120 lines
3.2 KiB
Java
120 lines
3.2 KiB
Java
import java.util.Arrays;
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import java.util.Random;
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public class AtomicUpdates
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{
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public static class Buckets
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{
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private final int[] data;
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public Buckets(int[] data)
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{
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this.data = data.clone();
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}
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public int getBucket(int index)
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{
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synchronized (data)
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{ return data[index]; }
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}
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public int transfer(int srcBucketIndex, int destBucketIndex, int amount)
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{
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if (amount == 0)
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return 0;
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// Negative transfers will happen in the opposite direction
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if (amount < 0)
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{
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int tempIndex = srcBucketIndex;
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srcBucketIndex = destBucketIndex;
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destBucketIndex = tempIndex;
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amount = -amount;
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}
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synchronized (data)
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{
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if (amount > data[srcBucketIndex])
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amount = data[srcBucketIndex];
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if (amount <= 0)
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return 0;
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data[srcBucketIndex] -= amount;
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data[destBucketIndex] += amount;
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return amount;
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}
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}
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public int[] getBuckets()
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{
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synchronized (data)
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{ return data.clone(); }
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}
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}
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public static int getTotal(int[] values)
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{
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int totalValue = 0;
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for (int i = values.length - 1; i >= 0; i--)
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totalValue += values[i];
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return totalValue;
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}
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public static void main(String[] args)
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{
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final int NUM_BUCKETS = 10;
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Random rnd = new Random();
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final int[] values = new int[NUM_BUCKETS];
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for (int i = 0; i < values.length; i++)
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values[i] = rnd.nextInt(10);
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System.out.println("Initial Array: " + getTotal(values) + " " + Arrays.toString(values));
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final Buckets buckets = new Buckets(values);
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new Thread(new Runnable() {
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public void run()
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{
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Random r = new Random();
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while (true)
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{
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int srcBucketIndex = r.nextInt(NUM_BUCKETS);
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int destBucketIndex = r.nextInt(NUM_BUCKETS);
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int amount = (buckets.getBucket(srcBucketIndex) - buckets.getBucket(destBucketIndex)) >> 1;
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if (amount != 0)
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buckets.transfer(srcBucketIndex, destBucketIndex, amount);
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}
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}
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}
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).start();
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new Thread(new Runnable() {
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public void run()
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{
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Random r = new Random();
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while (true)
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{
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int srcBucketIndex = r.nextInt(NUM_BUCKETS);
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int destBucketIndex = r.nextInt(NUM_BUCKETS);
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int srcBucketAmount = buckets.getBucket(srcBucketIndex);
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int destBucketAmount = buckets.getBucket(destBucketIndex);
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int amount = r.nextInt(srcBucketAmount + destBucketAmount + 1) - destBucketAmount;
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if (amount != 0)
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buckets.transfer(srcBucketIndex, destBucketIndex, amount);
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}
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}
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}
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).start();
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while (true)
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{
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long nextPrintTime = System.currentTimeMillis() + 3000;
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long curTime;
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while ((curTime = System.currentTimeMillis()) < nextPrintTime)
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{
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try
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{ Thread.sleep(nextPrintTime - curTime); }
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catch (InterruptedException e)
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{ }
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}
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int[] bucketValues = buckets.getBuckets();
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System.out.println("Current values: " + getTotal(bucketValues) + " " + Arrays.toString(bucketValues));
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}
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}
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}
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