Other problem-solving techniques Concisely stated, a genetic algorithm or GA for short is a programming technique that mimics biological evolution as a problem-solving strategy. Given a specific problem to solve, the input to the GA is a set of potential solutions to that problem, encoded in some fashion, and a metric called a fitness function that allows each candidate to be quantitatively evaluated. These candidates may be solutions already known to work, with the aim of the GA being to improve them, but more often they are generated at random. The GA then evaluates each candidate according to the fitness function.
Multi-step off-policy learning without importance sampling ratios. To estimate the value functions of policies from exploratory data, most model-free off-policy algorithms rely on importance sampling, where the use of importance sampling ratios often leads to estimates with severe variance. It is thus desirable to learn off-policy without using the ratios.
However, such an algorithm does not exist for multi-step learning with function approximation.
In this paper, we introduce the first such algorithm based on temporal-difference TD learning updates. We show that an explicit use of importance sampling ratios can be eliminated Radial basis function dissertation varying the amount of bootstrapping in TD updates in an action-dependent manner.
Our new algorithm achieves stability using a two-timescale gradient-based TD update. A prior algorithm based on lookup table representation called Tree Backup can also be retrieved using action-dependent bootstrapping, becoming a special case of our algorithm.
In two challenging off-policy tasks, we demonstrate that our algorithm is stable, effectively avoids the large variance issue, and can perform substantially better than its state-of-the-art counterpart.
Unifying seemingly disparate algorithmic ideas to produce better performing algorithms has been a longstanding goal in reinforcement learning.
Currently, there are a multitude of algorithms that can be used to perform TD control, including Sarsa, Q-learning, and Expected Sarsa. These methods are often studied in the one-step case, but they can be extended across multiple time steps to achieve better performance.
Each of these algorithms is seemingly distinct, and no one dominates the others for all problems. The mixture can also be varied dynamically which can result in even greater performance. Journal of Machine Learning Research We consider off-policy temporal-difference TD learning in discounted Markov decision processes, where the goal is to evaluate a policy in a model-free way by using observations of a state process generated without executing the policy.
These results not only lead immediately to a characterization of the convergence behavior of least-squares based implementation of our scheme, but also prepare the ground for further analysis of gradient-based implementations.
Fundamental Theory and Methods. Policy iteration PI is a recursive process of policy evaluation and improvement to solve an optimal decision-making, e.
In such continuous domain, we also propose four off-policy IPI methods—two are the ideal PI forms that use advantage and Q-functions, respectively, and the other two are natural extensions of the existing off-policy IPI schemes to our general RL framework.
Compared to the IPI methods in optimal control, the proposed IPI schemes can be applied to more general situations and do not require an initial stabilizing policy to run; they are also strongly relevant to the RL algorithms in CTS such as advantage updating, Q-learning, and value-gradient based VGB greedy policy improvement.
Our on-policy IPI is basically model-based but can be made partially model-free; each off-policy method is also either partially or completely model-free. The mathematical properties of the IPI methods—admissibility, monotone improvement, and convergence towards the optimal solution—are all rigorously proven, together with the equivalence of on- and off-policy IPI.
Finally, the IPI methods are simulated with an inverted-pendulum model to support the theory and verify the performance. Some Recent Applications of Reinforcement Learning.
Five relatively recent applications of reinforcement learning methods are described. These examples were chosen to illustrate a diversity of application types, the engineering needed to build applications, and most importantly, the impressive results that these methods are able to achieve.
Episodic memory is a psychology term which refers to the ability to recall specific events from the past. We suggest one advantage of this particular type of memory is the ability to easily assign credit to a specific state when remembered information is found to be useful.
Inspired by this idea, and the increasing popularity of external memory mechanisms to handle long-term dependencies in deep learning systems, we propose a novel algorithm which uses a reservoir sampling procedure to maintain an external memory consisting of a fixed number of past states.
The algorithm allows a deep reinforcement learning agent to learn online to preferentially remember those states which are found to be useful to recall later on. Critically this method allows for efficient online computation of gradient estimates with respect to the write process of the external memory.
Thus unlike most prior mechanisms for external memory it is feasible to use in an online reinforcement learning setting.
Communicative Capital for Prosthetic Agents.The radial basis function approach introduces a set of N basis functions, one for each data point, which take the form φ (x −x p) where φ (⋅) is some non-linear function whose form will be discussed shortly.
Publications of the Astronomical Society of the Pacific publishes original research in astronomy and astrophysics; innovations in instrumentation, data analysis, and software; tutorials, dissertation summaries, and conference summaries; and invited reviews on contemporary topics.
Full details about the journal's subject coverage can be found PASP's scope description. Analytical and Numerical Advances in Radial Basis Functions by C´ecile Piret B.S., Metropolitan State College of Denver, Analytical and Numerical Advances in Radial Basis Functions C Paper 3 On choosing a radial basis function and a shape parameter when solving a .
LSTMs are a powerful kind of RNN used for processing sequential data such as sound, time series (sensor) data or written natural language. ASME Biennial Stability and Damped Critical Speeds of a Flexible Rotor in Fluid-Film Bearings J.
W. Lund 1 ASME Biennial Experimental Verification of Torquewhirl-the Destabilizing Influence of Tangential Torque J.
M. Vance and K. B. Yim radial basis function differential quadrature method for the numerical solution of partial differential equations by daniel wade watson a dissertation.