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/* File: * mpi_hello.c * * Purpose: * A "hello,world" program that uses MPI * * Compile: * mpicc -g -Wall -std=C99 -o mpi_hello mpi_hello.c * Usage: * mpiexec -n ./mpi_hello * * Input: * None * Output: * A greeting from each process * * Algorithm: * Each process sends a message to process 0, which prints * the messages it has received, as well as its own message. * * IPP: Section 3.1 (pp. 84 and ff.) */ #include #include /* For strlen */ #include /* For MPI functions, etc */ const int MAX_STRING = 100; int main(void) { char greeting[MAX_STRING]; /* String storing message */ int comm_sz; /* Number of processes */ int my_rank; /* My process rank */ /* Start up MPI */ MPI_Init(NULL, NULL); /* Get the number of processes */ MPI_Comm_size(MPI_COMM_WORLD, &comm_sz); /* Get my rank among all the processes */ MPI_Comm_rank(MPI_COMM_WORLD, &my_rank); if (my_rank != 0) { /* Create message */ sprintf(greeting, "Greetings from process %d of %d!", my_rank, comm_sz); /* Send message to process 0 */ MPI_Send(greeting, strlen(greeting)+1, MPI_CHAR, 0, 0, MPI_COMM_WORLD); } else { /* Print my message */ printf("Greetings from process %d of %d!\n", my_rank, comm_sz); for (int q = 1; q < comm_sz; q++) { /* Receive message from process q */ MPI_Recv(greeting, MAX_STRING, MPI_CHAR, q, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE); /* Print message from process q */ printf("%s\n", greeting); } } /* Shut down MPI */ MPI_Finalize(); return 0; } /* main */