Sourcerer ASTs

Overview

Sourcerer is a large corpus of open source Java software. It was constructed by fully downloading the source code of 19 K projects, of which 6 K turned out to be empty. And, after performing the following operations:

Remove non-Java files

Remove SCM branches

Remove duplicate projects

Manually reviewed duplicate files

Remove test code

The authors have reduced the 390 GB corpus to 14.3 GB. The resulting corpus has been made publicly available.

Paper Abstract

Measuring the internal quality of source code is one of the traditional goals of making software development into an engineering discipline. Cyclomatic Complexity (CC) is an often used source code quality metric, next to Source Lines of Code (SLOC). However, the use of the CC metric is challenged by the repeated claim that CC is redundant with respect to SLOC due to strong linear correlation. We test this claim by studying a corpus of 17.8M methods in 13K open-source Java projects. Our results show that direct linear correlation between SLOC and CC is only moderate, as caused by high variance. We observe that aggregating CC and SLOC over larger units of code improves the correlation, which explains reported results of strong linear correlation in literature. We suggest that the primary cause of correlation is the aggregation. Our conclusion is that there is no strong linear correlation between CC and SLOC of Java methods, so we do not conclude that CC is redundant with SLOC. This conclusion contradicts earlier claims from literature, but concurs with the widely accepted practice of measuring of CC next to SLOC.