README.md

---
license: apache-2.0
library_name: transformers
pipeline_tag: image-classification
---

# Model Merging with Functional Dual Anchors

This repository is the official PyTorch implementation of the paper "[Model Merging with Functional Dual Anchors](https://huggingface.co/papers/2510.21223)", by Kexuan Shi, Yandong Wen, Weiyang Liu.

**Functional Dual Anchors (FDAs)** propose a novel framework for efficiently integrating knowledge from multiple fine-tuned checkpoints of a shared foundation model. Unlike existing methods that operate in the parameter space, FDAs model knowledge in the input-representation space. FDAs are synthetic inputs whose induced gradients align with task vectors, capturing task-specific functional shifts relative to the pre-trained model. This perspective bridges joint multi-task training and post-hoc merging, offering both robustness and flexibility across various tasks, including vision, natural language processing, and natural language generation.

<p align="center">
  <img src="https://github.com/Sphere-AI-Lab/fda/raw/main/docs/assets/framework_trajectory.png" width="90%" />
</p>

You can find more details on the [project page](https://spherelab.ai/fda/) and in the [official GitHub repository](https://github.com/Sphere-AI-Lab/fda/tree/main).

## 🚀 Quick Start

The official GitHub repository provides detailed instructions for setting up the environment, downloading checkpoints and corresponding FDAs, and running adaptation/construction scripts.

For vision, NLP, and NLG tasks, the framework leverages base models such as `RoBERTa` and `Llama-2` from Hugging Face.

### Checkpoints and Corresponding FDAs

The checkpoints for vision, NLP, and NLG tasks and their corresponding FDAs are available for download via the [official GitHub repository](https://github.com/Sphere-AI-Lab/fda/tree/main). Specifically, vision and NLU FDAs are hosted on Hugging Face: [fda_for_vision](https://huggingface.co/datasets/SphereLab/FDA_for_Vision) and [fda_for_nlu](https://huggingface.co/datasets/SphereLab/FDA_for_NLU/tree/main).

### Environment

For Vision and NLP tasks, the environment can be installed by:
```bash
cd FDA/Vision #cd FDA/NLU
# Create conda environment
conda env create -f environment.yaml
# Activate environment
conda activate fda
```
For NLG tasks, please use: ```NLG/environment.yaml```

### Adapt by FDAs

Please follow the path comments in the code file ```adapt.py```, replace them with the paths to your local checkpoints and FDAs, and then run the following commands to reproduce the FDA adaptation results:
```bash
cd FDA/Vision #cd FDA/NLU cd FDA/NLG
sh adapt.sh
```

For models in NLG tasks, please split the model first:
```bash
cd FDA/NLG
python split_model.py
```

### Construct FDAs

If you want to construct FDAs for your finetuned checkpoint, please follow the path comments in the code file ```construct_fda.py```, replace them with the paths to your finetuned checkpoints. Then,
```bash
sh construct.sh
```

## Citation
If you find this work useful, please consider citing:

```bibtex
@article{shi2025modelmergingfunctionaldual,
  title     = {Model Merging with Functional Dual Anchors},
  author    = {Shi, Kexuan and Wen, Yandong and Liu, Weiyang},
  year      = {2025},
  journal   = {arXiv preprint arXiv:2510.21223},
  archivePrefix = {arXiv},
  primaryClass  = {cs.LG},
  url       = {https://arxiv.org/abs/2510.21223}
}
```