NAME¶

mlpack::tree::TreeTraits< TreeType > - The TreeTraits class provides compile-time information on the characteristics of a given tree type.

SYNOPSIS¶

Static Public Attributes¶

static const bool FirstPointIsCentroid = false This is true if Point(0) is the centroid of the node. static const bool HasOverlappingChildren = true This is true if the subspaces represented by the children of a node can overlap. static const bool HasSelfChildren = false This is true if the points contained in the first child of a node (Child(0)) are also contained in that node. static const bool RearrangesDataset = false This is true if the tree rearranges points in the dataset when it is built.

Detailed Description¶

template<typename TreeType>class mlpack::tree::TreeTraits< TreeType >¶

The TreeTraits class provides compile-time information on the characteristics of a given tree type. These include traits such as whether or not a node knows the distance to its parent node, or whether or not the subspaces represented by children can overlap. These traits can be used for static compile-time optimization:

// This if statement will be optimized out at compile time!
if (TreeTraits<TreeType>::HasOverlappingChildren == false)
{
  // Do a simpler computation because no children overlap.
}
else
{
  // Do the full, complex calculation.
}

The traits can also be used in conjunction with SFINAE to write specialized versions of functions:

template<typename TreeType>
void Compute(TreeType& node,
             boost::enable_if<
                 TreeTraits<TreeType>::RearrangesDataset>::type*)
{
  // Computation where special dataset-rearranging tree constructor is
  // called.
}

template<typename TreeType>
void Compute(TreeType& node,
             boost::enable_if<
                 !TreeTraits<TreeType>::RearrangesDataset>::type*)
{
  // Computation where normal tree constructor is called.
}

In those two examples, the boost::enable_if<> class takes a boolean template parameter which allows that function to be called when the boolean is true. Each trait must be a static const value and not a function; only const values can be used as template parameters (with the exception of constexprs, which are a C++11 feature; but MLPACK is not using C++11). By default (the unspecialized implementation of TreeTraits), each parameter is set to make as few assumptions about the tree as possible; so, even if TreeTraits is not specialized for a particular tree type, tree-based algorithms should still work. When you write your own tree, you must specialize the TreeTraits class to your tree type and set the corresponding values appropriately. See mlpack/core/tree/binary_space_tree/traits.hpp for an example. Definition at line 88 of file tree_traits.hpp.

Member Data Documentation¶

template<typename TreeType > const bool mlpack::tree::TreeTraits< TreeType >::FirstPointIsCentroid = false [static]¶

This is true if Point(0) is the centroid of the node. Definition at line 100 of file tree_traits.hpp.

template<typename TreeType > const bool mlpack::tree::TreeTraits< TreeType >::HasOverlappingChildren = true [static]¶

This is true if the subspaces represented by the children of a node can overlap. Definition at line 95 of file tree_traits.hpp.

template<typename TreeType > const bool mlpack::tree::TreeTraits< TreeType >::HasSelfChildren = false [static]¶

This is true if the points contained in the first child of a node (Child(0)) are also contained in that node. Definition at line 106 of file tree_traits.hpp.

template<typename TreeType > const bool mlpack::tree::TreeTraits< TreeType >::RearrangesDataset = false [static]¶

This is true if the tree rearranges points in the dataset when it is built. Definition at line 111 of file tree_traits.hpp.

Author¶

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