Question

Develop a multithreaded app that can find the integer in the range 1 to 10000 that has the largest number of divisors. It should print that integer as well as the time spent to finish the calculation. use Java and Any API library.

Please provide the code and answer the following

1. How long it took your app to finish the job when using 1 thread?

2. How many threads your machine can run simultaneously?

3. How long it took your app to finish the job when using all available threads?

4. Did you use task or data parallelization for this program? Why?

Answer 1

b) It depends upon CPU thread handling mechanism and JVM installed.

c) around 80ms for 8 threads

d) Yeah, splitted the task into multiple parts.

Code

public class Temp {

    

    public static void main(String[] args) throws Exception{

        int N=4;  //number of threads

        Factorize[]f = new Factorize[N];  

        long start = System.currentTimeMillis();  //timer start

        for(int i=0;i<N;i++){

            f[i] = new Factorize(i*10000/N, (i+1)*10000/N);  //assign each hhtread task

            f[i].start();

        }

        for(int i=0;i<N;i++)

            f[i].join();

        long end = System.currentTimeMillis();  //stop timer

        int result=-1, maxFactor=0;

        for(int i=0;i<N;i++){   //gather maximum result

            if(f[i].maxFactor>maxFactor){

                maxFactor = f[i].maxFactor;

                result = f[i].result;

            }

        }

        System.out.println("Number: "+result);

        System.out.println("Factors: "+maxFactor);

        System.out.println("Number of Threads: "+N);

        System.out.println("Execution time (in ms): "+(end-start));

    }

}

class Factorize extends Thread{

    int lower, upper, result, maxFactor;

    Factorize(int l,int u){  //range of numbers to find answer

        lower = l ;

        upper = u ;

        maxFactor=0;

    }

    int numOfFactor(int n){  //factor of 1 number

        int count=0;

        for(int i=1;(i)<=n;i++)

            if(n%i==0)

                count++;

        return count;

    }

    @Override

    public void run() {

        for(int i=lower;i<=upper;i++){

            int f = numOfFactor(i);

            if(f>maxFactor){

                maxFactor=f;

                result=i;

            }

        }

    }

}