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 //////////////////////////////////////////////////////////////////////////
 //                            Node.cxx                                  //
 // =====================================================================//
 // This is the object implementation of a node, which is the            //
 // fundamental unit of a decision tree.                                 //
 // References include                                                   //
 //    *Elements of Statistical Learning by Hastie,                      //
 //     Tibshirani, and Friedman.                                        //
 //    *Greedy Function Approximation: A Gradient Boosting Machine.      //
 //     Friedman. The Annals of Statistics, Vol. 29, No. 5. Oct 2001.    //
 //    *Inductive Learning of Tree-based Regression Models. Luis Torgo.  //
 //                                                                      //
 //////////////////////////////////////////////////////////////////////////
 
 ///////////////////////////////////////////////////////////////////////////
 // _______________________Includes_______________________________________//
 ///////////////////////////////////////////////////////////////////////////
 
 #include "L1Trigger/L1TMuonEndCap/interface/bdt/Node.h"
 
 #include "TRandom3.h"
 #include "TStopwatch.h"
 #include <iostream>
 #include <fstream>
 
 //////////////////////////////////////////////////////////////////////////
 // _______________________Constructor(s)________________________________//
 //////////////////////////////////////////////////////////////////////////
 
 using namespace emtf;
 
 Node::Node() {
   name = "";
   leftDaughter = nullptr;
   rightDaughter = nullptr;
   parent = nullptr;
   splitValue = -99;
   splitVariable = -1;
   avgError = -1;
   totalError = -1;
   errorReduction = -1;
 }
 
 Node::Node(std::string cName) {
   name = cName;
   leftDaughter = nullptr;
   rightDaughter = nullptr;
   parent = nullptr;
   splitValue = -99;
   splitVariable = -1;
   avgError = -1;
   totalError = -1;
   errorReduction = -1;
 }
 
 //////////////////////////////////////////////////////////////////////////
 // ______________________Get/Set________________________________________//
 //////////////////////////////////////////////////////////////////////////
 
 void Node::setName(std::string sName) { name = sName; }
 
 std::string Node::getName() const { return name; }
 
 // ----------------------------------------------------------------------
 
 void Node::setErrorReduction(double sErrorReduction) { errorReduction = sErrorReduction; }
 
 double Node::getErrorReduction() const { return errorReduction; }
 
 // ----------------------------------------------------------------------
 
 void Node::setLeftDaughter(std::unique_ptr<Node> sLeftDaughter) { leftDaughter = std::move(sLeftDaughter); }
 
 Node* Node::getLeftDaughter() { return leftDaughter.get(); }
 const Node* Node::getLeftDaughter() const { return leftDaughter.get(); }
 
 void Node::setRightDaughter(std::unique_ptr<Node> sRightDaughter) { rightDaughter = std::move(sRightDaughter); }
 
 Node* Node::getRightDaughter() { return rightDaughter.get(); }
 const Node* Node::getRightDaughter() const { return rightDaughter.get(); }
 
 // ----------------------------------------------------------------------
 
 void Node::setParent(Node* sParent) { parent = sParent; }
 
 Node* Node::getParent() { return parent; }
 const Node* Node::getParent() const { return parent; }
 
 // ----------------------------------------------------------------------
 
 void Node::setSplitValue(double sSplitValue) { splitValue = sSplitValue; }
 
 double Node::getSplitValue() const { return splitValue; }
 
 void Node::setSplitVariable(int sSplitVar) { splitVariable = sSplitVar; }
 
 int Node::getSplitVariable() const { return splitVariable; }
 
 // ----------------------------------------------------------------------
 
 void Node::setFitValue(double sFitValue) { fitValue = sFitValue; }
 
 double Node::getFitValue() const { return fitValue; }
 
 // ----------------------------------------------------------------------
 
 void Node::setTotalError(double sTotalError) { totalError = sTotalError; }
 
 double Node::getTotalError() const { return totalError; }
 
 void Node::setAvgError(double sAvgError) { avgError = sAvgError; }
 
 double Node::getAvgError() const { return avgError; }
 
 // ----------------------------------------------------------------------
 
 void Node::setNumEvents(int sNumEvents) { numEvents = sNumEvents; }
 
 int Node::getNumEvents() const { return numEvents; }
 
 // ----------------------------------------------------------------------
 
 std::vector<std::vector<Event*> >& Node::getEvents() { return events; }
 
 void Node::setEvents(std::vector<std::vector<Event*> >& sEvents) {
   events = sEvents;
   numEvents = events[0].size();
 }
 
 ///////////////////////////////////////////////////////////////////////////
 // ______________________Performace_Functions___________________________//
 //////////////////////////////////////////////////////////////////////////
 
 void Node::calcOptimumSplit() {
   // Determines the split variable and split point which would most reduce the error for the given node (region).
   // In the process we calculate the fitValue and Error. The general aglorithm is based upon  Luis Torgo's thesis.
   // Check out the reference for a more in depth outline. This part is chapter 3.
 
   // Intialize some variables.
   double bestSplitValue = 0;
   int bestSplitVariable = -1;
   double bestErrorReduction = -1;
 
   double SUM = 0;
   double SSUM = 0;
   numEvents = events[0].size();
 
   double candidateErrorReduction = -1;
 
   // Calculate the sum of the target variables and the sum of
   // the target variables squared. We use these later.
   for (unsigned int i = 0; i < events[0].size(); i++) {
     double target = events[0][i]->data[0];
     SUM += target;
     SSUM += target * target;
   }
 
   unsigned int numVars = events.size();
 
   // Calculate the best split point for each variable
   for (unsigned int variableToCheck = 1; variableToCheck < numVars; variableToCheck++) {
     // The sum of the target variables in the left, right nodes
     double SUMleft = 0;
     double SUMright = SUM;
 
     // The number of events in the left, right nodes
     int nleft = 1;
     int nright = events[variableToCheck].size() - 1;
 
     int candidateSplitVariable = variableToCheck;
 
     std::vector<Event*>& v = events[variableToCheck];
 
     // Find the best split point for this variable
     for (unsigned int i = 1; i < v.size(); i++) {
       // As the candidate split point interates, the number of events in the
       // left/right node increases/decreases and SUMleft/right increases/decreases.
 
