dorsal/arxiv
View Schemamergetune: Continued fine-tuning of vision-language models
| Authors | Wenqing Wang, Da Li, Xiatian Zhu, Josef Kittler |
|---|---|
| Categories | |
| ArXiv ID | 2601.10497vv1 |
| URL | https://arxiv.org/abs/2601.10497 |
| License | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ |
Abstract
Fine-tuning vision-language models (VLMs) such as CLIP often leads to catastrophic forgetting of pretrained knowledge. Prior work primarily aims to mitigate forgetting during adaptation; however, forgetting often remains inevitable during this process. We introduce a novel paradigm, \emph{continued fine-tuning (CFT)}, which seeks to recover pretrained knowledge after a zero-shot model has already been adapted. We propose a simple, model-agnostic CFT strategy (named MERGETUNE) guided by linear mode connectivity (LMC), which can be applied post hoc to existing fine-tuned models without requiring architectural changes. Given a fine-tuned model, we continue fine-tuning its trainable parameters (e.g., soft prompts or linear heads) to search for a continued model which has two low-loss paths to the zero-shot (e.g., CLIP) and the fine-tuned (e.g., CoOp) solutions. By exploiting the geometry of the loss landscape, the continued model implicitly merges the two solutions, restoring pretrained knowledge lost in the fine-tuned counterpart. A challenge is that the vanilla LMC constraint requires data replay from the pretraining task. We approximate this constraint for the zero-shot model via a second-order surrogate, eliminating the need for large-scale data replay. Experiments show that MERGETUNE improves the harmonic mean of CoOp by +5.6\% on base-novel generalisation without adding parameters. % We show \emph{the first time} superior performance than CLIP on both DTD and EuroSAT, on cross-dataset transfer. On robust fine-tuning evaluations, the LMC-merged model from MERGETUNE surpasses ensemble baselines with lower inference cost, achieving further gains and state-of-the-art results when ensembled with the zero-shot model. Our code is available at \href{https://github.com/Surrey-UP-Lab/MERGETUNE}{https://github.com/Surrey-UP-Lab/MERGETUNE}.
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"abstract": "Fine-tuning vision-language models (VLMs) such as CLIP often leads to catastrophic forgetting of pretrained knowledge. Prior work primarily aims to mitigate forgetting during adaptation; however, forgetting often remains inevitable during this process. We introduce a novel paradigm, \\emph{continued fine-tuning (CFT)}, which seeks to recover pretrained knowledge after a zero-shot model has already been adapted. We propose a simple, model-agnostic CFT strategy (named MERGETUNE) guided by linear mode connectivity (LMC), which can be applied post hoc to existing fine-tuned models without requiring architectural changes. Given a fine-tuned model, we continue fine-tuning its trainable parameters (e.g., soft prompts or linear heads) to search for a continued model which has two low-loss paths to the zero-shot (e.g., CLIP) and the fine-tuned (e.g., CoOp) solutions. By exploiting the geometry of the loss landscape, the continued model implicitly merges the two solutions, restoring pretrained knowledge lost in the fine-tuned counterpart. A challenge is that the vanilla LMC constraint requires data replay from the pretraining task. We approximate this constraint for the zero-shot model via a second-order surrogate, eliminating the need for large-scale data replay. Experiments show that MERGETUNE improves the harmonic mean of CoOp by +5.6\\% on base-novel generalisation without adding parameters. % We show \\emph{the first time} superior performance than CLIP on both DTD and EuroSAT, on cross-dataset transfer. On robust fine-tuning evaluations, the LMC-merged model from MERGETUNE surpasses ensemble baselines with lower inference cost, achieving further gains and state-of-the-art results when ensembled with the zero-shot model. Our code is available at \\href{https://github.com/Surrey-UP-Lab/MERGETUNE}{https://github.com/Surrey-UP-Lab/MERGETUNE}.",
"arxiv_id": "2601.10497",
"authors": [
"Wenqing Wang",
"Da Li",
"Xiatian Zhu",
"Josef Kittler"
],
"categories": [
"cs.CV"
],
"license": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
"title": "mergetune: Continued fine-tuning of vision-language models",
"url": "https://arxiv.org/abs/2601.10497",
"version": "v1"
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