I. Introduction
The current development of the software industry has caused a rapid increase in the number of software, leading to a continuous increase in the number and scale of existing software codes, and bringing new problems to software maintenance and evolution. Measuring code similarity can effectively use existing code and reduce the consumption of manpower and material resources. Measuring software internal code similarity can detect software code clone [1], plagiarism [2], reuse [3] and other issues. Therefore, it is of great significance to measure the similarity of software code.