# Illustration of the dining philosophers problem in Golang

Five silent philosophers sit at a round table with bowls of spaghetti. Forks are placed between each pair of adjacent philosophers. Each philosopher must alternately think and eat. However, a philosopher can only eat spaghetti when they have both left and right forks. Each fork can be held by only one philosopher and so a philosopher can use the fork only if it is not being used by another philosopher. After an individual philosopher finishes eating, they need to put down both forks so that the forks become available to others. A philosopher can take the fork on their right or the one on their left as they become available, but cannot start eating before getting both forks. Eating is not limited by the remaining amounts of spaghetti or stomach space; an infinite supply and an infinite demand are assumed. The problem is how to design a discipline of behavior (a concurrent algorithm) such that no philosopher will starve; i.e., each can forever continue to alternate between eating and thinking, assuming that no philosopher can know when others may want to eat or think.

### Example

``````package main

import (
"hash/fnv"
"log"
"math/rand"
"os"
"sync"
"time"
)

// Number of philosophers is simply the length of this list.
var ph = []string{"Mark", "Russell", "Rocky", "Haris", "Root"}

const hunger = 3                // Number of times each philosopher eats
const think = time.Second / 100 // Mean think time
const eat = time.Second / 100   // Mean eat time

var fmt = log.New(os.Stdout, "", 0)

var dining sync.WaitGroup

func diningProblem(phName string, dominantHand, otherHand *sync.Mutex) {
fmt.Println(phName, "Seated")
h := fnv.New64a()
h.Write([]byte(phName))
rg := rand.New(rand.NewSource(int64(h.Sum64())))
rSleep := func(t time.Duration) {
time.Sleep(t/2 + time.Duration(rg.Int63n(int64(t))))
}
for h := hunger; h > 0; h-- {
fmt.Println(phName, "Hungry")
dominantHand.Lock() // pick up forks
otherHand.Lock()
fmt.Println(phName, "Eating")
rSleep(eat)
dominantHand.Unlock() // put down forks
otherHand.Unlock()
fmt.Println(phName, "Thinking")
rSleep(think)
}
fmt.Println(phName, "Satisfied")
dining.Done()
fmt.Println(phName, "Left the table")
}

func main() {
fmt.Println("Table empty")
fork0 := &sync.Mutex{}
forkLeft := fork0
for i := 1; i < len(ph); i++ {
forkRight := &sync.Mutex{}
go diningProblem(ph[i], forkLeft, forkRight)
forkLeft = forkRight
}
go diningProblem(ph[0], fork0, forkLeft)
dining.Wait() // wait for philosphers to finish
fmt.Println("Table empty")
}``````

### Output

``````Table empty
Mark seated
Mark Hungry
Mark Eating
..................
..................
Haris Thinking
Haris Satisfied
Haris Left the table
Table empty``````