Sixiang Ye

Large Language Models (LLMs) have significantly advanced software engineering (SE) tasks, with prompt engineering techniques enhancing their performance in code-related areas. However, the rapid development of foundational LLMs such as the non-reasoning models (GPT-4o and Claude 3.5 Sonnet) and the reasoning model o1 raises questions about the continued effectiveness of these prompt engineering techniques. This paper presents an extensive empirical study that reevaluates various prompt engineering techniques within the context of these advanced LLMs. Focusing on five representative SE tasks, i.e., code generation, code translation, program repair, code summarization, and commit message generation, we assess whether prompt engineering techniques still yield improvements with advanced models, the actual effectiveness of reasoning models compared to non-reasoning models, and whether the benefits of using these advanced models justify their increased costs. Our findings reveal that some novel prompt engineering techniques developed for earlier LLMs may provide diminished benefits or even hinder performance when applied to advanced models. In reasoning LLMs, the ability of sophisticated built-in reasoning reduces the impact of complex prompts, sometimes making simple zero-shot prompting more effective in some specific tasks. Prompt strategies that utilize execution feedback or precise task-specific guidance remain effective and are essential for improving performance on complex related-code problems. Furthermore, while reasoning models outperform non-reasoning models in tasks requiring complex reasoning, they offer minimal advantages in tasks that do not need reasoning and may incur unnecessary costs. Based on our study, we provide practical guidance for practitioners on selecting appropriate prompt engineering techniques and foundational LLMs, considering factors such as task requirements, operational costs, and environmental impact. Our work contributes to a deeper understanding of effectively harnessing advanced LLMs in SE tasks, informing future research and application development.

Code generation has gained increasing attention as a task to automate software development by transforming high-level descriptions into executable code. While large language models (LLMs) are effective in generating code, their performance heavily relies on the quality of input prompts. Current prompt engineering methods involve manual effort in designing prompts, which can be time-consuming and yield inconsistent results, potentially constraining the efficacy of LLMs in practical applications. This paper introduces Prochemy, a novel approach for automatically refining prompts iteratively to enhance code generation. Prochemy addresses the limitations of manual prompt engineering by automating the optimization process, ensuring prompt consistency during inference, and aligning with multi-agent systems. It iteratively refines prompts based on model performance, using an optimized final prompt to improve consistency and reliability across tasks. We evaluate Prochemy on both natural language-based code generation and code translation tasks using three series of LLMs. Results show that when combining Prochemy with existing approaches, it outperforms baseline prompting methods. It achieves improvements of 5.0% (GPT-3.5-Turbo) and 1.9% (GPT-4o) over zero-shot baselines on HumanEval. For the state-of-the-art LDB, Prochemy + LDB outperforms standalone methods by 1.2–1.8%. For code translation, Prochemy elevates GPT-4o’s performance on Java-to-Python (AVATAR) from 74.5 to 84.1 (+12.9%) and Python-to-Java from 66.8 to 78.2 (+17.1%). Furthermore, considering that the o1-mini model integrates prompt engineering techniques, Prochemy can continue to show good performance among it, further validating its effectiveness in code generation and translation tasks. Additionally, Prochemy is designed to be plug-and-play, optimizing prompts with minimal human intervention and seamlessly bridging the gap between simple prompts and complex frameworks.