Quantifying Contamination in Evaluating Code Generation Capabilities of Language Models
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Abstract (arXiv)
While large language models have achieved remarkable performance on various code generation benchmarks, there have been growing concerns regarding potential contamination of these benchmarks as they may be leaked into pretraining and finetuning data. While recent work has investigated contamination in natural language generation and understanding tasks, there has been less extensive research into how data contamination impacts the evaluation of code generation, which is critical for understanding the robustness and reliability of LLMs in programming contexts. In this work, we perform a comprehensive study of data contamination of popular code generation benchmarks, and precisely quantify their overlap with pretraining corpus through both surface-level and semantic-level matching. In our experiments, we show that there are substantial overlap between popular code generation benchmarks and open training corpus, and models perform significantly better on the subset of the benchmarks where similar solutions are seen during training. We also conduct extensive analysis on the factors that affects model memorization and generalization, such as model size, problem difficulty, and question length. We release all resulting files from our matching pipeline for future research.
Key facts. Cited by 62 papers in the map (data through 7 Oct 2026). Builds on 23 of its 41 references that are in the map. First posted on arXiv 6 Mar 2024.
Builds on
23 of 41 references.
References · 23
- 2020Scaling Laws for Neural Language Modelscited by 6,411
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- 2020The Pile: An 800GB Dataset of Diverse Text for Language Modelingcited by 2,346
- 2020Extracting Training Data from Large Language Modelscited by 2,144
- 2023Pythia: A Suite for Analyzing Large Language Models Across Training and Scalingcited by 1,734
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- 2021Documenting Large Webtext Corpora: A Case Study on the Colossal Clean Crawled Corpuscited by 481
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- 2023Proving Test Set Contamination in Black Box Language Modelscited by 227
- 2023Rethinking Benchmark and Contamination for Language Models with Rephrased Samplescited by 192
- 2018The Adverse Effects of Code Duplication in Machine Learning Models of Codecited by 123
- 2024Investigating Data Contamination for Pre-training Language Modelscited by 91
- 2022Language Contamination Helps Explain the Cross-lingual Capabilities of English Pretrained Modelscited by 90
- 2017Ethical Challenges in Data-Driven Dialogue Systemscited by 86
- 2020Understanding Unintended Memorization in Federated Learningcited by 36
- 2022ORCA: Interpreting Prompted Language Models via Locating Supporting Data Evidence in the Ocean of Pretraining Datacited by 34
- 2023L2CEval: Evaluating Language-to-Code Generation Capabilities of Large Language Modelscited by 22
- 2024Investigating the Impact of Data Contamination of Large Language Models in Text-to-SQL Translationcited by 21
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Citing papers per year: 2024: 18; 2025: 15; 2026: 29.
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- 2025LessLeak-Bench: A First Investigation of Data Leakage in LLMs Across 83 Software Engineering Benchmarkscited by 34
- 2025A Survey on Data Contamination for Large Language Modelscited by 33
- 2024Unveiling the Spectrum of Data Contamination in Language Models: A Survey from Detection to Remediationcited by 30
- 2024VarBench: Robust Language Model Benchmarking Through Dynamic Variable Perturbationcited by 29
- 2024On Leakage of Code Generation Evaluation Datasetscited by 29
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- 2026Quantifying the Effect of Test Set Contamination on Generative Evaluationscited by 1
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- 2026TRACER: A Semantic-Aware Framework for Fine-Grained Contamination Detection in Code LLMs22 May 2026
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- 2026Beyond the Training Distribution: Mapping Generalization Boundaries in Neural Program Synthesis30 Apr 2026
- 2026Defective Task Descriptions in LLM-Based Code Generation: Detection and Analysis27 Apr 2026
- 2026LLMs taking shortcuts in test generation: A study with SAP HANA and LevelDB15 Apr 2026
- 2026Investigating Autonomous Agent Contributions in the Wild: Activity Patterns and Code Change over Time1 Apr 2026
- 2026SecCodeBench-V2 Technical Report17 Feb 2026
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- 2026A Survey on Evaluating Quality and Trustworthiness in LLM-Generated Data25 Jan 2026
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- 2025Contamination Means Overestimation? A Fine-Grained Empirical Study in Code Intelligence3 Jun 2025
- 2025VeriContaminated: Assessing LLM-Driven Verilog Coding for Data Contamination17 Mar 2025
- 2025Memorize or Generalize? Evaluating LLM Code Generation with Code Rewriting4 Mar 2025
- 2025Code to Think, Think to Code: A Survey on Code-Enhanced Reasoning and Reasoning-Driven Code Intelligence in LLMs26 Feb 2025
- 2025Recent Advances in Large Langauge Model Benchmarks against Data Contamination: From Static to Dynamic Evaluation23 Feb 2025
- 2025A Survey on Data Contamination for Large Language Models20 Feb 2025
- 2025Unbiased Evaluation of Large Language Models from a Causal Perspective10 Feb 2025
- 2025LessLeak-Bench: A First Investigation of Data Leakage in LLMs Across 83 Software Engineering Benchmarks10 Feb 2025
