Write one program in C/C++ that implements word frequency count of a text file using the MapReduce framework, with the master using pthreads to create and synchronize the worker threads using semaphores.

The input data is partitioned into a set of M splits using a splitting function. The map invocations are distributed across M threads, i.e., the input splits are processed in parallel by different threads. Reduce invocations are distributed by partitioning the intermediate key space into R pieces. The input data, number of splits M, the splitting function, and the number of partitions R <= M are specified by command line parameters ./mr M R

My question is how do I use Map/Reduce. I know how to search for words and count the occurrences of each word. I've already searched online on what Map/Reduce is and how it works but I can't find anything simple enough for me to understand. Are they functions named Map and Reduce? Is it a library similar to ? What exactly does it do and how am I supposed to implement it?