#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/times.h>
#include <time.h>
 
int sum;


int factorial (int n)
{
    if (n == 0)
        return 1;
    else
        return (n * factorial (n-1));
}

int forkloop (int n)
{
    int i;

 
    if (n == 0)
        sum = 0;
        
    else if (n == 1)
        sum = 1;
    
    else {
        pid_t pid;
         for (i = n;  i > 0; i--) {
            if (fork() == 0) {
                int rv;
                rv = factorial(i);
                exit(rv);
        }
            else if (pid < 0) { /* error */
                fprintf(stderr, "Fork failed\n");
                return 1;
            }
            else /* parent process */
            {
                int val;              
                wait(&val);
                sum = sum + WEXITSTATUS(val);
                //return 0;
            }
        }
    }
    return 0;
}
 
int main()
{
    clock_t start, end;
    double elapsed = 1.0;
    struct tms tm;
    int i;
    int input;
    
  printf("Please input an integer value to be factored (keep it small): ");
  scanf("%d", &input);
 
    start = times(&tm);
    
    forkloop(input);
        
    end = clock();
    for(i = 0; i < 2000000; i++)
        elapsed += (i + elapsed)* (1 - 0.5*elapsed);
    end = times(&tm);
    
    printf("The final factoral sum of: %d is: %d\n", input, sum);
    printf("Start End are: %ld %ld\n", (long)start, (long)end);
    elapsed = end - start;
    printf("Elapsed time is %lf\n", elapsed);
    
    printf("TMS time User CPU time is %ld \n", (long) tm.tms_utime);
    
    return 0;
}