Helpful? Honest? Harmless? Make sure AI response in those 3 ways.
If not, we need RLHF is reduce the toxicity of the LLM.
Reinforcement learning: is a type of machine learning in which an agent learns to make decisions related to a specific goal by taking actions in an environment, with the objective of maximizing some notion of a cumulative reward. RLHF can help making personalized LLMs.
RLHF cycle: iterate until reward score is high:
- Select an instruct model, define your model alignment criterion (ex. helpfulness)
- obtain human feedback through labeler workforce to rate the completions
- Convert rankings into pairwise training data for the reward model
- Train reward model to predict preferred completion from {y_j, y_k} for prompt x
- Use the reward model as a binary classifier to automatically provide reward value for each prompt-completion pair
lower reward score, worse the performance
softmax(logits) = probabilities
RL Algorithm
- RL algorithm updates the weights off the LLM based on the reward is signed to the completions generated by the current version off the LLM
- ex. Q-Learning, PPO (Proximal Policy Optimization, the most popular method)
- PPO optimize LLM to more aligned with human preferences
Reward hacking: the model will achieve high reward score but it actually doesn't align with the criterion, the quality is not improved
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To avoid this, we can use the initial instruct model (aka reference model). * during training, we pass prompt dataset to both reference model and RL-updated LLM,
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Then, we calculate KL Divergence Shift Penalty (a statistical measure of how different two probability distributions are) between two models
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Add the penalty to the Reward Model, then go through PPO, PEFT, and back to reward model
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Constitutional AI
- First proposed in 2022 by researchers at Anthropic
- a method for training models using a set of rules and principles that govern the model's behavior.
Red Teaming: make it to generate harmful responses. Then, remove all harmful responses