README.md

---
language:
  - en
license: other
pipeline_tag: text-generation
tags:
  - llama
  - chat
  - sft
  - reasoning
  - cot
  - ultrachat
  - mixture-of-thoughts
  - dpo
base_model: meta-llama/Llama-3.2-1B
library_name: transformers
---

# PursuitOfDataScience/llama3.2-1b-thinking

This repository contains a three-stage fine-tuned version of **meta-llama/Llama-3.2-1B**:

1. **Supervised fine-tuning (SFT)** on a local copy of **HuggingFaceH4/ultrachat_200k**
   using an instruction-style, multi-turn chat objective.
2. **Reasoning training** to enhance step-by-step reasoning capabilities,
   building on the SFT model using the `open-r1/Mixture-of-Thoughts` dataset.
3. **Direct Preference Optimization (DPO)** alignment using the `mlabonne/orpo-dpo-mix-40k` dataset
   to improve response quality and alignment with human preferences.

## Model details

- **Base model**: `meta-llama/Llama-3.2-1B`
- **Stage 1 objective**: Supervised fine-tuning for helpful, concise chat responses
  on Ultrachat-style conversations.
- **Stage 2 objective**: Specialized reasoning training to improve logical reasoning and
  Chain of Thought (CoT) capabilities using step-by-step reasoning traces from `open-r1/Mixture-of-Thoughts`.
- **Stage 3 objective**: DPO alignment to refine responses based on preference data from `mlabonne/orpo-dpo-mix-40k`,
  enhancing safety, helpfulness, and adherence to user constraints.
- **Context length**: Up to 131072 tokens (subject to the base model config).
- **Training data**:
  - SFT: multi-turn dialogues from `HuggingFaceH4/ultrachat_200k`.
  - Reasoning: `open-r1/Mixture-of-Thoughts` dataset with step-by-step reasoning traces.
  - DPO: preference pairs from `mlabonne/orpo-dpo-mix-40k`.

## Inference usage

The model is trained in a **chat-style** setup. At inference time, prompts are built
as a list of `messages` and passed through the model's native `chat_template`
via `tokenizer.apply_chat_template`:

```python
from transformers import AutoTokenizer, AutoModelForCausalLM

repo_id = "PursuitOfDataScience/llama3.2-1b-thinking"

tokenizer = AutoTokenizer.from_pretrained(repo_id)
model = AutoModelForCausalLM.from_pretrained(
    repo_id,
    device_map="auto",
)

messages = [
    {
        "role": "system",
        "content": (
            "You are a helpful, concise assistant. "
            "Write clear, well-structured answers that follow the user's constraints."
        ),
    },
    {
        "role": "user",
        "content": "Explain how someone can build a consistent daily learning habit.",
    },
]

prompt_text = tokenizer.apply_chat_template(
    messages,
    tokenize=False,
    add_generation_prompt=True,
)

inputs = tokenizer(prompt_text, return_tensors="pt").to(model.device)

outputs = model.generate(
    **inputs,
    max_new_tokens=512,
    eos_token_id=tokenizer.eos_token_id,
    pad_token_id=tokenizer.eos_token_id,
    temperature=0.7,
    top_p=0.9,
    do_sample=True,
)

# Decode only the generated continuation (excluding the prompt tokens)
generated_tokens = outputs[0][inputs["input_ids"].shape[1]:]
response = tokenizer.decode(generated_tokens, skip_special_tokens=True)
print(response)
```

### Multi-turn example

```python
messages = [
    {
        "role": "system",
        "content": (
            "You are a helpful, concise assistant. "
            "Write clear, well-structured answers that follow the user's constraints."
        ),
    },
    {
        "role": "user",
        "content": "Describe the main trade-offs between using small and large language models.",
    },
    {
        "role": "assistant",
        "content": "Small models are cheaper and faster, while large models are usually more capable...",
    },
    {
        "role": "user",
        "content": "Give me a bullet-point summary from the perspective of a startup.",
    },
]

prompt_text = tokenizer.apply_chat_template(
    messages,
    tokenize=False,
    add_generation_prompt=True,
)

inputs = tokenizer(prompt_text, return_tensors="pt").to(model.device)
outputs = model.generate(
    **inputs,
    max_new_tokens=256,
    eos_token_id=tokenizer.eos_token_id,
    pad_token_id=tokenizer.eos_token_id,
    temperature=0.7,
    top_p=0.9,
    do_sample=True,
)
response = tokenizer.decode(
    outputs[0][inputs["input_ids"].shape[1]:],
    skip_special_tokens=True,
)
print(response)
```

### Chain of Thought (CoT) reasoning example

For reasoning tasks, the model can generate step-by-step thoughts using `<think>` tags:

```python
messages = [
    {
        "role": "system",
        "content": (
            "You are a helpful, concise assistant. "
            "Use Chain of Thought reasoning with <think> tags for complex problems."
        ),
    },
    {
        "role": "user",
        "content": "If a train travels 60 km in 1 hour, how long will it take to travel 180 km?",
    },
]

prompt_text = tokenizer.apply_chat_template(
    messages,
    tokenize=False,
    add_generation_prompt=True,
)

inputs = tokenizer(prompt_text, return_tensors="pt").to(model.device)
outputs = model.generate(
    **inputs,
    max_new_tokens=512,
    eos_token_id=tokenizer.eos_token_id,
    pad_token_id=tokenizer.eos_token_id,
    temperature=0.7,
    top_p=0.9,
    do_sample=True,
)
response = tokenizer.decode(
    outputs[0][inputs["input_ids"].shape[1]:],
    skip_special_tokens=True,
)
print(response)
# Example output: <think> The train travels 60 km in 1 hour, so speed is 60 km/h. For 180 km, time = distance / speed = 180 / 60 = 3 hours. </think> It will take 3 hours.
```

## Training pipeline (summary)

1. **Instruction SFT (Ultrachat)**:
   - Conversations are converted into lists of `messages`.
   - For each assistant turn, a single training example is built using
     `tokenizer.apply_chat_template`.
   - Loss is applied only on assistant tokens; system and user tokens are masked.

2. **Reasoning Training**:
   - Fine-tuning on the `open-r1/Mixture-of-Thoughts` dataset with step-by-step reasoning traces to enhance CoT capabilities.
   - Uses reinforcement learning or supervised methods to align with logical reasoning patterns.

3. **DPO Alignment**:
   - Fine-tuning with Direct Preference Optimization on the `mlabonne/orpo-dpo-mix-40k` dataset.
   - Optimizes the model to prefer chosen responses over rejected ones, improving overall alignment.

## Limitations

- This is a relatively small (1B parameter) model and may hallucinate or
  struggle on complex, multi-step reasoning tasks.
- Outputs may be inaccurate, unsafe, or biased. Always verify critical
  information before using it in production.