How can i Initilise PrimeRacers before anyworker Thread is Started?

[barnie stinson]

Hi All,

i would like to know how can i initialise all the primeRacers before any worker thread is started. In the following code:

package primea2;

import java.util.*;

public class PrimeRace extends Thread {
	// This code is adapted from A. Turner, "AtomicInteger, Volatile, Synchronized and Raw:
	// Performance and Safety", NerdsCentral blogspot, 24 November 2011.  Available: 
	// http://nerds-central.blogspot.co.nz/2011/11/atomicinteger-volatile-synchronized-and.html
	
	private static int timeLimit = 0; // how long the "race" will run, in milliseconds
	private static PROutputs pROutput = new PROutputs(); // all outputs from all primeRacer worker threads
	private volatile static boolean finished = false; // the finish flag -- polled by primeRacer worker threads
	
	// instance variables for primeRacers
        // Note: primeRacers are worker threads which execute the run() method of the PrimeRace class
	private int blocksize; 
	private String pName;
	private int pLane;
	private PrimeGeneratorInterface pg; 
	private ArrayList<Integer> pList; // the list of primes generated by this primeRacer
	
	public PrimeRace( ) {
	    // Note: the instance variables of primeRacers are initialized by main().
	}
	
	public void run() {
		while( !finished ) {
			pList = pg.generateAnotherBlockOfPrimes( blocksize ); // generate primes as fast as possible
		}
		pROutput.postResults( pLane, pList ); // report a list of primes, then terminate.
	}
	
	public static void main( String[] args ) {
			
		// references to our PrimeRacers
		ArrayList<Thread> primeRacerThreads = new ArrayList<Thread>();
		ArrayList<String> primeRacerNames = new ArrayList<String>();

		//Check arguments, entering them into argvec
		ArrayList<Integer> argvec = null; 
		try{ 
			argvec = checkArgs( args );  
		} catch (Exception e) { 
			System.out.println("Usage: PrimeRace t n1 b1 n2 b2 ... ni bi");	
			System.out.println(" -- where t is the time limit, in milliseconds, for this computation;");
			System.out.println(" -- ni is the prime number generation method used by the i-th worker thread,");
			System.out.println(" ---- ni = 1, for a Sieve of Eratosthenes");
			System.out.println(" ---- ni = 2, for a naive algorithm in Goetz's Introduction to Java threads");
			System.out.println(" ---- ni = 3, for a probabilistic prime finder in Java.math.BigInteger");
			System.out.println(" -- bi is the blocksize: the number of ints to be checked for primality");
			System.out.println("       by ni, between its polls of the time-limit flag");
			System.out.println(" -- Note that a large bi value makes it more likely that the i-th thread");
                        System.out.println("       will win the race to generate the most primes, because it will finish");
			System.out.println("       checking its current block of ints for primality before terminating.");
			System.exit(1);
		} 
		
		// construct the primeRacers by interpreting the argvec
		Iterator<Integer> i = argvec.iterator();

		// the first arg is the timeLimit (a class variable)
		timeLimit = i.next();
		
		// the remaining args are method# and blocksize parameters for each primeRacer
		int lane = 0; 
		while( i.hasNext() ) {
			
			lane++;  // add a new lane
			pROutput.addLane();
			
			// instantiate and initialize a new primeRacer
			PrimeRace t = new PrimeRace( );  
			t.pLane = lane;
			switch( i.next() ) {
				case 1: 		
					t.pName = "Eratosthenes" + lane;
					t.pg = new EratosthenesGen();
					break;
				case 2:
					t.pName = "Naive" + lane;
					t.pg = new NaiveGen();
					break;
				case 3:
					t.pName = "JavaMath" + lane;
					t.pg = new JavaMathGen();
					break;
			}
			t.blocksize = i.next();
	
			// main() needs to have a list of all racer threads, for the join().
			// All racers will be terminated by the time main() prints the results, 
			// so main() also keeps a list of names
			primeRacerThreads.add( t );
			primeRacerNames.add( t.pName );
			
