import java.util.*;
import java.util.concurrent.*;
import java.util.concurrent.atomic.*;
import java.util.concurrent.locks.*;
import easyIO.*;


class Oppgave5{
	   int [] a;
	   int n, antT;
	   CyclicBarrier sync ;

		public static void main (String [] args) {
			if ( args.length < 1 )	{
				System.out.println("use: >java Oppg4 <length of array> ");
		    } else {
			    new Oppgave5().doTest(args);
		    }
		 } // end main

	    void swap (int [] a, int left, int right ) {
				int temp,r = a.length-1;
				for (int j = left ; j < right; j++){
					temp = a[j];
					a[j] = a [r-j];
					a [r-j]=temp;
				}
	    } // end swap

       void  doTest (String [] args) {
			// initiate
			n = Integer.parseInt(args[0]);
			antT =   Runtime.getRuntime().availableProcessors();
			sync = new CyclicBarrier(antT +1);

			a = new int[n];
			Random r = new Random(1337);
			long tid ;
			int k;

			// ***************** Sekvensiell RadSort ******************
			 int sum =0;

			 // -- init a[][] -----
			 for (int i =0; i< a.length;i++){
				   a[i] = i;// random fill

			 } // end initarray

			 tid = System.nanoTime();       // start timer

			 swap ( a,0,n/2);
			 double  tt = (System.nanoTime()-tid)/1000000.0;
			 testRS(a, "Sekv ");

			 System.out.println("n: "+n+", num cores:"+ antT );
			 System.out.println("  Sequental  swaping in : "+  tt+ " ms. " );

			// ***************** Parallell RadSort ******************
			 for (int i =0; i< a.length;i++){
					 a[i] = i;
		     } // end initarray

            // a) regn ut radsum i parallell
			tid = System.nanoTime();       // start timer

			 Thread [ ] tr = new Thread[antT];
			 for (int i =0; i< antT;i++){
			     (tr[i] = new Thread(new Arbeider(i))).start();;
			 } // end initarray

	 	      try{
				 for (int i =0; i< antT;i++)
				 	 tr[i].join();
			  }catch(Exception e) {return;}

     /*        try{
				  sync.await();
			  } catch (Exception e) { return;}
      */
			  double ttt = (System.nanoTime()-tid)/1000000.0;
			   testRS(a, "Para ");

			 System.out.println("n: "+n+", num cores:"+ antT  );
			 System.out.println("  Parallel   swapping  in: "+  ttt+ " ms., speedup: "
			                     +Format.align (tt/ttt, 5,2) );

	    } // end doTest

	    void testRS(int [] rs, String s) {
			for (int i =1; i < rs.length; i++)
			    if (rs[i-1] < rs[i]) {
					System.out.println("ERROR:" + s+ ", at i ="+i);
				}
		} // end testRS


		class Arbeider implements Runnable {
			   int ind; // lokale data og metoder B
			   int part, left,right;

				Arbeider ( int in) {
					ind = in;
					part = n/(antT*2);
					left = ind*part;
					if (ind == antT-1) right = n/2;
					else right = left + part;
				}
				public void run( ) {
					// kalles n?r tr?den er startet
					swap(a,left,right);
	/*			    try{
					  sync.await();
				    } catch (Exception e) { return;}
     */
				} // end run
		 } // end indre klasse Arbeider

} // end Oppg.4