Last updated: 2023-11-06
Write a MPI program mpi-ring.c that implements a message exchange along a ring. Let \(P\) be the number of MPI processes; the program should behave according to the following specification:
The program receives an integer \(K \geq 1\) from the command line. \(K\) is the number of “turns” of the ring. Since all MPI processes have access to the command line parameters, they know the value \(K\) without the need to communicate.
Process 0 (the master) sends process 1 an integer, whose initial value is 1.
Every process \(p\) (including the master) receives a value \(v\) from the predecessor \(p-1\), and sends \((v + 1)\) to the successor \(p+1\). The predecessor of 0 is \((P - 1)\), and the successor of \((P - 1)\) is 0.
The master prints the value received after the \(K\)-th iteration and the program terminates. Given the number \(P\) of processes and the value of \(K\), what value should be printed by the master?
For example, if \(K = 2\) and there are \(P = 4\) processes, the communication should be as shown in Figure 1 (arrows are messages whose content is the number reported above them). There are \(K = 2\) turns of the ring; at the end, process 0 receives and prints 8.
To compile:
mpicc -std=c99 -Wall -Wpedantic mpi-ring.c -o mpi-ringTo execute:
mpirun -n 4 ./mpi-ring