add simple benchmarking helper

primitiveCollections/src/test/java/org/lucares/collections/BenchmarkHarness.java

@@ -0,0 +1,88 @@
+package org.lucares.collections;
+
+import java.util.ArrayList;
+import java.util.DoubleSummaryStatistics;
+import java.util.List;
+import java.util.stream.IntStream;
+
+public class BenchmarkHarness<T> {
+
+	static class IntListPair {
+		IntList a, b;
+	}
+
+	interface Generator<T> {
+		T generateInput();
+	}
+
+	interface Invocation<T> {
+		void run(T input);
+	}
+
+	public <P> void test(final String name, final Generator<P> generator, final Invocation<P> invoker,
+			final int iterations) {
+
+		final List<Double> durationsInMs = new ArrayList<>();
+
+		for (int i = 0; i < iterations; i++) {
+			final P input = generator.generateInput();
+
+			final long start = System.nanoTime();
+
+			invoker.run(input);
+
+			final long duration = (System.nanoTime() - start);
+
+			durationsInMs.add(duration / 1_000_000.0);
+		}
+
+		final DoubleSummaryStatistics statistics = durationsInMs.stream().mapToDouble(l -> l).summaryStatistics();
+
+		System.out.println(name + ": " + statistics.toString());
+
+	}
+
+	public static void main(final String[] args) {
+		final BenchmarkHarness<Object> harness = new BenchmarkHarness<>();
+
+		final Generator<IntList> generatorSorted = () -> {
+			final int values = 100_000;
+			final IntList result = IntList.of();
+			IntStream.range(0, values).forEachOrdered(i -> result.add(i));
+			result.sort();
+			return result;
+		};
+		final Generator<IntList> generatorUnsorted = () -> {
+			final IntList result = generatorSorted.generateInput();
+			result.shuffle();
+			return result;
+		};
+
+		final Generator<IntListPair> generatorSortedPair = () -> {
+			final IntListPair result = new IntListPair();
+
+			result.a = generatorSorted.generateInput();
+			result.b = generatorSorted.generateInput();
+
+			return result;
+		};
+
+		final Generator<IntListPair> generatorUnsortedPair = () -> {
+			final IntListPair result = new IntListPair();
+
+			result.a = generatorUnsorted.generateInput();
+			result.b = generatorUnsorted.generateInput();
+
+			return result;
+		};
+
+		final Invocation<IntListPair> union = p -> IntList.union(p.a, p.b);
+
+		for (int i = 0; i < 10; i++) {
+			harness.test("union(): unsorted" + i, generatorUnsortedPair, union, 100);
+		}
+		for (int i = 0; i < 10; i++) {
+			harness.test("union(): sorted" + i, generatorSortedPair, union, 100);
+		}
+	}
+}