Prompt-Tuning Decision Transformer with Preference Ranking

Original Paper: https://arxiv.org/abs/2305.09648

By: Shengchao Hu, Li Shen, Ya Zhang, Dacheng Tao

Abstract:

Prompt-tuning has emerged as a promising method for adapting pre-trained models to downstream tasks or aligning with human preferences. Prompt learning is widely used in NLP but has limited applicability to RL due to the complex physical meaning and environment-specific information contained within RL prompts. These factors require supervised learning to imitate the demonstrations and may result in a loss of meaning after learning. Additionally, directly extending prompt-tuning approaches to RL is challenging because RL prompts guide agent behavior based on environmental modeling and analysis, rather than filling in missing information, making it unlikely that adjustments to the prompt format for downstream tasks, as in NLP, can yield significant improvements. In this work, we propose the Prompt-Tuning DT algorithm to address these challenges by using trajectory segments as prompts to guide RL agents in acquiring environmental information and optimizing prompts via black-box tuning to enhance their ability to contain more relevant information, thereby enabling agents to make better decisions. Our approach involves randomly sampling a Gaussian distribution to fine-tune the elements of the prompt trajectory and using preference ranking function to find the optimization direction, thereby providing more informative prompts and guiding the agent towards specific preferences in the target environment. Extensive experiments show that with only 0.03% of the parameters learned, Prompt-Tuning DT achieves comparable or even better performance than full-model fine-tuning in low-data scenarios. Our work contributes to the advancement of prompt-tuning approaches in RL, providing a promising direction for optimizing large RL agents for specific preference tasks.

Summary Notes

Harnessing Prompt-Tuning in Reinforcement Learning: A Simplified Overview

The world of artificial intelligence (AI) is constantly evolving, with pre-trained large-scale models (PLMs) making significant strides in natural language processing (NLP).

Yet, applying these advances to reinforcement learning (RL) brings about unique challenges. This blog explores an innovative solution: the integration of prompt-tuning into RL through the Prompt-Tuning Decision Transformer (Prompt-Tuning DT).

Introduction: Merging NLP Techniques with RL

Prompt-tuning, a method that tweaks prompts to guide model behavior while keeping its core unchanged, has proven effective in NLP.

Transferring this method to RL isn't straightforward, as RL's decision-making based on environmental feedback differs from NLP's task structure. The introduction of Prompt-Tuning DT is a pivotal effort to bridge this gap.

The Innovative Approach: Prompt-Tuning DT

The Prompt-Tuning DT introduces a novel method for RL by using trajectory segments as prompts. This approach encompasses:

• Trajectory Segments as Prompts: Utilizing past experiences as prompts enables the model to make decisions based on similar past situations.
• Gaussian Distribution Sampling: This technique efficiently explores the space of possible trajectories, identifying the most promising ones for success.
• Preference Ranking for Optimization: By ranking trajectories according to their performance, the model refines its decision-making over time.

Testing the Approach: Experimentation and Results

The research team tested Prompt-Tuning DT across various RL scenarios, such as Cheetah-dir and Meta-World reach-v2, focusing on its ability to generalize from few examples and its efficiency.

The findings revealed:

• Outstanding Performance: Prompt-Tuning DT matched or surpassed the effectiveness of full-model tuning in most tests.
• High Efficiency: Remarkably, the model achieved these results by adjusting only 0.03% of the parameters, underscoring its efficiency.
• Effectiveness in Data-Sparse Conditions: The experiments confirmed the model's capability to adapt swiftly to new tasks with limited data.

Benefits of Prompt-Tuning DT

The Prompt-Tuning DT offers significant advantages, including:

• Reduced need for extensive re-training, enabling quicker deployment.
• Minimal computational demands, making it ideal for real-world application.
• Proven effectiveness in tasks with few-shot generalization, highlighting its versatility.

Conclusion: Pushing the Boundaries of RL

The development of the Prompt-Tuning DT marks a significant advancement in making AI models more adaptable and efficient. By incorporating NLP's prompt-tuning into RL, this approach opens up new possibilities for model adaptation across diverse tasks.

As research progresses, exploring more complex environments and larger models will further unveil prompt-tuning's potential in RL.

In essence, the Prompt-Tuning DT not only showcases a promising direction for future research but also highlights the growing synergy between different AI domains, leading to more versatile and efficient models.