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gtsam/gtsam/discrete/DecisionTree-inl.h

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/* ----------------------------------------------------------------------------
* GTSAM Copyright 2010, Georgia Tech Research Corporation,
* Atlanta, Georgia 30332-0415
* All Rights Reserved
* Authors: Frank Dellaert, et al. (see THANKS for the full author list)
* See LICENSE for the license information
* -------------------------------------------------------------------------- */
/**
* @file DecisionTree.h
* @brief Decision Tree for use in DiscreteFactors
* @author Frank Dellaert
* @author Can Erdogan
* @date Jan 30, 2012
*/
#pragma once
#include <gtsam/discrete/DecisionTree.h>
#include <algorithm>
#include <boost/format.hpp>
#include <boost/make_shared.hpp>
#include <boost/optional.hpp>
#include <cmath>
#include <fstream>
#include <list>
#include <map>
#include <set>
#include <sstream>
#include <string>
#include <vector>
namespace gtsam {
/****************************************************************************/
// Node
/****************************************************************************/
#ifdef DT_DEBUG_MEMORY
template<typename L, typename Y>
int DecisionTree<L, Y>::Node::nrNodes = 0;
#endif
/****************************************************************************/
// Leaf
/****************************************************************************/
template <typename L, typename Y>
struct DecisionTree<L, Y>::Leaf : public DecisionTree<L, Y>::Node {
/** constant stored in this leaf */
Y constant_;
/** The number of assignments contained within this leaf.
* Particularly useful when leaves have been pruned.
*/
size_t nrAssignments_;
/// Default constructor for serialization.
Leaf() {}
/// Constructor from constant
Leaf(const Y& constant, size_t nrAssignments = 1)
: constant_(constant), nrAssignments_(nrAssignments) {}
/// Return the constant
const Y& constant() const {
return constant_;
}
/// Return the number of assignments contained within this leaf.
size_t nrAssignments() const { return nrAssignments_; }
/// Leaf-Leaf equality
bool sameLeaf(const Leaf& q) const override {
return constant_ == q.constant_;
}
/// polymorphic equality: is q a leaf and is it the same as this leaf?
bool sameLeaf(const Node& q) const override {
return (q.isLeaf() && q.sameLeaf(*this));
}
/// equality up to tolerance
bool equals(const Node& q, const CompareFunc& compare) const override {
const Leaf* other = dynamic_cast<const Leaf*>(&q);
if (!other) return false;
return compare(this->constant_, other->constant_);
}
/// print
void print(const std::string& s, const LabelFormatter& labelFormatter,
const ValueFormatter& valueFormatter) const override {
std::cout << s << " Leaf " << valueFormatter(constant_) << std::endl;
}
/** Write graphviz format to stream `os`. */
void dot(std::ostream& os, const LabelFormatter& labelFormatter,
const ValueFormatter& valueFormatter,
bool showZero) const override {
std::string value = valueFormatter(constant_);
if (showZero || value.compare("0"))
os << "\"" << this->id() << "\" [label=\"" << value
<< "\", shape=box, rank=sink, height=0.35, fixedsize=true]\n";
}
/** evaluate */
const Y& operator()(const Assignment<L>& x) const override {
return constant_;
}
/** apply unary operator */
NodePtr apply(const Unary& op) const override {
NodePtr f(new Leaf(op(constant_), nrAssignments_));
return f;
}
/// Apply unary operator with assignment
NodePtr apply(const UnaryAssignment& op,
const Assignment<L>& assignment) const override {
NodePtr f(new Leaf(op(assignment, constant_), nrAssignments_));
return f;
}
// Apply binary operator "h = f op g" on Leaf node
// Note op is not assumed commutative so we need to keep track of order
// Simply calls apply on argument to call correct virtual method:
// fL.apply_f_op_g(gL) -> gL.apply_g_op_fL(fL) (below)
// fL.apply_f_op_g(gC) -> gC.apply_g_op_fL(fL) (Choice)
