private static final Grouper<String> GROUPER = new Grouper<String>() {
        @Override
        public String determineGroup(String s) {
            return String.valueOf(Math.abs(s.hashCode()) % 100);
        }

        @Override
        public int getNumberOfGroupingDirs() {
            return NUMBER_OF_GROUPING_DIRS;
        }
    };

    // TODO(jlevy): For optimal performance, use a binary search when
    // targets.size() < size() / log(size())
    // TODO(kevinb): see if we can share code with OrderedIterator after it
    // graduates from labs.
    if (targets instanceof Multiset) {
      targets = ((Multiset<?>) targets).elementSet();
    }
    if (!SortedIterables.hasSameComparator(comparator(), targets) || (targets.size() <= 1)) {

  AbstractTensorHandle* f_outputs[1];

  // Numerical Grad Check
  for (int i = 0; i < num_elems; i++) {
    // Get relative epsilon value
    float epsilon = theta_data[i] == 0 ? 1e-4 : std::abs(theta_data[i] * 1e-4);
    AbstractTensorHandlePtr two_eps;
    {
      AbstractTensorHandle* two_eps_raw = nullptr;
      TF_RETURN_IF_ERROR(TestScalarTensorHandle<float, TF_FLOAT>(

  if (!cst_op) return false;
  ElementsAttr value = cst_op.getValue();
  if (!value.isSplat()) return false;
  if (!value.getElementType().isF32()) return false;
  return std::abs(value.getSplatValue<float>() - val) < kTolerance;
}

// Determines if the given op is semantically that of the gauss error function.
bool MatchERF(Operation* op) {