Mixture of LoRA Experts (2404.13628v1)

Abstract: LoRA has gained widespread acceptance in the fine-tuning of large pre-trained models to cater to a diverse array of downstream tasks, showcasing notable effectiveness and efficiency, thereby solidifying its position as one of the most prevalent fine-tuning techniques. Due to the modular nature of LoRA's plug-and-play plugins, researchers have delved into the amalgamation of multiple LoRAs to empower models to excel across various downstream tasks. Nonetheless, extant approaches for LoRA fusion grapple with inherent challenges. Direct arithmetic merging may result in the loss of the original pre-trained model's generative capabilities or the distinct identity of LoRAs, thereby yielding suboptimal outcomes. On the other hand, Reference tuning-based fusion exhibits limitations concerning the requisite flexibility for the effective combination of multiple LoRAs. In response to these challenges, this paper introduces the Mixture of LoRA Experts (MoLE) approach, which harnesses hierarchical control and unfettered branch selection. The MoLE approach not only achieves superior LoRA fusion performance in comparison to direct arithmetic merging but also retains the crucial flexibility for combining LoRAs effectively. Extensive experimental evaluations conducted in both the NLP and Vision & Language (V&L) domains substantiate the efficacy of MoLE.

Mixture of LoRA Experts (MoLE): Enhancing Efficiency and Capability in Composite Pre-trained Model Adaptation

Introduction to LoRA and Its Composition Challenges

Recent advancements in model efficiency have highlighted LoRA as a viable technique for fine-tuning sizable pre-trained models without the substantial computational cost of full model re-training. Despite its initial success, operational challenges arise when attempting to synergistically combine multiple trained LoRAs—each possibly fine-tuned for different tasks or features—into a single coherent model. This process often results in a dilution of individual LoRA characteristics or, alternatively, in a computationally expensive re-training process if new attributes are to be integrated effectively.

Mixture of LoRA Experts (MoLE) Framework

Concept and Motivation

The newly proposed Mixture of LoRA Experts (MoLE) tackles the inefficiencies of existing composition methods by introducing a layer-wise gating mechanism that dynamically adjusts the contributions of individual LoRAs. This approach ensures that each layer's unique characteristics can be preserved or emphasized based on the domain-specific requirements, thus maintaining the effectiveness of the original LoRA traits while leveraging the collective power of multiple such adaptations.

Operational Details

MoLE operates by treating each trained LoRA's layer as an expert and implementing a learnable gating function that determines the optimal contribution of each layer towards achieving the specified task. This functionality not only preserves the unique character of individual LoRAs but also addresses the computational overhead associated with other methods such as re-training large models from scratch.

Empirical Validation and Results

MoLE's effectiveness is rigorously tested in domains of NLP and Vision Content Language (VCL). Experimental results confirm that MoLE substantially outperforms other LoRA composition methods, particularly in its ability to maintain high performance without compromising the generative abilities of the underlying model architecture. The introduction of a hierarchy in gating control further allows MoLE to fine-tune the influence of specific layers, providing a more nuanced control over the model output.

Theoretical and Practical Implications

1. Efficiency in Composition: MoLE introduces a methodologically sound and computationally efficient approach to compose multiple fine-tuned LoRAs.
2. Preservation of Traits: Unlike linear and arithmetic compositions which may dilute individual features, MoLE adeptly preserves distinct LoRA characteristics.
3. Scalable and Versatile Implementation: Demonstrated effectiveness in both NLP and VCL showcases MoLE's versatility and scalability across different types of large language and vision models.

Future Prospects in AI Development

Looking forward, the success of MoLE suggests a promising direction for further research into modular and scalable adaptation techniques for pre-trained models. It invites questions about how such systems can be improved to handle an even broader array of tasks and whether similar strategies might be applicable to other forms of model fine-tuning and adaptation.

In conclusion, the development of the MoLE framework marks a significant step towards resolving some of the persistent challenges in the effective use of LoRA for large model adaptations, paving the way for more personalized and computationally efficient AI systems.