NodePtr apply_f_op_g(const Node& g, const Binary& op) const override {
return g.apply_g_op_fL(*this, op);
}
// Applying binary operator to two leaves results in a leaf
NodePtr apply_g_op_fL(const Leaf& fL, const Binary& op) const override {
// fL op gL
NodePtr h(new Leaf(op(fL.constant_, constant_), nrAssignments_));
return h;
}
// If second argument is a Choice node, call it's apply with leaf as second
NodePtr apply_g_op_fC(const Choice& fC, const Binary& op) const override {
return fC.apply_fC_op_gL(*this, op); // operand order back to normal
}
/** choose a branch, create new memory ! */
NodePtr choose(const L& label, size_t index) const override {
return NodePtr(new Leaf(constant(), nrAssignments()));
}
bool isLeaf() const override { return true; }
private:
using Base = DecisionTree<L, Y>::Node;
/** Serialization function */
friend class boost::serialization::access;
template <class ARCHIVE>
void serialize(ARCHIVE& ar, const unsigned int /*version*/) {
ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Base);
ar& BOOST_SERIALIZATION_NVP(constant_);
ar& BOOST_SERIALIZATION_NVP(nrAssignments_);
}
}; // Leaf
/****************************************************************************/
// Choice
/****************************************************************************/
template<typename L, typename Y>
struct DecisionTree<L, Y>::Choice: public DecisionTree<L, Y>::Node {
/** the label of the variable on which we split */
L label_;
/** The children of this Choice node. */
std::vector<NodePtr> branches_;
private:
/**
* Incremental allSame.
* Records if all the branches are the same leaf.
*/
size_t allSame_;
using ChoicePtr = boost::shared_ptr<const Choice>;
public:
/// Default constructor for serialization.
Choice() {}
~Choice() override {
#ifdef DT_DEBUG_MEMORY
std::std::cout << Node::nrNodes << " destructing (Choice) " << this->id()
<< std::std::endl;
#endif
}
/// If all branches of a choice node f are the same, just return a branch.
static NodePtr Unique(const ChoicePtr& f) {
#ifndef GTSAM_DT_NO_PRUNING
if (f->allSame_) {
assert(f->branches().size() > 0);
NodePtr f0 = f->branches_[0];
size_t nrAssignments = 0;
for(auto branch: f->branches()) {
assert(branch->isLeaf());
nrAssignments +=
boost::dynamic_pointer_cast<const Leaf>(branch)->nrAssignments();
}
NodePtr newLeaf(
new Leaf(boost::dynamic_pointer_cast<const Leaf>(f0)->constant(),
nrAssignments));
return newLeaf;
} else
#endif
return f;
}
bool isLeaf() const override { return false; }
/// Constructor, given choice label and mandatory expected branch count.
Choice(const L& label, size_t count) :
label_(label), allSame_(true) {
branches_.reserve(count);
}
/// Construct from applying binary op to two Choice nodes.
Choice(const Choice& f, const Choice& g, const Binary& op) :
allSame_(true) {
// Choose what to do based on label
if (f.label() > g.label()) {
// f higher than g
label_ = f.label();
size_t count = f.nrChoices();
branches_.reserve(count);
for (size_t i = 0; i < count; i++)
push_back(f.branches_[i]->apply_f_op_g(g, op));
} else if (g.label() > f.label()) {
// f lower than g
label_ = g.label();
size_t count = g.nrChoices();
branches_.reserve(count);
for (size_t i = 0; i < count; i++)
push_back(g.branches_[i]->apply_g_op_fC(f, op));
} else {
// f same level as g
label_ = f.label();
size_t count = f.nrChoices();
branches_.reserve(count);
for (size_t i = 0; i < count; i++)
push_back(f.branches_[i]->apply_f_op_g(*g.branches_[i], op));
}
}
/// Return the label of this choice node.
const L& label() const {
return label_;
}
size_t nrChoices() const {
return branches_.size();
}
const std::vector<NodePtr>& branches() const {
return branches_;
}
/** add a branch: TODO merge into constructor */
void push_back(const NodePtr& node) {
// allSame_ is restricted to leaf nodes in a decision tree
if (allSame_ && !branches_.empty()) {
allSame_ = node->sameLeaf(*branches_.back());
}
branches_.push_back(node);
}
/// print (as a tree).
