Philos

Summary

In this project, I will learn the basics of threading a process. I will learn how to make threads. I will discover the mutex and semaphores of POSIX standard.

Task

• One or more 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 the 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 eating
  • 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 dying!

philo_one

1. One fork between each philosopher, therefore if they are multiple philosophers, there will be a fork at the right and the left of each philosopher.
2. To avoid philosophers duplicating forks, you should protect the forks state with a mutex for each of them.
3. Each philosopher should be a thread.

philo_two

1. All the forks are in the middle of the table.
2. They have no states in memory but the number of available forks is represented by a semaphore.
3. Each philosopher should be a thread.

philo_three

1. All the forks are in the middle of the table.
2. They have no states in memory but the number of available forks is represented by a semaphore.
3. Each philosopher should be a process and the main process should not be a philosopher.

How to compile

cd philo_<one/two/three>
make

You will got an executable file which will get 4 arguments. Example:

./philo_one 4 310 200 100

42 école project