Nadeeshan De Silva

Mehedi Sun, Antu Saha, Nadeeshan De Silva et al.

Understanding the reasons behind past code changes is critical for many software engineering tasks, including refactoring and reviewing code, diagnosing bugs, and implementing new features. Unfortunately, locating and reconstructing this rationale can be difficult for developers because the information is often fragmented, inconsistently documented, and scattered across different artifacts such as commit messages, issue reports, and PRs. In this paper, we address this challenge in two steps. First, we conduct an empirical study of 63 commits from five open-source Java projects to analyze how rationale components (e.g., a change's goal, need, and alternative) are distributed across artifacts. We find that the rationale is highly fragmented: commit messages and pull requests primarily capture goals, while needs and alternatives are more often found in issues and PRs. Other components are scarce but found in artifacts other than commit messages. No single artifact type captures all components, underscoring the need for cross-document reasoning and synthesis. Second, we introduce ARGUS, an LLM-based approach that identifies sentences expressing goal, need, and alternative across a commit's artifacts and creates concise rationale summaries to support code comprehension and maintenance tasks. We evaluated ARGUS on the 63 commits and compared its performance against baseline variants. The best-performing version achieved 51.4% precision and 93.2% recall for rationale identification, while producing rationale summaries rated as accurate. A user study with 12 Java developers further showed that these summaries were perceived as useful and helpful for tasks such as code review, documentation, and debugging. Our results highlight the need for multi-document reasoning in capturing rationale and demonstrate the potential of ARGUS to help developers understand and maintain software systems.

Erfan Arvan, Nadeeshan De Silva, Oscar Chaparro et al.

Prior work on code comprehension uses different comprehension proxies-for example, Likert-scale ratings or answers to input-output questions about program snippets, usually collected from students, to approximate whether code is comprehensible to software engineers, but the relative reliability of these proxies is not known. This paper investigates the relative reliability of a collection of proxies common in the extant literature with a pair of human studies. First, we conducted an expert-consensus study with a panel of five professional software engineers to establish a ground-truth comprehensibility ranking of eight code snippets by adapting the Delphi expert-consensus protocol. The Delphi protocol is widely used for expert consensus under conditions of uncertainty in other domains, such as medicine and national-security forecasting, but to our knowledge, this is its first application in software engineering. Second, we conducted a study with 44 student participants who completed tasks, allowing us to measure 14 comprehension proxies derived from the literature on the same set of eight code snippets. Finally, we conducted a correlation analysis on the results, concluding that proxies 1) derived from input-output questions and 2) that measure response time rather than accuracy are especially reliable. We also found that proxies derived from questions about program syntax (rather than semantics) are especially unreliable, regardless of measurement strategy, which draws into question the reliability of parts of the existing comprehensibility literature.

Nadeeshan De Silva, Martin Kellogg, Oscar Chaparro

Proponents of software verification suggest that code simplicity is linked to the effort to verify code, hypothesizing that formal verifiers produce fewer false positive warnings and require less manual intervention when analyzing simpler code. A recent meta-analysis study found empirical support for this hypothesis: a small correlation between the sum of verifier warnings and human-derived code comprehensibility metrics. Based on this finding, we conjectured that using the sum of verifier tool (verifier) warnings to represent program semantic information as an input feature to machine learning (ML) models for code comprehensibility prediction can enhance their performance, when combined with traditional syntactic and developer features. To test this conjecture, we performed a control-treatment experiment incorporating the verifier warning sum feature into machine learning models from the literature, and conducted a comparative analysis of their performance against models trained only on syntactic and developer features. We found no significant difference in the prediction performance of models with and without the warnings feature. Our findings suggest that while a correlation exists, the verifier warning sum offers limited discriminative power: combining syntactic and developer features is just as effective for predicting human-judged code comprehensibility.