HAM: Hierarchical Adapter Merging for Scalable Continual Learning

Fuente: arXiv
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Hauptverfasser: Coleman, Eric Nuertey, Quarantiello, Luigi, Mukherjee, Samrat, Hurtado, Julio, Lomonaco, Vincenzo
Format: Preprint
Veröffentlicht: 2025
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author Coleman, Eric Nuertey
Quarantiello, Luigi
Mukherjee, Samrat
Hurtado, Julio
Lomonaco, Vincenzo
author_facet Coleman, Eric Nuertey
Quarantiello, Luigi
Mukherjee, Samrat
Hurtado, Julio
Lomonaco, Vincenzo
contents Continual learning is an essential capability of human cognition, yet it poses significant challenges for current deep learning models. The primary issue is that new knowledge can interfere with previously learned information, causing the model to forget earlier knowledge in favor of the new, a phenomenon known as catastrophic forgetting. Although large pre-trained models can partially mitigate forgetting by leveraging their existing knowledge and over-parameterization, they often struggle when confronted with novel data distributions. Parameter-Efficient Fine-Tuning (PEFT) methods, such as LoRA, enable efficient adaptation to new knowledge. However, they still face challenges in scaling to dynamic learning scenarios and long sequences of tasks, as maintaining one adapter per task introduces complexity and increases the potential for interference. In this paper, we introduce Hierarchical Adapters Merging (HAM), a novel framework that dynamically combines adapters from different tasks during training. This approach enables HAM to scale effectively, allowing it to manage more tasks than competing baselines with improved efficiency. To achieve this, HAM maintains a fixed set of groups that hierarchically consolidate new adapters. For each task, HAM trains a low-rank adapter along with an importance scalar, then dynamically groups tasks based on adapter similarity. Within each group, adapters are pruned, scaled and merge, facilitating transfer learning between related tasks. Extensive experiments on three vision benchmarks show that HAM significantly outperforms state-of-the-art methods, particularly as the number of tasks increases.
format Preprint
id arxiv_https___arxiv_org_abs_2509_13211
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle HAM: Hierarchical Adapter Merging for Scalable Continual Learning
Coleman, Eric Nuertey
Quarantiello, Luigi
Mukherjee, Samrat
Hurtado, Julio
Lomonaco, Vincenzo
Machine Learning
Continual learning is an essential capability of human cognition, yet it poses significant challenges for current deep learning models. The primary issue is that new knowledge can interfere with previously learned information, causing the model to forget earlier knowledge in favor of the new, a phenomenon known as catastrophic forgetting. Although large pre-trained models can partially mitigate forgetting by leveraging their existing knowledge and over-parameterization, they often struggle when confronted with novel data distributions. Parameter-Efficient Fine-Tuning (PEFT) methods, such as LoRA, enable efficient adaptation to new knowledge. However, they still face challenges in scaling to dynamic learning scenarios and long sequences of tasks, as maintaining one adapter per task introduces complexity and increases the potential for interference. In this paper, we introduce Hierarchical Adapters Merging (HAM), a novel framework that dynamically combines adapters from different tasks during training. This approach enables HAM to scale effectively, allowing it to manage more tasks than competing baselines with improved efficiency. To achieve this, HAM maintains a fixed set of groups that hierarchically consolidate new adapters. For each task, HAM trains a low-rank adapter along with an importance scalar, then dynamically groups tasks based on adapter similarity. Within each group, adapters are pruned, scaled and merge, facilitating transfer learning between related tasks. Extensive experiments on three vision benchmarks show that HAM significantly outperforms state-of-the-art methods, particularly as the number of tasks increases.
title HAM: Hierarchical Adapter Merging for Scalable Continual Learning
topic Machine Learning
url https://arxiv.org/abs/2509.13211