Issue: Clarification on Environment Reset Behavior and Optimization for Debugging

[STAN-32]

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Issue: Clarification on Environment Reset Behavior and Optimization for Debugging

Hello,

I'm working with the mujoco_playground and have a question regarding how the environment's reset function is called within the OnPolicyRunner, especially when an environment finishes an episode (i.e., when done becomes 1).

Environment Reset Behavior

I've observed that in the provided examples, the reset function within the environment is used by the OnPolicyRunner. I'm trying to understand at what specific point this reset is invoked by the runner.

My current understanding is that when an environment's step function outputs done = 1, the environment should then be reset for the next episode. Could you please clarify if this is indeed how it works within OnPolicyRunner?

To debug and confirm environment resets, I added a jax.debug.print statement within my custom environment's reset method, like so:

class MyEnv(mjx_env.MjxEnv):
    def reset(self, rng):
        jax.debug.print("--- RESET FINISHED ---")
        # ... rest of the reset logic ...

However, the --- RESET FINISHED --- message only appears once at the very beginning of the terminal output. It stops appearing after the initial log information starts to show. How can I reliably confirm that mujoco_playground is successfully resetting the environment according to my code's logic, especially when done is triggered during an episode?

Reducing Initialization Time for Development

Additionally, I've noticed that the time from running the script to actually seeing the first log information in the terminal is quite long. I suspect this is due to JAX's JIT (Just-In-Time) compilation process.

This long initialization time makes it difficult to quickly test minor adjustments to the environment and verify if the overall pipeline works as expected. Are there any effective methods or best practices to significantly reduce this initial setup time, especially for rapid prototyping and debugging when making small changes to the environment?

Any insights or guidance on these two points would be greatly appreciated!

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[STAN-32]

The resetting problem has been solved.
BTW, is there any method that could shorten initialization time?

[bkpcoding]

You could probably use cache. https://docs.jax.dev/en/latest/persistent_compilation_cache.html

[STAN-32]

You could probably use cache. https://docs.jax.dev/en/latest/persistent_compilation_cache.html

It seems that complied was trigger every single time the reset() is called, even I have used this cache method.
Do I need to change the jit method for reset function?

[btaba]

@STAN-32 this discussion should be relevant as to why the reset jax debug prints once. #175. This is WAI.

As for the JAX compilation cache, I've had similar issues in the past. Please let us know if you get that working.