MapReduce–for those of you who aren’t familiar, it’s basically this programming technique for doing batch jobs across a huge amount of data. There’s two functions, if you programming functionally, map and reduce. Map basically says given this list of things, apply this function to it. And then reduce basically says given these two things, apply this function to it and combine it into one thing. So if you’re working over a huge chunk of data– Google made MapReduce famous building their indices for the web. Basically, they take all the webpages on the Internet and you can apply this function to it which is basically find the words in this document. And then you can reduce on that to basically reduce that content down to the kind of target output you want.