package class9_2_MemoryBarriers_start;// Dr. Yoder. MSOE. 11 May 2017

public class MemoryBarrierOnePrime {
    public static void main(String[] args) {
        new MemoryBarrierOnePrime().run();
    }

    private boolean isFound = false;
    private long currentPrime = 0;

    private void run() {
        new Thread(this::findPrimes).start();
        while(true) {
            while (!isFound) {
                /* busy-wait */
            }
            System.out.println("A prime was found!");
            System.out.println("prime = " + currentPrime);
        }
    }

    public void findPrimes() {
        for (long candidate = 100000000; candidate < Long.MAX_VALUE; candidate++) {
            if (isPrime(candidate)) {
                if(!isFound) {
                    isFound = true;
                    currentPrime = candidate;
                    System.out.println("A prime was foud: " + currentPrime);
                }
            }
        }
    }

    /**
     * Slow O((2^b)) or worse algorithm (where b is the number of bits in candidate)
     *
     * TODO: Implement Miller-Rabin Primality test to get O(n^12) or better performance.
     * http://en.wikipedia.org/wiki/Miller%E2%80%93Rabin_primality_test
     * (Why nine characters for one dash?
     *   Unicode character  Oct     Dec	    Hex	    HTML
     *            en dash   020023	8211	0x2013	&ndash;   )
     *
     * @param candidate candidate to test
     * @return true if candidate is prime.
     */
    private boolean isPrime(long candidate) {
        boolean isPrime = true;
        for(int divisor = 2; divisor < candidate && isPrime; divisor++) {
            if(candidate % divisor == 0) {
                isPrime = false;
            }
        }
        return isPrime;
    }

}