It doesn’t comply very well with the goal of making it as easy as possible to write MapReduce programs, but Dumbo mappers and reducers can also be written in C instead of Python. I just put an example on GitHub to illustrate this. Although it’s nowhere near as convenient as using Python, writing a mapper or reducer in C is not that hard since you get to use the nifty Python C API, and in some specific cases the speed gains might be worth the extra effort. Moreover, setuptools nicely takes care of all the building and compiling, and you can limit the C code to computationally expensive parts and still use Python for the rest.
Dumbo IP count in C