Do the fix ingredients already exist? An empirical inquiry into the redundancy assumptions of program repair approaches

Much initial research on automatic program repair has fo-cused on experimental results to probe their potential to find patches and reduce development effort. Relatively less effort has been put into understanding the hows and whys of such approaches. For example, a critical assumption of the Gen-Prog technique is that certain bugs can be fixed by copying and re-arranging existing code. In other words, GenProg as-sumes that the fix ingredients already exist elsewhere in the code. In this paper, we formalize these assumptions around the concept of “temporal redundancy”. A temporally redun-dant commit is only composed of what has already existed in previous commits. Our experiments show that a large pro-portion of commits that add existing code are temporally redundant. This validates the fundamental redundancy as-sumption of GenProg. 1