dpo-qwen-cot-merged

This repository provides a multi-stage fine-tuned version of Qwen3-4B-Instruct-2507.

The training pipeline consists of:

1. Supervised Fine-Tuning (SFT)
2. Stage-2 Hard SFT refinement
3. Direct Preference Optimization (DPO)

The LoRA adapters have been merged into the base model. This repository contains the final merged full-precision weights.

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Training Pipeline

Stage 1 — Supervised Fine-Tuning (SFT)

Base model: Qwen/Qwen3-4B-Instruct-2507
Dataset: u-10bei/structured_data_with_cot_dataset_512_v5

Configuration:

• Method: QLoRA (4-bit, Unsloth)
• LoRA: r=64, alpha=128
• Max sequence length: 512
• Epochs: 2
• Learning rate: 1e-4
• Batch size: 2
• Gradient accumulation: 8
• Warmup ratio: 0.05
• Weight decay: 0.0
• Seed: 3407
• CoT masking: Enabled (loss applied only to final outputs)

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Stage 2 — Hard Data Refinement

Dataset: daichira/structured-hard-sft-4k

Configuration:

• Epochs: 1
• Learning rate: 3e-5
• Same LoRA configuration as Stage 1

This stage improves robustness on difficult structured transformation tasks.

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Stage 3 — Direct Preference Optimization (DPO)

Dataset: u-10bei/dpo-dataset-qwen-cot

Configuration:

• Method: DPO via TRL + Unsloth
• LoRA: r=8, alpha=16
• Learning rate: 1e-7
• Beta: 0.1
• Max sequence length: 1024
• Max prompt length: 512
• Epochs: 1
• Optimizer: adamw_8bit
• Batch size: 2
• Gradient accumulation: 4
• Warmup ratio: 0.1
• Weight decay: 0.01
• Seed: 42

The objective is to align the model toward preferred Chain-of-Thought reasoning patterns using (prompt, chosen, rejected) preference data.

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Merge Status

All LoRA adapters have been merged into the base model.

No PEFT loading is required.

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Intended Use

This model is designed for:

• Structured transformation tasks
• Chain-of-Thought reasoning
• Preference-aligned generation
• Academic research experiments
• Competition submission

Research Notes

This work explores multi-stage fine-tuning combining:

• Structured SFT with CoT masking
• Hard data refinement
• Preference-based alignment via DPO

The training was performed using the Unsloth library for memory-efficient 4-bit fine-tuning.

License

This model follows the license of the base model:

Qwen/Qwen3-4B-Instruct-2507

Users must comply with the original base model license.

Usage

from transformers import AutoTokenizer, AutoModelForCausalLM
import torch

model_id = "HuiyuWang/dpo-qwen-cot-merged"

tokenizer = AutoTokenizer.from_pretrained(model_id)
model = AutoModelForCausalLM.from_pretrained(
    model_id,
    torch_dtype=torch.bfloat16,
    device_map="auto",
)

prompt = "Solve the following problem step by step: ..."
inputs = tokenizer(prompt, return_tensors="pt")

outputs = model.generate(
    **inputs,
    max_new_tokens=512,
    temperature=0.7,
)

print(tokenizer.decode(outputs[0], skip_special_tokens=True))