message-chain-persistent

Message chain with persistent communication

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. Implement the program described above using persistent communication, i.e. MPI_Send_init, MPI_Recv_init, MPI_Start and MPI_Wait. You may start from scratch or use the skeleton code (skeleton.cpp or skeleton.F90) as a starting point.

2. Write a version that uses MPI_Startall and MPI_Waitall instead of MPI_Starts and MPI_Waits.