Philosophers

Philosophers with threads and mutexes

Overview

Here are the things you need to know if you want to succeed this assignment:

• One or more philosophers sit at a round table. There is a large bowl of spaghetti in the middle of the table.

• The philosophers alternatively eat, think, or sleep. While they are eating, they are not thinking nor sleeping; while thinking, they are not eating nor sleeping; and, of course, while sleeping, they are not eating nor thinking.

• There are also forks on the table. There are as many forks as philosophers.

• Because serving and eating spaghetti with only one fork is very inconvenient, a philosopher takes their right and their left forks to eat, one in each hand.

• When a philosopher has finished eating, they put their forks back on the table and start sleeping. Once awake, they start thinking again. The simulation stops when a philosopher dies of starvation.

• Every philosopher needs to eat and should never starve.

• Philosophers don’t speak with each other.

• Philosophers don’t know if another philosopher is about to die.

• No need to say that philosophers should avoid dying!

Global rules

You have to write a program for the mandatory part and another one for the bonus part (if you decide to do the bonus part). They both have to comply with the following rules:

• Global variables are forbidden!

• Your(s) program(s) should take the following arguments: number_of_philosophers time_to_die time_to_eat time_to_sleep [number_of_times_each_philosopher_must_eat]

  • number_of_philosophers: The number of philosophers and also the number of forks

  • time_to_die (in milliseconds): If a philosopher didn’t start eating time_to_die milliseconds since the beginning of their last meal or the beginning of the simulation, they die.

  • time_to_eat (in milliseconds): The time it takes for a philosopher to eat. During that time, they will need to hold two forks.

  • time_to_sleep (in milliseconds): The time a philosopher will spend sleeping.

  • number_of_times_each_philosopher_must_eat (optional argument): If all philosophers have eaten at least number_of_times_each_philosopher_must_eat times, the simulation stops. If not specified, the simulation stops when a philosopher dies.

• Each philosopher has a number ranging from 1 to number_of_philosophers.

• Philosopher number 1 sits next to philosopher number number_of_philosophers. Any other philosopher number N sits between philosopher number N - 1 and philosopher number N + 1.

About the logs of your program:

• Any state change of a philosopher must be formatted as follows:

  • timestamp_in_ms X has taken a fork

  • timestamp_in_ms X is eating

  • timestamp_in_ms X is sleeping

  • timestamp_in_ms X is thinking

  • timestamp_in_ms X died

  Replace timestamp_in_ms with the current timestamp in milliseconds and X with the philosopher number.

• A displayed state message should not be mixed up with another message

• A message announcing a philosopher died should be displayed no more than 10 ms after the actual death of the philosopher.

• Again, philosophers should avoid dying!

Mandatory part

Program name	philo
Turn in files	Makefile, *.h, *.c, in directory philo/
Makefile	NAME, all, clean, fclean, re
Arguments	number_of_philosophers time_to_die time_to_eat time_to_sleep [number_of_times_each_philosopher_must_eat]
External functs.	memset, printf, malloc, free, write, usleep, gettimeofday, pthread_create, pthread_detach, pthread_join, pthread_mutex_init, pthread_mutex_destroy, pthread_mutex_lock, pthread_mutex_unlock
Libft authorized	No
Description	Philosophers with threads and mutexes

The specific rules for the mandatory part are:

• Each philosopher should be a thread.

• There is one fork between each pair of philosophers. Therefore, if there are several philosophers, each philosopher has a fork on their left side and a fork on their right side. If there is only one philosopher, there should be only one fork on the table.

• To prevent philosophers from duplicating forks, you should protect the forks state with a mutex for each of them.