DeCAF: Decentralized Consensus-And-Factorization for Low-Rank Adaptation of Foundation Models

Fuente: arXiv
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Main Authors: Saadati, Nastaran, Jiang, Zhanhong, Waite, Joshua R., Ganguly, Shreyan, Balu, Aditya, Hegde, Chinmay, Sarkar, Soumik
Format: Preprint
Published: 2025
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author Saadati, Nastaran
Jiang, Zhanhong
Waite, Joshua R.
Ganguly, Shreyan
Balu, Aditya
Hegde, Chinmay
Sarkar, Soumik
author_facet Saadati, Nastaran
Jiang, Zhanhong
Waite, Joshua R.
Ganguly, Shreyan
Balu, Aditya
Hegde, Chinmay
Sarkar, Soumik
contents Low-Rank Adaptation (LoRA) has emerged as one of the most effective, computationally tractable fine-tuning approaches for training Vision-Language Models (VLMs) and Large Language Models (LLMs). LoRA accomplishes this by freezing the pre-trained model weights and injecting trainable low-rank matrices, allowing for efficient learning of these foundation models even on edge devices. However, LoRA in decentralized settings still remains under explored, particularly for the theoretical underpinnings due to the lack of smoothness guarantee and model consensus interference (defined formally below). This work improves the convergence rate of decentralized LoRA (DLoRA) to match the rate of decentralized SGD by ensuring gradient smoothness. We also introduce DeCAF, a novel algorithm integrating DLoRA with truncated singular value decomposition (TSVD)-based matrix factorization to resolve consensus interference. Theoretical analysis shows TSVD's approximation error is bounded and consensus differences between DLoRA and DeCAF vanish as rank increases, yielding DeCAF's matching convergence rate. Extensive experiments across vision/language tasks demonstrate our algorithms outperform local training and rivals federated learning under both IID and non-IID data distributions.
format Preprint
id arxiv_https___arxiv_org_abs_2505_21382
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle DeCAF: Decentralized Consensus-And-Factorization for Low-Rank Adaptation of Foundation Models
Saadati, Nastaran
Jiang, Zhanhong
Waite, Joshua R.
Ganguly, Shreyan
Balu, Aditya
Hegde, Chinmay
Sarkar, Soumik
Machine Learning
Low-Rank Adaptation (LoRA) has emerged as one of the most effective, computationally tractable fine-tuning approaches for training Vision-Language Models (VLMs) and Large Language Models (LLMs). LoRA accomplishes this by freezing the pre-trained model weights and injecting trainable low-rank matrices, allowing for efficient learning of these foundation models even on edge devices. However, LoRA in decentralized settings still remains under explored, particularly for the theoretical underpinnings due to the lack of smoothness guarantee and model consensus interference (defined formally below). This work improves the convergence rate of decentralized LoRA (DLoRA) to match the rate of decentralized SGD by ensuring gradient smoothness. We also introduce DeCAF, a novel algorithm integrating DLoRA with truncated singular value decomposition (TSVD)-based matrix factorization to resolve consensus interference. Theoretical analysis shows TSVD's approximation error is bounded and consensus differences between DLoRA and DeCAF vanish as rank increases, yielding DeCAF's matching convergence rate. Extensive experiments across vision/language tasks demonstrate our algorithms outperform local training and rivals federated learning under both IID and non-IID data distributions.
title DeCAF: Decentralized Consensus-And-Factorization for Low-Rank Adaptation of Foundation Models
topic Machine Learning
url https://arxiv.org/abs/2505.21382