hydra

Hydra

Hydra: Bidirectional State Space Models Through Generalized Matrix Mixers
Sukjun Hwang*, Aakash Lahoti*, Tri Dao, Albert Gu
Paper: https://arxiv.org/abs/2407.09941
Blogpost: https://goombalab.github.io/blog/2024/hydra-part1-matrix-mixer/

About

Installation

Follow the installation section of Mamba; simply,

pip install mamba-ssm

[Option] For training BERT (./hydra/bert), install additional required packages via

pip install -r requirements.txt

Usage

Hydra Block

The quasiseparable matrix mixer, Hydra, is our best model for bidirectional sequence processing (details in Section 3).
The implementation is at ./hydra/modules/hydra.py.

import torch
from .hydra import Hydra

batch, length, dim = 2, 64, 16
x = torch.randn(batch, length, dim).to("cuda")
model = Hydra(
    d_model=dim, # Model dimension d_model
    d_state=64,  # SSM state expansion factor
    d_conv=7,    # Local non-causal convolution width
    expand=2,    # Block expansion factor
).to("cuda")
y = model(x)
assert y.shape == x.shape

Matrix Mixer Block

The matrix mixer framework is implemented at ./hydra/modules/matrix_mixer.py.
You can easily integrate your own mixer matrix by following our implementations of various sequence mixers located at ./hydra/modules/matrix_mixers/!

from .hydra import MatrixMixer

model = MatrixMixer(
    """
    matrix_mixer_type: options for matrix_mixer_type
        {'dense', 'toeplitz', 'vandermonde', 'cauchy', 'low_rank', 'attention', 'quasiseparable'}
    is_data_dependent: boolean flag to parameterize the mixer matrix to SAM
    """
    matrix_mixer_type=matrix_mixer_type,
    is_data_dependent=is_data_dependent,
    d_model=dim,    # Model dimension d_model
    qk_dim=qk_dim,  # dimension for QK
).to("cuda")
y = model(x)
assert y.shape == x.shape

BERT

Our code for training BERT (./hydra/bert/) is based on MosaicBERT and M2.

Follow the instructions of MosaicBERT (./hydra/bert/README.md) for details (e.g., setting up dataset and running code).
The default configurations for Hydra and MatrixMixer are located at:

• Pretrain: ./hydra/bert/yamls/pretrain
• Finetune: ./hydra/bert/yamls/finetune

Example commands:

Pretrain Hydra on C4 using a single GPU:

python main.py yamls/pretrain/hydra.yaml

Pretrain Hydra on C4 using 8 GPUs:

composer -n 8 main.py yamls/pretrain/hydra.yaml

Finetune Hydra on GLUE:

python glue.py yamls/finetune/hydra.yaml

Acknowledgement

We thank the authors of Mamba, MosaicBERT, and M2 for their wonderful codebases.

Citation

If you use this codebase, or otherwise find our work valuable, please cite Hydra:

@article{hydra,
  title={Hydra: Bidirectional State Space Models Through Generalized Matrix Mixers},
  author={Hwang, Sukjun and Lahoti, Aakash and Dao, Tri and Gu, Albert},
  journal={arXiv preprint arXiv:2407.09941},
  year={2024}
}