/* 
 *  Generic example of master/worker program.  "Tasks" just consist of
 *  sleeping for a specified time; times to wait are generatedly
 *  randomly from 0 to a specified maximum.
 *
 *  Command-line arguments:  total tasks, maximum task time,
 *    (optional) "--verbose" for verbose output
 *
 *  Sequential version using MPI timing function.
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <mpi.h>

/* a short function to print a message and exit */
void error_exit(char msg[]) {
    fprintf(stderr, "%s", msg);
    MPI_Abort(MPI_COMM_WORLD, EXIT_FAILURE);
}

/* function to generate a random integer in [start, end] */
int random_in_range(int start, int end) {
    /* use method described in "rand" man page */
    return start + ((double) (end-start+1) * rand()/(RAND_MAX + 1.0));
}

/* ---- main program ---- */

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

  int num_tasks;
  int max_task_time;

  double start_time, end_time;

  int i;
  int task_time;
  int total_task_time = 0;

  int verbose = 0;

  if (MPI_Init(&argc, &argv) != MPI_SUCCESS) {
      fprintf(stderr, "MPI initialization error\n"); 
      exit(EXIT_FAILURE);
  }

  if (argc < 3) {
      error_exit("usage:  master-worker num_tasks max_task_time (millisecs) [--verbose]\n");
  }
  num_tasks = atoi(argv[1]);
  max_task_time = atoi(argv[2]);
  if (argc > 3)
      verbose = 1;

  start_time = MPI_Wtime();

  for (i = 0; i < num_tasks; ++i) {

      task_time = random_in_range(1, max_task_time);
      total_task_time += task_time;
      if (verbose)
          printf("task time = %d\n", task_time);
      usleep(task_time * 1000);
  }

  end_time = MPI_Wtime();

  printf("\nsequential version\n");
  printf("number of tasks = %d\n", num_tasks);
  printf("max task time = %d\n", max_task_time);
  printf("total task time = %d\n", total_task_time);
  printf("running time = %g\n", end_time - start_time);

  MPI_Finalize();
  return EXIT_SUCCESS;
}