/* forktest.c */
//Adapted from http://www.tjhsst.edu/~dhyatt/supercomp/n402.html

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <unistd.h>

int main(int argc, char** argv)
{
  char name[10];
  FILE *outfile;
  unsigned int pnum, i, j, pid, start, finish;
  double b=1, c=1;
  int nproc;
  int pipes[2];
  int value;
 
//   srand(time(0));   
   pipe(pipes);

  
  if (argc > 1)
     nproc = atoi(argv[1]);
  else nproc = 2;

//  nice(5);  // The command "nice" will run the program at a lower priority

  printf("Number of processes  = %d\n", nproc);
  for(pnum=0; pnum<nproc; pnum++)  // Loop through 16 processes
  {
      /* Fork a duplicate child process that starts running at this location
         but with the inherited values of the variables. */ 
	 
 //         srand(time(0));        
          value = rand() % 100; 
      pid = fork();
      switch (pid)  
      {
        case -1: /* could not fork */
          printf("uh oh.\n");
          exit(1);
          break;

        case 0: /* child process */
//          sprintf(name,"file%d",pnum); // Use sprintf to create file name
//          outfile = fopen(name,"w");   // Open file for output
//          fprintf(outfile,"I am process %d\nMy PID is #%d",pnum,getpid());
//          fclose(outfile);
          printf("I am process with pnum=%d My PID is #%d Parent is %d, pid=%d ",
	               pnum,getpid(), getppid(), pid);
         
          start = pnum << 16;
	  finish = pnum+1 << 16;
	  printf("\nValue= %d Start=%d  Finish= %d\n", value, start, finish);
	  for (j=0; j < value; j++)
	  {
	     printf("j=%d ", j);
             for(i=start;  i < finish; i++) 
             {  // Make garbage computations.  Use bit shift to make huge numbers
                b = sin(b*i)+cos(c*i);
                c = sin(c*i)+cos(b*i);
             }
	  }
        
                   
          close(pipes[0]);
	  printf("Sending %d from process %d\n", value, pnum);
	  write(pipes[1], &value, sizeof(int));  
          exit(0);
        default: /* parent process */
	    close(pipes[1]);
	    read(pipes[0], &value, sizeof(int));
	    printf("Parent process receives %d from %d, myPID= %d, pnum=%d\n", 
	         value, pid, getpid(),pnum);
          break;
      }
  }

  return 0;
}