distributed_system_coursework/presentation/presentation.md

---
style: |
  img[alt~="center"] {
    display: block;
    margin: 0 auto;
  }

  h3 {
    font-size: 1.2em;
    position: fixed;
    top: 1em;
    left: 50%;
    transform: translateX(-50%);
  }

  h4 {
    text-align: center;
    font-size: 1.2em;
    text-align: center;
  }

  img[alt~="top-m"] {
    margin-top: 40px;
  }

---

# A Paxos implementation

Andre Henriques

---

# Basis of the implentation


![Structure](./structure.png) ![Steps](./steps.png)

---

# Steps

```elixir
receive do
  {:leader_elector, proc} -> ...
  {:propose, inst, value, t, pid_to_inform} -> ...
  {:prepare, proc, inst, ballot} -> ...
  {:nack, inst, ballot} -> ...
  {:prepared, inst, ballot, accepted_ballot, accepted_value} -> ...
  {:accept, inst, ballot, value} -> ...
  {:accepted, inst, ballot} -> ...
  {:decide, inst, value} -> ...
end
```

---

### Step 1 - "Requirements"

![50% center](./first-step.png)

---

### Step 2 - "Prepare"

![w:600 center](./second-step.png)

---

### Step 3 - "Accept"

![w:600 center](./third-step.png)

--- 

### Step 4 - "Leader Crash"

![w:600 center](./fourth-step.png)

---

# Application

---

### Atomas

![w:300 center top-m](./atomas.png)


---

## Safety
 - If a game state exists, then it was created by a user
 - The game state can not divert.

## Liveness
 - Eventually all users will have the same game state

--- 

#### Questions?