package be.ac.vub.ir.mpi;

import be.ac.vub.ir.util.Chrono;
import be.ac.vub.ir.util.GetOpt;


/**
 * Parallel and sequential implementation of a prime number counter
 */

public class CountPrimes {
		
	// Default program parameters
	final static int DEFAULTSIZE = 50000;

	public static void main(String[] args){		
		
		// *** INITIALIZE ***
		GetOpt options = new GetOpt("n:",args); // allows you to parse program options. 
		// ':' means that an argument is following after the option (here: -n 1000)
		String ns = options.getOptionParam('n');
		int arraySize = (ns != null) ? Integer.parseInt(ns) : DEFAULTSIZE ;
		
		int[] data = createAndFillArray(arraySize);
		
		// *** SEQUENTIAL RUN (master only) ***
		Chrono seqChrono = new Chrono();
		int nbrPrimesSeq = countPrimes(data);
		long seqtime = seqChrono.stop();
		
		System.out.println("Sequential solution found "+nbrPrimesSeq+" primes among "+arraySize+" odd numbers in "+seqChrono);
		
		
	}
	// *** Array Filling ***
	static int[] createAndFillArray(int n){ // fills with all odd numbers
		int[] data = new int[n];
		for (int i=0;i<n;i++)
			data[i] = 1 + 2*i;;
		return data;
	}
	
	// *** Sequential Prime Counting ***
	public static int countPrimes(int[] data) {
		int np = 0;
		for (int value: data)
			if (isPrime(value))
				np++;
		return np;		
	}
	
	public static boolean isPrime(int value){ // this is not the most efficient implementation, we know...
		for (int j=2 ; j<value ; j++){
			if ((value % j) == 0)
				return false;
		}
		return true;
	}
}