Actor-Critic: verliesberekeningen

Als laatste stap voordat je je agent met A2C kunt trainen, schrijf je een functie calculate_losses() die de verliezen voor beide netwerken teruggeeft.

Ter referentie: dit zijn respectievelijk de uitdrukkingen voor de verliesfuncties van de actor en de critic:

Deze oefening maakt deel uit van de cursus

Deep Reinforcement Learning in Python

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Oefeninstructies

Bereken de TD-doelwaarde.
Bereken het verlies voor het Actor-netwerk.
Bereken het verlies voor het Critic-netwerk.

Praktische interactieve oefening

Probeer deze oefening eens door deze voorbeeldcode in te vullen.

def calculate_losses(critic_network, action_log_prob, 
                     reward, state, next_state, done):
    value = critic_network(state)
    next_value = critic_network(next_state)
    # Calculate the TD target
    td_target = (____ + gamma * ____ * (1-done))
    td_error = td_target - value
    # Calculate the actor loss
    actor_loss = -____ * ____.detach()
    # Calculate the critic loss
    critic_loss = ____
    return actor_loss, critic_loss
  
actor_loss, critic_loss = calculate_losses(
        critic_network, action_log_prob, 
        reward, state, next_state, done
)
print(round(actor_loss.item(), 2), round(critic_loss.item(), 2))

Code bewerken en uitvoeren

Deze oefening maakt deel uit van de cursus

Deep Reinforcement Learning in Python

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4.8+

Begin de cursus gratis

Discover how deep reinforcement learning improves upon traditional Reinforcement Learning while studying and implementing your first Deep Q Learning algorithm.

Exercise 1: Introduction to deep reinforcement learning Exercise 2: Environment and neural network setup Exercise 3: DRL training loop Exercise 4: Introduction to deep Q learning Exercise 5: Deep learning and DQN Exercise 6: The Q-Network architecture Exercise 7: Instantiating the Q-Network Exercise 8: The barebone DQN algorithm Exercise 9: Barebone DQN action selection Exercise 10: Barebone DQN loss function Exercise 11: Training the barebone DQN

Dive into Deep Q-learning by implementing the original DQN algorithm, featuring Experience Replay, epsilon-greediness and fixed Q-targets. Beyond DQN, you will then explore two fascinating extensions that improve the performance and stability of Deep Q-learning: Double DQN and Prioritized Experience Replay.

Exercise 1: DQN with experience replay Exercise 2: The double-ended queue Exercise 3: Experience replay buffer Exercise 4: DQN with experience replay Exercise 5: The complete DQN algorithm Exercise 6: Epsilon-greediness Exercise 7: Fixed Q-targets Exercise 8: Implementing the complete DQN algorithm Exercise 9: Double DQN Exercise 10: Online network and target network in DDQN Exercise 11: Training the double DQN Exercise 12: Prioritized experience replay Exercise 13: Prioritized experience replay buffer Exercise 14: Sampling from the PER buffer Exercise 15: DQN with prioritized experience replay

Learn about the foundational concepts of policy gradient methods found in DRL. You will begin with the policy gradient theorem, which forms the basis for these methods. Then, you will implement the REINFORCE algorithm, a powerful approach to learning policies. The chapter will then guide you through Actor-Critic methods, focusing on the Advantage Actor-Critic (A2C) algorithm, which combines the strengths of both policy gradient and value-based methods to enhance learning efficiency and stability.

Exercise 1: Introductie tot policy gradient Exercise 2: De architectuur van het policy-netwerk Exercise 3: Werken met discrete verdelingen Exercise 4: Policy gradient en REINFORCE Exercise 5: Actieselectie in REINFORCE Exercise 6: De REINFORCE-algoritme trainen Exercise 7: Advantage Actor-Critic Exercise 8: Critic-netwerk Exercise 9: Actor-Critic: verliesberekeningen

Huidige oefening

Exercise 10: Het A2C-algoritme trainen

Explore Proximal Policy Optimization (PPO) for robust DRL performance. Next, you will examine using an entropy bonus in PPO, which encourages exploration by preventing premature convergence to deterministic policies. You'll also learn about batch updates in policy gradient methods. Finally, you will learn about hyperparameter optimization with Optuna, a powerful tool for optimizing performance in your DRL models.

Exercise 1: Proximal policy optimization Exercise 2: The clipped probability ratio Exercise 3: The clipped surrogate objective function Exercise 4: Entropy bonus and PPO Exercise 5: Entropy playground Exercise 6: Training the PPO algorithm Exercise 7: Batch updates in policy gradient Exercise 8: Minibatch and DRL Exercise 9: A2C with batch updates Exercise 10: Hyperparameter optimization with Optuna Exercise 11: Hyperparameter or not?Exercise 12: Hands-on with Optuna Exercise 13: Congratulations!