#include <mpi.h>
#include <stdio.h>
#include <string.h>
 
int main(int argc, char *argv[]) {
    int rank, size;
    MPI_Init(&argc, &argv);           // Initialize MPI environment
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);   // Get the rank of the process
    MPI_Comm_size(MPI_COMM_WORLD, &size);   // Get the total number of processes
 
    char message[20];
    if (rank % 2 == 0) {   // Even rank
        strcpy(message, "Hello World");
        if (rank + 1 < size) {   // Ensure the corresponding odd rank exists
            MPI_Send(message, strlen(message) + 1, MPI_CHAR, rank + 1, 0, MPI_COMM_WORLD);  // Send the message to the next odd rank
            printf("Even process %d sent message '%s' to odd process %d\n", rank, message, rank + 1);
        }
    } else {   // Odd rank
        MPI_Recv(message, 20, MPI_CHAR, rank - 1, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);  // Receive the message from the previous even rank
        printf("Odd process %d received message '%s' from even process %d\n", rank, message, rank - 1);
    }
 
    MPI_Finalize();   // Finalize MPI environment
    return 0;
}
 

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