Recently, Large Language Models (LLMs) have shown impressive abilities in code generation. However, existing LLMs' decoding strategies are designed for Natural Language (NL) generation, overlooking the differences between NL and programming languages (PL). Due to this oversight, a better decoding strategy for code generation remains an open question. In this paper, we conduct the first systematic study to explore a decoding strategy specialized in code generation. With an analysis of loss distributions of code tokens, we find that code tokens can be divided into two categories: challenging tokens that are difficult to predict and confident tokens that can be easily inferred. Among them, the challenging tokens mainly appear at the beginning of a code block. Inspired by the above findings, we propose a simple yet effective method: Adaptive Temperature (AdapT) sampling, which dynamically adjusts the temperature coefficient when decoding different tokens. We apply a larger temperature when sampling for challenging tokens, allowing LLMs to explore diverse choices. We employ a smaller temperature for confident tokens avoiding the influence of tail randomness noises. We apply AdapT sampling to LLMs with different sizes and conduct evaluations on two popular datasets. Results show that AdapT sampling significantly outperforms state-of-the-art decoding strategy.

How to evaluate Large Language Models (LLMs) in code generation remains an open question. Many benchmarks have been proposed, but they have two limitations, i.e., data leakage and lack of domain-specific evaluation.The former hurts the fairness of benchmarks, and the latter hinders practitioners from selecting superior LLMs for specific programming domains.To address these two limitations, we propose a new benchmark - EvoCodeBench, which has the following advances: (1) Evolving data. EvoCodeBench will be dynamically updated every period (e.g., 6 months) to avoid data leakage. This paper releases the first version - EvoCodeBench-2403, containing 275 samples from 25 repositories.(2) A domain taxonomy and domain labels. Based on the statistics of open-source communities, we design a programming domain taxonomy consisting of 10 popular domains. Based on the taxonomy, we annotate each sample in EvoCodeBench with a domain label. EvoCodeBench provides a broad platform for domain-specific evaluations.(3) Domain-specific evaluations. Besides the Pass@k, we compute the Domain-Specific Improvement (DSI) and define LLMs' comfort and strange domains. These evaluations help practitioners select superior LLMs in specific domains and discover the shortcomings of existing LLMs.Besides, EvoCodeBench is collected by a rigorous pipeline and aligns with real-world repositories in multiple aspects (e.g., code distributions).We evaluate 8 popular LLMs (e.g., gpt-4, DeepSeek Coder, StarCoder 2) on EvoCodeBench and summarize some insights. EvoCodeBench reveals the actual abilities of these LLMs in real-world repositories. For example, the highest Pass@1 of gpt-4 on EvoCodeBench-2403 is only 20.74%. Besides, we evaluate LLMs in different domains and discover their comfort and strange domains. For example, gpt-4 performs best in most domains but falls behind others in the Internet domain. StarCoder 2-15B unexpectedly performs well in the Database domain and even outperforms 33B LLMs. We release EvoCodeBench, all prompts, and LLMs' completions for further community analysis.

Large language models (LLMs) have shown great success in code generation. LLMs take as the input a prompt and output the code. How to make prompts (i.e., Prompting Techniques ) is a key question. Existing prompting techniques are designed for natural language generation and have low accuracy in code generation. In this article, we propose a new prompting technique named AceCoder . Our motivation is that code generation meets two unique challenges (i.e., requirement understanding and code implementation). AceCoder contains two novel mechanisms (i.e., guided code generation and example retrieval) to solve these challenges. ❶ Guided code generation asks LLMs first to analyze requirements and output an intermediate preliminary (e.g., test cases). The preliminary clarifies requirements and tells LLMs “what to write.” ❷ Example retrieval selects similar programs as examples in prompts, which provide lots of relevant content (e.g., algorithms, APIs) and teach LLMs “how to write.” We apply AceCoder to four LLMs (e.g., GPT-3.5, CodeGeeX) and evaluate it on three public benchmarks using the Pass@ \(k\) . Results show that AceCoder can significantly improve the performance of LLMs on code generation. In terms of Pass@1, AceCoder outperforms the SOTA baseline by up to 56.4% in MBPP, 70.7% in MBJP, and 88.4% in MBJSP . AceCoder is effective in LLMs with different sizes (i.e., 6B–13B) and different languages (i.e., Python, Java, and JavaScript). Human evaluation shows human developers prefer programs from AceCoder .

