Exercise 10

Create a 2-dimensional cartesian grid topology to communicate between processes.

In each task is initialized a variable with the local rank of the cartesian communicator. The exercise is divided in three steps:

1) Compare the local rank with the global MPI_COMM_WORLD rank. Are they the same number?

2) Calculate on each task the average between its local rank and the local rank from each of its neighbours (north, east, south, west). Notice that in order to do this the cartesian communicator has to be periodic (the bottom rank is neighbour of the top)

3) Calculate the average of the local ranks on each row and column. Create a family of sub-cartesian communicators to allow the communications between rows and columns