Demo class for calculating Pi using Reactor

ReactorDispatchingExample.java

import org.apache.commons.lang.time.StopWatch;
import reactor.Environment;
import reactor.fn.BiFunction;
import reactor.rx.Streams;

import java.util.concurrent.TimeUnit;

/**
 * Demo class for calculating Pi using Reactor.
 */
public class ReactorDispatchingExample {

	static {
		Environment.initializeIfEmpty().assignErrorJournal();
	}

	public static void main(String... args) throws InterruptedException {
		int iterations = 25000000;

		StopWatch watch = new StopWatch();
		watch.start();

		double pi = Streams
				.range(1, iterations)
				.dispatchOn(Environment.sharedDispatcher())
				.capacity(16 * 1024)
				.filter(i -> (i == 1 || i % 2 != 0))
				.map(i -> (double) 4 / i)
				.reduce(new PiReducer())
				.next()
				.await(30, TimeUnit.SECONDS);

		watch.stop();
		double throughput = iterations / (double) (watch.getTime() / 1000);
		System.out.println("pi calculated to " + pi + " / throughput: " + (long) throughput + " ops/s");
	}

	static final class PiReducer implements BiFunction<Double, Double, Double> {
		boolean subtract;

		@Override
		public Double apply(Double prev, Double next) {
			return ((subtract ^= true) ? prev - next : prev + next);
		}
	}

}