🍴 3 Philosophers (Small Table)

Dining Philosophers Problem simulated with virtual time
🎬 GenServerVirtualTime Actor Simulation
This diagram shows the interactions between philosophers and forks over virtual time. All synchronous fork requests, grants, and releases are captured.

The Problem

3 philosophers sit at a round table with 3 forks between them. Each philosopher alternates between thinking and eating. To eat, a philosopher needs both adjacent forks.

Challenge: How to prevent deadlock when all philosophers simultaneously grab their left fork?

Solution: Asymmetric fork acquisition - odd philosophers grab right fork first, even philosophers grab left fork first.

→→ Solid Arrow
Synchronous call (request/release fork)
Activation Box
Fork is processing a request
Timestamps
Virtual time progression
sequenceDiagram philosopher_2->>philosopher_2: {:start_hungry, :fork_2, :fork_0} Note over philosopher_2,philosopher_2: t=200ms philosopher_1->>philosopher_1: {:start_hungry, :fork_2, :fork_1} Note over philosopher_1,philosopher_1: t=200ms philosopher_0->>philosopher_0: {:start_hungry, :fork_0, :fork_1} Note over philosopher_0,philosopher_0: t=200ms philosopher_2->>philosopher_2: {:mumble, "I'm hungry!"} Note over philosopher_2,philosopher_2: t=200ms philosopher_1->>philosopher_1: {:mumble, "I'm hungry!"} Note over philosopher_1,philosopher_1: t=200ms philosopher_0->>philosopher_0: {:mumble, "I'm hungry!"} Note over philosopher_0,philosopher_0: t=200ms philosopher_2->>fork_2: {:request_fork, :philosopher_2} Note over philosopher_2,fork_2: t=200ms philosopher_1->>fork_2: {:request_fork, :philosopher_1} Note over philosopher_1,fork_2: t=200ms philosopher_0->>fork_0: {:request_fork, :philosopher_0} Note over philosopher_0,fork_0: t=200ms fork_2->>philosopher_2: {:fork_granted, :fork_2} Note over fork_2,philosopher_2: t=200ms fork_0->>philosopher_0: {:fork_granted, :fork_0} Note over fork_0,philosopher_0: t=200ms fork_2->>philosopher_1: {:fork_denied, :fork_2} Note over fork_2,philosopher_1: t=200ms philosopher_2->>fork_0: {:request_fork, :philosopher_2} Note over philosopher_2,fork_0: t=200ms philosopher_0->>fork_1: {:request_fork, :philosopher_0} Note over philosopher_0,fork_1: t=200ms fork_0->>philosopher_2: {:fork_denied, :fork_0} Note over fork_0,philosopher_2: t=200ms fork_1->>philosopher_0: {:fork_granted, :fork_1} Note over fork_1,philosopher_0: t=200ms philosopher_2->>fork_2: {:release_fork, :philosopher_2} Note over philosopher_2,fork_2: t=200ms philosopher_0->>philosopher_0: {:mumble, "I'm full!"} Note over philosopher_0,philosopher_0: t=300ms philosopher_0->>fork_0: {:release_fork, :philosopher_0} Note over philosopher_0,fork_0: t=300ms philosopher_0->>fork_1: {:release_fork, :philosopher_0} Note over philosopher_0,fork_1: t=300ms philosopher_0->>philosopher_0: {:start_hungry, :fork_0, :fork_1} Note over philosopher_0,philosopher_0: t=400ms philosopher_1->>philosopher_1: {:start_hungry, :fork_2, :fork_1} Note over philosopher_1,philosopher_1: t=400ms philosopher_2->>philosopher_2: {:start_hungry, :fork_2, :fork_0} Note over philosopher_2,philosopher_2: t=400ms