C language Homework

#include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <time.h> #include <unistd.h> // Change the constant below to change the number of philosophers // coming to lunch... #define PHILOSOPHER_COUNT 5 // Each philosopher is represented by one thread. Each thread independenly // runs the same "think/start eating/finish eating" program. pthread_t philosopher[PHILOSOPHER_COUNT]; // Each chopstick gets one mutex. If there are N philosophers, there are // N chopsticks. That's the whole problem. There's not enough chopsticks // for all of them to be eating at the same time. If they all cooperate, // everyone can eat. If they don't... or don't know how.... well.... // philosophers are going to starve. pthread_mutex_t chopstick[PHILOSOPHER_COUNT]; int Random_Int(int max) { return((rand() % (max+1))); } void *philosopher_program(int philosopher_number) { // In this version of the "philosopher program", the philosopher // will think and eat forever. int i_want_this; int i_want_this_too; while (1) { // Philosophers always think before they eat. They need to // build up a bit of hunger.... usleep(1); // That was a lot of thinking.... now hungry... this // philosopher is a jerk. He may not grap the chopsticks // closest to him. In fact, he may grab any two chopsticks at // the table.... because he is a jerk. i_want_this = Random_Int(PHILOSOPHER_COUNT); while ((i_want_this_too = Random_Int(PHILOSOPHER_COUNT)) == i_want_this); printf ("Jerk Philosopher %d wants chopsticks %d and %d\n", philosopher_number, i_want_this, i_want_this_too); pthread_mutex_lock(&chopstick[i_want_this]); pthread_mutex_lock(&chopstick[i_want_this_too]); // Hurray, if I got this far I'm eating printf ("Jerk Philosopher %d is eating with chopsticks %d and %d\n", philosopher_number, i_want_this, i_want_this_too); // I'm done eating. Now put the chopsticks back on the table pthread_mutex_unlock(&chopstick[i_want_this]); pthread_mutex_unlock(&chopstick[i_want_this_too]); } return(NULL); } int main() { int i; srand(time(NULL)); for(i=0;i<PHILOSOPHER_COUNT;i++) pthread_mutex_init(&chopstick[i],NULL); for(i=0;i<PHILOSOPHER_COUNT;i++) pthread_create(&philosopher[i],NULL,(void *)philosopher_program,(void *)i); for(i=0;i<PHILOSOPHER_COUNT;i++) pthread_join(philosopher[i],NULL); for(i=0;i<PHILOSOPHER_COUNT;i++) pthread_mutex_destroy(&chopstick[i]); return 0; }