Full fine-tuning can demand substantial GPU memory and computation, and updating every weight risks catastrophic forgetting. Parameter-efficient fine-tuning (PEFT) reduces training demands by adapting only a small fraction of model parameters. section 5.3.3
Two practical PEFT approaches are:
- LoRA freezes the base model and trains small adapter matrices added to selected model components. section 5.3.3
- QLoRA extends LoRA and uses less memory; its reported performance is somewhat lower than LoRA’s. section 5.3.3
Fine-tuning is useful for specialized tasks when prompting and retrieval alone are insufficient. High-quality, well-formatted training data remains important; combining fine-tuning with retrieval can provide live knowledge access alongside consistent reasoning. section 5.5
Table 5.2 Comparing different fine-tuning methods
|
Method
|
Parameter efficiency
|
Performance
|
Memory usage
|
When to choose
|
|---|---|---|---|---|
|
Full fine-tuning
|
Lowest (100%)
|
Highest
|
Highest
|
When you have multiple high-end GPUs and need maximum adaptation
|
|
LoRA
|
High (~0.1–1%)
|
Very high (95–99% of full)
|
Low
|
When you have a decent GPU and need strong performance
|
|
QLoRA
|
High (~0.1–1%)
|
High (90–95% of full)
|
Lowest
|
When you have limited GPU resources but need to fine-tune large models
|
Compare parameter efficiency, performance, memory use, and hardware guidance when choosing between full fine-tuning, LoRA, and QLoRA. section 5.3.3




