Detecting Semantic Code Clones by Building AST-based Markov Chains Model

Code clone detection aims to find functionally similar code fragments, which is becoming more and more important in the field of software engineering. Many code clone detection methods have been proposed, among which tree-based methods are able to handle semantic code clones. However, these methods are difficult to scale to big code due to the complexity of tree structures. In this paper, we design Amain, a scalable tree-based semantic code clone detector by building Markov chains models. Specifically, we propose a novel method to transform the original complex tree into simple Markov chains and measure the distance of all states in these chains. After obtaining all distance values, we feed them into a machine learning classifier to train a code clone detector. To examine the effectiveness of Amain, we evaluate it on two widely used datasets namely Google Code Jam and BigCloneBench. Experimental results show that Amain is superior to nine state-of-the-art code clone detection tools (i.e., SourcererCC, RtvNN, Deckard, ASTNN, TBCNN, CDLH, FCCA, DeepSim, and SCDetector).