HarmonicTest.java

/*
 * Copyright 2012, Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.facebook.LinkBench;

import junit.framework.TestCase;

import org.junit.Test;
import org.junit.experimental.categories.Category;

import com.facebook.LinkBench.distributions.ApproxHarmonic;
import com.facebook.LinkBench.distributions.Harmonic;
import com.facebook.LinkBench.testtypes.SlowTest;


@Category(SlowTest.class)
public class HarmonicTest extends TestCase {

  @Test
  @Category(SlowTest.class)
  public void testHarmonic() {
    assertEquals(1, Harmonic.generalizedHarmonic(1, 0.8), 0.001);
    assertEquals(1.99534, Harmonic.generalizedHarmonic(10, 1.5), 0.00001);
    assertEquals(61.8010, Harmonic.generalizedHarmonic(1000, 0.5), 0.001);
    assertEquals(207.541, Harmonic.generalizedHarmonic(1000000, 0.7), 0.002);
    assertEquals(2679914.0, Harmonic.generalizedHarmonic(12345678, 0.1),
                 1);
  }

  static final double SHAPES[] = {0.01, 0.1, 0.5, 0.9, 0.99};

  
  @Test
  public void testApproxFast() {
    for (long i = 0; i < 16; i+=4) {
      testApproxHelper(i);
    }
  }
  
  @Test
  @Category(SlowTest.class)
  public void testApproxSlow() {
    for (long i = 16; i < 30; i+=4) {
      testApproxHelper(i);
    }
  }

  /** Test that approximation is close to actual for a range of shapes and ns */
  private void testApproxHelper(long i) {
    long n = (long)Math.pow(2, i);
    for (double shape: SHAPES) {
      double exact = Harmonic.generalizedHarmonic(n, shape);
      long start = System.currentTimeMillis();
      double approx = ApproxHarmonic.generalizedHarmonic(n, shape);
      long end = System.currentTimeMillis();
      System.err.format("ApproxHarmonic.generalizedHarmonic(%d, %f) " +
                        "took %.3fs\n", n, shape, (end - start) / 1000.0);
      double err = approx - exact;
      double errPc = (err / exact) * 100.0;
      System.err.format("ApproxHarmonic.generalizedHarmonic(%d, %f) = %f. " +
                        "exact=%f err=%f err%%=%.2f\n", n, shape, approx,
                         exact, err, errPc);
      double errThresh = 0.05;
      assertTrue(String.format("Err%%=%.3f must be < 0.05%%", Math.abs(errPc)),
                               Math.abs(errPc) < errThresh);
    }
  }
}