Reinforcement Learning to solve Rubik's cube (and other complex problems!)

Half a year has passed since my book "Deep Reinforcement Learning Hands-On" has seen the light. It took me almost a year to write the book and after some time of rest from writing I've discovered that explaining RL methods and turning theoretical papers into working code is a lot of fun for me and I don't want to stop. Luckily, RL domain is evolving, so, there are lots of topics to write about. In mass perception, Deep Reinforcement Learning is a tool to be used mostly for game playing. This is not surprising, given the fact, that historically, the first success in the field was achieved in Atari game suite by Deep Mind in 2015. Atari benchmark suite turned out to be very successful for RL problems and, even now, lots of research papers are using it for demonstrating the efficiency of their methods. As the RL field progresses, the classical 53 Atari games continue to become less and less challenging (at the time of writing more than half of games are solved with super-human accuracy) and researches turn to more complex games, like StarCraft and Dota2. But this bias towards games creates a false impression "RL is about playing games'', which is very far from the truth. In my book, published in June 2018, I've tried to counterbalance this by accompanying Atari games with the examples from other domains, including stock trading (chapter 8), chatbots and NLP problems (chapter 12), web navigation automation (chapter 13), continuous control (chapters 14…16) and boards games (chapter 18). In fact RL having very flexible MDP model potentially could be applied to a wide variety of domains, where computer games is just one convenient and spectacular example of the complicated decision making. In this article I've tried to write a detailed description of the recent attempt to apply RL to a field of combinatorial optimisation. The paper discussed was published by the group of researchers from UCI (University of California, Irvine) and called "Solving the Rubik's Cube Without Human Knowledge''.