Differential Privacy Test Util, extracted from https://github.com/google/differential-privacy/blob/c2376f0daaf406e1524b462accaa9cbb548fd6d1/java/main/com/google/privacy/differentialprivacy/testing/StatisticalTestsUtil.java

DPTestUtil.java

 public static <T> boolean verifyApproximateDp(
      T[] samplesA, T[] samplesB, double epsilon, double delta, double deltaTolerance) {
    Map<T, Long> histogramA = buildHistogram(samplesA);
    Map<T, Long> histogramB = buildHistogram(samplesB);
    double testValueA = computeAproximateDpTestValue(histogramA, histogramB, epsilon, samplesA.length);
    double testValueB = computeAproximateDpTestValue(histogramB, histogramA, epsilon, samplesA.length);
    return testValueA < delta + deltaTolerance && testValueB < delta + deltaTolerance;
  }

  private static <T> double computeAproximateDpTestValue(
      Map<T, Long> histogramA, Map<T, Long> histogramB, double epsilon, int numOfSamples) {
    double testValue = 0;
    for (T sample : histogramA.keySet()) {
      double sampleCountA = histogramA.get(sample);
      if (histogramB.containsKey(sample)) {
        double sampleCountB = histogramB.get(sample);
        testValue += max(0.0, (sampleCountA - Math.exp(epsilon) * sampleCountB) / numOfSamples);
      } else {
        testValue += sampleCountA / numOfSamples;
      }
    }
    return testValue;
  }

  private static <T> Map<T, Long> buildHistogram(T[] samples) {
    Map<T, Long> histogram = new HashMap<>();
    for (T sample : samples) {
      if (histogram.containsKey(sample)) {
        histogram.put(sample, histogram.get(sample) + 1);
      } else {
        histogram.put(sample, 1L);
      }
    }
    return histogram;
  }
}