CoreBasedCounter.java

package counter;

import java.util.concurrent.atomic.AtomicIntegerArray;

public class CoreBasedCounter implements Counter {
    private AtomicIntegerArray atomicArray = new AtomicIntegerArray(Runtime
            .getRuntime().availableProcessors());

    int mode = Runtime.getRuntime().availableProcessors() - 1;

    @Override
    public int inc() {
        int id = (int) Thread.currentThread().getId();
        int index = id & mode;
        int fail = 0;
        while (true) {
            int currVal = atomicArray.get(index);
            if (atomicArray.compareAndSet(index, currVal, currVal + 1))
                break;
            fail++;
        }

        return fail;

    }

    @Override
    public int get() {
        int sum = 0;
        for (int i = 0; i < mode + 1; i++) {
            sum += atomicArray.get(i);
        }
        return sum;
    }


}