Solved

README.md

@@ -1,3 +1,4 @@
+[![Review Assignment Due Date](https://classroom.github.com/assets/deadline-readme-button-22041afd0340ce965d47ae6ef1cefeee28c7c493a6346c4f15d667ab976d596c.svg)](https://classroom.github.com/a/qcWcnElX)
 # Java concurrency
 
 # Цели и задачи л/р:

build.gradle.kts

@@ -12,6 +12,8 @@ repositories {
 dependencies {
     testImplementation(platform("org.junit:junit-bom:5.10.0"))
     testImplementation("org.junit.jupiter:junit-jupiter")
+    testImplementation("org.openjdk.jmh:jmh-core:1.37")
+    testImplementation("org.openjdk.jmh:jmh-generator-annprocess:1.37")
 }
 
 tasks.test {

src/main/java/org/labs/Main.java

@@ -1,7 +1,14 @@
 package org.labs;
 
 public class Main {
+    public static final boolean DEBUG = true;
+
     public static void main(String[] args) {
-        System.out.println("Hello, World!");
+        Restaurant restaurant = new Restaurant(100, 2, 1_000_000, false);
+        restaurant.start();
+        restaurant.join();
+        if (DEBUG) {
+            System.out.println("Нечестность = " + restaurant.getUnfairness());
+        }
     }
 }

src/main/java/org/labs/Programmer.java

@@ -0,0 +1,71 @@
+package org.labs;
+
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class Programmer extends Thread {
+    private static final AtomicInteger ID_CNT = new AtomicInteger();
+
+    private final BlockingQueue<Waiter> waiters;
+    private final Spoon first;
+    private final Spoon second;
+    private volatile boolean hasSoup;
+    private long ate = 0;
+
+    public Programmer(BlockingQueue<Waiter> waiters, Spoon leftSpoon, Spoon rightSpoon) {
+        setName(Programmer.class.getName() + '.' + ID_CNT.incrementAndGet());
+        setDaemon(true);
+        this.waiters = waiters;
+        this.hasSoup = true;
+        if (leftSpoon.compareTo(rightSpoon) > 0) {
+            this.first = rightSpoon;
+            this.second = leftSpoon;
+        } else {
+            this.first = leftSpoon;
+            this.second = rightSpoon;
+        }
+    }
+
+    @Override
+    public void run() {
+        while (true) {
+            if (hasSoup) {
+                eat();
+            } else {
+                requestMoreSoup();
+            }
+        }
+    }
+
+    public synchronized void addMoreSoup() {
+        this.hasSoup = true;
+        notify();
+    }
+
+    private void eat() {
+        first.lock();
+        second.lock();
+        hasSoup = false;
+        if (Main.DEBUG) {
+            ate++;
+        }
+        first.unlock();
+        second.unlock();
+    }
+
+    private synchronized void requestMoreSoup() {
+        try {
+            this.waiters.take().requestSoup(this);
+            wait();
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public long getAte() {
+        if (!Main.DEBUG) {
+            throw new UnsupportedOperationException("Debug is not enabled!");
+        }
+        return ate;
+    }
+}

src/main/java/org/labs/Restaurant.java

@@ -0,0 +1,40 @@
+package org.labs;
+
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class Restaurant {
+    private final Table table;
+    private final AtomicInteger portionsLeft;
+    private final BlockingQueue<Waiter> waitersQueue;
+
+    public Restaurant(int programmersCnt, int waitersCnt, int portions, boolean fairLock) {
+        this.portionsLeft = new AtomicInteger(portions - programmersCnt);
+        this.waitersQueue = new ArrayBlockingQueue<>(waitersCnt, fairLock);
+        for (int i = 0; i < waitersCnt; i++) {
+            try {
+                this.waitersQueue.put(new Waiter(this.portionsLeft, this.waitersQueue));
+            } catch (InterruptedException e) {
+                throw new RuntimeException(e);
+            }
+        }
+
+        this.table = new Table(this.waitersQueue, programmersCnt, fairLock);
+    }
+
+    public void start() {
+        for (Waiter waiter : waitersQueue) {
+            waiter.start();
+        }
+        table.start();
+    }
+
+    public void join() {
+        while (portionsLeft.get() > 0) ;
+    }
+
+    public double getUnfairness() {
+        return table.getUnfairness();
+    }
+}

