Qwen3.5-0.65B-Base-Rearchitected

Model Description

This model is a surgically optimized and distilled version of Qwen3.5-0.8B-Base, created with the techniques covered in Chapter 6 in the book "Rearchitecting LLMs".

• Book: Rearchitecting LLMs
• Framework: OptiPFair
• Technique: Depth Pruning + Knowledge Distillation (Labels-Only with Skew KL Divergence)
• Chapter: Chapter 6 - Knowledge Recovery

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Performance & Retention Metrics

The goal of this optimization was twofold: to maximize parameter efficiency through structural pruning, and to perform a stylistic domain adaptation to the Cosmopedia dataset while retaining the Teacher's core reasoning capabilities.

Retention Summary (vs Teacher Baseline)

Metric	Value	Description
PPL Retention	109.62%	Linguistic quality preserved (Teacher PPL / Student PPL × 100)
Capabilities Retention	89.21%	Reasoning power retained across benchmarks (Avg Student / Avg Teacher × 100)
Overall Retention	92.11%	Combined health score (average of PPL + Capabilities retention)

Capability Benchmarks (LM Evaluation Harness)

Recovery = How much of the pruning degradation was recovered through distillation.

Benchmark	Teacher	Pruned (No KD)	(After KD)
Arc Easy	67.5%	56.3%	60.7%
Winogrande	59.4%	55.5%	55.9%
Hellaswag	54.9%	44.0%	47.2%
Lambada Openai	50.9%	8.4%	39.9%
Piqa	71.5%	63.6%	67.7%
Average	60.8%	45.5%	54.3%

Linguistic Quality

• Final Perplexity (PPL): 6.70
• Teacher Baseline PPL: 7.34
• Pruned (No KD) PPL: 24.29

Note on Perplexity: The Student achieves a lower (better) PPL than the Teacher. This highlights the Domain Adaptation effect of the distillation process. The Student successfully specialized in the tone and structure of the Cosmopedia training corpus, refining its style while recovering structural knowledge.

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Architecture Details

• Teacher Model: Qwen3.5-0.8B-Base (752,393,024 parameters)
• Student Model: Pruned to (666,171,584 parameters)
• Layers Removed: 4 Tranformer blocks removed (indices: [21, 20, 9, 22])
• Parameter Reduction: 11.46%

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Training Procedure

Dataset

• Source: Cosmopedia-v2
• Samples: 40,000 (balanced across 4 subsets: stories, wikihow, openstax, web_samples)
• Train/Val Split: 80% / 20%

Hyperparameters

• Epochs: 1
• Batch Size: 12 (effective: 48 with gradient accumulation)
• Learning Rate: 4e-05
• Loss Function: α·CrossEntropy + β·Skew-KLD
  • Task Loss Weight (α): 0.5
  • Logits Loss Weight (β): 0.5
  • Skew Interpolation Factor: 0.0
  • Temperature: 2.0
• Optimizer: AdamW
• Gradient Clipping: 1.0

Hardware & Training Time

• GPU: NVIDIA A100-SXM4-80GB
• Training Time: 4011.1s (66.85 minutes)
• Avg Time per Epoch: 4011.1s

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How to Use

from transformers import AutoModelForCausalLM, AutoTokenizer

# Load model and tokenizer
model_id = "oopere/Qwen3.5-0.65B-Base-Rearchitected"
tokenizer = AutoTokenizer.from_pretrained(model_id)
model = AutoModelForCausalLM.from_pretrained(model_id)

# Generate text
prompt = "Paris is the capital of"
inputs = tokenizer(prompt, return_tensors="pt")
outputs = model.generate(
    **inputs,
    max_new_tokens=50,
    do_sample=False,
    num_beams=3
)
print(tokenizer.decode(outputs[0], skip_special_tokens=True))

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Limitations & Intended Use

Intended Use

This is an educational model created as part of the Hands-on Lab in Chapter 6 of "Rearchitecting LLMs". It demonstrates:

• Surgical depth pruning using data-driven layer importance analysis
• Knowledge recovery through labels-only distillation with Skew KL Divergence
• The complete optimization pipeline: Prune → Distill → Evaluate

Not intended for production use. This model serves as a learning artifact and baseline for readers to improve upon.

Limitations

• Training Data: General-purpose Cosmopedia corpus (not domain-specialized)
• Knowledge Coverage: Reduced compared to full-scale models due to structural pruning
• Capabilities: Best suited for simple completion tasks; complex reasoning may be degraded
• Language: English only

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Citation

If you use this model or the techniques described in your research or projects, please cite:

Book

@book{martra2026rearchitecting,
  author    = {Pere Martra},
  title     = {Rearchitecting LLMs: Structural techniques for efficient models},
  publisher = {Manning Publications},
  year      = {2026},
  url       = {https://hubs.la/Q040tvtp0}
}

Framework

@software{optipfair2024,
  author = {Pere Martra},
  title  = {OptiPFair: Structural Pruning and Bias Analysis for LLMs},
  year   = {2024},
  url    = {https://github.com/peremartra/optipfair}
}

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Acknowledgments

This model was created following the methodologies taught in "Rearchitecting LLMs" (Manning Publications, 2026). Special thanks to the Manning editorial team and the open-source community behind Hugging Face Transformers and PyTorch.

Challenge for readers: Can you improve the retention metrics beyond 92.1%? Try adjusting:

• Layer selection strategy (use cosine similarity analysis)
• Distillation dataset (domain-specific data)
• Loss function weights (α, β, temperature)
• Training epochs and learning rate

Share your results in the book's discussion forum!