MPI master & slave 模式的基本框架

rank 0为master其余都是slave http://www.lam-mpi.org/tutorials/one-step/ezstart.php ~~~ #include <mpi.h> #define WORKTAG 1 #define DIETAG 2 /* Local functions */ static void master(void); static void slave(void); static unit_of_work_t get_next_work_item(void); static void process_results(unit_result_t result); static unit_result_t do_work(unit_of_work_t work); int main(int argc, char **argv) { int myrank; /* Initialize MPI */ MPI_Init(&argc, &argv); /* Find out my identity in the default communicator */ MPI_Comm_rank(MPI_COMM_WORLD, &myrank); if (myrank == 0) { master(); } else { slave(); } /* Shut down MPI */ MPI_Finalize(); return 0; } static void master(void) { int ntasks, rank; unit_of_work_t work; unit_result_t result; MPI_Status status; /* Find out how many processes there are in the default communicator */ MPI_Comm_size(MPI_COMM_WORLD, &ntasks); /* Seed the slaves; send one unit of work to each slave. */ for (rank = 1; rank < ntasks; ++rank) { /* Find the next item of work to do */ work = get_next_work_item(); /* Send it to each rank */ MPI_Send(&work, /* message buffer */ 1, /* one data item */ MPI_INT, /* data item is an integer */ rank, /* destination process rank */ WORKTAG, /* user chosen message tag */ MPI_COMM_WORLD); /* default communicator */ } /* Loop over getting new work requests until there is no more work to be done */ work = get_next_work_item(); while (work != NULL) { /* Receive results from a slave */ MPI_Recv(&result, /* message buffer */ 1, /* one data item */ MPI_DOUBLE, /* of type double real */ MPI_ANY_SOURCE, /* receive from any sender */ MPI_ANY_TAG, /* any type of message */ MPI_COMM_WORLD, /* default communicator */ &status); /* info about the received message */ /* Send the slave a new work unit */ MPI_Send(&work, /* message buffer */ 1, /* one data item */ MPI_INT, /* data item is an integer */ status.MPI_SOURCE, /* to who we just received from */ WORKTAG, /* user chosen message tag */ MPI_COMM_WORLD); /* default communicator */ /* Get the next unit of work to be done */ work = get_next_work_item(); } /* There's no more work to be done, so receive all the outstanding results from the slaves. */ for (rank = 1; rank < ntasks; ++rank) { MPI_Recv(&result, 1, MPI_DOUBLE, MPI_ANY_SOURCE, MPI_ANY_TAG, MPI_COMM_WORLD, &status); } /* Tell all the slaves to exit by sending an empty message with the DIETAG. */ for (rank = 1; rank < ntasks; ++rank) { MPI_Send(0, 0, MPI_INT, rank, DIETAG, MPI_COMM_WORLD); } } static void slave(void) { unit_of_work_t work; unit_result_t results; MPI_Status status; while (1) { /* Receive a message from the master */ MPI_Recv(&work, 1, MPI_INT, 0, MPI_ANY_TAG, MPI_COMM_WORLD, &status); /* Check the tag of the received message. */ if (status.MPI_TAG == DIETAG) { return; } /* Do the work */ result = do_work(work); /* Send the result back */ MPI_Send(&result, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD); } } static unit_of_work_t get_next_work_item(void) { /* Fill in with whatever is relevant to obtain a new unit of work suitable to be given to a slave. */ } static void process_results(unit_result_t result) { /* Fill in with whatever is relevant to process the results returned by the slave */ } static unit_result_t do_work(unit_of_work_t work) { /* Fill in with whatever is necessary to process the work and generate a result */ } ~~~