Finding: backedge reuse from the head of DFS tree doesn't work

orientation before mutation

README.md

@@ -1 +1,2 @@
-This branch tests the idea of using fuzzing to choose the direction of mutation
+The objective of this branch is to measure the number of removed edges between
+preserved and mutated parts of the DFS tree.

deferred_planarity_test/include/mps.h

@@ -33,6 +33,12 @@ enum node_type {
 	AE_VIRTUAL_ROOT = 3
 };
 
+enum back_edge_type {
+    RETAINED = 0,
+    MUTATED_REMOVE = 1,
+    NON_MUTATED_REMOVE = 2
+};
+
 class node
 {
 public:
@@ -56,12 +62,11 @@ public:
 	node* adj(int i);
 	void set_adj_list(vector<node*> vec);
 	void DFS_visit(vector<node*> &dfsList, int &index);
-    void guided_DFS_visit(vector<node *> &dfsList,
+	void guided_DFS_visit(vector<node*> &dfsList, 
-                          vector<node *> &node_list,
+                          vector<node*> &node_list, 
-                          int &return_index,
+                          int &return_index, 
-                          vector<int> rev_post_order,
+                          vector<int> rev_post_order);
-                          int prev_node);
+	void mutated_DFS_visit(vector<node*> &dfsList, 
-    void mutated_DFS_visit(vector<node*> &dfsList, 
                            vector<node*> &node_list, 
                            int &index, 
                            int &traversal_index, 
@@ -156,19 +161,22 @@ public:
 	maximal_planar_subgraph_finder();
 	~maximal_planar_subgraph_finder();
 	int find_mps(string input_file);
-	int compute_removed_edge_size(string input_file, vector<int> post_order);
+	int compute_removed_edge_size(string input_file, vector<int> post_order, int mutate_point);
+	void print_removed_edge_stats(string input_file, vector<int> post_order, int mutate_point);
 	vector<int> generate_post_order(string input_file);
-	vector<int> generate_mutated_post_order(string input_file, vector<int> post_order);
 	vector<int> generate_guided_post_order(string input_file, vector<int> post_order);
+	vector<int> generate_mutated_post_order(string input_file, vector<int> post_order, int mutate_point);
+    void set_mutate_point(int mutate_point);
+    int get_mutate_point();
 	node* get_new_node(node_type t);
     void read_from_gml(string input_file);
-	int output_removed_edge_size();
+	void output_print_removed_edge_stats();
+	int output_int_removed_edge_size();
     vector<int> return_post_order();
 	void postOrderTraversal();
+	void mutatedPostOrderTraversal(vector<int> post_order, int mutate_point);
 	void guidedPostOrderTraversal(vector<int> post_order);
-	void mutatedPostOrderTraversal(vector<int> post_order);
+    void set_post_order(vector<int> post_order);
-    // void set_post_order(vector<int> post_order);
-    void print_post_order();
 	void sort_adj_list();
 	void determine_edges();
 	void back_edge_traversal();
@@ -194,8 +202,9 @@ private:
 	vector<pair<node*, node*> > _edge_list; // Edges in DFS-tree. These edges must be contained in the maximal planar subgraph that we found.
 	vector<node*> _post_order_list; //The sorted version (increasing with post-order-index) of _node_list.
 	vector<pair<node*, node*> > _back_edge_list; // Edges other than that in DFS-tree. (The first node's index is higher than the second's.)
-	vector<bool> _is_back_edge_eliminate; //Record that if the back-edge has been eliminated or not.
+	vector<back_edge_type> _is_back_edge_eliminate; //Record that if the back-edge has been eliminated or not.
 	vector<node*> _new_node_list; //Newly added nodes.
+    int _mutate_point; // store the mutate_point
 };
 
 #endif

deferred_planarity_test/makefile

@@ -31,4 +31,4 @@ $(BIN_DIR) $(OBJ_DIR):
 
 .PHONY: clean
 clean:
-	rm -r $(BIN_DIR) $(OBJ_DIR)
+	rm -r $(OBJ_DIR)

deferred_planarity_test/src/main.cpp

@@ -11,52 +11,60 @@
 #include <iterator>
 #include <random>
 #include <vector>
- 
 #include <ogdf/fileformats/GraphIO.h>
-#define START_TEMP 100
 
 using namespace std;
 
-int compute_removed_edge_size(string input_file, vector<int> post_order);
 
+// functions defined in mps_test.cpp
+int compute_removed_edge_size(string input_file, vector<int> post_order, int mutate_point);
+void print_removed_edge_stats(string input_file, vector<int> post_order, int mutate_point);
 vector<int> generate_post_order(string input_file);
-vector<int> generate_mutated_post_order(string input_file, vector<int> post_order);
 vector<int> generate_guided_post_order(string input_file, vector<int> post_order);
+vector<int> generate_mutated_post_order_at_x(string input_file, vector<int> post_order, int mutate_point);
 
