0x7d4 / philosophers

Dining philosophers problem with twist of threads and mutexes

philosophers

Dining philosophers problem with twist of threads and mutexes.

Brief

This project aims to provide a solution for a multi-threaded system AKA dining philosophers problem. Assuming we have a table with N philos and forks, we should try to keep the agents alive as long as they could not eat anymore (e.g. the forks are occupied).

Methodology

The forks are locks (mutexes) and each philo has a seperate thread; I have used pthread module to work with threads and mutexes. To make philosophers avoid dying, I have used the following policy on which fork is picked up:

$$ fork_{right}(i, n) = (i + (i \mod 2)) \mod n $$

Where:

• i is the index of the target philosopher
• n is the number of the forks

Note the left fork is right fork - 1

This ensures that the harmonic aspect of picking the forks is applied.

Interface

Following arguments are passed to ./philo respectively:

• 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.

Arguments' description copied from 42 Network Subject Version 11

Example

make && ./philo 3 100 60 100

0 1 is thinking
0 1 has taken a fork
0 1 has taken a fork
0 2 is thinking
0 2 has taken a fork
0 2 has taken a fork
0 3 is thinking
0 2 is eating
0 1 is eating
60 1 is sleeping
60 2 is sleeping
60 3 has taken a fork
60 3 has taken a fork
60 3 is eating
101 1 died