philosopher_0->>fork_0: {:request_fork, :philosopher_0} Note over philosopher_0,fork_0: t=400ms philosopher_1->>fork_2: {:request_fork, :philosopher_1} Note over philosopher_1,fork_2: t=400ms philosopher_2->>fork_2: {:request_fork, :philosopher_2} Note over philosopher_2,fork_2: t=400ms fork_0->>philosopher_0: {:fork_granted, :fork_0} Note over fork_0,philosopher_0: t=400ms fork_2->>philosopher_1: {:fork_granted, :fork_2} Note over fork_2,philosopher_1: t=400ms fork_2->>philosopher_2: {:fork_denied, :fork_2} Note over fork_2,philosopher_2: t=400ms philosopher_0->>fork_1: {:request_fork, :philosopher_0} Note over philosopher_0,fork_1: t=400ms philosopher_1->>fork_1: {:request_fork, :philosopher_1} Note over philosopher_1,fork_1: t=400ms fork_1->>philosopher_0: {:fork_granted, :fork_1} Note over fork_1,philosopher_0: t=400ms fork_1->>philosopher_1: {:fork_denied, :fork_1} Note over fork_1,philosopher_1: t=400ms philosopher_1->>fork_2: {:release_fork, :philosopher_1} Note over philosopher_1,fork_2: t=400ms philosopher_0->>philosopher_0: {:mumble, "I'm full!"} Note over philosopher_0,philosopher_0: t=500ms philosopher_0->>fork_0: {:release_fork, :philosopher_0} Note over philosopher_0,fork_0: t=500ms philosopher_0->>fork_1: {:release_fork, :philosopher_0} Note over philosopher_0,fork_1: t=500ms philosopher_2->>philosopher_2: {:start_hungry, :fork_2, :fork_0} Note over philosopher_2,philosopher_2: t=600ms philosopher_1->>philosopher_1: {:start_hungry, :fork_2, :fork_1} Note over philosopher_1,philosopher_1: t=600ms philosopher_0->>philosopher_0: {:start_hungry, :fork_0, :fork_1} Note over philosopher_0,philosopher_0: t=600ms philosopher_2->>fork_2: {:request_fork, :philosopher_2} Note over philosopher_2,fork_2: t=600ms philosopher_1->>fork_2: {:request_fork, :philosopher_1} Note over philosopher_1,fork_2: t=600ms philosopher_0->>fork_0: {:request_fork, :philosopher_0} Note over philosopher_0,fork_0: t=600ms fork_2->>philosopher_2: {:fork_granted, :fork_2} Note over fork_2,philosopher_2: t=600ms fork_0->>philosopher_0: {:fork_granted, :fork_0} Note over fork_0,philosopher_0: t=600ms fork_2->>philosopher_1: {:fork_denied, :fork_2} Note over fork_2,philosopher_1: t=600ms philosopher_2->>fork_0: {:request_fork, :philosopher_2} Note over philosopher_2,fork_0: t=600ms philosopher_0->>fork_1: {:request_fork, :philosopher_0} Note over philosopher_0,fork_1: t=600ms fork_0->>philosopher_2: {:fork_denied, :fork_0} Note over fork_0,philosopher_2: t=600ms fork_1->>philosopher_0: {:fork_granted, :fork_1} Note over fork_1,philosopher_0: t=600ms philosopher_2->>fork_2: {:release_fork, :philosopher_2} Note over philosopher_2,fork_2: t=600ms philosopher_0->>philosopher_0: {:mumble, "I'm full!"