---
library_name: peft
base_model: google/gemma-3-4b-it
language:
- nso
- en
tags:
- translation
- african-languages
- scientific-translation
- afriscience-mt
- lora
- peft
- gemma
license: apache-2.0
pipeline_tag: translation
model-index:
- name: gemma_3_4b_it-lora-r16-nso-eng
  results:
  - task:
      type: translation
    metrics:
    - name: BLEU (test)
      type: bleu
      value: 37.07
    - name: chrF (test)
      type: chrf
      value: 57.33
    - name: SSA-COMET (test)
      type: comet
      value: 65.06
---

# gemma_3_4b_it-lora-r16-nso-eng

[![Model on HF](https://huggingface.co/datasets/huggingface/badges/raw/main/model-on-hf-sm.svg)](https://huggingface.co/AfriScience-MT/gemma_3_4b_it-lora-r16-nso-eng)

This is a **LoRA adapter** for the AfriScience-MT project, enabling efficient scientific machine translation for African languages.

## Adapter Description

| Property | Value |
|----------|-------|
| **Base Model** | [google/gemma-3-4b-it](https://huggingface.co/google/gemma-3-4b-it) |
| **Translation Direction** | Northern Sotho → English |
| **LoRA Rank (r)** | 16 |
| **LoRA Alpha** | 32 |
| **Training Method** | QLoRA (4-bit quantization) |
| **Domain** | Scientific/Academic texts |

### Why LoRA?

LoRA (Low-Rank Adaptation) enables efficient fine-tuning by training only a small number of additional parameters. This adapter adds only **~8.0M parameters** to the base model while achieving strong translation performance.

## Evaluation Results

Performance on the AfriScience-MT test set:

| Split | BLEU | chrF | SSA-COMET |
|-------|------|------|-----------|
| Validation | 41.69 | 61.46 | 66.46 |
| **Test** | **37.07** | **57.33** | **65.06** |

**Metrics explanation:**
- **BLEU**: Measures n-gram overlap with reference translations (0-100, higher is better)
- **chrF**: Character-level F-score, robust for morphologically rich languages (0-100, higher is better)
- **SSA-COMET**: Neural metric trained for Sub-Saharan African languages, shown as percentage (0-100, higher is better) ([McGill-NLP/ssa-comet-stl](https://huggingface.co/McGill-NLP/ssa-comet-stl))

## Usage

### Quick Start

```python
from transformers import AutoModelForCausalLM, AutoTokenizer, BitsAndBytesConfig
from peft import PeftModel
import torch

# Configure 4-bit quantization (recommended for memory efficiency)
bnb_config = BitsAndBytesConfig(
    load_in_4bit=True,
    bnb_4bit_compute_dtype=torch.bfloat16,
    bnb_4bit_quant_type="nf4",
    bnb_4bit_use_double_quant=True,
)

# Load base model
base_model = AutoModelForCausalLM.from_pretrained(
    "google/gemma-3-4b-it",
    quantization_config=bnb_config,
    device_map="auto",
    torch_dtype=torch.bfloat16,
)
tokenizer = AutoTokenizer.from_pretrained("google/gemma-3-4b-it")

# Load LoRA adapter
adapter_name = "AfriScience-MT/gemma_3_4b_it-lora-r16-nso-eng"
model = PeftModel.from_pretrained(base_model, adapter_name)
model.eval()

# Prepare translation prompt
source_text = "Climate change significantly impacts agricultural productivity in sub-Saharan Africa."
instruction = "Translate the following Northern Sotho scientific text to English."

# Format for Gemma chat template
messages = [{"role": "user", "content": f"{instruction}\n\n{source_text}"}]
prompt = tokenizer.apply_chat_template(messages, tokenize=False, add_generation_prompt=True)

# Generate translation
inputs = tokenizer(prompt, return_tensors="pt").to(model.device)
with torch.no_grad():
    outputs = model.generate(
        **inputs,
        max_new_tokens=256,
        num_beams=5,
        early_stopping=True,
        pad_token_id=tokenizer.pad_token_id,
    )

# Decode only the generated part
generated = outputs[0][inputs["input_ids"].shape[1]:]
translation = tokenizer.decode(generated, skip_special_tokens=True)
print(translation)
```

### Without Quantization (Full Precision)

```python
# For GPUs with sufficient memory (>24GB for larger models)
base_model = AutoModelForCausalLM.from_pretrained(
    "google/gemma-3-4b-it",
    device_map="auto",
    torch_dtype=torch.bfloat16,
)
model = PeftModel.from_pretrained(base_model, "AfriScience-MT/gemma_3_4b_it-lora-r16-nso-eng")
```

## Training Details

### Hyperparameters

| Parameter | Value |
|-----------|-------|
| LoRA Rank (r) | 16 |
| LoRA Alpha | 32 |
| LoRA Dropout | 0.05 |
| Target Modules | q_proj, k_proj, v_proj, o_proj, gate_proj, up_proj, down_proj |
| Epochs | 3 |
| Batch Size | 2 |
| Learning Rate | 2e-04 |
| Max Sequence Length | 512 |
| Gradient Accumulation | 4 |

### Hardware Requirements

| Configuration | VRAM Required |
|---------------|---------------|
| 4-bit (QLoRA) | ~8-12 GB |
| 8-bit | ~16-20 GB |
| Full precision | ~24-40 GB |


## Reproducibility

To reproduce this adapter:

```bash
# Clone the AfriScience-MT repository
git clone https://github.com/afriscience-mt/afriscience-mt.git
cd afriscience-mt

# Install dependencies
pip install -r requirements.txt

# Run LoRA training
python -m afriscience_mt.scripts.run_lora_training \
    --data_dir ./data \
    --source_lang nso \
    --target_lang eng \
    --model_name google/gemma-3-4b-it \
    --model_type gemma \
    --lora_rank 16 \
    --output_dir ./output \
    --num_epochs 3 \
    --batch_size 4 \
    --load_in_4bit
```

## Limitations

- **Domain Specificity**: Optimized for scientific/academic texts; may underperform on casual or colloquial language.
- **Language Direction**: Only supports Northern Sotho → English translation.
- **Base Model Required**: Must be used with the [google/gemma-3-4b-it](https://huggingface.co/google/gemma-3-4b-it) base model.
- **Context Length**: Maximum context is model-dependent; longer texts should be chunked.

## Citation

If you use this adapter, please cite the AfriScience-MT project:

```bibtex
@inproceedings{afriscience-mt-2025,
  title={AfriScience-MT: Machine Translation for African Scientific Literature},
  author={AfriScience-MT Team},
  year={2025},
  url={https://github.com/afriscience-mt/afriscience-mt}
}
```

## License

This adapter is released under the [Apache 2.0 License](https://www.apache.org/licenses/LICENSE-2.0).

## Acknowledgments

- Base model: [google/gemma-3-4b-it](https://huggingface.co/google/gemma-3-4b-it)
- LoRA implementation: [PEFT](https://github.com/huggingface/peft)
- Evaluation: [SSA-COMET](https://huggingface.co/McGill-NLP/ssa-comet-stl) for African language assessment