src/main/java/org/labs/Spoon.java

@@ -0,0 +1,25 @@
+package org.labs;
+
+import java.util.concurrent.locks.ReentrantLock;
+
+public class Spoon extends ReentrantLock implements Comparable<Spoon> {
+    private final int id;
+
+    public Spoon(int id) {
+        this(id, true);
+    }
+
+    public Spoon(int id, boolean fair) {
+        super(fair);
+        this.id = id;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    @Override
+    public int compareTo(Spoon o) {
+        return this.id - o.id;
+    }
+}

src/main/java/org/labs/Table.java

@@ -0,0 +1,44 @@
+package org.labs;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.BlockingQueue;
+
+public class Table {
+    final private List<Programmer> programmers;
+
+    public Table(BlockingQueue<Waiter> waiters, int programmersCnt, boolean fairLock) {
+        programmers = new ArrayList<>(programmersCnt);
+        List<Spoon> spoons = new ArrayList<>(programmersCnt);
+        for (int i = 0; i < programmersCnt; i++) {
+            if (i % 2 == 0) {
+                spoons.add(new Spoon(i / 2, fairLock));
+            } else {
+                spoons.add(new Spoon(programmersCnt - (i / 2), fairLock));
+            }
+        }
+        for (int i = 0; i < programmersCnt; i++) {
+            Spoon left = spoons.get(i);
+            Spoon right = spoons.get((i + 1) % programmersCnt);
+            programmers.add(new Programmer(waiters, left, right));
+        }
+    }
+
+    public void start() {
+        for (Programmer programmer : this.programmers) {
+            programmer.start();
+        }
+    }
+
+    public double getUnfairness() {
+        double mean = 0;
+        for (Programmer programmer: programmers) {
+            mean += ((double) programmer.getAte()) / programmers.size();
+        }
+        double unfairness = 0;
+        for (Programmer programmer: programmers) {
+            unfairness += Math.abs(programmer.getAte() - mean) / (programmers.size());
+        }
+        return unfairness / mean;
+    }
+}

src/main/java/org/labs/Waiter.java

@@ -0,0 +1,58 @@
+package org.labs;
+
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.SynchronousQueue;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.logging.Logger;
+
+public class Waiter extends Thread {
+    private final static Logger LOG = Logger.getLogger(Waiter.class.getName());
+    private final static AtomicInteger ID_CNT = new AtomicInteger();
+    private final BlockingQueue<Programmer> waitingProgrammers = new SynchronousQueue<>();
+    private final AtomicInteger portionLeft;
+    private final BlockingQueue<Waiter> waiters;
+    private int delivered = 0;
+
+    public Waiter(AtomicInteger portionLeft, BlockingQueue<Waiter> waiters) {
+        setName(Waiter.class.getName() + '.' + ID_CNT.incrementAndGet());
+        this.portionLeft = portionLeft;
+        this.waiters = waiters;
+    }
+
+    @Override
+    public void run() {
+        while (true) {
+            try {
+                Programmer programmer = waitingProgrammers.take();
+                if (tryToTakeSoup()) {
+                    programmer.addMoreSoup();
+                    if (Main.DEBUG) {
+                        delivered++;
+                    }
+                } else {
+                    LOG.info("Официант покинул работу");
+                    return;
+                }
+                waiters.put(this);
+            } catch (InterruptedException e) {
+                throw new RuntimeException(e);
+            }
+        }
+    }
+
+    public void requestSoup(Programmer programmer) throws InterruptedException {
+        waitingProgrammers.put(programmer);
+    }
+
+    private boolean tryToTakeSoup() {
+        while (true) {
+            int currentPortionsLeft = portionLeft.get();
+            if (currentPortionsLeft <= 0) {
+                return false;
+            }
+            if (portionLeft.compareAndSet(currentPortionsLeft, currentPortionsLeft - 1)) {
+                return true;
+            }
+        }
+    }
+}