void print(const std::string& s, const LabelFormatter& labelFormatter,
const ValueFormatter& valueFormatter) const override {
std::cout << s << " Choice(";
std::cout << labelFormatter(label_) << ") " << std::endl;
for (size_t i = 0; i < branches_.size(); i++)
branches_[i]->print((boost::format("%s %d") % s % i).str(),
labelFormatter, valueFormatter);
}
/** output to graphviz (as a a graph) */
void dot(std::ostream& os, const LabelFormatter& labelFormatter,
const ValueFormatter& valueFormatter,
bool showZero) const override {
os << "\"" << this->id() << "\" [shape=circle, label=\"" << label_
<< "\"]\n";
size_t B = branches_.size();
for (size_t i = 0; i < B; i++) {
const NodePtr& branch = branches_[i];
// Check if zero
if (!showZero) {
const Leaf* leaf = dynamic_cast<const Leaf*>(branch.get());
if (leaf && valueFormatter(leaf->constant()).compare("0")) continue;
}
os << "\"" << this->id() << "\" -> \"" << branch->id() << "\"";
if (B == 2 && i == 0) os << " [style=dashed]";
os << std::endl;
branch->dot(os, labelFormatter, valueFormatter, showZero);
}
}
/// Choice-Leaf equality: always false
bool sameLeaf(const Leaf& q) const override {
return false;
}
/// polymorphic equality: if q is a leaf, could be...
bool sameLeaf(const Node& q) const override {
return (q.isLeaf() && q.sameLeaf(*this));
}
/// equality
bool equals(const Node& q, const CompareFunc& compare) const override {
const Choice* other = dynamic_cast<const Choice*>(&q);
if (!other) return false;
if (this->label_ != other->label_) return false;
if (branches_.size() != other->branches_.size()) return false;
// we don't care about shared pointers being equal here
for (size_t i = 0; i < branches_.size(); i++)
if (!(branches_[i]->equals(*(other->branches_[i]), compare)))
return false;
return true;
}
/// evaluate
const Y& operator()(const Assignment<L>& x) const override {
#ifndef NDEBUG
typename Assignment<L>::const_iterator it = x.find(label_);
if (it == x.end()) {
std::cout << "Trying to find value for " << label_ << std::endl;
throw std::invalid_argument(
"DecisionTree::operator(): value undefined for a label");
}
#endif
size_t index = x.at(label_);
NodePtr child = branches_[index];
return (*child)(x);
}
/// Construct from applying unary op to a Choice node.
Choice(const L& label, const Choice& f, const Unary& op) :
label_(label), allSame_(true) {
branches_.reserve(f.branches_.size()); // reserve space
for (const NodePtr& branch : f.branches_) {
push_back(branch->apply(op));
}
}
/**
* @brief Constructor which accepts a UnaryAssignment op and the
* corresponding assignment.
*
* @param label The label for this node.
* @param f The original choice node to apply the op on.
* @param op Function to apply on the choice node. Takes Assignment and
* value as arguments.
* @param assignment The Assignment that will go to op.
*/
Choice(const L& label, const Choice& f, const UnaryAssignment& op,
const Assignment<L>& assignment)
: label_(label), allSame_(true) {
branches_.reserve(f.branches_.size()); // reserve space
Assignment<L> assignment_ = assignment;
for (size_t i = 0; i < f.branches_.size(); i++) {
assignment_[label_] = i; // Set assignment for label to i
const NodePtr branch = f.branches_[i];
push_back(branch->apply(op, assignment_));
// Remove the assignment so we are backtracking
auto assignment_it = assignment_.find(label_);
assignment_.erase(assignment_it);
}
}
/// apply unary operator.
