LLM Fine-Tuning

Fine-tune large language models efficiently using parameter-efficient methods.

Overview

LLM fine-tuning adapts pre-trained models to specific tasks or domains. This skill covers efficient techniques like LoRA, QLoRA, and full fine-tuning strategies.

Quick Reference

Core Principles

1. Parameter Efficiency - Update small subset of parameters
2. Task Adaptation - Specialize model for specific use case
3. Data Quality - High-quality training data is critical
4. Evaluation - Rigorous testing on held-out data
5. Monitoring - Track metrics to prevent degradation

Fine-Tuning Methods

LoRA (Low-Rank Adaptation)

Inject trainable low-rank matrices into model layers.

Advantages:

• 0.1-1% of parameters trainable
• Fast training
• Multiple adapters for one base model
• No inference latency

Hyperparameters:

• Rank (r): 4-64 typical
• Alpha: Scaling factor
• Target modules: Which layers to adapt

QLoRA (Quantized LoRA)

LoRA with 4-bit quantized base model.

Benefits:

• Fine-tune 65B model on single GPU
• Minimal performance loss
• Extreme memory efficiency

Requirements:

• bitsandbytes library
• NVIDIA GPU with compute capability ≥ 7.0

Full Fine-Tuning

Update all model parameters.

When to Use:

• Abundant compute resources
• Significant domain shift
• Maximum performance needed

Challenges:

• High memory requirements
• Risk of catastrophic forgetting
• Expensive

Training Process

1. Data Preparation

• Collect high-quality examples
• Format as instruction-response pairs
• Split into train/validation/test
• Typical size: 1K-100K examples

2. Model Selection

• Choose base model (Llama, Mistral, GPT)
• Consider size vs performance trade-off
• Check license for commercial use

3. Training

• Set hyperparameters (LR, batch size, epochs)
• Monitor training and validation loss
• Use gradient accumulation for large batches
• Apply early stopping

4. Evaluation

• Test on held-out data
• Human evaluation for quality
• Compare to base model
• Check for regressions

Using the Reference Files

/references/peft-methods.md — LoRA, QLoRA, Prefix Tuning, Adapter layers, implementation with Hugging Face PEFT library.

/references/full-finetuning.md — Supervised fine-tuning, instruction tuning, data preparation, training strategies, and hyperparameter tuning.

/references/alignment.md — RLHF (Reinforcement Learning from Human Feedback), DPO (Direct Preference Optimization), safety considerations.

Best Practices

• Start with LoRA/QLoRA for efficiency
• Use high-quality, diverse training data
• Monitor validation loss to prevent overfitting
• Use learning rate warm-up
• Apply gradient clipping
• Save checkpoints regularly
• Evaluate thoroughly before deployment
• Document training process

Common Pitfalls to Avoid

• Insufficient or low-quality training data
• Overfitting to small datasets
• Learning rate too high (catastrophic forgetting)
• Not using validation set
• Ignoring base model capabilities
• Training too many epochs
• Not testing on diverse inputs
• Deploying without human evaluation