template<typename InputType, typename OutputType>
    void Train(const InputType& trainingData,
               const OutputType& trainingLabels,
               const InputType& validationData,
               const OutputType& validationLabels)
    {
      // This generates [0 1 2 3 ... (ElementCount(trainingData) - 1)]. The
      // sequence will be used to iterate through the training data.
      index = arma::linspace<arma::Col<size_t> >(0,
          ElementCount(trainingData) - 1, ElementCount(trainingData));
      epoch = 0;

      while(true)
      {
        if (shuffle)
          index = arma::shuffle(index);

        Train(const_cast<InputType&>(trainingData),
              const_cast<OutputType&>(trainingLabels));
        Evaluate(const_cast<InputType&>(validationData),
                 const_cast<OutputType&>(validationLabels));

        if (validationError <= tolerance)
          break;

        if (maxEpochs > 0 && ++epoch >= maxEpochs)
          break;
      }
    }