bag_of_words_encoding_policy.hpp

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#ifndef MLPACK_CORE_DATA_STR_ENCODING_POLICIES_BAG_OF_WORDS_ENCODING_POLICY_HPP
#define MLPACK_CORE_DATA_STR_ENCODING_POLICIES_BAG_OF_WORDS_ENCODING_POLICY_HPP

#include <mlpack/prereqs.hpp>
#include <mlpack/core/data/string_encoding_policies/policy_traits.hpp>
#include <mlpack/core/data/string_encoding.hpp>

namespace mlpack {
namespace data {

class BagOfWordsEncodingPolicy
{
 public:
  static void Reset()
  {
    // Nothing to do.
  }

  template<typename MatType>
  static void InitMatrix(MatType& output,
                         const size_t datasetSize,
                         const size_t /* maxNumTokens */,
                         const size_t dictionarySize)
  {
    output.zeros(dictionarySize, datasetSize);
  }

  template<typename ElemType>
  static void InitMatrix(std::vector<std::vector<ElemType>>& output,
                         const size_t datasetSize,
                         const size_t /* maxNumTokens */,
                         const size_t dictionarySize)
  {
    output.resize(datasetSize, std::vector<ElemType>(dictionarySize));
  }

  template<typename MatType>
  static void Encode(MatType& output,
                     const size_t value,
                     const size_t line,
                     const size_t /* index */)
  {
    // The labels are assigned sequentially starting from one.
    output(value - 1, line) += 1;
  }

  template<typename ElemType>
  static void Encode(std::vector<std::vector<ElemType>>& output,
                     const size_t value,
                     const size_t line,
                     const size_t /* index */)
  {
    // The labels are assigned sequentially starting from one.
    output[line][value - 1] += 1;
  }

  static void PreprocessToken(size_t /* line */,
                              size_t /* index */,
                              size_t /* value */)
  { }

  template<typename Archive>
  void serialize(Archive& /* ar */, const uint32_t /* version */)
  {
    // Nothing to serialize.
  }
};

template<typename TokenType>
using BagOfWordsEncoding = StringEncoding<BagOfWordsEncodingPolicy,
                                          StringEncodingDictionary<TokenType>>;
} // namespace data
} // namespace mlpack

#endif