Finding File Clones in FreeBSD Ports Collection

1. Finding File Clones in FreeBSD Ports Collection Yusuke Sasaki Tetsuo Yamamoto Yasuhiro Hayase Katsuro Inoue

2. File Clones • Two or more files with the same content • Comments and code indentation ignored • Inside a project or between different projects • Research about file-clones is scarce • Get new knowledge about file-clones Project A Project B int main() { printf(“Hello msr!”); return 0; }

3. FCFinder • Input • .c and .h files • Output • File-clone sets • Faster than other tools • Detection • Tokenization • MD5 Hash Calculation • Exact Matching

4. Experiment • Target • Only .c and .h files inthe FreeBSD Ports Collection • ~1.4M files • ~12 GB • 17.16 hours • We measured: • File size • Number of files in each project • Size of each file-clone set • Number of file-clones in a project These values follow the power law

5. File-clone Set Size Left：used in PHP5 Right：used in PHP4 used in both of PHP4 and 5 D E L:650 sets R:500 sets 419 sets 120 file clones 100 5 10 50 L:61 file clones R:59 file clones file clone set size R*2 =0.8508

6. File-clones per Project Right：PHP4 modules Center：projects related bin-utils Left：PHP5 modules G 5 10 50 100 500 1K 5K 10K number of file clone sets R*2 =0.8263

7. File-clones Between Projects (1/3) * Nodes show the projects * Edges between projects show the number of file clones between two projects • Ex) gcc41 and gfortran shares 7691 file clones

8. File-clones Between Projects (2/3) * Nodes show the projects * Edges between projects show the number of file clones between two projects

9. File-clones Between Projects (3/3) * Nodes show the projects * Edges between projects show the number of file clones between two projects

10. Conclusions & Future Work Conclusions • Measured several features of the FreeBSD Ports collection. • Found that the measured features follow the power law Future Work • Projects logical coupling investigation