source: benchmark/schedint/JavaThread.java @ 954821df

class Monitor {
        public static volatile Boolean go = false;
        public static volatile Boolean next = false;
}

class Signaller extends Thread {
        Monitor m;
        Signaller(Monitor m) {
                this.m = m;
        }

        public void run() {
                Monitor.go = true;
                while( Monitor.go ) {
                        synchronized(this.m) {
                                Monitor.next = false;
                                this.m.notify();
                        }
                        while( ! Monitor.next && Monitor.go );  // spin until woken
                }
        }
}

public class JavaThread {
        // Simplistic low-quality Marsaglia Shift-XOR pseudo-random number generator.
        // Bijective   
        // Cycle length for non-zero values is 4G-1.
        // 0 is absorbing and should be avoided -- fixed point.
        // The returned value is typically masked to produce a positive value.
        static volatile int Ticket = 0 ; 

        private static int nextRandom (int x) {
                if (x == 0) { 
                        // reseed the PRNG
                        // Ticket is accessed infrequently and does not constitute a coherence hot-spot. 
                        // Note that we use a non-atomic racy increment -- the race is rare and benign. 
                        // If the race is a concern switch to an AtomicInteger.  
                        // In addition accesses to the RW volatile global "Ticket"  variable are not 
                        // (readily) predictable at compile-time so the JIT will not be able to elide 
                        // nextRandom() invocations.  
                        x = ++Ticket ; 
                        if (x == 0) x = 1 ; 
                }
                x ^= x << 6;
                x ^= x >>> 21;
                x ^= x << 7;
                return x ;   
        }
        static int x = 2;

        static private int times = Integer.parseInt("1000000");

        public static void helper( Monitor m ) throws InterruptedException {
                for(int i = 1; i <= times; i += 1) {
                        m.wait();               // relase monitor lock
                        m.next = true;
                }
        }
        public static void InnerMain() throws InterruptedException {
                Monitor m = new Monitor();
                long start, end;
                Signaller s = new Signaller(m);
                synchronized(m) {
                        s.start();
                        while( ! Monitor.go ) { // waiter must start first
                                Thread.yield();
                        }
                        start = System.nanoTime();
                        helper( m );
                        end = System.nanoTime();
                }
                Monitor.go = false;
                s.join();
                System.out.println( (end - start) / times);
        }
        public static void main(String[] args) throws InterruptedException {
                if ( args.length > 2 ) System.exit( 1 );
                if ( args.length == 2 ) { times = Integer.parseInt(args[1]); }

                for (int n = Integer.parseInt("5"); --n >= 0 ; ) { 
                        InnerMain();
                        Thread.sleep(2000);     // 2 seconds
                        x = nextRandom(x);
                }
                if ( x == 0 ) System.out.println(x);
        }
}

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