NodePtr apply(const Unary& op) const override {
auto r = boost::make_shared<Choice>(label_, *this, op);
return Unique(r);
}
/// Apply unary operator with assignment
NodePtr apply(const UnaryAssignment& op,
const Assignment<L>& assignment) const override {
auto r = boost::make_shared<Choice>(label_, *this, op, assignment);
return Unique(r);
}
// Apply binary operator "h = f op g" on Choice node
// Note op is not assumed commutative so we need to keep track of order
// Simply calls apply on argument to call correct virtual method:
// fC.apply_f_op_g(gL) -> gL.apply_g_op_fC(fC) -> (Leaf)
// fC.apply_f_op_g(gC) -> gC.apply_g_op_fC(fC) -> (below)
NodePtr apply_f_op_g(const Node& g, const Binary& op) const override {
return g.apply_g_op_fC(*this, op);
}
// If second argument of binary op is Leaf node, recurse on branches
NodePtr apply_g_op_fL(const Leaf& fL, const Binary& op) const override {
auto h = boost::make_shared<Choice>(label(), nrChoices());
for (auto&& branch : branches_)
h->push_back(fL.apply_f_op_g(*branch, op));
return Unique(h);
}
// If second argument of binary op is Choice, call constructor
NodePtr apply_g_op_fC(const Choice& fC, const Binary& op) const override {
auto h = boost::make_shared<Choice>(fC, *this, op);
return Unique(h);
}
// If second argument of binary op is Leaf
template<typename OP>
NodePtr apply_fC_op_gL(const Leaf& gL, OP op) const {
auto h = boost::make_shared<Choice>(label(), nrChoices());
for (auto&& branch : branches_)
h->push_back(branch->apply_f_op_g(gL, op));
return Unique(h);
}
/** choose a branch, recursively */
NodePtr choose(const L& label, size_t index) const override {
if (label_ == label) return branches_[index]; // choose branch
// second case, not label of interest, just recurse
auto r = boost::make_shared<Choice>(label_, branches_.size());
for (auto&& branch : branches_)
r->push_back(branch->choose(label, index));
return Unique(r);
}
private:
using Base = DecisionTree<L, Y>::Node;
/** Serialization function */
friend class boost::serialization::access;
template <class ARCHIVE>
void serialize(ARCHIVE& ar, const unsigned int /*version*/) {
ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Base);
ar& BOOST_SERIALIZATION_NVP(label_);
ar& BOOST_SERIALIZATION_NVP(branches_);
ar& BOOST_SERIALIZATION_NVP(allSame_);
}
}; // Choice
/****************************************************************************/
// DecisionTree
/****************************************************************************/
template<typename L, typename Y>
DecisionTree<L, Y>::DecisionTree() {
}
template<typename L, typename Y>
DecisionTree<L, Y>::DecisionTree(const NodePtr& root) :
root_(root) {
}
/****************************************************************************/
template<typename L, typename Y>
DecisionTree<L, Y>::DecisionTree(const Y& y) {
root_ = NodePtr(new Leaf(y));
}
/****************************************************************************/
template <typename L, typename Y>
DecisionTree<L, Y>::DecisionTree(const L& label, const Y& y1, const Y& y2) {
auto a = boost::make_shared<Choice>(label, 2);
NodePtr l1(new Leaf(y1)), l2(new Leaf(y2));
a->push_back(l1);
a->push_back(l2);
root_ = Choice::Unique(a);
}
/****************************************************************************/
template <typename L, typename Y>
DecisionTree<L, Y>::DecisionTree(const LabelC& labelC, const Y& y1,
const Y& y2) {
if (labelC.second != 2) throw std::invalid_argument(
"DecisionTree: binary constructor called with non-binary label");
auto a = boost::make_shared<Choice>(labelC.first, 2);
NodePtr l1(new Leaf(y1)), l2(new Leaf(y2));
a->push_back(l1);
a->push_back(l2);
root_ = Choice::Unique(a);
}
/****************************************************************************/
template<typename L, typename Y>
DecisionTree<L, Y>::DecisionTree(const std::vector<LabelC>& labelCs,
const std::vector<Y>& ys) {
// call recursive Create
root_ = create(labelCs.begin(), labelCs.end(), ys.begin(), ys.end());
}
/****************************************************************************/
template<typename L, typename Y>
DecisionTree<L, Y>::DecisionTree(const std::vector<LabelC>& labelCs,
const std::string& table) {
// Convert std::string to values of type Y
std::vector<Y> ys;
std::istringstream iss(table);
copy(std::istream_iterator<Y>(iss), std::istream_iterator<Y>(),
back_inserter(ys));
// now call recursive Create
root_ = create(labelCs.begin(), labelCs.end(), ys.begin(), ys.end());
}
/****************************************************************************/
template<typename L, typename Y>
template<typename Iterator> DecisionTree<L, Y>::DecisionTree(
Iterator begin, Iterator end, const L& label) {
root_ = compose(begin, end, label);
}
/****************************************************************************/
template<typename L, typename Y>
DecisionTree<L, Y>::DecisionTree(const L& label,
const DecisionTree& f0, const DecisionTree& f1) {
const std::vector<DecisionTree> functions{f0, f1};
root_ = compose(functions.begin(), functions.end(), label);
}
/****************************************************************************/
template <typename L, typename Y>
template <typename X, typename Func>
DecisionTree<L, Y>::DecisionTree(const DecisionTree<L, X>& other,
Func Y_of_X) {
// Define functor for identity mapping of node label.
