Nghi Bui


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DocChecker: Bootstrapping Code Large Language Model for Detecting and Resolving Code-Comment Inconsistencies
Anh Dau | Jin L.c. Guo | Nghi Bui
Proceedings of the 18th Conference of the European Chapter of the Association for Computational Linguistics: System Demonstrations

Comments in source code are crucial for developers to understand the purpose of the code and to use it correctly. However, keeping comments aligned with the evolving codebase poses a significant challenge. With increasing interest in automated solutions to identify and rectify discrepancies between code and its associated comments, most existing methods rely heavily on heuristic rules. This paper introduces DocChecker, a language model-based framework adept at detecting inconsistencies between code and comments and capable of generating synthetic comments. This functionality allows DocChecker to identify and rectify cases where comments do not accurately represent the code they describe.The efficacy of DocChecker is demonstrated using the Just-In-Time and CodeXGlue datasets in various scenarios. Notably, DocChecker sets a new benchmark in the Inconsistency Code-Comment Detection (ICCD) task, achieving 72.3% accuracy, and scoring 33.64 in BLEU-4 on the code summarization task. These results surpass other Large Language Models (LLMs), including GPT 3.5 and CodeLlama.DocChecker is accessible for use and evaluation. It can be found on and at For a more comprehensive understanding of its functionality, a demonstration video is available on

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HierarchyNet: Learning to Summarize Source Code with Heterogeneous Representations
Minh Nguyen | Nghi Bui | Truong Son Hy | Long Tran-Thanh | Tien Nguyen
Findings of the Association for Computational Linguistics: EACL 2024

Code representation is important to machine learning models in the code-related applications. Existing code summarization approaches primarily leverage Abstract Syntax Trees (ASTs) and sequential information from source code to generate code summaries while often overlooking the critical consideration of the interplay of dependencies among code elements and code hierarchy. However, effective summarization necessitates a holistic analysis of code snippets from three distinct aspects: lexical, syntactic, and semantic information. In this paper, we propose a novel code summarization approach utilizing Heterogeneous Code Representations (HCRs) and our specially designed HierarchyNet. HCRs adeptly capture essential code features at lexical, syntactic, and semantic levels within a hierarchical structure. HierarchyNet processes each layer of the HCR separately, employing a Heterogeneous Graph Transformer, a Tree-based CNN, and a Transformer Encoder. In addition, HierarchyNet demonstrates superior performance compared to fine-tuned pre-trained models, including CodeT5, and CodeBERT, as well as large language models that employ zero/few-shot settings, such as CodeLlama, StarCoder, and CodeGen. Implementation details can be found at


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Better Language Models of Code through Self-Improvement
Hung To | Nghi Bui | Jin L.C. Guo | Tien Nguyen
Findings of the Association for Computational Linguistics: ACL 2023

Pre-trained language models for code (PLMCs) have gained attention in recent research. These models are pre-trained on large-scale datasets using multi-modal objectives. However, fine-tuning them requires extensive supervision and is limited by the size of the dataset provided. We aim to improve this issue by proposing a data augmentation framework using knowledge distillation. Our framework utilizes knowledge gained during the pre-training and fine-tuning stage to augment training data, which is then used for the next step. We incorporate this framework into the state-of-the-art language models, such as CodeT5, CodeBERT, and UnixCoder. The results show that our framework significantly improves PLMCs’ performance in sequence-generation tasks, such as code summarization and code generation in the CodeXGLUE benchmark.

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The Vault: A Comprehensive Multilingual Dataset for Advancing Code Understanding and Generation
Dung Nguyen | Le Nam | Anh Dau | Anh Nguyen | Khanh Nghiem | Jin Guo | Nghi Bui
Findings of the Association for Computational Linguistics: EMNLP 2023

We present The Vault, an open-source dataset of high quality code-text pairs in multiple programming languages for training large language models to understand and generate code. We propose methods for thoroughly extracting samples that use both rules and deep learning to ensure that they contain high-quality pairs of code and text, resulting in a dataset of 43 million high-quality code-text pairs. We thoroughly evaluated this dataset and discovered that when used to train common code language models (such as CodeT5, CodeBERT, and CodeGen), it outperforms the same models train on other datasets such as CodeSearchNet. These evaluations included common coding tasks such as code generation, code summarization, and code search. The Vault can be used by researchers and practitioners to train a wide range of big language models that understand code. Alternatively, researchers can use our data cleaning methods and scripts to improve their own datasets. We anticipate that using The Vault to train large language models will improve their ability to understand and generate code, propelling AI research and software development forward. We are releasing our source code and a framework to make it easier for others to replicate our results.

