calculate fibonacci number

.idea/workspace.xml

@@ -4,15 +4,10 @@
     <option name="autoReloadType" value="SELECTIVE" />
   </component>
   <component name="ChangeListManager">
-    <list default="true" id="bd82bf16-4018-4075-b7d4-6d792f3cd58b" name="Changes" comment="">
-      <change afterPath="$PROJECT_DIR$/.gitignore" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/.idea/encodings.xml" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/.idea/misc.xml" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/.idea/vcs.xml" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/pom.xml" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/src/main/java/Service/NumOfOccurrences.java" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/src/test/java/NumOfOccurrencesTest.java" afterDir="false" />
+    <list default="true" id="bd82bf16-4018-4075-b7d4-6d792f3cd58b" name="Changes" comment="Find the number of occurrences of a number in an array">
+      <change afterPath="$PROJECT_DIR$/src/main/java/Service/Fibonacci.java" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/src/test/java/FibonacciTest.java" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
     </list>
     <option name="SHOW_DIALOG" value="false" />
     <option name="HIGHLIGHT_CONFLICTS" value="true" />
@@ -54,6 +49,14 @@
       <option name="presentableId" value="Default" />
       <updated>1679420459839</updated>
     </task>
+    <task id="LOCAL-00001" summary="Find the number of occurrences of a number in an array">
+      <created>1679420949412</created>
+      <option name="number" value="00001" />
+      <option name="presentableId" value="LOCAL-00001" />
+      <option name="project" value="LOCAL" />
+      <updated>1679420949412</updated>
+    </task>
+    <option name="localTasksCounter" value="2" />
     <servers />
   </component>
   <component name="Vcs.Log.Tabs.Properties">
@@ -67,4 +70,8 @@
       </map>
     </option>
   </component>
+  <component name="VcsManagerConfiguration">
+    <MESSAGE value="Find the number of occurrences of a number in an array" />
+    <option name="LAST_COMMIT_MESSAGE" value="Find the number of occurrences of a number in an array" />
+  </component>
 </project>
\ No newline at end of file

src/main/java/Service/Fibonacci.java

+package Service;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.RecursiveTask;
+
+
+/*
+However, besides being a dumb way to compute Fibonacci functions (there is a simple fast linear algorithm that you'd use in practice),
+ this is likely to perform poorly because the smallest subtasks are too small to be worthwhile splitting up.
+ Instead, as is the case for nearly all fork/join applications,
+ you'd pick some minimum granularity size (for example 10 here) for which you always sequentially solve rather than subdividing.
+ */
+
+public class Fibonacci extends RecursiveTask<Integer> {
+    final int n;
+
+    public static HashMap <Integer, Integer> fibValues = new HashMap<Integer, Integer>(); /////
+    public Fibonacci(int n) { this.n = n; }
+
+    public Integer compute() {
+
+        if(n > 20) {
+            if (n <= 1)
+                return n;
+            Fibonacci f1 = new Fibonacci(n - 1);
+            f1.fork();
+            Fibonacci f2 = new Fibonacci(n - 2);
+            return f2.compute() + f1.join();
+        }else{
+            return computeSeq();
+        }
+    }
+
+    public Integer computeSeq() {
+        if (n <= 1)
+            return n;
+        else if (fibValues.containsKey(n))
+            return fibValues.get(n);
+        else {
+            Fibonacci f1 = new Fibonacci(n - 1);
+            Fibonacci f2 = new Fibonacci(n - 2);
+            int value=f2.computeSeq() + f1.computeSeq();
+            fibValues.put(n,value);
+            return value;
+        }
+
+    }
+
+}

src/test/java/FibonacciTest.java

+import Service.Fibonacci;
+import junit.framework.TestCase;
+
+
+public class FibonacciTest extends TestCase {
+
+    int n=40;
+
+    public void testFiboPP(){
+        long start = System.currentTimeMillis();
+        Fibonacci fib = new Fibonacci(n);
+        int res = fib.compute();
+        long end = System.currentTimeMillis()-start;
+        System.out.printf("Fibonacci for %d is %d, and parallel execution took %d ms\n",n,res,end);
+//        Fibonacci parallel takes 144269 fon n = 50 before enhancement 1
+    }
+
+    public void testFiboSeq(){
+        long start = System.currentTimeMillis();
+        Fibonacci fib = new Fibonacci(n);
+        int res = fib.computeSeq();
+        long end = System.currentTimeMillis()-start;
+        System.out.printf("Fibonacci for %d is %d, and sequential execution took %d ms\n",n,res,end);
+        //Fibonacci Sequential takes 86495 fon n = 50 before enhancement 1
+    }
+}