			// t is now ready to run -- it's on the "starting block" of our racecourse
			
			// There's no "starting gun"!! primeRacers start as soon as they're ready.  
			// Nobody said this would be a fair race ;-)
			t.start(); 
		}

		// All primeRacers have been started.  The main thread sleeps until the end of the race.
		try { 
			Thread.sleep( timeLimit );
		} 
		catch (InterruptedException e) { 
			System.out.println("Interrupted Exception to sleep() was ignored in main()!");
			// If the println() above produces any console output, then this fall-through is unsafe.
			// But, most likely, the exception was raised by a ^c console input that is terminating the
			// entire JVM -- in which case, the println() above will not produce any console output and main()
			// will be abnormally terminated very soon.
		} 
		
		// Time's up!  All primeRacers will stop generating primes after they finish their current block
		finished = true; 
		
		System.out.println("The race is over.  Waiting for primeRunners to finish & report..." );
		long tFinish = System.currentTimeMillis();
		
		// The main thread waits (patiently and trustingly ;-) for all racers to terminate.
		Iterator<Thread> j = primeRacerThreads.iterator();
		int pc = 1;
		while( j.hasNext() ) {
			try {
				j.next().join(); // blocks main() until racer #j has stopped running
				System.out.println( "The primeRunner in lane " + pc + " joined main() "
						    + (System.currentTimeMillis()-tFinish)
						    + " msec after the race was over." );
			} catch (InterruptedException e){
				System.out.println("Interrupted Exception to join() was ignored in main()!");
				// If the println() above produces any console output, then this fall-through is unsafe.
				// However it's most likely that the exception was raised by a ^c console input which is terminating the
				// entire JVM -- in which case, the println() above will not produce any console output and main()
				// will be abnormally terminated very soon.
			}
		}
		
		// Who won?  Was there any disagreement on which numbers are prime?
		Iterator<String> kn = primeRacerNames.iterator();
		Iterator<ArrayList<Integer>> kp = pROutput.get().iterator();
		while( kp.hasNext() ) {
			ArrayList<Integer> kl = kp.next();
			if( kl.size() <= 5 ) {
				System.out.println( kn.next() + ":" + kl.toString() + ". Found " 
						+ kl.size() + " primes." );				
			} else {
				Iterator<Integer> kpp = kl.iterator();
				System.out.println( kn.next() + ": " + kpp.next() + ", " + kpp.next() + ", " + kpp.next() +
						" ... " + kl.get( kl.size() - 2 ) + ", " + kl.get( kl.size() - 1 ) + ". Found " 
						+ kl.size() + " primes." );
			}
		}

		System.out.println("The fastest primeRunner was in lane " + pROutput.lanesOfLongestLists().toString() );
		System.out.println("Most primes found: " + pROutput.longest() );
		System.out.println("Least primes found: " + pROutput.shortest() );
	} // end main
	
	public static ArrayList<Integer> checkArgs( String [] args ) throws Exception { 
		// Validate input, copying it into argvec
		// Note: this is a static method, so main() can access it easily.  (Worker threads
		// don't use this routine.)
		ArrayList<Integer> argvec = new ArrayList<Integer>();
		// There must be an odd number of args >= 3: at least one worker thread
		if( (args.length %2 != 1) || (args.length < 3) ) {
			throw new Exception();
		} else { 
			// read args into argvec, checking bounds
			for( int i=0; i<args.length; i++ ) {
				Integer a = Integer.valueOf(args[i]); // todo: an exception is possible here, is it handled correctly?
				if( a <= 0 ) { // all inputs must be greater than zero 
					throw new Exception();
				} else if ( (i%2 == 1) && (( a < 1) || ( a > 3)) ) { // 1 <= ni <= 3, for all i
					throw new Exception();
				} else {
					argvec.add( a );
				}
			}
		}
		return argvec;
	} //end checkArgs
}

[Jelle Klap]

I think the easiest way would be to have all the threads rendezvous at a CountDownLatch.