auto L_of_L = [](const L& label) { return label; };
root_ = convertFrom<L, X>(other.root_, L_of_L, Y_of_X);
}
/****************************************************************************/
template <typename L, typename Y>
template <typename M, typename X, typename Func>
DecisionTree<L, Y>::DecisionTree(const DecisionTree<M, X>& other,
const std::map<M, L>& map, Func Y_of_X) {
auto L_of_M = [&map](const M& label) -> L { return map.at(label); };
root_ = convertFrom<M, X>(other.root_, L_of_M, Y_of_X);
}
/****************************************************************************/
// Called by two constructors above.
// Takes a label and a corresponding range of decision trees, and creates a
// new decision tree. However, the order of the labels needs to be respected,
// so we cannot just create a root Choice node on the label: if the label is
// not the highest label, we need a complicated/ expensive recursive call.
template <typename L, typename Y>
template <typename Iterator>
typename DecisionTree<L, Y>::NodePtr DecisionTree<L, Y>::compose(
Iterator begin, Iterator end, const L& label) const {
// find highest label among branches
boost::optional<L> highestLabel;
size_t nrChoices = 0;
for (Iterator it = begin; it != end; it++) {
if (it->root_->isLeaf())
continue;
boost::shared_ptr<const Choice> c =
boost::dynamic_pointer_cast<const Choice>(it->root_);
if (!highestLabel || c->label() > *highestLabel) {
highestLabel.reset(c->label());
nrChoices = c->nrChoices();
}
}
// if label is already in correct order, just put together a choice on label
if (!nrChoices || !highestLabel || label > *highestLabel) {
auto choiceOnLabel = boost::make_shared<Choice>(label, end - begin);
for (Iterator it = begin; it != end; it++)
choiceOnLabel->push_back(it->root_);
return Choice::Unique(choiceOnLabel);
} else {
// Set up a new choice on the highest label
auto choiceOnHighestLabel =
boost::make_shared<Choice>(*highestLabel, nrChoices);
// now, for all possible values of highestLabel
for (size_t index = 0; index < nrChoices; index++) {
// make a new set of functions for composing by iterating over the given
// functions, and selecting the appropriate branch.
std::vector<DecisionTree> functions;
for (Iterator it = begin; it != end; it++) {
// by restricting the input functions to value i for labelBelow
DecisionTree chosen = it->choose(*highestLabel, index);
functions.push_back(chosen);
}
// We then recurse, for all values of the highest label
NodePtr fi = compose(functions.begin(), functions.end(), label);
choiceOnHighestLabel->push_back(fi);
}
return Choice::Unique(choiceOnHighestLabel);
}
}
/****************************************************************************/
// "create" is a bit of a complicated thing, but very useful.
// It takes a range of labels and a corresponding range of values,
// and creates a decision tree, as follows:
// - if there is only one label, creates a choice node with values in leaves
// - otherwise, it evenly splits up the range of values and creates a tree for
// each sub-range, and assigns that tree to first label's choices
// Example:
// create([B A],[1 2 3 4]) would call
// create([A],[1 2])
// create([A],[3 4])
// and produce
// B=0
// A=0: 1
// A=1: 2
// B=1
// A=0: 3
// A=1: 4
// Note, through the magic of "compose", create([A B],[1 3 2 4]) will produce
// exactly the same tree as above: the highest label is always the root.
