multiple_random_dimension_select.hpp

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#ifndef MLPACK_METHODS_DECISION_TREE_MULTIPLE_RANDOM_DIMENSION_SPLIT_HPP
#define MLPACK_METHODS_DECISION_TREE_MULTIPLE_RANDOM_DIMENSION_SPLIT_HPP

namespace mlpack {
namespace tree {

class MultipleRandomDimensionSelect
{
 public:
  MultipleRandomDimensionSelect(const size_t numDimensions = 0) :
        numDimensions(numDimensions),
        i(0),
        dimensions(0)
  { }

  size_t Begin()
  {
    // Reset if possible.
    if (numDimensions == 0 || numDimensions > dimensions)
      numDimensions = (size_t) std::sqrt(dimensions);

    values.set_size(numDimensions + 1);

    // Try setting new values.
    for (size_t i = 0; i < numDimensions; ++i)
    {
      // Generate random different numbers.
      bool unique = false;
      size_t value;
      while (!unique)
      {
        value = math::RandInt(dimensions);

        // Check if we already have the value.
        unique = true;
        for (size_t j = 0; j < i; ++j)
        {
          if (values[j] == value)
          {
            unique = false;
            break;
          }
        }
      }

      values[i] = value;
    }

    values[numDimensions] = std::numeric_limits<size_t>::max();

    i = 0;
    return values[0];
  }

  size_t End() const { return size_t(-1); }

  size_t Next()
  {
    return values[++i];
  }

  size_t Dimensions() const { return dimensions; }
  size_t& Dimensions() { return dimensions; }

 private:
  size_t numDimensions;
  arma::Col<size_t> values;
  size_t i;
  size_t dimensions;
};

} // namespace tree
} // namespace mlpack

#endif