philosophers_prep/rendu/simple_philosophers.c

/* ************************************************************************** */
/*                                                                            */
/*                                                        :::      ::::::::   */
/*   simple_philosophers.c                              :+:      :+:    :+:   */
/*                                                    +:+ +:+         +:+     */
/*   By: ruiferna <ruiferna@student.42porto.com>    +#+  +:+       +#+        */
/*                                                +#+#+#+#+#+   +#+           */
/*   Created: 2025/10/09 11:16:23 by ruiferna          #+#    #+#             */
/*   Updated: 2025/10/09 18:58:45 by ruiferna         ###   ########.fr       */
/*                                                                            */
/* ************************************************************************** */

#include "simple_philosophers.h"

#define PHILOS 3
#define FORKS 3

typedef struct s_shared
{
	int	philos;
	int alive;
	pthread_mutex_t alive_mutex;
	pthread_mutex_t philo_mutex;
	pthread_mutex_t printf_lock;
	pthread_mutex_t forks[FORKS];
}	t_shared;

void message(long long timestamp, int id,
	char *action, pthread_mutex_t *mutex)
{
	pthread_mutex_lock(mutex);
	printf("[%lld] Philosopher %i is %s.\n", timestamp, id, action);
	// printf("%lld %i %s\n", timestamp, id, action);
	pthread_mutex_unlock(mutex);
}

void *philo_routine(void *arg)
{
	t_shared *shared;
	int philo_id;
	long long timestamp;
	
	shared = (t_shared *) arg;
	timestamp = get_current_time();
	pthread_mutex_lock(&shared->philo_mutex);
	shared->philos += 1;
	/* convert to 0-based id for indexing forks */
	philo_id = shared->philos - 1;
	pthread_mutex_unlock(&shared->philo_mutex);
	/* small stagger to reduce simultaneous contention: odd threads sleep briefly */
	if (philo_id % 2 == 1)
		precise_sleep(50);
	while (1)
	{
		/* check alive flag */
		pthread_mutex_lock(&shared->alive_mutex);
		if (!shared->alive)
		{
			pthread_mutex_unlock(&shared->alive_mutex);
			break;
		}
		pthread_mutex_unlock(&shared->alive_mutex);

		message(get_current_time()-timestamp,
			philo_id + 1, "thinking", &shared->printf_lock);
		precise_sleep(1000);
		int left = philo_id;
		int right = (philo_id + 1) % FORKS;
		int first = left;
		int second = right;
		if (first > second) {
			int tmp = first;
			first = second;
			second = tmp;
		}
	
		pthread_mutex_lock(&shared->forks[first]);
		message(get_current_time()-timestamp,
			philo_id + 1, "grabbed first fork", &shared->printf_lock);
		/* try to grab the second fork; if unavailable, release first and retry/check alive */
		if (pthread_mutex_trylock(&shared->forks[second]) != 0)
		{
			/* couldn't get second fork: release first and go back to loop */
			pthread_mutex_unlock(&shared->forks[first]);
			message(get_current_time()-timestamp,
				philo_id + 1, "released first fork", &shared->printf_lock);
			/* brief pause with per-philosopher jitter to reduce contention */
			precise_sleep(10 + ((philo_id * 37) % 50));
			/* check alive before continuing */
			pthread_mutex_lock(&shared->alive_mutex);
			if (!shared->alive)
			{
				pthread_mutex_unlock(&shared->alive_mutex);
				break;
			}
			pthread_mutex_unlock(&shared->alive_mutex);
			continue;
		}
		message(get_current_time()-timestamp,
			philo_id + 1, "grabbed second fork", &shared->printf_lock);
		message(get_current_time()-timestamp,
			philo_id + 1, "eating", &shared->printf_lock);
		precise_sleep(1000);
	
		pthread_mutex_unlock(&shared->forks[first]);
		message(get_current_time()-timestamp,
			philo_id + 1, "released first fork", &shared->printf_lock);
		pthread_mutex_unlock(&shared->forks[second]);
		message(get_current_time()-timestamp,
			philo_id + 1, "released second fork", &shared->printf_lock);
	}
	return (NULL);
}

void *monitor_routine(void *arg)
{
	t_shared *shared = (t_shared *)arg;
	/* run for 10 seconds then flip alive to 0 */
	precise_sleep(10000);
	pthread_mutex_lock(&shared->alive_mutex);
	shared->alive = 0;
	pthread_mutex_unlock(&shared->alive_mutex);
	return NULL;
}

int main()
{
	pthread_t *philos;
	t_shared shared;
	pthread_t monitor;

	pthread_mutex_init(&shared.philo_mutex, NULL);
	pthread_mutex_init(&shared.printf_lock, NULL);
	pthread_mutex_init(&shared.alive_mutex, NULL);
	/* initialize fork mutexes */
	for (int i = 0; i < FORKS; ++i)
		pthread_mutex_init(&shared.forks[i], NULL);
	shared.philos = 0;
	shared.alive = 1;
	/* allocate correct size for pthread_t array */
	philos = malloc(sizeof(pthread_t) * PHILOS);
	int i = 0;
	while (i < PHILOS)
	{
		pthread_create(&philos[i++], NULL, philo_routine, &shared);
	}
	/* start monitor to stop after 10 seconds */
	pthread_create(&monitor, NULL, monitor_routine, &shared);
	i = 0;
	while (i < PHILOS)
	{
		pthread_join(philos[i++], NULL);
	}
	/* wait for monitor (it may have already finished) */
	pthread_join(monitor, NULL);
	/* cleanup */
	for (int j = 0; j < FORKS; ++j)
		pthread_mutex_destroy(&shared.forks[j]);
	pthread_mutex_destroy(&shared.philo_mutex);
	pthread_mutex_destroy(&shared.printf_lock);
	pthread_mutex_destroy(&shared.alive_mutex);
	free(philos);
	return (0);


}