Generative adversarial networks don’t just produce pretty pictures. They can build world models, too.

What’s new: A GAN generated a fully functional replica of the classic video game Pac-Man. Researchers from Nvidia, MIT, the University of Toronto, and Vector Institute developed GameGAN to celebrate the original Pac-Man’s 40th anniversary. The company plans to release the code in a few months.

How it works: GameGAN learned to reproduce the game by watching it in action for 50,000 hours. During gameplay, the system synthesizes the action frame by frame using three neural networks.

  • An LSTM-style network learned how user actions change the game’s state. For example, pressing the system’s joystick equivalent upward moves the Pac-Man character forward one space.
  • A network inspired by neural Turing machines allows the system to store information about previously generated frames. In a maze game, retracing your steps should look familiar, and that would be difficult without memory.
  • Based on the memory, updated game state, and latest user action, GameGAN’s generator produces the next frame.

Behind the news: While Nvidia is the first to use a generative adversarial network to reproduce a video game, other researchers have used machine learning for this purpose.

  • An earlier model from Georgia Tech learns approximate representations of classic titles to create new games.
  • The Metacreation Lab at Simon Fraser University is working on models that generate new levels for existing games.
  • Researchers from Queen Mary University trained a neural network to duplicate a video game’s underlying mechanics by observing pixels.

Yes, but: Compared to the original arcade game, Pac-Man’s GAN-driven twin requires orders of magnitude more computation to run.

Why it matters: Autonomous systems such as self-driving cars and robots are often trained in elaborate simulators. Nvidia hopes that GAN-based sims can save time and money.

We’re thinking: Fifty thousand hours is an awful lot of Pac-Man — or anything else! Simulation makes it possible to amass training data that would be virtually impossible to collect in the real world. It’s also a crutch that leads researchers to develop algorithms that work well in simulated environments but are hard to generalize to real-world conditions. Until better small-data algorithms emerge, GAN-based simulation looks like an exciting new direction.


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