namespace tensorflow {
namespace tracing {
typedef absl::flat_hash_map<std::string, tracing::FactoryFunction> FactoriesMap;

static FactoriesMap& GetFactories() {
  static FactoriesMap* factories = new FactoriesMap;
  return *factories;
}

static tracing::FactoryFunction default_factory;

void RegisterTracingEngineFactory(const string& name, FactoryFunction factory) {
  assert((!GetFactories().count(name)) ||

   * is returned.
   *
   * @deprecated Use {@code table.rowKeySet().comparator()} instead.
   */
  @Deprecated
  public Comparator<? super R> rowComparator() {
    /*
     * requireNonNull is safe because the factories require non-null Comparators, which they pass on
     * to the backing collections.
     */
    return requireNonNull(rowKeySet().comparator());
  }

  /**

   *
   * <ul>
   *   <li>The visible constructor or visible static factory method with the most parameters is used
   *       to construct the sample instances. In case of tie, the candidate constructors or
   *       factories are tried one after another until one can be used to construct sample
   *       instances.
   *   <li>For the constructor or static factory method used to construct instances, it's checked

  // plus https://github.com/google/guava/issues/989
  public static <C extends Comparable> Ordering<C> natural() {
    return (Ordering<C>) NaturalOrdering.INSTANCE;
  }

  // Static factories

  /**
   * Returns an ordering based on an <i>existing</i> comparator instance. Note that it is
   * unnecessary to create a <i>new</i> anonymous inner class implementing {@code Comparator} just

  // plus https://github.com/google/guava/issues/989
  public static <C extends Comparable> Ordering<C> natural() {
    return (Ordering<C>) NaturalOrdering.INSTANCE;
  }

  // Static factories

  /**
   * Returns an ordering based on an <i>existing</i> comparator instance. Note that it is
   * unnecessary to create a <i>new</i> anonymous inner class implementing {@code Comparator} just

   *
   * <ul>
   *   <li>The visible constructor or visible static factory method with the most parameters is used
   *       to construct the sample instances. In case of tie, the candidate constructors or
   *       factories are tried one after another until one can be used to construct sample
   *       instances.
   *   <li>For the constructor or static factory method used to construct instances, it's checked

   * @since 19.0 (since 1.0 as constant {@code SINGLE_WIDTH})
   */
  @Deprecated
  public static CharMatcher singleWidth() {
    return SingleWidth.INSTANCE;
  }

  // Static factories

  /** Returns a {@code char} matcher that matches only one specified BMP character. */
  public static CharMatcher is(final char match) {
    return new Is(match);
  }

  /**

    static final int ACCESS_MASK = 1;
    static final int WRITE_MASK = 2;
    static final int WEAK_MASK = 4;

    /** Look-up table for factories. */
    static final EntryFactory[] factories = {
      STRONG,
      STRONG_ACCESS,
      STRONG_WRITE,
      STRONG_ACCESS_WRITE,
      WEAK,
      WEAK_ACCESS,
      WEAK_WRITE,
      WEAK_ACCESS_WRITE,
    };

   * <p>This uses an efficient binary recursive algorithm to compute the factorial with balanced
   * multiplies. It also removes all the 2s from the intermediate products (shifting them back in at
   * the end).
   *
   * @throws IllegalArgumentException if {@code n < 0}
   */
  public static BigInteger factorial(int n) {
    checkNonNegative("n", n);

    // If the factorial is small enough, just use LongMath to do it.

    long expected = 1;
    for (int i = 0; i < LongMath.factorials.length; i++, expected *= i) {
      assertEquals(expected, LongMath.factorials[i]);
    }
    assertThrows(
        ArithmeticException.class,
        () ->
            LongMath.checkedMultiply(
                LongMath.factorials[LongMath.factorials.length - 1], LongMath.factorials.length));
  }

  @GwtIncompatible // TODO