I nije bas "famozan" kod, ali je lepo zamisljeno.
Evo malko boljeg primera iz literature koji je vec toliko prozvakan da me cudi da nije primenjena neka slicna analogija. Ovde je samo stavljen QuickSort kao primer, ali lako se daju ubaciti i ostali.
//----------------------------------------------------------------------------
#include <sys/types.h>
#include <unistd.h>
#include <sys/time.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
/* timer variables for seconds and microseconds */
#define start_sec 9
#define start_usec 0
#define max_usec 1000000
/* declare variables common to the process environment */
static int signal_1_flag = 0;
static int signal_2_flag = 0;
static void signal_start_handler (int signo) {
/* function to start processing in child by setting signal 1 flag*/
if (signo == SIGUSR1) {
printf ("Starting work in child process.\n");
signal_1_flag = 1;
return;
}
else {
printf ("Error handling signal to child process.\n");
exit (1);
}
}
static void signal_compute_time (int signo) {
/* function to start computation of elapsed time by setting signal 2 flag */
if (signo == SIGUSR2) {
printf ("Starting elapsed-time computation in parent.\n");
signal_2_flag = 1;
return;
}
else {
printf ("Error handling signal to parent process.\n");
exit (1);
}
}
/* child will perform quicksort on n elements as work to be timed */
#define array_size 100000
void quicksort (int a[], int n);
int main (void) {
pid_t pid; /* variable to record process id of child */
int temp; /* temporary variable, not used for real data */
struct itimerval ival; /* variable to set timer values */
struct itimerval real_time; /* variable to retrieve times from timer */
printf ("Starting program in which parent times work in child process\n\n");
/* prepare the signal handlers for two signals */
if (signal(SIGUSR1, signal_start_handler) == SIG_ERR)
printf ("Initial setup error: unable to create handler for SIGUSR1.\n");
if (signal(SIGUSR2, signal_compute_time) == SIG_ERR)
printf ("Initial setup error: unable to create handler for SIGUSR2.\n");
/* spawn child process */
pid = fork(); /* create new process */
if (-1 == pid) /* check for error in spawning child process */
{ perror ("Error in fork");
exit (1);
}
if (0 == pid) /* check if this is the new child process */
{ /* processing for child */
printf ("Starting child process\n");
printf ("Child pid: %d; parent pid: %d\n", getpid(), getppid());
/* waste time until SIGUSR1 signal tells child to start */
while (!signal_1_flag) /* terminates when SIGUSR1 signal is received */
temp = 1;
/* meaningful work goes here */
{ /* set up array for quicksort */
int i;
int a[array_size];
for (i = 0; i < array_size; i++)
a
= rand ();
quicksort (a, array_size);
}
/* signal parent process when done */
kill (getppid(), SIGUSR2);
/* end child process */
printf ("Exiting child process\n");
exit (0);
}
else
{ /* processing for parent */
printf ("Continuing processing in parent process.\n");
/* set interval timer */
ival.it_interval.tv_sec = start_sec; /* initialize second field */
ival.it_interval.tv_usec = start_usec; /* initialize microsecond field */
ival.it_value.tv_sec = start_sec; /* reset second field */
ival.it_value.tv_usec = start_usec; /* reset microsecond field */
setitimer(ITIMER_REAL, &ival, NULL);
/* signal child with SIGUSR1 */
kill (pid, SIGUSR1);
/* waste time until SIGUSR2 signal indicates child's work done */
while (!signal_2_flag) /* terminates when SIGUSR2 signal is received */
temp = 1;
/* above loop will stop only when SIGUSR2 signal is received */
getitimer(ITIMER_REAL, &real_time);
printf ("Elapsed time is %d seconds, %d microseconds\n",
start_sec - real_time.it_value.tv_sec - 1,
max_usec - real_time.it_value.tv_usec);
/* end parent process */
printf ("Exiting parent process\n");
exit (0);
}
}
/* functions for the quicksort */
void partition (int a[], int left, int right, int *middle) {
/* places a[left] in position a[*middle],
permuting a[left]..a[right] so a[left]..a[middle-1] <= a[*middle]
and a[*middle] <= a[(*middle)+1]..a[right] */
int l_spot = left+1;
int r_spot = right;
int temp;
while (l_spot <= r_spot) {
while ((l_spot <= r_spot)&&(a[left] <= a[r_spot]))
r_spot--;
while ((l_spot <= r_spot)&&(a[l_spot] <= a[left]))
l_spot++;
if (l_spot <= r_spot) {
temp = a[r_spot];
a[r_spot] = a[l_spot];
a[l_spot] = temp;
}
}
temp = a[r_spot];
a[r_spot] = a[left];
a[left] = temp;
*middle = r_spot;
}
void quicksort (int a[], int n) {
/* performs quicksort to order elements in array a */
int mid;
if (n > 1) {
partition (a, 0, n-1, &mid);
quicksort (a, mid);
quicksort (a+mid+1,n - (mid+1));
}
}
//----------------------------------------------------------------------------
ISO/IEC JTC1/SC22/WG14-ISO/IEC 9899:1999
Re: Kako napraviti niz od 30 miliona elemenata??
