holiday-wishes-2015.c

gistfile1.c

/* You will need a C99 compiler and an implementation of
   the POSIX human interface function feel_joy(3). */

#include <mpi.h>
#include <time.h>
#include <sys/time.h>
#include <stdlib.h>

enum wish_t {
    HAPPY_HANUKKAH,
    MERRY_CHRISTMAS,
    HAPPY_KWANZAA,
    HAPPY_NEW_YEAR,
    HAPPY_FESTIVUS,
    NWISHES
};

void do_blog_author(void)
{
    struct tm tm = {
        .tm_sec = 0,
        .tm_min = 0,
        .tm_hour = 0,
        .tm_mday = 2,
        .tm_mon = 0,
        .tm_year = 2015 - 1900
    };
    time_t done;
    done = mktime(&tm);

    int size;
    MPI_Comm_size(MPI_COMM_WORLD, &size);

    int *wishes;
    wishes = calloc(size, sizeof(int));
    for (int i = 0; i < size * 2; ++i) {
        wishes[i] = i % NWISHES;
    }

    struct timeval tv;
    gettimeofday(&tv, NULL);

    int i = 0;
    int wish;
    while (tv.tv_sec < done) {
        MPI_Scatter(wishes + i, 1, MPI_INT,
                    &wish, 1, MPI_INT,
                    0, MPI_COMM_WORLD);

        feel_joy(wish);

        i = (i + 1) % size;
        gettimeofday(&tv, NULL);
    }

    for (int i = 0; i < size; ++i) {
        wishes[i] = -1;
    }
    MPI_Scatter(wishes, 1, MPI_INT,
                &wish, 1, MPI_INT,
                0, MPI_COMM_WORLD);

    free(wishes);
}

void do_blog_reader(void)
{
    int wish;
    do {
        MPI_Scatter(NULL, 0, MPI_DATATYPE_NULL,
                    &wish, 1, MPI_INT,
                    0, MPI_COMM_WORLD);
    } while (feel_joy(wish));
}

int main(int argc, char* argv[])
{
    MPI_Init(&argc, &argv);

    int rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    if (0 == rank) {
        do_blog_author();
    } else {
        do_blog_reader();
    }

    MPI_Finalize();

    return 0;
}