This project is a training to multi-threads && multi-processes programming with the use of mutex and semaphores. It contains 2 different programs (processes part and threads part) simulating a twist of the famous Dining Philosophers problem, all with the same basic rules. This project is also a good lesson in C optimization as we need to save every bit of CPU usage we can to ensure the survival of all our philosophers.

philo/ : multi-threads and use of mutex philo_bonus/ : multi-processes and use of semaphore

for unix-like users you can basically paste this command in terminal

git clone {Repo link} philosophers

then to compile multi-threads part:

cd philosophers/philo/ && make && ./philo 6 500 200 200 6

or for multi-processes part:

cd philosophers/philo_bonus && make bonus && ./philo_bonus 6 500 200 200 5

(*) Avoid testing time aguments with values less than 60ms

(**) Avoid testing with number_of_philosophers > 200 (if you did your compuer may crash)

• This project is to be coded in C, following the 42 Norm. Any leak, crash, undefined behavior or norm error means 0 to the project.

• A number of philosophers are sitting at a round table doing one of three things: eating, thinking or sleeping.

• While eating, they are not thinking or sleeping, while sleeping, they are not eating or thinking and of course, while thinking, they are not eating or sleeping.

• The philosophers sit at a circular table with a large bowl of spaghetti in the center. • There are some forks on the table.

• As spaghetti is difficult to serve and eat with a single fork, it is assumed that a philosopher must eat with two forks, one for each hand.

• The philosophers must never be starving.

• Every philosopher needs to eat.

• Philosophers don’t speak with each other.

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

• Each time a philosopher has finished eating, he will drop his forks and start sleeping.

• When a philosopher is done sleeping, he will start thinking.

• The simulation stops when a philosopher dies.

• Each program should have the same options: number_of_philosophers time_to_die time_to_eat time_to_sleep [number_of_times_each_philosopher_must_eat]

◦ number_of_philosophers: is the number of philosophers and also the number of forks

◦ time_to_die: is in milliseconds, if a philosopher doesn’t start eating ’time_to_die’ milliseconds after starting his last meal or the beginning of the simulation, it dies

◦ time_to_eat: is in milliseconds and is the time it takes for a philosopher to eat. During that time he will need to keep the two forks.

◦ time_to_sleep: is in milliseconds and is the time the philosopher will spend sleeping.

◦ number_of_times_each_philosopher_must_eat: argument is optional, if all philosophers eat at least ’number_of_times_each_philosopher_must_eat’ the simulation will stop. If not specified, the simulation will stop only at the death of a philosopher.

• Each philosopher should be given a number from 1 to ’number_of_philosophers’.

• Philosopher number 1 is next to philosopher number ’number_of_philosophers’. Any other philosopher with number N is seated between philosopher N - 1 and philosopher N + 1

• Any change of status of a philosopher must be written as follows (with X replaced with the philosopher number and timestamp_in_ms the current timestamp in milliseconds) ◦ timestamp_in_ms X has taken a fork
◦ timestamp_in_ms X is sleeping
◦ timestamp_in_ms X is thinking
◦ timestamp_in_ms X died

• The status printed should not be scrambled or intertwined with another philosopher’s status.

• You can’t have more than 10 ms between the death of a philosopher and when it will print its death.

• Again, philosophers should avoid to die!