// However, it will be *way* faster if labels are given highest to lowest.
template<typename L, typename Y>
template<typename It, typename ValueIt>
typename DecisionTree<L, Y>::NodePtr DecisionTree<L, Y>::create(
It begin, It end, ValueIt beginY, ValueIt endY) const {
// get crucial counts
size_t nrChoices = begin->second;
size_t size = endY - beginY;
// Find the next key to work on
It labelC = begin + 1;
if (labelC == end) {
// Base case: only one key left
// Create a simple choice node with values as leaves.
if (size != nrChoices) {
std::cout << "Trying to create DD on " << begin->first << std::endl;
std::cout << boost::format(
"DecisionTree::create: expected %d values but got %d "
"instead") %
nrChoices % size
<< std::endl;
throw std::invalid_argument("DecisionTree::create invalid argument");
}
auto choice = boost::make_shared<Choice>(begin->first, endY - beginY);
for (ValueIt y = beginY; y != endY; y++)
choice->push_back(NodePtr(new Leaf(*y)));
return Choice::Unique(choice);
}
// Recursive case: perform "Shannon expansion"
// Creates one tree (i.e.,function) for each choice of current key
// by calling create recursively, and then puts them all together.
std::vector<DecisionTree> functions;
size_t split = size / nrChoices;
for (size_t i = 0; i < nrChoices; i++, beginY += split) {
NodePtr f = create<It, ValueIt>(labelC, end, beginY, beginY + split);
functions.emplace_back(f);
}
return compose(functions.begin(), functions.end(), begin->first);
}
/****************************************************************************/
template <typename L, typename Y>
template <typename M, typename X>
typename DecisionTree<L, Y>::NodePtr DecisionTree<L, Y>::convertFrom(
const typename DecisionTree<M, X>::NodePtr& f,
std::function<L(const M&)> L_of_M,
std::function<Y(const X&)> Y_of_X) const {
using LY = DecisionTree<L, Y>;
// Ugliness below because apparently we can't have templated virtual
// functions.
// If leaf, apply unary conversion "op" and create a unique leaf.
using MXLeaf = typename DecisionTree<M, X>::Leaf;
if (auto leaf = boost::dynamic_pointer_cast<const MXLeaf>(f)) {
return NodePtr(new Leaf(Y_of_X(leaf->constant()), leaf->nrAssignments()));
}
// Check if Choice
using MXChoice = typename DecisionTree<M, X>::Choice;
auto choice = boost::dynamic_pointer_cast<const MXChoice>(f);
if (!choice) throw std::invalid_argument(
"DecisionTree::convertFrom: Invalid NodePtr");
// get new label
const M oldLabel = choice->label();
const L newLabel = L_of_M(oldLabel);
// put together via Shannon expansion otherwise not sorted.
std::vector<LY> functions;
for (auto&& branch : choice->branches()) {
functions.emplace_back(convertFrom<M, X>(branch, L_of_M, Y_of_X));
}
return LY::compose(functions.begin(), functions.end(), newLabel);
}
/****************************************************************************/
/**
* Functor performing depth-first visit to each leaf with the leaf value as
* the argument.
*
* NOTE: We differentiate between leaves and assignments. Concretely, a 3
* binary variable tree will have 2^3=8 assignments, but based on pruning, it
* can have less than 8 leaves. For example, if a tree has all assignment
* values as 1, then pruning will cause the tree to have only 1 leaf yet 8
* assignments.
*/
template <typename L, typename Y>
struct Visit {
using F = std::function<void(const Y&)>;
explicit Visit(F f) : f(f) {} ///< Construct from folding function.
F f; ///< folding function object.
/// Do a depth-first visit on the tree rooted at node.
void operator()(const typename DecisionTree<L, Y>::NodePtr& node) const {
using Leaf = typename DecisionTree<L, Y>::Leaf;
if (auto leaf = boost::dynamic_pointer_cast<const Leaf>(node))
return f(leaf->constant());
using Choice = typename DecisionTree<L, Y>::Choice;
auto choice = boost::dynamic_pointer_cast<const Choice>(node);
if (!choice)
throw std::invalid_argument("DecisionTree::Visit: Invalid NodePtr");
for (auto&& branch : choice->branches()) (*this)(branch); // recurse!
}
};
template <typename L, typename Y>
template <typename Func>
void DecisionTree<L, Y>::visit(Func f) const {
Visit<L, Y> visit(f);
visit(root_);
}
/****************************************************************************/
/**
* Functor performing depth-first visit to each leaf with the Leaf object
* passed as an argument.
