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// https://en.wikipedia.org/wiki/Dining_philosophers_problem
#include <stdio.h>
#include <time.h>
#include <stc/crand.h>
#include <stc/coroutine.h>
// Define the number of philosophers and forks
enum {
num_philosophers = 5,
num_forks = num_philosophers,
};
struct Philosopher {
int id;
cco_timer tm;
cco_sem* left_fork;
cco_sem* right_fork;
int cco_state; // required
};
struct Dining {
// Define semaphores for the forks
cco_sem forks[num_forks];
struct Philosopher ph[num_philosophers];
int cco_state; // required
};
// Philosopher coroutine
int philosopher(struct Philosopher* p)
{
double duration;
cco_routine(p) {
while (1) {
duration = 1.0 + crandf()*2.0;
printf("Philosopher %d is thinking for %.0f minutes...\n", p->id, duration*10);
cco_await_timer(&p->tm, duration);
printf("Philosopher %d is hungry...\n", p->id);
cco_await_sem(p->left_fork);
cco_await_sem(p->right_fork);
duration = 0.5 + crandf();
printf("Philosopher %d is eating for %.0f minutes...\n", p->id, duration*10);
cco_await_timer(&p->tm, duration);
cco_sem_release(p->left_fork);
cco_sem_release(p->right_fork);
}
cco_final:
printf("Philosopher %d finished\n", p->id);
}
return 0;
}
// Dining coroutine
int dining(struct Dining* d)
{
cco_routine(d) {
for (int i = 0; i < num_forks; ++i)
cco_sem_set(&d->forks[i], 1); // all forks available
for (int i = 0; i < num_philosophers; ++i) {
cco_reset(&d->ph[i]);
d->ph[i].id = i + 1;
d->ph[i].left_fork = &d->forks[i];
d->ph[i].right_fork = &d->forks[(i + 1) % num_forks];
}
while (1) {
// per-"frame" logic resume each philosopher
for (int i = 0; i < num_philosophers; ++i) {
philosopher(&d->ph[i]);
}
cco_yield(); // suspend, return control back to main
}
cco_final:
for (int i = 0; i < num_philosophers; ++i) {
cco_stop(&d->ph[i]);
philosopher(&d->ph[i]);
}
puts("Dining finished");
}
return 0;
}
int main(void)
{
struct Dining dine;
cco_reset(&dine);
int n=0;
cco_timer tm = cco_timer_from(15.0); // seconds
csrand((uint64_t)time(NULL));
cco_blocking_call(dining(&dine))
{
if (cco_timer_expired(&tm))
cco_stop(&dine);
cco_sleep(0.001);
++n;
}
printf("n=%d\n", n);
}
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