Proving Thread-Safety of SimplexOctaveGenerator#generateNoise

test.java

import org.bukkit.util.noise.SimplexOctaveGenerator;
import org.junit.jupiter.api.Assertions;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ThreadLocalRandom;

public class OctaveGeneratorThreadTest {

    public static void main(String[] args) throws InterruptedException {
        int threadCount = 500; // set this to the number of threads to use in testing
        CountDownLatch start = new CountDownLatch(1);
        CountDownLatch end = new CountDownLatch(threadCount);

        SimplexOctaveGenerator generator = new SimplexOctaveGenerator(100, 8);
        generator.setScale(0.05);

        for (int h = 0; h < threadCount; h++) {
            new Thread(() -> {
                try {
                    int x = ThreadLocalRandom.current().nextInt(100_000);
                    int y = ThreadLocalRandom.current().nextInt(100_000);
                    int cmp = height(generator, x, y);
                    // tell the main thread setup is done
                    end.countDown();
                    // wait for the start signal
                    start.await();
                    // and we're off!
                    for (int i = 0; i < 1000; i++) {
                        Assertions.assertEquals(cmp, height(generator, x, y));
                    }
                    // tell the main thread we're done
                    end.countDown();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }).start();
        }

        // wait for everyone to finish setup
        end.await();
        // give the start signal
        start.countDown();
        // wait for everyone to finish
        end.await();
    }

    // get the height of the terrain at the given coordinates
    private static int height(SimplexOctaveGenerator generator, int x, int y) {
        double d = generator.noise(x, y, 0.5, 0.5, true);
        double temp = 50 + 20 * d;
        return temp >= 0 ? (int) temp : (int) temp - 1;
    }
}