message-chain-cartesian

Message chain with Cartesian communicator

Write a program where every MPI task sends data to the next one. Let ntasks be the number of the tasks, and myid the rank of the current task. Your program should work as follows:

• Every task with a rank less than ntasks-1 sends a message to task myid+1. For example, task 0 sends a message to task 1.
• The message content is an integer array where each element is initialised to myid.
• The message tag is the receiver's rank.
• The sender prints out the number of elements it sends and the tag it used.
• All tasks with rank > 0 receive messages.
• Each receiver prints out their myid and the first element in the received array.

1. Create a Cartesian topology for the chain. Utilize MPI_Cart_shift for finding the neighbouring ranks and implement the communication with MPI point-to-point routines (either blocking or non-blocking). Use cpp/skeleton.cpp or skeleton.F90 as a starting point.

2. Make a version where the chain is periodic, i.e. task ntasks-1 sends to task 0 and every task receives.