- 2024Reasoning Through Execution: Unifying Process and Outcome Rewards for Code Generation19 Dec 2024
- 2024EXAONE 3.5: Series of Large Language Models for Real-world Use Cases6 Dec 2024
- 2024Does Data Contamination Detection Work (Well) for LLMs? A Survey and Evaluation on Detection Assumptions24 Oct 2024
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- 2024Learning Code Preference via Synthetic Evolution4 Oct 2024
- 2024Data Contamination Report from the 2024 CONDA Shared Task31 Jul 2024
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- 2026LoopArena: Benchmarking Models as Runtime Controllers for Loop Engineeringcited by 1
- 2026Self-Refining Topology Optimization via an LLM-Based Multi-Agent Frameworkcited by 0
- 2026SWE-Future: Forecast-Conditioned Data Synthesis for Future-Oriented Software Engineering Agentscited by 0
- 2026Reliable and Developer-Aligned Evaluation of Agents for Software Engineeringcited by 0
- 2026Reveree: Diagnosing LLM Reverse-Engineering Agentscited by 0
- 2026RECLAIM: Can Agents Reproduce the Claims of Machine Learning Papers?cited by 0
- 2026RECLAIM: Can Agents Reproduce the Claims of Machine Learning Papers?23 Sep 2026
- 2026Reveree: Diagnosing LLM Reverse-Engineering Agents1 Sep 2026
- 2026LoopArena: Benchmarking Models as Runtime Controllers for Loop Engineering28 Aug 2026
- 2026Reliable and Developer-Aligned Evaluation of Agents for Software Engineering7 Jul 2026
- 2026SWE-Future: Forecast-Conditioned Data Synthesis for Future-Oriented Software Engineering Agents17 Jun 2026
- 2026Self-Refining Topology Optimization via an LLM-Based Multi-Agent Framework22 May 2026
- 2026Coding Agents Don't Know When to Act8 May 2026
- 2026Investigating Autonomous Agent Contributions in the Wild: Activity Patterns and Code Change over Time1 Apr 2026
- 2025NaturalGAIA: A Verifiable Benchmark and Hierarchical Framework for Long-Horizon GUI Tasks2 Aug 2025
- 2024LiveCodeBench: Holistic and Contamination Free Evaluation of Large Language Models for Codecited by 1,906
- 2025Code to Think, Think to Code: A Survey on Code-Enhanced Reasoning and Reasoning-Driven Code Intelligence in LLMscited by 47
- 2024Reasoning Through Execution: Unifying Process and Outcome Rewards for Code Generationcited by 21
- 2026Reasoning effort, not tool access, buys first-try reliability in agentic code generation: an observational studycited by 2
- 2025UniCode: Augmenting Evaluation for Code Reasoningcited by 1
- 2026Autoregressive Mosaics: Probing 2D Spatial Reasoning in Text-Only Language Modelscited by 0
- 2026Autoregressive Mosaics: Probing 2D Spatial Reasoning in Text-Only Language Models31 Aug 2026
- 2026Reasoning effort, not tool access, buys first-try reliability in agentic code generation: an observational study2 Jul 2026
- 2025UniCode: Augmenting Evaluation for Code Reasoning16 Oct 2025
- 2025Code to Think, Think to Code: A Survey on Code-Enhanced Reasoning and Reasoning-Driven Code Intelligence in LLMs26 Feb 2025
- 2024Reasoning Through Execution: Unifying Process and Outcome Rewards for Code Generation19 Dec 2024
- 2024LiveCodeBench: Holistic and Contamination Free Evaluation of Large Language Models for Code12 Mar 2024
- 2024Benchmark Data Contamination of Large Language Models: A Surveycited by 138
- 2024What's Wrong with Your Code Generated by Large Language Models? An Extensive Studycited by 52
- 2024EXAONE 3.5: Series of Large Language Models for Real-world Use Casescited by 50
- 2024Top Leaderboard Ranking = Top Coding Proficiency, Always? EvoEval: Evolving Coding Benchmarks via LLMcited by 38
- 2025Recent Advances in Large Langauge Model Benchmarks against Data Contamination: From Static to Dynamic Evaluationcited by 38
- 2025LessLeak-Bench: A First Investigation of Data Leakage in LLMs Across 83 Software Engineering Benchmarkscited by 34
- 2025A Survey on Data Contamination for Large Language Modelscited by 33
- 2024Unveiling the Spectrum of Data Contamination in Language Models: A Survey from Detection to Remediationcited by 30
- 2024VarBench: Robust Language Model Benchmarking Through Dynamic Variable Perturbationcited by 29
- 2024On Leakage of Code Generation Evaluation Datasetscited by 29
- 2024Data Contamination Can Cross Language Barrierscited by 26
- 2024Does Data Contamination Detection Work (Well) for LLMs? A Survey and Evaluation on Detection Assumptionscited by 26
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- 2026Memorization Diagnostics for Code LLMs Should be Scale-Aware13 Aug 2026
- 2026Is This Your Final Answer? Cross-Contextual Consistency as a Measure of LLM Credibility10 Aug 2026
- 2026Temporal Leakage in LLM Backtesting: Measurement, Validation, and Adjusted Scores4 Aug 2026
- 2026Spaghetti Architect: A Contamination-Resistant, By-Construction-Labelled, Multi-Language Code Dataset Generator21 Jul 2026
- 2026ReqGenX: An Empirical Study of Atomic Decomposition, Artifact Regeneration, and Reconstruction for Legacy SRS Documents18 Jul 2026
- 2026SrDetection: A Self-Referential Framework for Data Leakage Detection in Code Large Language Models29 Jun 2026
- 2026OpenAnt: LLM-Powered Vulnerability Discovery Through Code Decomposition, Adversarial Verification, and Dynamic Testing17 Jun 2026
- 2026TRACER: A Semantic-Aware Framework for Fine-Grained Contamination Detection in Code LLMs22 May 2026
- 2026ASSEMBLAGE-DEEPHISTORY: A Cross-Build Binary Dataset with Temporal Coverage20 May 2026
- 2026Beyond the Training Distribution: Mapping Generalization Boundaries in Neural Program Synthesis30 Apr 2026
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