Code search has been a critical software development activity in facilitating developers to retrieve a proper code snippet from open-source repositories given a user intent. In recent years, large-scale pre-trained models have shown impressive performance on code representation learning and have achieved state-of-the-art performance on code search task. However, it is challenging for these models to distinguish the functionally equivalent code snippets with dissimilar implementations or the non-equivalent code snippets that look similar. Due to the diversity of the code implementations, it is necessary for the code search engines to identify the functional similarities or dissimilarities of source code so as to return the functionally matched source code for a given query. Besides, existing pre-trained models mainly focus on learning the semantic representations of code snippets. The semantic correlation between the code snippet and natural language query is not sufficiently exploited. An effective code search tool not only needs to understand the relationship between queries and code snippets but also needs to identify the relationship between diversified code snippets. To address these limitations, we propose a novel multi-view contrastive learning model MCodeSearcher for code retrieval, aiming at sufficiently exploiting (1) the semantic correlation between queries and code snippets, and (2) the relationship between functionally equivalent code snippets. To achieve this, we design contrastive training objectives from three views and pre-train our model with these objectives. The experimental results on five representative code search datasets show that our approach significantly outperforms the state-of-the-art methods.

Code generation aims to automatically generate the source code based on given natural language (NL) descriptions, which is of great significance for automated software development. Some code generation models follow a language model-based paradigm (LMBP) to generate source code tokens sequentially. Some others focus on deriving the grammatical structure by generating the program’s abstract syntax tree (AST), i.e., using the grammatical structure-based paradigm (GSBP). Existing studies are trying to generate code through one of the above two models. However, human developers often consider both paradigms: building the grammatical structure of the code and writing source code sentences according to the language model. Therefore, we argue that code generation should consider both GSBP and LMBP. In this paper, we use mutual learning to combine two classes of models to make the two different paradigms train together. To implement the mutual learning framework, we design alignment methods between code and AST. Under this framework, models can be enhanced through shared encoders and knowledge interaction in aligned training steps. We experiment on three Python-based code generation datasets. Experimental results and ablation analysis confirm the effectiveness of our approach. Our results demonstrate that considering both GSBP and LMBP is helpful in improving the performance of code generation.

Transformers are now widely used in code representation, and several recent works further develop tree Transformers to capture the syntactic structure in source code.Specifically, novel tree positional encodings have been proposed to incorporate inductive bias into Transformer.In this work, we propose a novel tree Transformer encoding node positions based on our new description method for tree structures.Technically, local and global soft bias shown in previous works is both introduced as positional encodings of our Transformer model.Our model finally outperforms strong baselines on code summarization and completion tasks across two languages, demonstrating our model's effectiveness.Besides, extensive experiments and ablation study shows that combining both local and global paradigms is still helpful in improving model performance.We release our code at https://github.com/ AwdHanPeng/TreeTransformer.

Learning distributed representation of source code requires modelling its syntax and semantics. Recent state-of-the-art models leverage highly structured source code representations, such as the syntax trees and paths therein. In this paper, we investigate two representative path encoding methods shown in previous research work and integrate them into the attention module of Transformer. We draw inspiration from the ideas of positional encoding and modify them to incorporate these path encoding. Specifically, we encode both the pairwise path between tokens of source code and the path from the leaf node to the tree root for each token in the syntax tree. We explore the interaction between these two kinds of paths by integrating them into the unified Transformer framework. The detailed empirical study for path encoding methods also leads to our novel state-of-the-art representation model TPTrans, which finally outperforms strong baselines. Extensive experiments and ablation studies on code summarization across four different languages demonstrate the effectiveness of our approaches. We release our code at \url{https://github.com/AwdHanPeng/TPTrans}.

Code completion is one of the most useful features in the Integrated Development Environments (IDEs), which can accelerate software development by suggesting the next probable token based on the contextual code in real-time. Recent studies have shown that statistical language modeling techniques can improve the performance of code completion tools through learning from large-scale software repositories. However, these models suffer from two major drawbacks: a) Existing research uses static embeddings, which map a word to the same vector regardless of its context. The differences in the meaning of a token in varying contexts are lost when each token is associated with a single representation; b) Existing language model based code completion models perform poor on completing identifiers, and the type information of the identifiers is ignored in most of these models. To address these challenges, in this paper, we develop a multi-task learning based pre-trained language model for code understanding and code generation with a Transformer-based neural architecture. We pre-train it with hybrid objective functions that incorporate both code understanding and code generation tasks. Then we fine-tune the pre-trained model on code completion. During the completion, our model does not directly predict the next token. Instead, we adopt multi-task learning to predict the token and its type jointly and utilize the predicted type to assist the token prediction. Experiments results on two real-world datasets demonstrate the effectiveness of our model when compared with state-of-the-art methods.