When map-reduce divides a task and sends the data to each worker process, does it also transmit the instructions for how to operate on the data?
For example, let's say Google has some huge array of computers that use map-reduce to index webpages. If they wanted to temporarily use that same array of systems to do something else, would they have to reconfigure each system manually, or does map-reduce handle transmitting the new executable instructions to the workers?