ml-agents/docs/FAQ.md

Frequently Asked Questions

Scripting Runtime Environment not setup correctly

If you haven't switched your scripting runtime version from .NET 3.5 to .NET 4.6 or .NET 4.x, you will see such error message:

error CS1061: Type `System.Text.StringBuilder' does not contain a definition for `Clear' and no extension method `Clear' of type `System.Text.StringBuilder' could be found. Are you missing an assembly reference?

This is because .NET 3.5 doesn't support method Clear() for StringBuilder, refer to Setting Up The ML-Agents Toolkit Within Unity for solution.

TensorFlowSharp flag not turned on

If you have already imported the TensorFlowSharp plugin, but haven't set ENABLE_TENSORFLOW flag for your scripting define symbols, you will see the following error message:

UnityAgentsException: The brain 3DBallLearning was set to inference mode but the TensorFlow library is not present in the Unity project.

This error message occurs because the TensorFlowSharp plugin won't be used without the ENABLE_TENSORFLOW flag, refer to Setting Up The ML-Agents Toolkit Within Unity for solution.

Environment Permission Error

If you directly import your Unity environment without building it in the editor, you might need to give it additional permissions to execute it.

If you receive such a permission error on macOS, run:

chmod -R 755 *.app

or on Linux:

chmod -R 755 *.x86_64

On Windows, you can find instructions.

Environment Connection Timeout

If you are able to launch the environment from UnityEnvironment but then receive a timeout error like this:

UnityAgentsException: The Communicator was unable to connect. Please make sure the External process is ready to accept communication with Unity.

There may be a number of possible causes:

• Cause: There may be no LearningBrain with Control option checked in the Broadcast Hub of the Academy. In this case, the environment will not attempt to communicate with Python. Solution: Click Add New in your Academy's Broadcast Hub, and drag your LearningBrain asset into the Brains field, and check the Control toggle. Also you need to assign this LearningBrain asset to all of the Agents you wish to do training on.
• Cause: On OSX, the firewall may be preventing communication with the environment. Solution: Add the built environment binary to the list of exceptions on the firewall by following instructions.
• Cause: An error happened in the Unity Environment preventing communication. Solution: Look into the log files generated by the Unity Environment to figure what error happened.
• Cause: You have assigned HTTP_PROXY and HTTPS_PROXY values in your environment variables. Solution: Remove these values and try again.

Communication port {} still in use

If you receive an exception "Couldn't launch new environment because communication port {} is still in use. ", you can change the worker number in the Python script when calling

UnityEnvironment(file_name=filename, worker_id=X)

Mean reward : nan

If you receive a message Mean reward : nan when attempting to train a model using PPO, this is due to the episodes of the Learning Environment not terminating. In order to address this, set Max Steps for either the Academy or Agents within the Scene Inspector to a value greater than 0. Alternatively, it is possible to manually set done conditions for episodes from within scripts for custom episode-terminating events.

Problems with training on AWS

Please refer to Training on Amazon Web Service FAQ