts of the environment in parallel. For more specific information about the models, training procedures, and environments used in our experiments, please refer to the Appendix.
A predictive world model can help us extract useful representations of space and time. By using these features as inputs of a controller, we can train a compact and minimal controller to perform a continuous control task, such as learning to drive from pixel inputs for a top-down car racing environment.
In this section, we describe how we can train the Agent model described earlier to solve a car racing task. To our knowledge, our agent is the first known solution to achieve the score required to solve this task. We find this task interesting because although it is not difficult to train an agent to wobble around randomly generated tracks and obtain a mediocre score, CarRacing-v0 defines "solving" as getting average reward of over consecutive trials, which means the agent can only afford very few driving mistakes.
In this environment, the tracks are randomly generated for each trial, and our agent is rewarded for visiting as many tiles as possible in the least amount of time. To train our V model, we first collect a dataset of 10, random rollouts of the environment.
We will discuss an iterative training procedure later on for more complicated environments where a random policy is not sufficient. We use this dataset to train V to learn a latent space of each frame observed. We train our VAE to encode each frame into low dimensional latent vector z z z by minimizing the difference between a given frame and the reconstructed version of the frame produced by the decoder from z z z. The following demo shows the results of our VAE after training:.
Although in principle, we can train V and M together in an end-to-end manner, we found that training each separately is more practical, achieves satisfactory results, and does not require exhaustive hyperparameter tuning. As images are not required to train M on its own, we can even train on large batches of long sequences of latent vectors encoding the entire frames of an episode to capture longer term dependencies, on a single GPU. In this experiment, the world model V and M has no knowledge about the actual reward signals from the environment.
Its task is simply to compress and predict the sequence of image frames observed. Only the Controller C Model has access to the reward information from the environment. Since there are a mere parameters inside the linear controller model, evolutionary algorithms such as CMA-ES are well suited for this optimization task. The figure below compares actual the observation given to the agent and the observation captured by the world model.
Training an agent to drive is not a difficult task if we have a good representation of the observation. Previous works have shown that with a good set of hand-engineered information about the observation, such as LIDAR information, angles, positions and velocities, one can easily train a small feed-forward network to take this hand-engineered input and output a satisfactory navigation policy.
Although the agent is still able to navigate the race track in this setting, we notice it wobbles around and misses the tracks on sharper corners. The driving is more stable, and the agent is able to seemingly attack the sharp corners effectively. Furthermore, we see that in making these fast reflexive driving decisions during a car race, the agent does not need to plan ahead and roll out hypothetical scenarios of the future.
Like a seasoned Formula One driver or the baseball player discussed earlier, the agent can instinctively predict when and where to navigate in the heat of the moment.
Traditional Deep RL methods often require pre-processing of each frame, such as employing edge-detection , in addition to stacking a few recent frames into the input.
In contrast, our world model takes in a stream of raw RGB pixel images and directly learns a spatial-temporal representation. To our knowledge, our method is the first reported solution to solve this task. Since our world model is able to model the future, we are also able to have it come up with hypothetical car racing scenarios on its own.
We can put our trained C back into this dream environment generated by M. The following demo shows how our world model can be used to generate the car racing environment:.
We have just seen that a policy learned inside of the real environment appears to somewhat function inside of the dream environment. This begs the question -- can we train our agent to learn inside of its own dream, and transfer this policy back to the actual environment? If our world model is sufficiently accurate for its purpose, and complete enough for the problem at hand, we should be able to substitute the actual environment with this world model.
After all, our agent does not directly observe the reality, but only sees what the world model lets it see. In this experiment, we train an agent inside the dream environment generated by its world model trained to mimic a VizDoom environment. The agent must learn to avoid fireballs shot by monsters from the other side of the room with the sole intent of killing the agent.
There are no explicit rewards in this environment, so to mimic natural selection, the cumulative reward can be defined to be the number of time steps the agent manages to stay alive during a rollout. The setup of our VizDoom experiment is largely the same as the Car Racing task, except for a few key differences.