Add first question solution

.idea/workspace.xml

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+      <change afterPath="$PROJECT_DIR$/src/main/java/org/example/ArrayOccurrencesCount.java" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/src/test/java/ArrayOccurrencesCountTest.java" afterDir="false" />
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+      <module name="ArrayOccurrencesCount" />
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+      <module name="ArrayOccurrencesCount" />
+      <option name="PACKAGE_NAME" value="" />
+      <option name="MAIN_CLASS_NAME" value="ArrayOccurrencesCountTest" />
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+      <module name="ArrayOccurrencesCount" />
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+    <configuration name="ArrayOccurrencesCountTest.testArraySumSeq" type="JUnit" factoryName="JUnit" temporary="true" nameIsGenerated="true">
+      <module name="ArrayOccurrencesCount" />
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+      <option name="MAIN_CLASS_NAME" value="ArrayOccurrencesCountTest" />
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@@ -36,6 +117,14 @@
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@@ -49,4 +138,8 @@
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+    <MESSAGE value="Initial commit" />
+    <option name="LAST_COMMIT_MESSAGE" value="Initial commit" />
+  </component>
 </project>
\ No newline at end of file

README.md

+# Parallel Programming HW1
+
+> Important Note: Please make sure to change JVM memory heap settings to enable making an array of a billion elements
\ No newline at end of file

pom.xml

@@ -7,6 +7,14 @@
     <groupId>org.example</groupId>
     <artifactId>ArrayOccurancesCount</artifactId>
     <version>1.0-SNAPSHOT</version>
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.13.2</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
 
     <properties>
         <maven.compiler.source>17</maven.compiler.source>

src/main/java/org/example/ArrayOccurrencesCount.java

+package org.example;
+
+import java.util.Arrays;
+import java.util.concurrent.RecursiveAction;
+
+public class ArrayOccurrencesCount extends RecursiveAction {
+
+    public long occurrences;
+    int arr[], lo, hi;
+
+    int targetElement;
+
+    public ArrayOccurrencesCount(int[] arr, int lo, int hi, int targetElement) {
+        this.arr = arr;
+        this.lo = lo;
+        this.hi = hi;
+        this.targetElement = targetElement;
+    }
+
+    public long computeSeq(){
+        for (int i = lo; i <= hi; ++i) {
+            if(arr[i] == targetElement) occurrences++;
+        }
+        return occurrences;
+    }
+
+    @Override
+    protected void compute() {
+        if (hi - lo > 1_000_000) {
+            int mid = (lo + hi) / 2;
+            ArrayOccurrencesCount left = new ArrayOccurrencesCount(arr, lo, mid, targetElement);
+            ArrayOccurrencesCount right = new ArrayOccurrencesCount(arr, mid + 1, hi, targetElement);
+            left.fork();
+            right.compute();
+            left.join();
+            occurrences = left.occurrences + right.occurrences;
+        } else {
+            occurrences =computeSeq();
+        }
+    }
+
+    public void computeStreamSeq() {
+        occurrences = Arrays.stream(arr).asLongStream().reduce(0, (acc, elm) -> acc + (elm == targetElement ? 1 : 0));
+    }
+
+    public void computeStreamPP() {
+        occurrences = Arrays.stream(arr).asLongStream().parallel().reduce(0, (acc, elm) -> acc + (elm == targetElement ? 1 : 0));
+    }
+}

src/main/java/org/example/Main.java

-package org.example;
-
-public class Main {
-    public static void main(String[] args) {
-        System.out.println("Hello world!");
-    }
-}
\ No newline at end of file

src/test/java/ArrayOccurrencesCountTest.java

+import junit.framework.TestCase;
+import org.example.ArrayOccurrencesCount;
+import java.util.Random;
+import java.util.concurrent.ForkJoinPool;
+import java.util.stream.IntStream;
+
+public class ArrayOccurrencesCountTest extends TestCase {
+
+    private int[] randomArray(int size) {
+        Random rand = new Random();
+        int[] arr = new int[size];
+        for (int i = 0; i < size; i++) {
+            arr[i] = rand.nextInt(size);
+        }
+        return arr;
+    }
+
+    private int[] intStream(int size) {
+        IntStream intStream = IntStream.range(1, size);
+        return intStream.toArray();
+    }
+
+    public void testArrayOccurrencesCountSeq() {
+
+//        int size = 1000_000_000;
+        int size = 100000000;
+
+        int target = 5;
+
+//        int[] arr = randomArray(size);
+        int[] arr = intStream(size);
+
+        ArrayOccurrencesCount array = new ArrayOccurrencesCount(arr, 0, arr.length - 1, target);
+        long start = System.currentTimeMillis();
+        long occurrences = array.computeSeq();
+        long endTimer = System.currentTimeMillis() - start;
+        System.out.printf("Sequential Time execution for Random Array of size %d is %d ms number of occurrences is %d\n", size, endTimer, occurrences);
+    }
+
+    public void testArrayOccurrencesCountPP() {
+        System.setProperty("java.util.concurrent.ForkJoinPool.common.parallelism","7");
+
+//        int size = 1000_000_000;
+        int size = 100000000;
+//        int[] arr = randomArray(size);
+        int[] arr = intStream(size);
+
+        int target = 5;
+
+        ArrayOccurrencesCount occurrences = new ArrayOccurrencesCount(arr, 0, arr.length - 1, target);
+        long start = System.currentTimeMillis();
+        ForkJoinPool.commonPool().invoke(occurrences);
+        long endTimer = System.currentTimeMillis() - start;
+        System.out.printf("Parallel Time execution for Random Array of size %d is %d ms sum is %d\n", size, endTimer, occurrences.occurrences);
+    }
+
+    public void testArrayOccurrencesCountStreamSeq() {
+        System.setProperty("java.util.concurrent.ForkJoinPool.common.parallelism","7");
+
+//        int size = 1000_000_000;
+        int size = 100000000;
+//        int[] arr = randomArray(size);
+        int[] arr = intStream(size);
+
+        int target = 5;
+
+        ArrayOccurrencesCount occurrences = new ArrayOccurrencesCount(arr, 0, arr.length - 1, target);
+        long start = System.currentTimeMillis();
+        occurrences.computeStreamSeq();
+        long endTimer = System.currentTimeMillis() - start;
+        System.out.printf("Parallel Stream Time execution for Random Array of size %d is %d ms sum is %d\n", size, endTimer, occurrences.occurrences);
+    }
+
+    public void testArrayOccurrencesCountStreamPP() {
+        System.setProperty("java.util.concurrent.ForkJoinPool.common.parallelism","7");
+
+//        int size = 1000_000_000;
+        int size = 100000000;
+//        int[] arr = randomArray(size);
+        int[] arr = intStream(size);
+
+        int target = 5;
+
+        ArrayOccurrencesCount occurrences = new ArrayOccurrencesCount(arr, 0, arr.length - 1, target);
+        long start = System.currentTimeMillis();
+        occurrences.computeStreamPP();
+        long endTimer = System.currentTimeMillis() - start;
+        System.out.printf("Parallel Stream Time execution for Random Array of size %d is %d ms sum is %d\n", size, endTimer, occurrences.occurrences);
+    }
+
+}