Researchers Detect Functional Memorization in Code Language Models Beyond Textual Overlap
A new study on arXiv demonstrates that large language models trained on code can memorize and reproduce functional logic from training data even when the generated code differs textually from the original. The research used a controlled experiment comparing Olmo-3-32B models with and without exposure to target code, measuring both textual and functional similarity through execution-based testing. This finding suggests that current auditing methods relying on textual overlap alone may miss important memorization risks in code generation systems.
Researchers have identified a previously underexamined form of memorization in code language models called functional memorization, where models extract and reproduce the logical behavior of training code without necessarily reproducing the exact text. Using a counterfactual experimental design, the team compared a version of Olmo-3-32B that had been exposed to target code against a pretrained reference model without such exposure. By prompting both models with Python function signatures and evaluating outputs using both textual similarity metrics and functional similarity measures (including LLM-as-a-judge and execution-based testing), they found clear evidence that models can memorize functional logic. The study highlights a critical gap in current memorization detection methods, which typically focus on textual overlap and may therefore fail to identify cases where functionally identical or near-identical code is generated with different syntax or structure.
What's missing
The study's own limitations and scope constraints are not detailed in the abstract provided. Additionally, the implications for other code models beyond Olmo-3-32B, the practical severity of functional memorization for real-world deployment, and potential mitigation strategies are not addressed in the available excerpt.
What different sources said
- arXiv cs.CLCenter
Detecting Functional Memorization in Code Language Models
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