---
license: apache-2.0
base_model: Qwen/Qwen3-8B-Base
arvix: arxiv:2507.02279
tags:
  - pruning
  - layer-pruning
  - laco
  - compressed
  - qwen3
  - llm
  - efficient
library_name: transformers
pipeline_tag: text-generation
language:
  - en
  - zh
  - multilingual
datasets:
  - wikipedia
model-index:
  - name: Qwen3-8B-LaCo-Pruned
    results:
      - task:
          type: text-generation
          name: Text Generation
        dataset:
          name: HellaSwag
          type: hellaswag
        metrics:
          - type: accuracy_norm
            value: 48.52
            name: Accuracy (Normalized)
      - task:
          type: text-generation
          name: Text Generation
        dataset:
          name: PIQA
          type: piqa
        metrics:
          - type: accuracy_norm
            value: 65.67
            name: Accuracy (Normalized)
      - task:
          type: text-generation
          name: Text Generation
        dataset:
          name: BoolQ
          type: boolq
        metrics:
          - type: accuracy
            value: 61.77
            name: Accuracy
      - task:
          type: text-generation
          name: Text Generation
        dataset:
          name: MMLU
          type: mmlu
        metrics:
          - type: accuracy
            value: 25.12
            name: Accuracy (5-shot)
---

# Qwen3-8B-LaCo-Pruned

This model is a **layer-pruned** version of [Qwen3-8B-Base](https://huggingface.co/Qwen/Qwen3-8B-Base) using the [LaCo (Layer Collapse)](https://arxiv.org/abs/2402.11187) structured pruning method.

## Model Summary

| Attribute | Value |
|-----------|-------|
| **Base Model** | [Qwen/Qwen3-8B-Base](https://huggingface.co/Qwen/Qwen3-8B-Base) |
| **Pruning Method** | LaCo (Layer Collapse) |
| **Original Layers** | 36 |
| **Pruned Layers** | 26 |
| **Layers Removed** | 10 |
| **Compression** | 27.8% |
| **Parameters** | ~5.8B (reduced from ~8B) |

## Intended Use

- **Research** on model compression and efficiency
- **Fine-tuning base** for domain-specific applications
- **Inference optimization** where speed/memory matters more than factual accuracy
- **Edge deployment** scenarios with limited computational resources

## ⚠️ Important Limitations

This pruned model has **significantly reduced factual knowledge capabilities**. It performs at near-random levels on knowledge-intensive benchmarks like MMLU.

| Use Case | Status |
|----------|--------|
| Physical reasoning tasks | ✅ Good (82.6% retained) |
| Reading comprehension | ⚠️ Acceptable (74.3% retained) |
| Common sense reasoning | ⚠️ Degraded (61.8% retained) |
| Factual question answering | ❌ Not recommended |
| Knowledge-intensive tasks | ❌ Not recommended |

**Recommendation:** Fine-tune this model on your target domain before deployment.

---

## Pruning Details

### LaCo Hyperparameters

| Parameter | Value | Description |
|-----------|-------|-------------|
| MERGE_LAYERS (C) | 3 | Layers merged per operation |
| LOWEST_LAY (L) | 4 | Minimum layer index for merging |
| HIGHEST_LAY (H) | 28 | Maximum layer index for merging |
| INTERVAL (I) | 2 | Minimum gap between merge points |
| THRESHOLD (T) | 0.85 | Cosine similarity threshold |
| MAX_COMPRESSION | 30% | Maximum allowed compression |

### Pruning Statistics

| Metric | Value |
|--------|-------|
| Successful Merges | 5 |
| Rejected Merges | 0 |
| Total Iterations | 6 |
| Final Compression | 27.8% |

### Hidden State Similarity (Calibration Set)

| Metric | Value |
|--------|-------|
| Average | 0.9680 |
| Min | 0.9492 |
| Max | 0.9766 |

Individual similarities: `[0.9492, 0.9727, 0.9609, 0.9766, 0.9688, 0.9648, 0.9648, 0.9766, 0.9727, 0.9727]`

### Perplexity Results

| Model | Perplexity | Ratio |
|-------|------------|-------|
| Original (Qwen3-8B-Base) | 26.19 | 1.00× |
| Pruned (this model) | 71.48 | **2.73×** |

