Section 12.4

// Guide to Java, Second Edition
// Copyright 2023, by J.T. Streib and T. Soma

public class InnerProductParallel {
   public static void main(String[] args) {
      int numThreads, vecSize;
      int innerProduct;
      innerProduct = 0;
      numThreads = Integer.parseInt(args[0]);
      vecSize = Integer.parseInt(args[1]);
      int[] a, b;
      a = new int[vecSize];
      b = new int[vecSize];
      getVec(a);
      getVec(b); 

      // parallel section
      //#omp parallel num_threads(numThreads) 
             shared(numThreads, innerProduct, vecSize, a, b)
      {
         int myPart, myID, myFirstPos, myLastPos;
         int myInnerProduct;
         myInnerProduct = 0;
         myPart = vecSize / numThreads;
         myID = Pyjama.omp_get_thread_num();
         myFirstPos = myPart * myID;
         if(myID == numThreads-1)
            myLastPos = vecSize;
         else
            myLastPos = myFirstPos + myPart;

         // multiplication and addition 
         for(int i=myFirstPos; i<myLastPos; i++)
            myInnerProduct = myInnerProduct + (a[i] * b[i]);

         // critical section: update innerProduct
         //#omp critical 
         {
            innerProduct += myInnerProduct; 
         } // end of critical section
      } // end of parallel section

      // print the contents of vectors if the size is small
      if(vecSize <= 10) {
         System.out.print("a = [");
         for(int i=0; i<vecSize; i++) 
            System.out.print(a[i] + " ");
         System.out.println("]");
         System.out.print("b = [");
         for(int i=0; i<vecSize; i++) 
            System.out.print(b[i] + " ");
         System.out.println("]");
      }
      System.out.println("Inner Product is " + innerProduct);
   }

   public static void getVec(int[] array) {
      for(int i=0; i<array.length; i++)
         array[i] = (int)(Math.floor(Math.random() * 1000));
   }
}