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CodeT5+: Open Code Large Language Models for Code Understanding and Generation
Yue Wang | Hung Le | Akhilesh Gotmare | Nghi Bui | Junnan Li | Steven Hoi
Proceedings of the 2023 Conference on Empirical Methods in Natural Language Processing

Large language models (LLMs) pretrained on vast source code have achieved prominent progress in code intelligence. However, existing code LLMs have two main limitations. First, they often adopt a specific architecture (encoder-only or decoder-only) or rely on a unified encoder-decoder network for different downstream tasks, lacking the flexibility to operate in the optimal architecture for a specific task. Secondly, they often employ a limited set of pretraining objectives which might not be relevant to some tasks and hence result in substantial performance degrade. To address these limitations, we propose “CodeT5+”, a family of encoder-decoder LLMs for code in which component modules can be flexibly combined to suit a wide range of code tasks. Such flexibility is enabled by our proposed mixture of pretraining objectives, which cover span denoising, contrastive learning, text-code matching, and causal LM pretraining tasks, on both unimodal and bimodal multilingual code corpora. Furthermore, we propose to initialize CodeT5+ with frozen off-the-shelf LLMs without training from scratch to efficiently scale up our models, and explore instruction-tuning to align with natural language instructions. We extensively evaluate CodeT5+ on over 20 code-related benchmarks in different settings, including zero-shot, finetuning, and instruction-tuning. We observe state-of-the-art (SoTA) performance on various code-related tasks, and our instruction-tuned CodeT5+ 16B achieves new SoTA results of 35.0% pass@1 and 54.5% pass@10 on the HumanEval code generation task against other open code LLMs, even surpassing the OpenAI code-cushman-001 model.

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Class based Influence Functions for Error Detection
Thang Nguyen-Duc | Hoang Thanh-Tung | Quan Hung Tran | Dang Huu-Tien | Hieu Nguyen | Anh T. V. Dau | Nghi Bui
Proceedings of the 61st Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers)

Influence functions (IFs) are a powerful tool for detecting anomalous examples in large scale datasets. However, they are unstable when applied to deep networks. In this paper, we provide an explanation for the instability of IFs and develop a solution to this problem. We show that IFs are unreliable when the two data points belong to two different classes. Our solution leverages class information to improve the stability of IFs.Extensive experiments show that our modification significantly improves the performance and stability of IFs while incurring no additional computational cost.


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Detect-Localize-Repair: A Unified Framework for Learning to Debug with CodeT5
Nghi Bui | Yue Wang | Steven C.H. Hoi
Findings of the Association for Computational Linguistics: EMNLP 2022

Automated software debugging is a crucial task for improving the productivity of software developers. Many neural-based techniques have been proven effective for debugging-related tasks such as bug localization and program repair (or bug fixing). However, these techniques often focus only on either one of them or approach them in a stage-wise manner, ignoring the mutual benefits between them. In this work, we propose a novel unified Detect-Localize-Repair framework based on a pretrained programming language model CodeT5 to seamlessly address these tasks, named CodeT5-DLR. Specifically, we propose three objectives to adapt the generic CodeT5 for debugging: a bug detection objective to determine whether a given code snippet is buggy or not, a bug localization objective to identify the buggy lines, and a program repair objective to translate the buggy code to its fixed version. We evaluate it on each of these tasks and their combined setting on two newly collected line-level debugging datasets in Java and Python. Extensive results show that our model significantly outperforms existing baselines from both NLP and software engineering domains.