package eu.ase.hpc.multith.paralel;

public class ProgMainParalel {
	private static final int NTHREADS=4;
	public static void main(String[] args) {
		int dimVect=40_000_000;
		int[] v = new int[dimVect];
		for(int i=0;i<dimVect;i++)
			v[i]=1+i;



		int startIdx =0, stopIdx=0;
		long startTime =0, stopTime=0;
		Long[] vectSum =new Long[NTHREADS];


		//1. seq
		Long sum = new Long(0);
		startTime=System.currentTimeMillis();
		for(int i=0;i<dimVect; i++) {
			sum+=v[i];
		}
		stopTime=System.currentTimeMillis();
		System.out.println("1. Seq time = "+ (stopTime-startTime)+ ", sum = " +sum);


		//2. standart multi threading

		sum = new Long(0);
		startTime=System.currentTimeMillis();

		Thread[] vectThreads = new Thread[NTHREADS];
		MyMultiThArray[] vectRThreads= new MyMultiThArray[NTHREADS];

		for(int it=0; it<NTHREADS; it++) {
			startIdx = it* (dimVect/NTHREADS);
			stopIdx=(it+1)* (dimVect/NTHREADS)-1;
			vectSum[it]= new Long(0);
			vectRThreads[it]= new MyMultiThArray(v, startIdx, stopIdx);
			vectThreads[it]= new Thread(vectRThreads[it]);
		}

		for(int it=0;it<NTHREADS;it++) {
			vectThreads[it].start();
		}

		for(int it=0;it<NTHREADS;it++) {
			try {
			vectThreads[it].join();
			}catch(InterruptedException e) {
				e.printStackTrace();
			}
		}

		for(int it=0;it<NTHREADS;it++) {
			vectSum[it]=vectRThreads[it].getSum();
			sum+= vectSum[it];
		}

		stopTime=System.currentTimeMillis();
		System.out.println("2. Multi threading time = "+ (stopTime-startTime)+ ", sum = " +sum);

	}
}




package eu.ase.hpc.multith.paralel;

public class MyMultiThArray implements Runnable {
	private int[] vinp;
	private int start;
	private int stop;
	private Long sum;


	public MyMultiThArray(int[] v, int startIdx, int stopIdx) {
		this.vinp=v;
		this.start= startIdx;
		this.stop=stopIdx;

	}

	@Override
	public void run() {
		long s=0;
		for(int idx=this.start;idx<=this.stop;idx++) {
			s+= this.vinp[idx];
		}
		this.sum=new Long(s);
	}

	public Long getSum() {
		return this.sum;
	}

}