at::Tensor __call__()

in fx/native_interpreter/interpreter.cpp [48:121]

• 56 lines of code
• 13 McCabe index (conditional complexity)

  at::Tensor __call__(std::vector<at::Tensor> inputs) {
    // Environment to hold local variables
    std::unordered_map<std::string, at::Tensor> environment;

    // Load inputs according to the specified names
    if (inputs.size() != input_names_.size()) {
      std::stringstream err;
      err << "Expected " << input_names_.size() << " inputs, but got "
          << inputs.size() << "!";
      throw std::runtime_error(err.str());
    }
    for (size_t i = 0; i < inputs.size(); ++i) {
      environment[input_names_[i]] = inputs[i];
    }

    if (!output_name_) {
      throw std::runtime_error("Output name not specified!");
    }

    for (InstructionType &instr : instructions_) {
      // Retrieve all input values for this op
      std::vector<at::Tensor> inputs;
      for (const auto &input_name : std::get<1>(instr)) {
        // Operator output values shadow constants.
        // Imagine all constants are defined in statements at the beginning
        // of a function (a la K&R C). Any definition of an output value must
        // necessarily come after constant definition in textual order. Thus,
        // We look up values in the environment first then the constant table
        // second to implement this shadowing behavior
        if (environment.find(input_name) != environment.end()) {
          inputs.push_back(environment.at(input_name));
        } else if (constants_.find(input_name) != constants_.end()) {
          inputs.push_back(constants_.at(input_name));
        } else {
          std::stringstream err;
          err << "Instruction referenced unknown value " << input_name << "!";
          throw std::runtime_error(err.str());
        }
      }

      // Run the specified operation
      at::Tensor result;
      const auto &op = std::get<0>(instr);
      if (op == "add") {
        if (inputs.size() != 2) {
          throw std::runtime_error("Unexpected number of inputs for add op!");
        }
        result = inputs[0] + inputs[1];
      } else if (op == "mul") {
        if (inputs.size() != 2) {
          throw std::runtime_error("Unexpected number of inputs for mul op!");
        }
        result = inputs[0] * inputs[1];
      } else {
        std::stringstream err;
        err << "Unknown operator " << op << "!";
        throw std::runtime_error(err.str());
      }

      // Write back result into environment
      const auto &output_name = std::get<2>(instr);
      environment[output_name] = std::move(result);
    }

    if (!environment.count(*output_name_)) {
      std::stringstream err;
      err << "Execution expected an output value with name ";
      err << *output_name_;
      err << " but no instruction produced a value with that name!";
      throw std::runtime_error(err.str());
    }

    return environment.at(*output_name_);
  }