# SODA-VEC Negative Sampling: Biomedical Sentence Embeddings

## Model Overview

**SODA-VEC Negative Sampling** is a specialized sentence embedding model trained on 26.5M biomedical text pairs using the MultipleNegativesRankingLoss from sentence-transformers. This model is optimized for biomedical and life sciences applications, providing high-quality semantic representations for scientific literature.

## Key Features

- 🧬 **Biomedical Specialization**: Trained exclusively on PubMed abstracts and titles
- 🔬 **Large Scale**: 26.5M training pairs from complete PubMed baseline (July 2024)
- ⚡ **Modern Architecture**: Based on ModernBERT-embed-base with 768-dimensional embeddings
- 🎯 **Negative Sampling**: Uses standard MultipleNegativesRankingLoss for robust contrastive learning
- 📊 **Production Ready**: Optimized training with FP16, gradient clipping, and cosine scheduling

## Model Details

### Base Model
- **Architecture**: ModernBERT-embed-base (nomic-ai/modernbert-embed-base)
- **Embedding Dimension**: 768
- **Max Sequence Length**: 768 tokens
- **Parameters**: ~110M

### Training Configuration
- **Loss Function**: MultipleNegativesRankingLoss (sentence-transformers)
- **Training Data**: 26,473,900 biomedical text pairs
- **Epochs**: 3
- **Effective Batch Size**: 256 (32 per GPU × 4 GPUs × 2 gradient accumulation)
- **Learning Rate**: 1e-5 with cosine scheduling
- **Optimization**: AdamW with weight decay (0.01)
- **Precision**: FP16 for efficiency
- **Hardware**: 4x Tesla V100-DGXS-32GB

## Dataset

### Source Data
- **Origin**: Complete PubMed baseline (July 2024)
- **Content**: Scientific abstracts and titles from biomedical literature
- **Quality**: 99.7% retention after filtering (128-6,000 character abstracts)
- **Splits**: 99.6% train / 0.2% validation / 0.2% test

### Data Processing
- Error pattern removal and quality filtering
- Balanced train/validation/test splits
- Character length filtering for optimal training
- Duplicate detection and removal

## Performance & Use Cases

### Intended Applications
- **Literature Search**: Semantic search across biomedical publications
- **Research Discovery**: Finding related papers and concepts
- **Knowledge Mining**: Extracting relationships from scientific text
- **Document Classification**: Categorizing biomedical documents
- **Similarity Analysis**: Comparing research abstracts and papers

### Biomedical Domains
- Molecular Biology
- Clinical Medicine
- Pharmacology
- Genetics & Genomics
- Biochemistry
- Neuroscience
- Public Health

## Usage

### Installation
```bash
pip install sentence-transformers
```

### Basic Usage
```python
from sentence_transformers import SentenceTransformer

# Load the model
model = SentenceTransformer('EMBO/soda-vec-negative-sampling')

# Encode biomedical texts
texts = [
    "CRISPR-Cas9 gene editing in human embryos",
    "mRNA vaccine efficacy against COVID-19 variants",
    "Protein folding mechanisms in neurodegenerative diseases"
]

embeddings = model.encode(texts)
print(f"Embeddings shape: {embeddings.shape}")  # (3, 768)
```

### Semantic Search
```python
import numpy as np
from sklearn.metrics.pairwise import cosine_similarity

# Query and corpus
query = "Alzheimer's disease biomarkers"
corpus = [
    "Tau protein aggregation in neurodegeneration",
    "COVID-19 vaccine development strategies", 
    "Beta-amyloid plaques in dementia patients"
]

# Encode
query_embedding = model.encode([query])
corpus_embeddings = model.encode(corpus)

# Find most similar
similarities = cosine_similarity(query_embedding, corpus_embeddings)[0]
best_match = np.argmax(similarities)
print(f"Best match: {corpus[best_match]} (similarity: {similarities[best_match]:.3f})")
```

## Training Details

### Loss Function
The model uses **MultipleNegativesRankingLoss**, which:
- Treats all other samples in a batch as negatives
- Optimizes for high similarity between related texts
- Provides robust contrastive learning without explicit negative sampling
- Well-established in sentence-transformers ecosystem

### Training Process
- **Duration**: ~4 days on 4x V100 GPUs
- **Steps**: 310,239 total training steps
- **Evaluation**: Every 1000 steps (310 evaluations, 1.8% overhead)
- **Monitoring**: Real-time TensorBoard logging
- **Checkpointing**: Model saved at end of each epoch

### Optimization Features
- Gradient clipping (max_norm=5.0) for training stability
- Weight decay regularization for generalization
- Cosine learning rate scheduling
- Loss-only evaluation for efficiency
- Reproducible training (seed=42)

## Technical Specifications

### Hardware Requirements
- **Training**: 4x Tesla V100-DGXS-32GB (recommended)
- **Inference**: Any GPU with 4GB+ VRAM, or CPU
- **Memory**: ~2GB GPU memory for inference

### Software Dependencies
- sentence-transformers >= 2.0.0
- transformers >= 4.20.0
- torch >= 1.12.0
- Python >= 3.8

## Comparison with SODA-VEC (VICReg)

| Feature | SODA-VEC (VICReg) | SODA-VEC Negative Sampling |
|---------|-------------------|----------------------------|
| Loss Function | VICReg (custom biomedical) | MultipleNegativesRankingLoss |
| Optimization | Empirically tuned coefficients | Standard contrastive learning |
| Training Data | Same (26.5M pairs) | Same (26.5M pairs) |
| Use Case | Biomedical research focus | General semantic similarity |
| Framework | Custom implementation | sentence-transformers standard |

## Limitations

- **Domain Specificity**: Optimized for biomedical text, may not generalize to other domains
- **Language**: English-only training data
- **Recency**: Training data cutoff at July 2024
- **Bias**: May reflect biases present in PubMed literature

## Citation

If you use this model in your research, please cite:

```bibtex
@misc{soda-vec-negative-sampling-2024,
  title={SODA-VEC Negative Sampling: Biomedical Sentence Embeddings},
  author={EMBO},
  year={2024},
  url={https://huggingface.co/EMBO/soda-vec-negative-sampling},
  note={Trained on 26.5M PubMed text pairs using MultipleNegativesRankingLoss}
}
```

## License

This model is released under the same license as the base ModernBERT model. Please refer to the original model card for licensing details.

## Acknowledgments

- **Base Model**: nomic-ai/modernbert-embed-base
- **Training Framework**: sentence-transformers
- **Data Source**: PubMed/MEDLINE database
- **Infrastructure**: EMBO computational resources

## Model Card Contact

For questions about this model, please contact EMBO or open an issue in the associated repository.

---

**Last Updated**: August 2024  
**Model Version**: 1.0  
**Training Completion**: In Progress (ETA: 4 days)