       SUMleft = SUMleft + v[i - 1]->data[0];
       SUMright = SUMright - v[i - 1]->data[0];
 
       // No need to check the split point if x on both sides is equal
       if (v[i - 1]->data[candidateSplitVariable] < v[i]->data[candidateSplitVariable]) {
         // Finding the maximum error reduction for Least Squares boils down to maximizing
         // the following statement.
         candidateErrorReduction = SUMleft * SUMleft / nleft + SUMright * SUMright / nright - SUM * SUM / numEvents;
         //                std::cout << "candidateErrorReduction= " << candidateErrorReduction << std::endl << std::endl;
 
         // if the new candidate is better than the current best, then we have a new overall best.
         if (candidateErrorReduction > bestErrorReduction) {
           bestErrorReduction = candidateErrorReduction;
           bestSplitValue = (v[i - 1]->data[candidateSplitVariable] + v[i]->data[candidateSplitVariable]) / 2;
           bestSplitVariable = candidateSplitVariable;
         }
       }
 
       nright = nright - 1;
       nleft = nleft + 1;
     }
   }
 
   // Store the information gained from our computations.
 
   // The fit value is the average for least squares.
   fitValue = SUM / numEvents;
   //    std::cout << "fitValue= " << fitValue << std::endl;
 
   // n*[ <y^2>-k^2 ]
   totalError = SSUM - SUM * SUM / numEvents;
   //    std::cout << "totalError= " << totalError << std::endl;
 
   // [ <y^2>-k^2 ]
   avgError = totalError / numEvents;
   //    std::cout << "avgError= " << avgError << std::endl;
 
   errorReduction = bestErrorReduction;
   //    std::cout << "errorReduction= " << errorReduction << std::endl;
 
   splitVariable = bestSplitVariable;
   //    std::cout << "splitVariable= " << splitVariable << std::endl;
 
   splitValue = bestSplitValue;
   //    std::cout << "splitValue= " << splitValue << std::endl;
 
   //if(bestSplitVariable == -1) std::cout << "splitVar = -1. numEvents = " << numEvents << ". errRed = " << errorReduction << std::endl;
 }
 
 // ----------------------------------------------------------------------
 
 void Node::listEvents() {
   std::cout << std::endl << "Listing Events... " << std::endl;
 
   for (unsigned int i = 0; i < events.size(); i++) {
     std::cout << std::endl << "Variable " << i << " vector contents: " << std::endl;
     for (unsigned int j = 0; j < events[i].size(); j++) {
       events[i][j]->outputEvent();
     }
     std::cout << std::endl;
   }
 }
 
 // ----------------------------------------------------------------------
 
 void Node::theMiracleOfChildBirth() {
   // Create Daughter Nodes
   leftDaughter = std::make_unique<Node>(name + " left");
   rightDaughter = std::make_unique<Node>(name + " right");
 
   // Link the Nodes Appropriately
   leftDaughter->setParent(this);
   rightDaughter->setParent(this);
 }
 
 // ----------------------------------------------------------------------
 
 void Node::filterEventsToDaughters() {
   // Keeping sorted copies of the event vectors allows us to save on
   // computation time. That way we don't have to resort the events
   // each time we calculate the splitpoint for a node. We sort them once.
   // Every time we split a node, we simply filter them down correctly
   // preserving the order. This way we have O(n) efficiency instead
   // of O(nlogn) efficiency.
 
   // Anyways, this function takes events from the parent node
   // and filters an event into the left or right daughter
   // node depending on whether it is < or > the split point
   // for the given split variable.
 
   unsigned int sv = splitVariable;
   double sp = splitValue;
 
   Node* left = leftDaughter.get();
   Node* right = rightDaughter.get();
 
   std::vector<std::vector<Event*> > l(events.size());
   std::vector<std::vector<Event*> > r(events.size());
 
   for (unsigned int i = 0; i < events.size(); i++) {
     for (unsigned int j = 0; j < events[i].size(); j++) {
       Event* e = events[i][j];
       // Prevent out-of-bounds access
       if (sv >= e->data.size())
         continue;
       if (e->data[sv] < sp)
         l[i].push_back(e);
       if (e->data[sv] > sp)
         r[i].push_back(e);
     }
   }
 
   events = std::vector<std::vector<Event*> >();
 
   left->getEvents().swap(l);
   right->getEvents().swap(r);
 
   // Set the number of events in the node.
   left->setNumEvents(left->getEvents()[0].size());
   right->setNumEvents(right->getEvents()[0].size());
 }
 
 // ----------------------------------------------------------------------
 
 Node* Node::filterEventToDaughter(Event* e) {
   // Anyways, this function takes an event from the parent node
   // and filters an event into the left or right daughter
   // node depending on whether it is < or > the split point
   // for the given split variable.
 
   unsigned int sv = splitVariable;
   double sp = splitValue;
 
   Node* left = leftDaughter.get();
   Node* right = rightDaughter.get();
   Node* nextNode = nullptr;
 
   // Prevent out-of-bounds access
   if (left == nullptr || right == nullptr || sv >= e->data.size())
     return nullptr;
 
   if (e->data[sv] < sp)
     nextNode = left;
   if (e->data[sv] >= sp)
     nextNode = right;
 
   return nextNode;
 }

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