If you're a computer programmer and don't have much computer code, then refactoring is easy. You start up your IDE, fill out a little dialog box, and there you go. But if you're part of an organization of 1000s of engineers who have been cranking out code for several years, then refactoring (or other code analysis/transformation/whatever) is not so easy. You try to load all that code in your IDE... and are then dismayed when your workstation bursts into flames and falls off of your desk. But what if some of your 1000s of engineers had set up a distributed programming network you could use? Then you might end up with something like Clang MapReduce. This tool is pretty amazing.