TrieMapPerformanceTest.java

package com.blazebit.collection;

import java.util.Map;
import org.junit.Test;

/**
 * 
 * @author Christian Beikov
 */
public final class TrieMapPerformanceTest {

	private static final Object VALUE = new Object();
	private static final int MAX_DEPTH = 4;
	private static final int WARMUP_RUNS = 20;
	private static final int TEST_RUNS = 15;

	@Test
	public void testPerformance() throws Exception {
		final int warmup = WARMUP_RUNS;
		final int runs = TEST_RUNS;
		final Map<CharSequence, Object> map = map(new TrieMap<Object>());
		final long sumGet;
		final long sumPut;
		long start;

		/* Warmup */
		for (int i = 0; i < warmup; i++) {
			get(map(new TrieMap<Object>()));
		}

		/* Test put performance */
		start = System.nanoTime();
		for (int i = 0; i < runs; i++) {
			map(new TrieMap<Object>());
		}
		sumPut = System.nanoTime() - start;

		/* Test get performance */
		start = System.nanoTime();
		for (int i = 0; i < runs; i++) {
			get(map);
		}
		sumGet = System.nanoTime() - start;

		/* Output */
		final int operations = (int) Math.pow(26, MAX_DEPTH);
		System.out.println("TrieMap.put - " + ((sumPut / runs) / 1000000)
				+ " ms for " + operations
				+ " operations. Average per operation - "
				+ ((sumPut / runs) / operations) + " ns");
		System.out.println("TrieMap.get - " + ((sumGet / runs) / 1000000)
				+ " ms for " + operations
				+ " operations. Average per operation - "
				+ ((sumGet / runs) / operations) + " ns");
	}

	private Map<CharSequence, Object> map(final Map<CharSequence, Object> map) {
		fill(map, "", 0, MAX_DEPTH);

		return map;
	}

	private void fill(Map<CharSequence, Object> map, String prefix, int depth,
			int maxDepth) {
		if (depth == maxDepth) {
			return;
		}

		final Object value = VALUE;
		final StringBuilder sb = new StringBuilder(prefix.length() + 1);
		sb.append(prefix);
		sb.append(' ');

		for (int i = 0; i < 26; i++) {
			sb.setCharAt(prefix.length(), (char) ('a' + i));
			final String newPrefix = sb.toString();
			map.put(newPrefix, value);
			fill(map, newPrefix, depth + 1, maxDepth);
		}
	}

	private void get(Map<CharSequence, Object> map) {
		get(map, "", 0, MAX_DEPTH);
	}

	private void get(Map<CharSequence, Object> map, String prefix, int depth,
			int maxDepth) {
		if (depth == maxDepth) {
			return;
		}

		final StringBuilder sb = new StringBuilder(prefix.length() + 1);
		sb.append(prefix);
		sb.append(' ');

		for (int i = 0; i < 26; i++) {
			sb.setCharAt(prefix.length(), (char) ('a' + i));
			final String newPrefix = sb.toString();
			map.get(newPrefix);
			get(map, newPrefix, depth + 1, maxDepth);
		}
	}
}