src/test/java/org/labs/RestaurantPerformanceTest.java

@@ -0,0 +1,112 @@
+package org.labs;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.RepeatedTest;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+import org.junit.jupiter.params.provider.CsvSource;
+
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+
+@DisplayName("Restaurant Performance Tests")
+public class RestaurantPerformanceTest {
+
+    @BeforeAll
+    public static void disableLogging() {
+        Logger rootLogger = Logger.getLogger("");
+        rootLogger.setLevel(Level.OFF);
+    }
+
+    @ParameterizedTest
+    @ValueSource(ints = {2, 4, 8, 16, 32})
+    @DisplayName("Тестирование производительности при различном количестве программистов")
+    public void testProgrammerCountPerformance(int programmersCnt) {
+        int waitersCnt = 2;
+        boolean fairLock = true;
+
+        long executionTime = measurePerformance(programmersCnt, waitersCnt, fairLock);
+
+        System.out.printf("Программистов: %d, Официантов: %d, Fair Lock: %s%n", programmersCnt, waitersCnt, fairLock);
+        System.out.printf("Время выполнения: %dмс%n", executionTime);
+    }
+
+    @ParameterizedTest
+    @ValueSource(ints = {1, 2, 4, 8})
+    @DisplayName("Тестирование производительности при различном количестве официантов")
+    public void testWaiterCountPerformance(int waitersCnt) {
+        int programmersCnt = 16;
+        boolean fairLock = true;
+
+        long executionTime = measurePerformance(programmersCnt, waitersCnt, fairLock);
+
+        System.out.printf("Программистов: %d, Официантов: %d, Fair Lock: %s%n", programmersCnt, waitersCnt, fairLock);
+        System.out.printf("Время выполнения: %dms%n", executionTime);
+    }
+
+    @ParameterizedTest
+    @CsvSource({"4, 2, true", "4, 2, false", "8, 2, true", "8, 2, false", "16, 4, true", "16, 4, false"})
+    @DisplayName("Тестирование производительности при различных типах блокировок")
+    public void testFairVsUnfairLockPerformance(int programmersCnt, int waitersCnt, boolean fairLock) {
+        long executionTime = measurePerformance(programmersCnt, waitersCnt, fairLock);
+
+        System.out.printf("Программистов: %d, Официантов: %d, Fair Lock: %s%n", programmersCnt, waitersCnt, fairLock);
+        System.out.printf("Время выполнения: %dмс%n", executionTime);
+    }
+
+    @Test
+    @DisplayName("Стресс-тест с высокой конкурентостью")
+    public void stressTest() {
+        int programmersCnt = 64;
+        int waitersCnt = 16;
+        boolean fairLock = true;
+
+        long executionTime = measurePerformance(programmersCnt, waitersCnt, fairLock);
+
+        System.out.printf("Стресс-тест - Программистов: %d, Официантов: %d%n", programmersCnt, waitersCnt);
+        System.out.printf("Время выполнения: %dms%n", executionTime);
+    }
+
+    private long measurePerformance(int programmersCnt, int waitersCnt, boolean fairLock) {
+        final int warmupIterations = 2;
+        final int measurementIterations = 4;
+
+        // Прогрев
+        System.out.printf("Прогрев (%d итераций)...%n", warmupIterations);
+        for (int i = 0; i < warmupIterations; i++) {
+            runSingleIteration(programmersCnt, waitersCnt, fairLock);
+        }
+
+        // Измерения для усреднения
+        System.out.printf("Измерение производительности (%d итераций)...%n", measurementIterations);
+        long totalTime = 0;
+        for (int i = 0; i < measurementIterations; i++) {
+            long iterationTime = runSingleIteration(programmersCnt, waitersCnt, fairLock);
+            totalTime += iterationTime;
+            System.out.printf("\tИтерация %d: %dмс%n", i + 1, iterationTime);
+        }
+
+        long averageTime = totalTime / measurementIterations;
+        System.out.printf("Среднее время: %d мс\n", averageTime);
+
+        return averageTime;
+    }
+
+    private long runSingleIteration(int programmersCnt, int waitersCnt, boolean fairLock) {
+        long startTime = System.currentTimeMillis();
+
+        Restaurant restaurant = new Restaurant(programmersCnt, waitersCnt, 100_000, fairLock);
+        restaurant.start();
+        restaurant.join();
+
+        System.out.println("Нечестность = " + restaurant.getUnfairness());
+        assert !fairLock || restaurant.getUnfairness() < 0.1;
+        long endTime = System.currentTimeMillis();
+
+        return endTime - startTime;
+    }
+
+}