DRL - PPO - Soccer

Udacity Deep Reinforcement Learning Nanodegree Program

Observations:

• To run the project just execute the soccer.ipynb file.
• If you are not using a windows environment, you will need to download the corresponding "Soccer" version for you OS system. Mail me if you need more details about the environment .exe file.
• The checkpoint.pth has the expected average score already hit.

Requeriments:

• tensorflow: 1.7.1
• Pillow: 4.2.1
• matplotlib
• numpy: 1.11.0
• pytest: 3.2.2
• docopt
• pyyaml
• protobuf: 3.5.2
• grpcio: 1.11.0
• torch: 0.4.1
• pandas
• scipy
• ipykernel
• jupyter: 5.6.0

The problem:

• The task involves a soccer game with 2 teams, each one having 2 players: 1 striker and one 1 keeper.
• There is no goal defined for default, so I decided to train against a random team until my agents archive a score of 95 wins into 100 games.
• The goalies have 4 actions.
• The strikers have 6 actions.

The solution:

• The biggest problem in this scenario is to control the exploration vs. exploitation rate. I tried approaches such as Double DQN with an exponential exploration rating decay as well as the DDPG approach with prioritized replay experience for diversification of the experiences on learning, but I couldn't find the right configuration for the hyperparameters that could make the agents converge. So I changed the approach for a PPO strategy since this kind of method is easier to configure and controls the exploration very well by itself using probabilistic decisions. After a lot of different implementations, I've reached the current solution.
• An actor critic neural modelis employed here and is using a proximal policy optimization learning function with the trusted region approach. The learning happens after each episode (controlled by the environment), and it uses mini-batches from the episode experiences after the reward calculation using the N-Step method that combines the temporal difference discount with monte carlo tree search exploration (in this case the N-Step range is the role episode).
• For now, I'll try other variations changing when the learning happens and using multi teams for experience gathering. I hope I can archive superhuman results with 5000 episodes or less (the agents are good but not super humans with 5000 episodes).
• One last consideration: To beat a random team looks easier at the beginning, but if you consider that random agents win 1/3 of the games and the draw rate of random games is 1/3, the AI has overcome a big challenge reaching a 95% win rate. It's incredible how a random agent can score with just a few steps.

The hyperparameters:

• The file with the hyperparameters configuration is the soccer.ipynb.

• If you want you can change the model configuration to into the model.py file.

• The actual configuration of the hyperparameters is:

  • Learning Rate Goalie: 8e-5
  • Learning Rate Striker: 1e-4
  • Gamma: 0.995
  • Batch Size: 32
  • Epsilon: 0.1
  • Entropy Weight: 0.001

• For the neural models:

  • Actor

    • Hidden: (input, 256) - ReLU
    • Hidden: (256, 128) - ReLU
    • Output: (128, action_size) - Softmax

  • Critic

    • Hidden: (input, 256) - ReLU
    • Hidden: (256, 128) - ReLU
    • Output: (128, 1) - Linear