In-Context Alignment: Chat with Vanilla Language Models Before Fine-Tuning (2308.04275v1)

Abstract: In this note, we explore inference-time alignment through in-context learning. We consider a vanilla pretrained LLM Llama-2 before any fine-tuning and retrieve an average of 9 demonstration alignment examples when the model is prompted to follow chat-style instructions. Compared to direct prompting, the in-context alignment without changing model weights leads to a 7x increase in win-rate w.r.t. the text-davinci-003 model from OpenAI, making the vanilla LLM comparable to strong baselines with alignment fine-tuning.

In-Context Alignment: Chat with Vanilla LLMs Before Fine-Tuning

This paper explores the potential of in-context learning as an alternative to fine-tuning for aligning pretrained LLMs to follow chat-style instructions. Specifically, the paper investigates whether a vanilla pretrained LLM such as LLaMA-2 can be effectively aligned at inference time without modifying its weights, thus maintaining the model's original state.

Summary of Key Findings

The research focuses on using demonstration alignment examples retrieved in-context to enable the LLM to generate responses consistent with given instructions. The paper contrasts direct prompting with an in-context alignment approach, wherein approximately 9 demonstration examples are used on average. Notably, this approach leads to a 7x increase in win rate compared to OpenAI's text-davinci-003 model, positioning the unaltered LLaMA-2 on par with baseline models that undergo alignment fine-tuning.

In benchmarking exercises, the model's performance using in-context alignment is measured relative to both the text-davinci-003 and more recent OpenAI benchmarks such as ChatGPT. The results indicate that the approach is competitive, demonstrating a win-rate against text-davinci-003 that is higher than that of the 13 billion parameter Guanaco, yet marginally lower than the 13 billion LLaMA-2-chat model.

Methodological Approach

1. Model and Data: The paper utilizes LLaMA-2, a 13B-parameter vanilla model, pretrained on extensive internet datasets. The alignment data pool consists of exemplar prompt-response pairs designed for canonical SFT alignment.
2. Inference-Time Alignment: This approach employs a retrieval system (specifically the Contriever retriever) to fetch pertinent demonstration examples at runtime. These demonstrations are concatenated with the input prompts within a 3000-token limit, facilitating the model’s alignment without altering its weights.
3. Evaluation: The performance evaluation involves automatically comparing the model's outputs against strong baselines using an evaluation set and providing win or win-or-draw metrics against established LLMs.
4. Ablation Studies: These experiments assess the impact of different base models and retrieval strategies on alignment success, underscoring the importance of both a high-quality base model and effective retrieval techniques.

Implications and Future Directions

The paper provides compelling evidence for in-context alignment as a viable alternative to traditional fine-tuning, particularly in scenarios where resource constraints preclude extensive model retraining. This method allows for flexible deployment across varied alignment tasks, adopting different styles or data sources without altering the underlying model weights. Moreover, the interpretability and transparency of in-context alignment enhance the ability to diagnose and improve alignment datasets effectively.

While the results are promising, they prompt further exploration regarding the limitations and capabilities of in-context learning for alignment tasks. The paper suggests potential areas of investigation, including the feasibility of reinforcement learning with human feedback (RLHF) as a form of in-context alignment and strategies for handling more complex, multi-turn conversational tasks.

In summary, this paper highlights a minimal-resource approach for making LLMs instruction-following entities using in-context alignment, promising both practical efficiencies and opportunities for further research refinement in artificial intelligence development.