关键词: 克隆代码, 克隆跟踪, 演化模式, 修改日志

Abstract: Recently, most clone tracking is based on release version of software, which loses much change information of clone code during the process of software development. Definition of evolution pattern is unclear, and its perspective is not distinguished. This paper proposes a method of tracing clone code based on modify log, and identifies clone evolution pattern by different perspectives（clone class, clone fragment, clone code content）. Firstly, regarding each submission as one small version, and detecting clone of each version by NiCad; Secondly, mapping clone class initially based on levenshtein distance of token; Thirdly, mapping clone fragment based on modify log; Fourthly, revising clone class mapping based on the result of clone fragment mapping; Finally, identifying clone evolution pattern in different perspectives. The experiment is conducted on nearly 8 thousand versions of 6 open-source software. The results show that more than 97% clone code is in “stable” evolution pattern, “separate”, “merge”, “complex” is no more than 0.01%, and “consistent change”, “inconsistent change” is less than 2%. Contrast to the similar tool named gCad, recall （increased by 2%） and precision （increased by 2%） of this method are significantly higher, and running speed is also faster in the same environment.

Key words: clone code, clone tracking, evolution pattern, modify log