Astraios: Parameter-Efficient Instruction Tuning Code Large Language Models

TL;DR

Astraios introduces 28 instruction-tuned models across various sizes and methods, revealing that full fine-tuning generally outperforms PEFT, but LoRA offers a good cost-performance balance, with larger models showing reduced robustness and security.

Contribution

The paper provides a comprehensive evaluation of 28 instruction-tuned models using multiple tuning methods across different model sizes, highlighting the trade-offs and effectiveness of PEFT methods like LoRA.

Findings

FFT generally yields the best downstream performance.

LoRA offers the best cost-performance trade-off.

Larger models show reduced robustness and security.

Abstract

The high cost of full-parameter fine-tuning (FFT) of Large Language Models (LLMs) has led to a series of parameter-efficient fine-tuning (PEFT) methods. However, it remains unclear which methods provide the best cost-performance trade-off at different model scales. We introduce Astraios, a suite of 28 instruction-tuned OctoCoder models using 7 tuning methods and 4 model sizes up to 16 billion parameters. Through investigations across 5 tasks and 8 different datasets encompassing both code comprehension and code generation tasks, we find that FFT generally leads to the best downstream performance across all scales, and PEFT methods differ significantly in their efficacy based on the model scale. LoRA usually offers the most favorable trade-off between cost and performance. Further investigation into the effects of these methods on both model robustness and code security reveals that larger models tend to demonstrate reduced robustness and less security. At last, we explore the relationships among updated parameters, cross-entropy loss, and task performance. We find that the tuning effectiveness observed in small models generalizes well to larger models, and the validation loss in instruction tuning can be a reliable indicator of overall downstream performance.