---

## Benchmark Results

### Comparison with Original Qwen3-8B-Base

| Benchmark | Original | Pruned | Retention | Status |
|-----------|----------|--------|-----------|--------|
| **PIQA** | 79.54% | 65.67% | 82.6% | ✅ Good |
| **BoolQ** | 83.09% | 61.77% | 74.3% | ⚠️ Acceptable |
| **HellaSwag** | 78.55% | 48.52% | 61.8% | ⚠️ Degraded |
| **MMLU (5-shot)** | 76.89% | 25.12% | 32.7% | ❌ Near random |

*Original scores from [Qwen3 Technical Report](https://arxiv.org/abs/2505.09388)*

### Key Findings

1. **Physical reasoning preserved:** PIQA retained 82.6% of original performance
2. **Factual knowledge destroyed:** MMLU collapsed to random-chance (25% for 4-way MCQ)
3. **Perplexity underestimates damage:** 2.73× PPL ratio doesn't predict the benchmark collapse
4. **Layer-specific knowledge:** Factual knowledge appears encoded in specific removed layers

---

## Usage

### Basic Inference

```python
from transformers import AutoModelForCausalLM, AutoTokenizer

model_name = "Mercity/Qwen3-8B-LaCo-Pruned"

tokenizer = AutoTokenizer.from_pretrained(model_name, trust_remote_code=True)
model = AutoModelForCausalLM.from_pretrained(
    model_name,
    torch_dtype="auto",
    device_map="auto",
    trust_remote_code=True
)

# Text generation
prompt = "The process of photosynthesis"
inputs = tokenizer(prompt, return_tensors="pt").to(model.device)
outputs = model.generate(**inputs, max_new_tokens=100, do_sample=True, temperature=0.7)
print(tokenizer.decode(outputs[0], skip_special_tokens=True))
```

### With 4-bit Quantization (Further Compression)

```python
from transformers import AutoModelForCausalLM, AutoTokenizer, BitsAndBytesConfig

quantization_config = BitsAndBytesConfig(
    load_in_4bit=True,
    bnb_4bit_compute_dtype="float16",
    bnb_4bit_quant_type="nf4",
)

model = AutoModelForCausalLM.from_pretrained(
    "Mercity/Qwen3-8B-LaCo-Pruned",
    quantization_config=quantization_config,
    device_map="auto",
    trust_remote_code=True
)
```

---

## Recovery Recommendations

To restore performance after pruning:

### Option 1: LoRA Fine-tuning (Recommended)
```python
from peft import LoraConfig, get_peft_model

lora_config = LoraConfig(
    r=32,
    lora_alpha=64,
    target_modules=["q_proj", "k_proj", "v_proj", "o_proj", 
                    "gate_proj", "up_proj", "down_proj"],
    lora_dropout=0.05,
)
model = get_peft_model(model, lora_config)
# Fine-tune on OpenOrca, Alpaca, or domain-specific data
```

### Option 2: Knowledge Distillation
Use original Qwen3-8B-Base as teacher to transfer knowledge back.

### Expected Recovery
- With fine-tuning: +15-25% on MMLU
- With knowledge distillation: +25-35% on MMLU

---

## Technical Specifications

| Attribute | Value |
|-----------|-------|
| Architecture | Transformer decoder-only |
| Parameters | ~5.8B |
| Layers | 26 |
| Hidden Size | 4096 |
| Attention Heads (Q) | 32 |
| Attention Heads (KV) | 8 (GQA) |
| Intermediate Size | 12288 |
| Vocabulary Size | 151,669 |
| Max Context Length | 32,768 tokens |
| Precision | bfloat16 |

---

## Citation

If you use this model, please cite the original LaCo paper and Qwen3:

```bibtex
@article{yang2024laco,
  title={LaCo: Large Language Model Pruning via Layer Collapse},
  author={Yang, Yifei and Cao, Zouying and Zhao, Hai},
  journal={arXiv preprint arXiv:2402.11187},
  year={2024}
}

@misc{qwen3technicalreport,
  title={Qwen3 Technical Report},
  author={Qwen Team},
  year={2025},
  eprint={2505.09388},
  archivePrefix={arXiv},
  primaryClass={cs.CL},
  url={https://arxiv.org/abs/2505.09388}
}
```

## References

- [LaCo Paper](https://arxiv.org/abs/2402.11187)
- [LaCo Official Implementation](https://github.com/yangyifei729/LaCo)
- [Qwen3 Technical Report](https://arxiv.org/abs/2505.09388)
- [Qwen3-8B-Base](https://huggingface.co/Qwen/Qwen3-8B-Base)

## License

Apache 2.0 (same as base Qwen3 model)

## Acknowledgments

- Qwen Team for the excellent Qwen3-8B-Base model
- LaCo authors for the pruning methodology
- Hugging Face for model hosting