## 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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