} Note over philosopher_0,philosopher_0: t=700ms philosopher_0->>fork_0: {:release_fork, :philosopher_0} Note over philosopher_0,fork_0: t=700ms philosopher_0->>fork_1: {:release_fork, :philosopher_0} Note over philosopher_0,fork_1: t=700ms philosopher_0->>philosopher_0: {:start_hungry, :fork_0, :fork_1} Note over philosopher_0,philosopher_0: t=800ms philosopher_1->>philosopher_1: {:start_hungry, :fork_2, :fork_1} Note over philosopher_1,philosopher_1: t=800ms philosopher_2->>philosopher_2: {:start_hungry, :fork_2, :fork_0} Note over philosopher_2,philosopher_2: t=800ms philosopher_0->>fork_0: {:request_fork, :philosopher_0} Note over philosopher_0,fork_0: t=800ms philosopher_1->>fork_2: {:request_fork, :philosopher_1} Note over philosopher_1,fork_2: t=800ms philosopher_2->>fork_2: {:request_fork, :philosopher_2} Note over philosopher_2,fork_2: t=800ms fork_2->>philosopher_1: {:fork_granted, :fork_2} Note over fork_2,philosopher_1: t=800ms fork_0->>philosopher_0: {:fork_granted, :fork_0} Note over fork_0,philosopher_0: t=800ms fork_2->>philosopher_2: {:fork_denied, :fork_2} Note over fork_2,philosopher_2: t=800ms philosopher_1->>fork_1: {:request_fork, :philosopher_1} Note over philosopher_1,fork_1: t=800ms philosopher_0->>fork_1: {:request_fork, :philosopher_0} Note over philosopher_0,fork_1: t=800ms fork_1->>philosopher_1: {:fork_granted, :fork_1} Note over fork_1,philosopher_1: t=800ms fork_1->>philosopher_0: {:fork_denied, :fork_1} Note over fork_1,philosopher_0: t=800ms philosopher_0->>fork_0: {:release_fork, :philosopher_0} Note over philosopher_0,fork_0: t=800ms philosopher_1->>philosopher_1: {:mumble, "I'm full!"} Note over philosopher_1,philosopher_1: t=900ms philosopher_1->>fork_2: {:release_fork, :philosopher_1} Note over philosopher_1,fork_2: t=900ms philosopher_1->>fork_1: {:release_fork, :philosopher_1} Note over philosopher_1,fork_1: t=900ms philosopher_2->>philosopher_2: {:start_hungry, :fork_2, :fork_0} Note over philosopher_2,philosopher_2: t=1000ms philosopher_1->>philosopher_1: {:start_hungry, :fork_2, :fork_1} Note over philosopher_1,philosopher_1: t=1000ms philosopher_0->>philosopher_0: {:start_hungry, :fork_0, :fork_1} Note over philosopher_0,philosopher_0: t=1000ms philosopher_2->>fork_2: {:request_fork, :philosopher_2} Note over philosopher_2,fork_2: t=1000ms philosopher_1->>fork_2: {:request_fork, :philosopher_1} Note over philosopher_1,fork_2: t=1000ms philosopher_0->>fork_0: {:request_fork, :philosopher_0} Note over philosopher_0,fork_0: t=1000ms fork_2->>philosopher_2: {:fork_granted, :fork_2} Note over fork_2,philosopher_2: t=1000ms fork_0->>philosopher_0: {:fork_granted, :fork_0} Note over fork_0,philosopher_0: t=1000ms fork_2->>philosopher_1: {:fork_denied, :fork_2} Note over fork_2,philosopher_1: t=1000ms philosopher_2->>fork_0: {:request_fork, :philosopher_2} Note over philosopher_2,fork_0: t=1000ms philosopher_0->>fork_1: {:request_fork, :philosopher_0} Note over philosopher_0,fork_1: t=1000ms fork_0->>philosopher_2: {:fork_denied, :fork_0} Note over fork_0,philosopher_2: t=1000ms fork_1->>philosopher_0: {:fork_granted, :fork_1} Note over fork_1,philosopher_0: t=1000ms philosopher_2->>fork_2: {:release_fork, :philosopher_2} Note over philosopher_2,fork_2: t=1000ms

Simulation Source Code

simulation =
DiningPhilosophers.create_simulation(
num_philosophers: 3,
think_time: 150,
eat_time: 75,
trace: true
)
|> ActorSimulation.run(duration: 800)

What the Diagram Shows

🔗 Source & Links

📚 GitHub Repository 🧪 Test Source 📖 Documentation 📦 Hex Package