Task: Dining philosophers




Go: package main

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



var ph = []string{"Aristotle", "Kant", "Spinoza", "Marx", "Russell"}

const hunger = 3                
const think = time.Second / 100 
const eat = time.Second / 100   

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

var done = make(chan bool)



type fork byte








func philosopher(phName string,
    dominantHand, otherHand chan fork, done chan bool) {
    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 
        <-otherHand
        fmt.Println(phName, "eating")
        rSleep(eat)
        dominantHand <- 'f' 
        otherHand <- 'f'
        fmt.Println(phName, "thinking")
        rSleep(think)
    }
    fmt.Println(phName, "satisfied")
    done <- true
    fmt.Println(phName, "left the table")
}

func main() {
    fmt.Println("table empty")
    
    
    place0 := make(chan fork, 1)
    place0 <- 'f' 
    placeLeft := place0
    for i := 1; i < len(ph); i++ {
        placeRight := make(chan fork, 1)
        placeRight <- 'f'
        go philosopher(ph[i], placeLeft, placeRight, done)
        placeLeft = placeRight
    }
    
    
    
    go philosopher(ph[0], place0, placeLeft, done)
    
    for range ph {
        <-done 
    }
    fmt.Println("table empty")
}


Java: package diningphilosophers;

import java.util.ArrayList;
import java.util.Random;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;

enum PhilosopherState { Get, Eat, Pon }

class Fork {
    public static final int ON_TABLE = -1;
    static int instances = 0;
    public int id;
    public AtomicInteger holder = new AtomicInteger(ON_TABLE);

    Fork() { id = instances++; }
}

class Philosopher implements Runnable {
    static final int maxWaitMs = 100;                          
    static AtomicInteger token = new AtomicInteger(0);
    static int instances = 0;
    static Random rand = new Random();
    AtomicBoolean end = new AtomicBoolean(false);
    int id;
    PhilosopherState state = PhilosopherState.Get;
    Fork left;
    Fork right;
    int timesEaten = 0;

    Philosopher() {
        id = instances++;
        left = Main.forks.get(id);
        right = Main.forks.get((id+1)%Main.philosopherCount);
    }

    void sleep() { try { Thread.sleep(rand.nextInt(maxWaitMs)); }
        catch (InterruptedException ex) {} }

    void waitForFork(Fork fork) {
        do {
            if (fork.holder.get() == Fork.ON_TABLE) {
                fork.holder.set(id);                
                return;
            } else {                                
                sleep();                            
            }
        } while (true);
    }

    public void run() {
        do {
            if (state == PhilosopherState.Pon) {    
                state = PhilosopherState.Get;       
            } else { 
                if (token.get() == id) {            
                    waitForFork(left);
                    waitForFork(right);             
                    token.set((id+2)% Main.philosopherCount);
                    state = PhilosopherState.Eat;
                    timesEaten++;
                    sleep();                        
                    left.holder.set(Fork.ON_TABLE);
                    right.holder.set(Fork.ON_TABLE);
                    state = PhilosopherState.Pon;   
                    sleep();
                } else {                    
                    sleep();
                }
            }
        } while (!end.get());
    }
}

public class Main {
    static final int philosopherCount = 5; 
    static final int runSeconds = 15;
    static ArrayList<Fork> forks = new ArrayList<Fork>();
    static ArrayList<Philosopher> philosophers = new ArrayList<Philosopher>();

    public static void main(String[] args) {
        for (int i = 0 ; i < philosopherCount ; i++) forks.add(new Fork());
        for (int i = 0 ; i < philosopherCount ; i++)
            philosophers.add(new Philosopher());
        for (Philosopher p : philosophers) new Thread(p).start();
        long endTime = System.currentTimeMillis() + (runSeconds * 1000);

        do {                                                    
            StringBuilder sb = new StringBuilder("|");

            for (Philosopher p : philosophers) {
                sb.append(p.state.toString());
                sb.append("|");            
            }                              

            sb.append("     |");

            for (Fork f : forks) {
                int holder = f.holder.get();
                sb.append(holder==-1?"   ":String.format("P%02d",holder));
                sb.append("|");
            }
            
            System.out.println(sb.toString());
            try {Thread.sleep(1000);} catch (Exception ex) {}
        } while (System.currentTimeMillis() < endTime);

        for (Philosopher p : philosophers) p.end.set(true);
        for (Philosopher p : philosophers)
            System.out.printf("P%02d: ate %,d times, %,d/sec\n",
                p.id, p.timesEaten, p.timesEaten/runSeconds);
    }
}