dining philosophers

philosophers.go

package main

import (
	"fmt"
	"math/rand"
	"sync"
	"time"
)

type Philosopher struct {
	Id    int
	Left  *Fork
	Right *Fork
}

type Fork struct {
	sync.Mutex
	Id     int
}

func Seat(numPhilosophers int) []*Philosopher {
	zeroFork := &Fork{Id: 0}
	prevFork := zeroFork
	philosophers := []*Philosopher{}
	for i := 0; i < numPhilosophers - 1; i++ {
		thisFork := &Fork{Id: i + 1}
		philosophers = append(philosophers, &Philosopher{Id: i, Left: prevFork, Right: thisFork})
		prevFork = thisFork
	}
	philosophers = append(philosophers, &Philosopher{Id: numPhilosophers - 1, Left: prevFork, Right: zeroFork})
	philosophers[0].Left, philosophers[0].Right = philosophers[0].Right, philosophers[0].Left
	return philosophers
}

func (phil *Philosopher) Eat(eating, thinking chan int) {
	for {

		phil.Right.Lock()
		time.Sleep(time.Duration(rand.Int63n(1e7)))
		phil.Left.Lock()
		eating <- phil.Id
		time.Sleep(time.Duration(rand.Int63n(1e8)))

		phil.Right.Unlock()
		time.Sleep(time.Duration(rand.Int63n(1e7)))
		phil.Left.Unlock()
		thinking <- phil.Id
		time.Sleep(time.Duration(rand.Int63n(1e8)))

	}
}

func (phil *Philosopher) String() string {
	return fmt.Sprintf("[Philosopher: Id: %d, Left: %d, Right: %d]", phil.Id, phil.Left.Id, phil.Right.Id)
}

func printStatus(thinkCount []int, eatCount []int, mu *sync.Mutex) {
	mu.Lock()
	for i, val := range thinkCount {
		fmt.Print("(", val, ",", eatCount[i], ")", "\t")
	}
	fmt.Print("\n")
	mu.Unlock()
}

func main() {
	numPhilosophers := 20
	philosophers := Seat(numPhilosophers)

	for _, phil := range philosophers {
		fmt.Println(phil)
	}

	eating := make(chan int)
	thinking := make(chan int)
	for _, phil := range philosophers {
		go phil.Eat(eating, thinking)
	}
	eatCount, thinkCount := make([]int, numPhilosophers), make([]int, numPhilosophers)
	writeLock := new(sync.Mutex)
	go func() {
		for id := range eating {
			eatCount[id]++
			printStatus(thinkCount, eatCount, writeLock)
		}
	}()
	for id := range thinking {
		thinkCount[id]++
		printStatus(thinkCount, eatCount, writeLock)
	}
}