*
* NOTE: We differentiate between leaves and assignments. Concretely, a 3
* binary variable tree will have 2^3=8 assignments, but based on pruning, it
* can have <8 leaves. For example, if a tree has all assignment values as 1,
* then pruning will cause the tree to have only 1 leaf yet 8 assignments.
*/
template <typename L, typename Y>
struct VisitLeaf {
using F = std::function<void(const typename DecisionTree<L, Y>::Leaf&)>;
explicit VisitLeaf(F f) : f(f) {} ///< Construct from folding function.
F f; ///< folding function object.
/// Do a depth-first visit on the tree rooted at node.
void operator()(const typename DecisionTree<L, Y>::NodePtr& node) const {
using Leaf = typename DecisionTree<L, Y>::Leaf;
if (auto leaf = boost::dynamic_pointer_cast<const Leaf>(node))
return f(*leaf);
using Choice = typename DecisionTree<L, Y>::Choice;
auto choice = boost::dynamic_pointer_cast<const Choice>(node);
if (!choice)
throw std::invalid_argument("DecisionTree::VisitLeaf: Invalid NodePtr");
for (auto&& branch : choice->branches()) (*this)(branch); // recurse!
}
};
template <typename L, typename Y>
template <typename Func>
void DecisionTree<L, Y>::visitLeaf(Func f) const {
VisitLeaf<L, Y> visit(f);
visit(root_);
}
/****************************************************************************/
/**
* Functor performing depth-first visit to each leaf with the leaf's
* `Assignment<L>` and value passed as arguments.
*
* NOTE: Follows the same pruning semantics as `visit`.
*/
template <typename L, typename Y>
struct VisitWith {
using F = std::function<void(const Assignment<L>&, const Y&)>;
explicit VisitWith(F f) : f(f) {} ///< Construct from folding function.
Assignment<L> assignment; ///< Assignment, mutating through recursion.
F f; ///< folding function object.
/// Do a depth-first visit on the tree rooted at node.
void operator()(const typename DecisionTree<L, Y>::NodePtr& node) {
using Leaf = typename DecisionTree<L, Y>::Leaf;
if (auto leaf = boost::dynamic_pointer_cast<const Leaf>(node))
return f(assignment, leaf->constant());
using Choice = typename DecisionTree<L, Y>::Choice;
auto choice = boost::dynamic_pointer_cast<const Choice>(node);
if (!choice)
throw std::invalid_argument("DecisionTree::VisitWith: Invalid NodePtr");
for (size_t i = 0; i < choice->nrChoices(); i++) {
assignment[choice->label()] = i; // Set assignment for label to i
(*this)(choice->branches()[i]); // recurse!
// Remove the choice so we are backtracking
auto choice_it = assignment.find(choice->label());
assignment.erase(choice_it);
}
}
};
template <typename L, typename Y>
template <typename Func>
void DecisionTree<L, Y>::visitWith(Func f) const {
VisitWith<L, Y> visit(f);
visit(root_);
}
/****************************************************************************/
template <typename L, typename Y>
size_t DecisionTree<L, Y>::nrLeaves() const {
size_t total = 0;
visit([&total](const Y& node) { total += 1; });
return total;
}
/****************************************************************************/
// fold is just done with a visit
template <typename L, typename Y>
template <typename Func, typename X>
X DecisionTree<L, Y>::fold(Func f, X x0) const {
visit([&](const Y& y) { x0 = f(y, x0); });
return x0;
}
/****************************************************************************/
/**
* Get (partial) labels by performing a visit.
*
* This method performs a depth-first search to go to every leaf and records
* the keys assignment which leads to that leaf. Since the tree can be pruned,
* there might be a leaf at a lower depth which results in a partial
* assignment (i.e. not all keys are specified).
*
* E.g. given a tree with 3 keys, there may be a branch where the 3rd key has
* the same values for all the leaves. This leads to the branch being pruned
* so we get a leaf which is arrived at by just the first 2 keys and their
* assignments.
