An overview of all my projects can be found here: ahokcool
This project was created as part of my studies at: 42 Lisboa
program that simulates the life of a group of philosophers to learn the basics of threading a process an mutexes.
- multithreading in C
- race condition
- C mutex lock
- deadlocks
$ git clone https://github.com/ahokcool/philosophers.git # Clone
$ cd philosophers # Change directory
$ make # Compile
$ ./philo 800 200 200 7 # Run
This project is a version of the dinning philosopher problem
->Wikipedia
| Common Problems | My Solution |
|---|---|
| independent philos | -> using threads |
| race conditions | -> using pthread_mutex |
| deadlocks | -> resource hierarchy solution |
| the starvation | -> wait for a lap time |
Every philo can see how many other philos are sitting at the table. Always half of the philos (result rounded down) can eat at the same time (exception: there is only one philo). Since in this variant all philos always eat the same amount of time, it can be calculated how long it takes until all have started to eat once. If each philo now waits until at least this time has passed before he eats again, nobody starves anymore. HOORAY!
Formula
table->min_wait_time = ((table->num_philos - (int)(table->num_philos / 2) - 1) * table->dur_eat) + (table->dur_eat * 0.5)
Note:
I noticed that this wastes 0.5*dur_eat ms per food round. So a philo could eat, but he does not.
So, since I did not come up with a solution, I simply adjusted the formula and waste now only 5ms. (which is still not ideal)
New formula
table->min_wait_time = ((table->num_philos - (int)(table->num_philos / 2) - 1) * table->dur_eat) + 5;