Coherent clusters in source code

This paper presents the results of a large scale empirical study of coherent dependence clusters. All statements in a coherent dependence cluster depend upon the same set of statements and a↵ect the same set of statements; a coherent cluster’s statements have ‘coherent’ shared backward and forward dependence. We introduce an approximation to efficiently locate coherent clusters and show that it has a minimum precision of 97.76%. Our empirical study also finds that, despite their tight coherence constraints, coherent dependence clusters are in abundance: 23 of the 30 programs studied have coherent clusters that contain at least 10% of the whole program. Studying patterns of clustering in these programs reveals that most programs contain multiple significant coherent clusters. A series of case studies reveals that these major clusters map to logical functionality and program structure. For example, we show that for the program acct, the top five coherent clusters all map to specific, yet otherwise non-obvious, functionality. Cluster visualization can also reveal subtle deficiencies in program structure and identify potential candidates for refactoring e↵orts. Finally a study of inter-cluster dependence is used to highlight how coherent clusters built are connected to each other, revealing higher-level structures, which can be used in reverse engineering