*/
template <typename L, typename Y>
std::set<L> DecisionTree<L, Y>::labels() const {
std::set<L> unique;
auto f = [&](const Assignment<L>& assignment, const Y&) {
for (auto&& kv : assignment) {
unique.insert(kv.first);
}
};
visitWith(f);
return unique;
}
/****************************************************************************/
template <typename L, typename Y>
bool DecisionTree<L, Y>::equals(const DecisionTree& other,
const CompareFunc& compare) const {
return root_->equals(*other.root_, compare);
}
template <typename L, typename Y>
void DecisionTree<L, Y>::print(const std::string& s,
const LabelFormatter& labelFormatter,
const ValueFormatter& valueFormatter) const {
root_->print(s, labelFormatter, valueFormatter);
}
template<typename L, typename Y>
bool DecisionTree<L, Y>::operator==(const DecisionTree& other) const {
return root_->equals(*other.root_);
}
template<typename L, typename Y>
const Y& DecisionTree<L, Y>::operator()(const Assignment<L>& x) const {
return root_->operator ()(x);
}
template<typename L, typename Y>
DecisionTree<L, Y> DecisionTree<L, Y>::apply(const Unary& op) const {
// It is unclear what should happen if tree is empty:
if (empty()) {
throw std::runtime_error(
"DecisionTree::apply(unary op) undefined for empty tree.");
}
return DecisionTree(root_->apply(op));
}
/// Apply unary operator with assignment
template <typename L, typename Y>
DecisionTree<L, Y> DecisionTree<L, Y>::apply(
const UnaryAssignment& op) const {
// It is unclear what should happen if tree is empty:
if (empty()) {
throw std::runtime_error(
"DecisionTree::apply(unary op) undefined for empty tree.");
}
Assignment<L> assignment;
return DecisionTree(root_->apply(op, assignment));
}
/****************************************************************************/
template<typename L, typename Y>
DecisionTree<L, Y> DecisionTree<L, Y>::apply(const DecisionTree& g,
const Binary& op) const {
// It is unclear what should happen if either tree is empty:
if (empty() || g.empty()) {
throw std::runtime_error(
"DecisionTree::apply(binary op) undefined for empty trees.");
}
// apply the operaton on the root of both diagrams
NodePtr h = root_->apply_f_op_g(*g.root_, op);
// create a new class with the resulting root "h"
DecisionTree result(h);
return result;
}
/****************************************************************************/
// The way this works:
// We have an ADT, picture it as a tree.
// At a certain depth, we have a branch on "label".
// The function "choose(label,index)" will return a tree of one less depth,
// where there is no more branch on "label": only the subtree under that
// branch point corresponding to the value "index" is left instead.
// The function below get all these smaller trees and "ops" them together.
// This implements marginalization in Darwiche09book, pg 330
template<typename L, typename Y>
DecisionTree<L, Y> DecisionTree<L, Y>::combine(const L& label,
size_t cardinality, const Binary& op) const {
DecisionTree result = choose(label, 0);
for (size_t index = 1; index < cardinality; index++) {
DecisionTree chosen = choose(label, index);
result = result.apply(chosen, op);
}
return result;
}
/****************************************************************************/
template <typename L, typename Y>
void DecisionTree<L, Y>::dot(std::ostream& os,
const LabelFormatter& labelFormatter,
const ValueFormatter& valueFormatter,
bool showZero) const {
os << "digraph G {\n";
root_->dot(os, labelFormatter, valueFormatter, showZero);
os << " [ordering=out]}" << std::endl;
}
template <typename L, typename Y>
void DecisionTree<L, Y>::dot(const std::string& name,
const LabelFormatter& labelFormatter,
const ValueFormatter& valueFormatter,
bool showZero) const {
std::ofstream os((name + ".dot").c_str());
dot(os, labelFormatter, valueFormatter, showZero);
int result =
system(("dot -Tpdf " + name + ".dot -o " + name + ".pdf >& /dev/null")
.c_str());
if (result == -1)
throw std::runtime_error("DecisionTree::dot system call failed");
}
template <typename L, typename Y>
std::string DecisionTree<L, Y>::dot(const LabelFormatter& labelFormatter,
const ValueFormatter& valueFormatter,
bool showZero) const {
std::stringstream ss;
dot(ss, labelFormatter, valueFormatter, showZero);
return ss.str();
}
/******************************************************************************/
} // namespace gtsam
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