Q-SS-0.5B-Reasoning-Math

A compact, fast, and structured mathematical reasoning model — built to think before it answers.

Q-SS-0.5B-Reasoning-Math is a fine-tuned version of Qwen/Qwen2.5-0.5B-Instruct, trained using Group Relative Policy Optimization (GRPO) reinforcement learning — the same technique behind DeepSeek-R1. The model is designed to reason explicitly and transparently through mathematical problems before producing a clean, parseable final answer.

💾 Looking for the lightweight CPU version? See Q-SS-0.5B-Reasoning-Math-GGUF for the Q4_K_M quantized model (~300MB).

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✨ Highlights

• 🧠 Thinks out loud — explicit step-by-step reasoning inside <thought> tags before every answer
• 🎯 Clean structured output — final answer always isolated in <answer> tags, trivial to parse
• 🔁 RL-trained — learned through reward signals, not just imitation
• 🔧 Fine-tunable — full FP16 weights, ready for further training or fine-tuning
• 🔓 Apache 2.0 — free for personal and commercial use

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📋 Model Details

Property	Details
Model Name	Q-SS-0.5B-Reasoning-Math
Base Model	Qwen/Qwen2.5-0.5B-Instruct
Parameters	500M
Training Method	SFT Warm-up + GRPO Reinforcement Learning
Trained On	GSM8K + OpenR1-Math-220k
Precision	FP16 (merged, no adapter needed)
License	Apache 2.0
Developer	Saad Salman

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💬 Output Format

Every response follows this strict structure:

<thought>
[Step-by-step reasoning and calculations]
</thought>
<answer>
[Final numerical answer only]
</answer>

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🚀 Quick Start

from transformers import AutoModelForCausalLM, AutoTokenizer
import torch

model_name = "saadxsalman/Q-SS-0.5B-Reasoning-Math"

tokenizer = AutoTokenizer.from_pretrained(model_name)
model = AutoModelForCausalLM.from_pretrained(
    model_name,
    torch_dtype = torch.float16,
    device_map  = "auto",
)

SYSTEM_PROMPT = \"\"\"You are a mathematical reasoning engine.
Solve the problem step-by-step inside <thought> tags, then give ONLY the
final numerical or LaTeX result inside <answer> tags.

<thought>
[Your internal reasoning and calculations here]
</thought>
<answer>
[Final answer only]
</answer>\"\"\"

def solve(problem):
    messages = [
        {"role": "system", "content": SYSTEM_PROMPT},
        {"role": "user",   "content": problem},
    ]
    inputs = tokenizer.apply_chat_template(
        messages,
        tokenize              = True,
        add_generation_prompt = True,
        return_tensors        = "pt",
    ).to(model.device)

    with torch.no_grad():
        outputs = model.generate(
            input_ids      = inputs,
            max_new_tokens = 384,
            temperature    = 0.1,
            do_sample      = True,
            pad_token_id   = tokenizer.eos_token_id,
        )

    response = tokenizer.decode(outputs[0], skip_special_tokens=True)
    if "<answer>" in response:
        return response.split("<answer>")[-1].split("</answer>")[0].strip()
    return response

print(solve("Janet has 3 cats. Each cat eats 2 cans of food per day. How many cans does she need for 7 days?"))
# Output: 42

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📝 Example Outputs

Problem: Janet has 3 cats. Each cat eats 2 cans of food per day. How many cans does she need for 7 days?

<thought>
Each cat eats 2 cans per day.
Janet has 3 cats, so they eat 3 × 2 = 6 cans per day together.
For 7 days: 6 × 7 = 42 cans total.
</thought>
<answer>
42
</answer>

Problem: Tom has $50. He buys a book for $12 and a pen for $3. How much money does he have left?

<thought>
Tom starts with $50.
He spends $12 on a book and $3 on a pen.
Total spent: 12 + 3 = $15.
Money remaining: 50 - 15 = $35.
</thought>
<answer>
35
</answer>

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✅ What It's Good At

Problem Type	Support
Basic arithmetic	✅ Reliable
Multi-step word problems	✅ Reliable
Problems with units and currency	✅ Reliable
Basic algebra	⚠️ Partial
Competition math (AMC/AIME)	❌ Beyond capacity

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📦 Related Models

Repo	Format	Size	Best For
Q-SS-0.5B-Reasoning-Math	FP16	~988MB	GPU inference & further fine-tuning
Q-SS-0.5B-Reasoning-Math-GGUF	Q4_K_M	~300MB	Local CPU inference

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⚠️ Limitations

• Optimized for English language math problems only
• Complex abstract reasoning, geometry, and calculus are beyond reliable capacity at 0.5B scale
• Always verify critical calculations — the model may occasionally produce confident but incorrect answers

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🙏 Acknowledgements

• Unsloth — efficient fine-tuning framework
• Qwen Team — Qwen2.5-0.5B-Instruct base model
• HuggingFace TRL — GRPO implementation
• OpenR1 — OpenR1-Math-220k dataset
• OpenAI — GSM8K dataset

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📄 Citation

@misc{qss-reasoning-math-2025,
  author       = {Saad Salman},
  title        = {Q-SS-0.5B-Reasoning-Math},
  year         = {2025},
  publisher    = {HuggingFace},
  howpublished = {\\url{https://huggingface.co/saadxsalman/Q-SS-0.5B-Reasoning-Math}},
}