#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>

double drandom(void)
{
  return (double)random() / 2147483648.0;
}

int main(int argc, char **argv)
{
  long inside, rounds, truerounds, childinside, childrounds;
  long i;
  double x, y;
  unsigned seed = 12345;
  int j;
  int children;
  int child;
  int (*cpipe)[2];
  int *cpid;

  if (argc < 3 || 1!= sscanf(argv[1], "%ld", &rounds)) {
    fprintf(stderr,"Usage: %s rounds seed [seed...]\n", argv[0]);
    return 1;
  }

  children = argc - 2;
  cpipe = malloc(2*children*sizeof(int));
  cpid = malloc(children*sizeof(int));

  for (j = 2; j < argc; j++) {
    if (1!=sscanf(argv[j],"%u", &seed)) {
      fprintf(stderr, "invalid seed '%s'\n", argv[j]);
      return 1;
    }
    child = j-2;
    childrounds = rounds / (children - child);
    rounds -= childrounds;
    printf("starting child %d with seed %s\n", child, argv[j]);
    if (pipe(cpipe[child])) {
      perror("pipe");
      return 1;
    }
    if (!(cpid[child] = fork())) {
      close(cpipe[child][0]);
      srandom(seed);
      inside = 0;
      i = childrounds;
      while (i--) {
	x = drandom();
	y = drandom();
	if (x*x + y*y < 1) inside++;
      }
      write(cpipe[child][1],&inside,sizeof(inside));
      write(cpipe[child][1],&childrounds,sizeof(childrounds));
      close(cpipe[child][1]);
      return 0;
    } else if (cpid[child] < 0) {
      perror("fork");
      return 0;
    }
    close(cpipe[child][1]);
  }

  inside = 0;
  truerounds = 0;
  for (child = 0; child < children; child++) {
    waitpid(cpid[child],NULL,0);
    read(cpipe[child][0],&childinside,sizeof(childinside));
    read(cpipe[child][0],&childrounds,sizeof(childrounds));
    close(cpipe[child][0]);
    printf("child %d reported %ld:%ld -> %f\n", child,
	   childinside, childrounds, (double)childinside/childrounds * 4);
    inside += childinside;
    truerounds += childrounds;
  }

  
  printf("Total: %ld:%ld -> %f\n", inside, truerounds, (double)inside/truerounds * 4);

  return 0;
}