examples/tutorial/rl/reward_classifier_example.py

import torch

from lerobot.datasets import LeRobotDataset
from lerobot.rewards import RewardClassifierConfig, make_reward_model, make_reward_pre_post_processors


def main():
    # Device to use for training
    device = "mps"  # or "cuda", or "cpu"

    # Load the dataset used for training
    repo_id = "lerobot/example_hil_serl_dataset"
    dataset = LeRobotDataset(repo_id)

    # Configure the policy to extract features from the image frames
    camera_keys = dataset.meta.camera_keys

    config = RewardClassifierConfig(
        num_cameras=len(camera_keys),
        device=device,
        # backbone model to extract features from the image frames
        model_name="microsoft/resnet-18",
    )

    # Make reward model, preprocessor, and optimizer
    reward_model = make_reward_model(config, dataset_stats=dataset.meta.stats)
    optimizer = config.get_optimizer_preset().build(reward_model.parameters())
    preprocessor, _ = make_reward_pre_post_processors(config, dataset_stats=dataset.meta.stats)

    classifier_id = "<user>/reward_classifier_hil_serl_example"

    # Instantiate a dataloader
    dataloader = torch.utils.data.DataLoader(dataset, batch_size=16, shuffle=True)

    # Training loop
    num_epochs = 5
    for epoch in range(num_epochs):
        total_loss = 0
        total_accuracy = 0
        for batch in dataloader:
            # Preprocess the batch and move it to the correct device.
            batch = preprocessor(batch)

            # Forward pass
            loss, output_dict = reward_model.forward(batch)

            # Backward pass and optimization
            optimizer.zero_grad()
            loss.backward()
            optimizer.step()

            total_loss += loss.item()
            total_accuracy += output_dict["accuracy"]

        avg_loss = total_loss / len(dataloader)
        avg_accuracy = total_accuracy / len(dataloader)
        print(f"Epoch {epoch + 1}/{num_epochs}, Loss: {avg_loss:.4f}, Accuracy: {avg_accuracy:.2f}%")

    print("Training finished!")

    # You can now save the trained reward model.
    reward_model.push_to_hub(classifier_id)


if __name__ == "__main__":
    main()