Breakout-v0 environment freezing during training sessions

Other Questions OpenAI
1

I’m experiencing weird behavior while working with the Breakout-v0 environment in OpenAI gym. The game seems to freeze randomly during training where the ball completely disappears from the screen for multiple consecutive frames. During these periods, nothing happens and the ball doesn’t respawn for quite a while.

I’m not sure if this is a bug in the gym environment or if it’s actually part of how the original Breakout game works. Has anyone else encountered this issue?

Also, I’m trying to understand the action space better. From my testing, it seems like:

  • Action 0: No movement (paddle stays still)
  • Action 1: Also no movement (same as 0?)
  • Action 2: Move paddle right
  • Action 3: Move paddle left

Can someone confirm if these action mappings are correct? The freezing issue is really affecting my training performance and I need to figure out if this is expected behavior or something I should work around.

2

That freezing is totally normal for Breakout-v0. When you lose a life, there’s a built-in delay of 30-80 frames before the next ball gets served. The screen just sits there during this time, which is exactly what you’re seeing. Your action mappings are mostly right, but there’s one thing to note. Actions 0 and 1 both keep the paddle still, but action 1 is technically ‘fire’ - it matters at the start of each life to serve the ball. During actual gameplay though, they do the same thing. Actions 2 and 3 are right and left movement. You’ll need to handle this delay in your training algorithm. Most people either skip these frames or just treat them as normal game flow. Just make sure your agent doesn’t get thrown off by these dead periods.