Merge pull request #8442 from Thabo08/work-stealing-3

t.ntsoko@gmail.com - Work stealing framework

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/workstealing/PrimeNumbers.java

@@ -0,0 +1,85 @@
+package com.baeldung.workstealing;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.ForkJoinTask;
+import java.util.concurrent.RecursiveAction;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class PrimeNumbers extends RecursiveAction {
+
+    private int lowerBound;
+    private int upperBound;
+    private int granularity;
+    static final List<Integer> GRANULARITIES
+      = Arrays.asList(1, 10, 100, 1000, 10000);
+    private AtomicInteger noOfPrimeNumbers;
+
+    PrimeNumbers(int lowerBound, int upperBound, int granularity, AtomicInteger noOfPrimeNumbers) {
+        this.lowerBound = lowerBound;
+        this.upperBound = upperBound;
+        this.granularity = granularity;
+        this.noOfPrimeNumbers = noOfPrimeNumbers;
+    }
+
+    PrimeNumbers(int upperBound) {
+        this(1, upperBound, 100, new AtomicInteger(0));
+    }
+
+    private PrimeNumbers(int lowerBound, int upperBound, AtomicInteger noOfPrimeNumbers) {
+        this(lowerBound, upperBound, 100, noOfPrimeNumbers);
+    }
+
+    private List<PrimeNumbers> subTasks() {
+        List<PrimeNumbers> subTasks = new ArrayList<>();
+
+        for (int i = 1; i <= this.upperBound / granularity; i++) {
+            int upper = i * granularity;
+            int lower = (upper - granularity) + 1;
+            subTasks.add(new PrimeNumbers(lower, upper, noOfPrimeNumbers));
+        }
+        return subTasks;
+    }
+
+    @Override
+    protected void compute() {
+        if (((upperBound + 1) - lowerBound) > granularity) {
+            ForkJoinTask.invokeAll(subTasks());
+        } else {
+            findPrimeNumbers();
+        }
+    }
+
+    void findPrimeNumbers() {
+        for (int num = lowerBound; num <= upperBound; num++) {
+            if (isPrime(num)) {
+                noOfPrimeNumbers.getAndIncrement();
+            }
+        }
+    }
+
+    private boolean isPrime(int number) {
+        if (number == 2) {
+            return true;
+        }
+
+        if (number == 1 || number % 2 == 0) {
+            return false;
+        }
+
+        int noOfNaturalNumbers = 0;
+
+        for (int i = 1; i <= number; i++) {
+            if (number % i == 0) {
+                noOfNaturalNumbers++;
+            }
+        }
+
+        return noOfNaturalNumbers == 2;
+    }
+
+    public int noOfPrimeNumbers() {
+        return noOfPrimeNumbers.intValue();
+    }
+}

core-java-modules/core-java-concurrency-advanced-3/src/test/java/com/baeldung/workstealing/PrimeNumbersUnitTest.java

@@ -0,0 +1,101 @@
+package com.baeldung.workstealing;
+
+import org.junit.Test;
+import org.openjdk.jmh.annotations.*;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.RunnerException;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.ForkJoinPool;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.logging.Logger;
+
+import static org.junit.Assert.fail;
+
+public class PrimeNumbersUnitTest {
+
+    private static Logger logger = Logger.getAnonymousLogger();
+
+    @Test
+    public void givenPrimesCalculated_whenUsingPoolsAndOneThread_thenOneThreadSlowest() {
+        Options opt = new OptionsBuilder()
+          .include(Benchmarker.class.getSimpleName())
+          .forks(1)
+          .build();
+
+        try {
+            new Runner(opt).run();
+        } catch (RunnerException e) {
+            fail();
+        }
+    }
+
+    @Test
+    public void givenNewWorkStealingPool_whenGettingPrimes_thenStealCountChanges() {
+        StringBuilder info = new StringBuilder();
+
+        for (int granularity : PrimeNumbers.GRANULARITIES) {
+            int parallelism = ForkJoinPool.getCommonPoolParallelism();
+            ForkJoinPool pool =
+              (ForkJoinPool) Executors.newWorkStealingPool(parallelism);
+
+            stealCountInfo(info, granularity, pool);
+        }
+        logger.info("\nExecutors.newWorkStealingPool ->" + info.toString());
+    }
+
+    @Test
+    public void givenCommonPool_whenGettingPrimes_thenStealCountChangesSlowly() {
+        StringBuilder info = new StringBuilder();
+
+        for (int granularity : PrimeNumbers.GRANULARITIES) {
+            ForkJoinPool pool = ForkJoinPool.commonPool();
+            stealCountInfo(info, granularity, pool);
+        }
+        logger.info("\nForkJoinPool.commonPool ->" + info.toString());
+    }
+
+    private void stealCountInfo(StringBuilder info, int granularity, ForkJoinPool forkJoinPool) {
+        PrimeNumbers primes = new PrimeNumbers(1, 10000, granularity, new AtomicInteger(0));
+        forkJoinPool.invoke(primes);
+        forkJoinPool.shutdown();
+
+        long steals = forkJoinPool.getStealCount();
+        String output = "\nGranularity: [" + granularity + "], Steals: [" + steals + "]";
+        info.append(output);
+    }
+
+
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.MILLISECONDS)
+    @State(Scope.Benchmark)
+    @Fork(value = 2, warmups = 1, jvmArgs = {"-Xms2G", "-Xmx2G"})
+    public static class Benchmarker {
+
+        @Benchmark
+        public void singleThread() {
+            PrimeNumbers primes = new PrimeNumbers(10000);
+            primes.findPrimeNumbers(); // get prime numbers using a single thread
+        }
+
+        @Benchmark
+        public void commonPoolBenchmark() {
+            PrimeNumbers primes = new PrimeNumbers(10000);
+            ForkJoinPool pool = ForkJoinPool.commonPool();
+            pool.invoke(primes);
+            pool.shutdown();
+        }
+
+        @Benchmark
+        public void newWorkStealingPoolBenchmark() {
+            PrimeNumbers primes = new PrimeNumbers(10000);
+            int parallelism = ForkJoinPool.getCommonPoolParallelism();
+            ForkJoinPool stealer = (ForkJoinPool) Executors.newWorkStealingPool(parallelism);
+            stealer.invoke(primes);
+            stealer.shutdown();
+        }
+    }
+}

parent-java/pom.xml

@@ -27,11 +27,22 @@
             <artifactId>commons-io</artifactId>
             <version>${commons.io.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
     </dependencies>
 
     <properties>
         <guava.version>23.0</guava.version>
         <commons.io.version>2.6</commons.io.version>
+        <jmh.version>1.19</jmh.version>
     </properties>
 
 </project>