* returns the low 64 bits of the result.
   *
   * @since 14.0
   */
  public UnsignedLong plus(UnsignedLong val) {
    return fromLongBits(this.value + checkNotNull(val).value);
  }

  /**
   * Returns the result of subtracting this and {@code val}. If the result would have more than 64
   * bits, returns the low 64 bits of the result.
   *
   * @since 14.0
   */

  private static long shiftMix(long val) {
    return val ^ (val >>> 47);
  }

  /** Implementation of Hash128to64 from util/hash/hash128to64.h */
  @VisibleForTesting
  static long hash128to64(long high, long low) {
    long a = (low ^ high) * K3;
    a ^= a >>> 47;
    long b = (high ^ a) * K3;
    b ^= b >>> 47;
    b *= K3;
    return b;
  }

  /**

      result +=
        when {
          c.isSurrogate() -> {
            val low = (if (i + 1 < limit) this[i + 1] else '\u0000')
            if (c.isLowSurrogate() || !low.isLowSurrogate()) {
              '?'.code
            } else {
              i++
              0x010000 + (c.code and 0x03ff shl 10 or (low.code and 0x03ff))
            }
          }

          else -> {
            c.code

    val isMacOsX = OperatingSystem.current().isMacOsX
    val isIntel: Boolean = architecture == "x86_64" || architecture == "x86"
    val isSlowInternetConnection
        get() = System.getProperty("slow.internet.connection", "false")!!.toBoolean()
    val agentNum: Int
        get() {
            if (System.getenv().containsKey("USERNAME")) {

   */
  static class ExpensiveComputation implements Function<Integer, BigInteger> {
    @Override
    public BigInteger apply(Integer from) {
      BigInteger v = BigInteger.valueOf(from);
      // Math.sin is very slow for values outside 4*pi
      // Need to take absolute value to avoid inverting the value.
      for (double i = 0; i < 100; i += 20) {
        v =
            v.add(
                v.multiply(

   */
  static class ExpensiveComputation implements Function<Integer, BigInteger> {
    @Override
    public BigInteger apply(Integer from) {
      BigInteger v = BigInteger.valueOf(from);
      // Math.sin is very slow for values outside 4*pi
      // Need to take absolute value to avoid inverting the value.
      for (double i = 0; i < 100; i += 20) {
        v =
            v.add(
                v.multiply(

    testExhaustively(Ordering.<String>natural(), "a", "b", "d");
  }

  @GwtIncompatible // too slow
  public void testCombinationsExhaustively_startingFromExplicit() {
    testExhaustively(Ordering.explicit("a", "b", "c", "d"), "a", "b", "d");
  }

  @GwtIncompatible // too slow
  public void testCombinationsExhaustively_startingFromUsingToString() {
    testExhaustively(Ordering.usingToString(), 1, 12, 2);

    testExhaustively(Ordering.<String>natural(), "a", "b", "d");
  }

  @GwtIncompatible // too slow
  public void testCombinationsExhaustively_startingFromExplicit() {
    testExhaustively(Ordering.explicit("a", "b", "c", "d"), "a", "b", "d");
  }

  @GwtIncompatible // too slow
  public void testCombinationsExhaustively_startingFromUsingToString() {
    testExhaustively(Ordering.usingToString(), 1, 12, 2);

    // Two differing invalid pairs.
    assertThat(Strings.commonSuffix("abc\uDCAB\uDCABdef", "abc\uDCAC\uDCABdef"))
        .isEqualTo("\uDCABdef");
    // One orphan low surrogate.
    assertThat(Strings.commonSuffix("x\uD8AB\uDCAB", "\uDCAB")).isEqualTo("");
    // Two orphan low surrogates.
    assertThat(Strings.commonSuffix("\uDCAB", "\uDCAB")).isEqualTo("\uDCAB");
  }

  public void testValidSurrogatePairAt() {

          .that(percentiles().index(index).compute(PSEUDORANDOM_DATASET))
          .isWithin(ALLOWED_ERROR)
          .of(expectedLargeDatasetPercentile(index));
    }
  }

  @AndroidIncompatible // slow
  public void testPercentiles_index_computeInPlace() {
    // Assert that the computation gives the correct result for all possible percentiles.
    for (int index = 0; index <= 100; index++) {