The TreeTraits class provides compile-time information on the characteristics of a given tree type. More...
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 | HasParentDistance = false |
This is true if TreeType::ParentDistance() exists and works. | |
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. |
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>::HasParentDistance>::type*) { // Computation with TreeType::ParentDistance(). } template<typename TreeType> void Compute(TreeType& node, boost::enable_if< !TreeTraits<TreeType>::HasParentDistance>::type*) { // Computation without TreeType::ParentDistance(). }
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 87 of file tree_traits.hpp.
const bool mlpack::tree::TreeTraits< TreeType >::FirstPointIsCentroid = false [static] |
This is true if Point(0) is the centroid of the node.
Definition at line 106 of file tree_traits.hpp.
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 101 of file tree_traits.hpp.
const bool mlpack::tree::TreeTraits< TreeType >::HasParentDistance = false [static] |
This is true if TreeType::ParentDistance() exists and works.
The ParentDistance() function returns the distance between the center of a node and the center of its parent.
Definition at line 95 of file tree_traits.hpp.
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 112 of file tree_traits.hpp.