Finding relevant functions in millions of lines of code

Source code search engines locate and display fragments of code relevant to user queries. These fragments are often isolated and detached from one another. Programmers need to see how source code interacts in order to understand the concepts implemented in that code, however. In this paper, we present Portfolio, a source code search engine that retrieves and visualizes relevant functions as chains of function invocations. We evaluated Portfolio against Google Code Search and Koders in a case study with 49 professional programmers. Portfolio outperforms both of these engines in terms of relevance and visualization of the returned results.