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README.md
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# QLoRA Instruction Tuning on Pythia-1B
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This repository provides a **Hugging Faceโcompatible LoRA adapter** trained via **QLoRA (4-bit quantization + LoRA adapters)** on the **EleutherAI Pythia-1B-deduped** base model.
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The project focuses on **producing and publishing a reusable LoRA adapter** using a modern, memory-efficient instruction-tuning pipeline built with Hugging Face Transformers, PEFT, and BitsAndBytes. It is designed for **learning, experimentation, and small-GPU environments (e.g. Colab)**.
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---
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## โจ Key Features (Adapter-Centric)
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* ๐ **Frozen base model**: Pythia-1B-deduped (not included in this repository)
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* ๐ง **QLoRA training** with 4-bit NF4 quantization
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* ๐งฉ **LoRA adapters only** are trainable (<1% parameters)
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* ๐พ Optimized for **low GPU memory usage**
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* ๐ Clear, minimal pipeline for understanding instruction tuning
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---
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## ๐ง What This Adapter Represents
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This adapter demonstrates how to:
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* Load a **4-bit quantized causal language model**
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* Prepare it for k-bit training
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* Apply **LoRA adapters** for parameter-efficient fine-tuning
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* Perform **instruction tuning** using causal LM loss
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* Train using the Hugging Face `Trainer` API
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Formally, training follows:
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```
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Frozen Base Model (4-bit)
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+ Trainable LoRA ฮW
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โ Instruction-following behavior
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```
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---
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## ๐๏ธ Model & Training Setup
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### Base Model
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* **Model**: `EleutherAI/pythia-1B-deduped`
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* **Architecture**: Decoder-only Transformer
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* **Quantization**: 4-bit NF4 (BitsAndBytes)
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### LoRA Configuration
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| Parameter | Value | Description |
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| -------------- | ----------- | -------------------------------- |
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| `r` | 32 | LoRA rank (expressiveness) |
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| `lora_alpha` | 32 | Scaling factor |
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| `lora_dropout` | 0.05 | Regularization |
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| `bias` | `none` | Only LoRA parameters are trained |
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| `task_type` | `CAUSAL_LM` | Causal language modeling |
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Only **LoRA parameters** are trainable; all base model weights remain frozen.
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---
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## ๐ฆ Dataset
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* **Type**: Instruction-formatted text dataset
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* **Format**: Each example contains a `text` field
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* **Tokenization**:
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* Max length: 512
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* Padding: `max_length`
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* Truncation enabled
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Loss is computed using **standard causal language modeling**, meaning the model learns to predict the full sequence (instruction + response).
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---
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## ๐ Adapter Training & Usage Pipeline
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### 1. Load tokenizer and model
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* Load Pythia tokenizer
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* Set `pad_token = eos_token`
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* Load model with 4-bit quantization
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### 2. Prepare for QLoRA training
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* Enable gradient checkpointing
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* Cast critical layers for numerical stability
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* Freeze base model parameters
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### 3. Apply LoRA adapters
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* Inject LoRA modules into attention and MLP layers
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* Print trainable parameter count
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### 4. Training configuration
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| Setting | Value |
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| --------------------- | ------------------ |
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| Epochs | 3 |
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| Batch size | 6 |
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| Gradient accumulation | 4 |
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| Effective batch size | 24 |
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| Learning rate | 2e-4 |
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| Optimizer | `paged_adamw_8bit` |
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| Precision | FP16 |
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### 5. Start
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```python
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```
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---
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## ๐ Why QLoRA?
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Compared to full fine-tuning:
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* โ
~10ร lower GPU memory usage
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* โ
Faster experimentation
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* โ
No catastrophic forgetting
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* โ
Easy adapter reuse and sharing
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This approach mirrors how many modern instruction-tuned LLMs are trained at scale.
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---
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## ๐ Expected Behavior When Using This Adapter
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After training, the model should:
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* Follow instructions more directly
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* Produce more structured and task-aligned responses
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* Show clear behavioral differences **with vs without** LoRA adapters
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Adapter ablation (disabling LoRA) should revert behavior close to the base model.
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---
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## ๐ฎ Possible Extensions
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* Mask loss to train **response-only instruction tuning**
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* Train multiple LoRA adapters for different tasks
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* Merge or switch adapters at inference time
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* Combine with evaluation datasets
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* Compare different LoRA ranks (`r=8`, `r=16`, `r=32`)
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---
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## ๐ ๏ธ Requirements
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* Python 3.9+
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* PyTorch
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* transformers
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* peft
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* bitsandbytes
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* accelerate
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---
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## ๐ License & Usage Notes
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This repository publishes **only LoRA adapter weights** and configuration files. The base model must be obtained separately under its original license.
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This adapter is intended for **research, experimentation, and non-production use** unless further evaluated.
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---
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This repository provides a **clean, minimal reference implementation** of QLoRA-based instruction tuning on a 1B-scale language model.
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