Function FixOperatorOrdering

tensorflow/lite/toco/tooling_util.cc:1107–1220

}

void FixOperatorOrdering(Model* model) {
  std::unordered_set<string> arrays_behind_us;
  for (const auto& array_entry : model->GetArrayMap()) {
    if (!GetOpWithOutput(*model, array_entry.first)) {
      arrays_behind_us.insert(array_entry.first);
    }
  }
  arrays_behind_us.insert(model->optional_arrays.begin(),
                          model->optional_arrays.end());
  std::vector<std::unique_ptr<Operator>> old_operators;
  std::swap(old_operators, model->operators);
  std::set<std::size_t> remaining;
  for (std::size_t i = 0; i < old_operators.size(); i++) {
    remaining.insert(i);
  }
  std::unordered_map<string, string> reason_why_leftover;
  while (true) {
    bool inserted_something = false;
    for (const auto& i : remaining) {
      bool can_insert = true;
      auto& op = old_operators[i];
      CHECK(op);
      for (const auto& input : op->inputs) {
        if (!IsConstantParameterArray(*model, input) &&
            !arrays_behind_us.count(input)) {
          for (const string& output : op->outputs) {
            reason_why_leftover[output] = input;
          }
          can_insert = false;
          break;
        }
      }
      if (can_insert) {
        model->operators.emplace_back(nullptr);
        for (const auto& output : op->outputs) {
          arrays_behind_us.insert(output);
        }
        std::swap(op, model->operators.back());
        remaining.erase(i);
        inserted_something = true;
        break;
      }
    }
    if (!inserted_something) {
      break;
    }
  }
  if (!remaining.empty()) {
    LOG(ERROR)
        << "No viable ordering of operators was found. "
        << "Here is a 'backtrace' of at least one part of the graph that is "
        << "problematic. It starts with the first operator that has as "
        << "problematic input array, and then walks back the graph to "
        << "the operator that produced that input array, etc., until we find "
        << "the root cause:";
    LOG(ERROR) << "BEGIN TRACE OF OPERATOR WITH BAD INPUT";
    LOG(ERROR) << "Here is the first-encountered operator with a bad input: ";
    const Operator* bad_op = old_operators[*remaining.begin()].get();