---
library_name: transformers
pipeline_tag: zero-shot-image-classification
tags:
- vision
- uncertainty
- hyperbolic
---

# UNCHA: Uncertainty-guided Compositional Hyperbolic Alignment

## Overview

UNCHA is a hyperbolic vision-language model that improves part–whole compositional understanding by modeling **semantic representativeness as uncertainty**.


Unlike conventional vision-language models, UNCHA explicitly captures the fact that:

* Not all parts contribute equally to representing a scene
* Some regions (e.g., main objects) are more informative than others

To address this, UNCHA introduces **uncertainty-aware alignment in hyperbolic space**, enabling better hierarchical and compositional reasoning.

- **Project Page:** [https://jeeit17.github.io/UNCHA-project_page/](https://jeeit17.github.io/UNCHA-project_page/)
- **Paper:** [Uncertainty-guided Compositional Alignment with Part-to-Whole Semantic Representativeness in Hyperbolic Vision-Language Models](https://arxiv.org/abs/2603.22042)
- **Code:** [https://github.com/jeeit17/UNCHA](https://github.com/jeeit17/UNCHA)

--- 
## Download 

```python
from huggingface_hub import snapshot_download

repo_path = snapshot_download("hayeonkim/uncha")

print("Repo downloaded to:", repo_path)
```

---

## Key Idea

UNCHA models **part-to-whole semantic representativeness** using uncertainty:

* **Low uncertainty** → highly representative part
* **High uncertainty** → less informative / noisy part

This uncertainty is integrated into:

* **Contrastive loss** → adaptive temperature scaling
* **Entailment loss** → calibrated hierarchical structure with entropy regularization

This leads to improved alignment in hyperbolic embedding space and stronger compositional reasoning.

---

## Model Details

* Architecture: Hyperbolic Vision-Language Model
* Backbone: ViT-S/16 or ViT-B/16
* Training data: GRIT dataset (20.5M pairs, 35.9M part annotations)

---

## Performance

UNCHA achieves strong performance across multiple tasks:

### Zero-shot classification (ViT-B/16)

| Method | ImageNet | CIFAR-10 | CIFAR-100 | SUN397 | Caltech-101 | STL-10 |
|--------|:--------:|:--------:|:---------:|:------:|:-----------:|:------:|
| CLIP   | 40.6 | 78.9 | 48.3 | 43.0 | 70.7 | 92.4 |
| MERU   | 40.1 | 78.6 | 49.3 | 43.0 | 73.0 | 92.8 |
| HyCoCLIP | 45.8 | 88.8 | 60.1 | 57.2 | 81.3 | 95.0 |
| **UNCHA (Ours)** | **48.8** | **90.4** | **63.2** | **57.7** | **83.9** | **95.7** |

### Multi-object representation (ViT-B/16, mAP)

| Method | ComCo 2obj | ComCo 5obj | SimCo 2obj | SimCo 5obj | VOC | COCO |
|--------|:----------:|:----------:|:----------:|:----------:|:---:|:----:|
| CLIP   | 77.55 | 80.22 | 77.15 | 88.48 | 78.56 | 53.94 |
| HyCoCLIP | 72.90 | 72.90 | 75.71 | 82.85 | 80.43 | 58.12 |
| **UNCHA (Ours)** | **77.92** | **81.18** | **79.72** | **90.65** | **82.14** | **59.43** |


---

## Training

Training requires preprocessing GRIT dataset:

```bash
python utils/prepare_GRIT_webdataset.py \
    --raw_webdataset_path datasets/train/GRIT/raw \
    --processed_webdataset_path datasets/train/GRIT/processed
```

Then run:

```bash
./scripts/train.sh \
    --config configs/train_uncha_vit_b.py \
    --num-gpus 4
```

---

## 📈 Evaluation

### Zero-shot classification

```bash
python scripts/evaluate.py \
    --config configs/eval_zero_shot_classification.py \
    --checkpoint-path /path/to/ckpt
```

### Retrieval

```bash
python scripts/evaluate.py \
    --config configs/eval_zero_shot_retrieval.py \
    --checkpoint-path /path/to/ckpt
```

---

## Citation

```bibtex
@inproceedings{kim2026uncha,
  author    = {Kim, Hayeon and Jang, Ji Ha and Kim, Junghun James and Chun, Se Young},
  title     = {UNCHA: Uncertainty-guided Compositional Alignment with Part-to-Whole Semantic Representativeness in Hyperbolic Vision-Language Models},
  booktitle = {CVPR},
  year      = {2026},
}
```
---

## Acknowledgements

This work is supported by IITP, NRF, MSIT, and Seoul National University programs.
We also acknowledge prior works including MERU, HyCoCLIP, and ATMG.