83 lines
2.7 KiB
Java
83 lines
2.7 KiB
Java
// threads/FastSimulation.java
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// (c)2016 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
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import java.util.concurrent.*;
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import java.util.concurrent.atomic.*;
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import java.util.*;
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public class FastSimulation {
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static final int N_ELEMENTS = 100000;
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static final int N_GENES = 30;
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static final int N_EVOLVERS = 50;
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static final AtomicInteger[][] GRID =
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new AtomicInteger[N_ELEMENTS][N_GENES];
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static SplittableRandom rand = new SplittableRandom(47);
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private static volatile boolean running = true;
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public static void stop() { running = false; }
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static class Evolver implements Runnable {
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@Override
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public void run() {
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while(running) {
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// Randomly select an element to work on:
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int element = rand.nextInt(N_ELEMENTS);
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for(int i = 0; i < N_GENES; i++) {
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int previous = element - 1;
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if(previous < 0) previous = N_ELEMENTS - 1;
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int next = element + 1;
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if(next >= N_ELEMENTS) next = 0;
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int oldvalue = GRID[element][i].get();
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// Perform some kind of modeling calculation:
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int newvalue = oldvalue +
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GRID[previous][i].get() + GRID[next][i].get();
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newvalue /= 3; // Average the three values
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if(!GRID[element][i]
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.compareAndSet(oldvalue, newvalue)) {
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// Policy here to deal with failure. Here, we
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// just report it and ignore it; our model
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// will eventually deal with it.
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System.out.println(
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"Old value changed from " + oldvalue);
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}
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}
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}
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}
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}
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public static void
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main(String[] args) throws Exception {
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ExecutorService es = Executors.newCachedThreadPool();
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for(int i = 0; i < N_ELEMENTS; i++)
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for(int j = 0; j < N_GENES; j++)
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GRID[i][j] =
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new AtomicInteger(rand.nextInt(1000));
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for(int i = 0; i < N_EVOLVERS; i++)
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es.execute(new Evolver());
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TimeUnit.SECONDS.sleep(4);
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FastSimulation.stop();
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es.shutdownNow();
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}
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}
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/* Output: (First and last 10 Lines)
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Old value changed from 542
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Old value changed from 447
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Old value changed from 446
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Old value changed from 643
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Old value changed from 419
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Old value changed from 573
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Old value changed from 668
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Old value changed from 710
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Old value changed from 800
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Old value changed from 406
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________...________...________...________...________
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Old value changed from 458
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Old value changed from 436
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Old value changed from 475
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Old value changed from 501
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Old value changed from 526
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Old value changed from 465
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Old value changed from 467
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Old value changed from 368
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Old value changed from 404
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Old value changed from 428
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*/
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