🔄 LieRE: Generalizing Rotary Position Encodings

🔍 Overview

While Rotary Position Embeddings (RoPE) have become widely adopted for large language models, their application across other modalities has been limited. This repository introduces Lie group Relative position Encodings (LieRE), which extends beyond RoPE to support n-dimensional inputs.

<p align="center"> <img src="liere_sketch.png" alt="LieRE Overview" width="80%"/> </p>

📈 Performance Highlights

LieRE demonstrates significant improvements compared to baselines (DeiT III, RoPE-Mixed, and Vision-Llama):

• 🎯 Accuracy: Up to 9.7% increase for 2D tasks and 25.5% for 3D tasks compared to DeiT III (absolute position encoding)
• ⚡ Training Efficiency: 3.5x reduction in training time compared to DeiT III (absolute position encoding)
• 📊 Data Efficiency: 30% improvement in data utilization compared to DeiT III (absolute position encoding)

Checkpoints

[08/12/2025] Update: We made the checkpoints available at huggingface. Let us know if you find something new and exciting about them!

💻 Implementation Details

LieRE represents rotation matrices as the matrix exponential of skew-symmetric matrices, making them learnable by parametrizing the rotations with generators before applying the matrix exponential.

# Core Implementation
generator_raw_params = nn.Parameter(
    torch.rand(
        input_dimensionality,
        head_dim,
        head_dim,
    ) * 2 * math.pi
)
upper_triangle = (
    torch.triu(generator_raw_params, diagonal=1)
)
skew_bases = upper_triangle - torch.transpose(upper_triangle, -1, -2)
in_basis_positions = (
    positions.reshape(list(positions.shape) + [1] * 2) * skew_bases
)
generator_pos = torch.sum(in_basis_positions, dim=-3)
rotation = torch.matrix_exp(generator_pos.to(dtype=torch.float32)).to(dtype=positions.dtype)

🚀 Getting Started

📦 Dependencies

• PyTorch >= 1.7.0
• PyTorch Lightning
• torchvision

🔧 Installation

git clone https://github.com/yourusername/liere-position-encodings.git
cd liere-position-encodings
pip install -r requirements.txt

🏃‍♂️ Usage

To reproduce the CIFAR-100 results, use:

./lightning_cifar100.sh

You can switch between different position encoding methods in the lightning_cifar100.sh by using the following options:

• liere: Our proposed method
• rope_mixed: RoPE-Mixed baseline
• absolute: Standard absolute position encoding
• visionllama: Vision-Llama encoding

🧩 Base Repository

This implementation builds upon the transformer implementation and hyperparameters from vision-transformers-cifar10.

📝 Citation

If you find this work useful, please cite:

@article{ostmeier2024liere,
  title={LieRE: Generalizing Rotary Position Encodings},
  author={Ostmeier, Sophie and Axelrod, Brian and Moseley, Michael E and Chaudhari, Akshay and Langlotz, Curtis},
  journal={arXiv preprint arXiv:2406.10322},
  year={2024}
}

⚖️ License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgments

• Much of the code was branched from vision-transformers-cifar10
• Thanks to all contributors and supporters of this research