/*
* Recursively compute the specified number. If print is
* true, print it. Otherwise, provide it to my parent process.
*
* NOTE: The solution must be recursive and it must fork
* a new child for each call. Each process should call
* doFib() exactly once.
*/
static void
doFib(int n, int doPrint)
{
// Kyung driving now
int status1 = 0, status2 = 0;
pid_t child1, child2;
if(n == 0 || n == 1) { /* base case */
if(doPrint) {
fprintf(stdout, "%d\n", n);
}
exit(n);
}
else {
child1 = fork();
if(child1 == 0) { /* child process 1 */
doFib(n-1, 0);
}
wait(&status1);
child2 = fork();
if(child2 == 0) { /* child process 2 */
doFib(n-2, 0);
}
wait(&status2);
if(doPrint) { /* parent process */
fprintf(stdout, "%d\n", WEXITSTATUS(status1) + WEXITSTATUS(status2));
}
exit(WEXITSTATUS(status1) + WEXITSTATUS(status2));
}
// end of Kyung driving
}
int main(int argc, char **argv)
{
int arg;
int print;
if(argc != 2){
fprintf(stderr, "Usage: fib <num>\n");
exit(-1);
}
if(argc >= 3){
print = 1;
}
arg = atoi(argv[1]);
if(arg < 0 || arg > MAX){
fprintf(stderr, "number must be between 0 and %d\n", MAX);
exit(-1);
}
doFib(arg, 1);
return 0;
}
/*
* Recursively compute the specified number. If print is
* true, print it. Otherwise, provide it to my parent process.
*
* NOTE: The solution must be recursive and it must fork
* a new child for each call. Each process should call
* doFib() exactly once.
*/
static void doFib(int n, int doPrint)
{
pid_t pid1;
pid_t pid2;
int status1;
int status2;
int x = 0;
if(n <= 1)
{
if(doPrint)
{
printf("%d\n",n);
}
x = n;
exit(x);
}
//child1
if((pid1 = fork()) == 0)
{
doFib(n-1,0);
exit(x);
}
//child 2
if((pid2 = fork()) == 0)
{
doFib(n-2,0);
exit(x);
}
//parent
waitpid(pid1,&status1,0);
waitpid(pid2,&status2,0);
if(WIFEXITED(status1) && WIFEXITED(status2))
{
x = WEXITSTATUS(status1) + WEXITSTATUS(status2);
if(doPrint)
{
printf("%d\n",x);
}
exit(x);
}
}
// Max driving now
static void
doFib(int n, int doPrint)
{
pid_t pid = Fork();
int r;
if (pid == 0) {
if (n == 0 || n == 1) {
exit(n);
} else {
pid_t pid1 = Fork();
pid_t pid2;
int r1;
int r2;
if (pid1 != 0) {
pid2 = Fork();
}
if (pid1 == 0) {
doFib(n-1, 0);
} else if (pid2 == 0) {
doFib(n-2, 0);
} else {
waitpid(pid1, &r1, 0);
waitpid(pid2, &r2, 0);
exit(WEXITSTATUS(r1) + WEXITSTATUS(r2));
}
}
} else {
wait(&r);
int status = WEXITSTATUS(r);
if (doPrint) {
printf("%d\n", status);
} else {
exit(status);
}
}
}
/*
* fork a new process to compute fib for n
* parent proces will wait for the result and use it
* as return value
*/
int doFibChild(int n)
{
pid_t cpid;
int status;
cpid = fork();
if (-1 == cpid)
unix_error("fork failure");
if (0 == cpid){ /* code executed by child */
doFib(n, 0);
}
else{ /* code executed by parent */
if (-1 == waitpid(cpid, &status, 0))
unix_error("wait failure");
if (WIFEXITED(status)) /* status ok, get the return value from child */
return WEXITSTATUS(status);
else
unix_error("ERROR STATUS OF CHILD PROCESS");
}
}