 
-vector<int> repeated_mutation(string input_file, int k_max) {
+void vector_printer(vector<int> state) {
-    // generate first post order
+    for (int i = 0; i < state.size(); ++i) {
-    std::cout << "generate first post order" << std::endl;
+        std::cout << state[i] << ",";
+    }
+    std::cout << std::endl;
+}
+
+
+
+void measure_removed_edges(string input_file, int k_max, int mutate_point) {
+    // generate first state
     vector<int> state_old = generate_post_order(input_file);
     vector<int> state_new;
-    int num_removed_edges;
+
+
+    int removed_old = compute_removed_edge_size(input_file, state_old, mutate_point);
+    int removed_new;
+
     for (int k = 0; k < k_max; ++k) {
-        // rotate it first
+        std::cout << "first post order" << std::endl;
-        std::cout << "cycle:" << k << std::endl;
+        vector_printer(state_old);
-        std::cout << "rotate the dfs tree" << std::endl;
+
-        state_new = generate_guided_post_order(input_file, state_old);
+        // run mutation on canonical representation directly
-        // then the next traversal will rotate it back
+        state_new = generate_mutated_post_order_at_x(input_file, state_old, mutate_point);
-        std::cout << "mutate the dfs tree" << std::endl;
+        // rotate output of mutated state to canonical representation
-        state_new = generate_mutated_post_order(input_file, state_new);
-        // num_removed_edges = compute_removed_edge_size(input_file, state_new);
-        // first time will rotate the tree
-        std::cout << "rotate the dfs tree" << std::endl;
         state_new = generate_guided_post_order(input_file, state_new);
-        // second time will rotate back the rotated tree
+        // tree produced should be the same as tree from mutation
-        std::cout << "print the mutated tree again" << std::endl;
+        removed_new = compute_removed_edge_size(input_file, state_new, mutate_point);
-        state_new = generate_guided_post_order(input_file, state_new);
+
-        std::cout << std::endl;
+        std::cout << "mutated post order" << std::endl;
+        vector_printer(state_new);
+
+        
+        // std::cout << "removed edges in old: " << removed_old << std::endl;
+        // std::cout << "removed edges in new: " << removed_new << std::endl;
+        print_removed_edge_stats(input_file, state_new, mutate_point);
+
     }
-    return state_new;
-}
 
-void test_correctness(string input_file) {
-    vector<int> state_old = generate_post_order(input_file);
-    int num_removed_edges;
-    num_removed_edges = compute_removed_edge_size(input_file, state_old);
 }
 
-
 int get_graph_size(string input_file) {
     ogdf::Graph G;
 
@@ -76,17 +84,10 @@ int get_graph_size(string input_file) {
 int main(int argc, char* argv[]) {
     string input_file = argv[1];
     int k_max = std::stoi(argv[2]);
+    int mutate_point = std::stoi(argv[3]);
 
     // generate order here
-    vector<int> post_order = repeated_mutation(input_file, k_max);
+    measure_removed_edges(input_file, k_max, mutate_point);
-    // test_correctness(input_file);
-
-    // // print final order and number of edges
-    // // print post_order
-    // std::copy(post_order.begin(), post_order.end(), std::ostream_iterator<int>(std::cout, ","));
-    // std::cout << std::endl;
-    // int removed_edges = compute_removed_edge_size(input_file, post_order);
-    // std::cout << "Number of removed edges: " << removed_edges << std::endl;
 
 	return 0;
 }

deferred_planarity_test/src/mps.cpp

@@ -3,9 +3,7 @@
 //-----------------------------------------------------------------------------------
 
 #include "mps.h"
-#include <iterator>
+#include <cassert>
-
-// #define DEBUG
 
 // constructor can be made empty
 maximal_planar_subgraph_finder::maximal_planar_subgraph_finder() {}
@@ -22,6 +20,17 @@ maximal_planar_subgraph_finder::get_new_node(node_type t) {
 	return _new_node_list[_new_node_list.size()-1];
 }
 
+// setter and getter for mutate_point
+void
+maximal_planar_subgraph_finder::set_mutate_point(int mutate_point) {
+    _mutate_point = mutate_point;
+}
+
+int
+maximal_planar_subgraph_finder::get_mutate_point() {
+    return _mutate_point;
+}
+
 vector<int>
 maximal_planar_subgraph_finder::return_post_order() {
     vector<int> post_order;
@@ -31,11 +40,11 @@ maximal_planar_subgraph_finder::return_post_order() {
     return post_order;
 }
 
+
 //Determine the post-order-list by a DFS-traversal.
 void
 maximal_planar_subgraph_finder::postOrderTraversal() {
 	node::init_mark();
-    // always start with node 0
 	int postOrderID = 0;
 	for (int i = 0; i < _node_list.size(); ++i) {
 		if (!_node_list[i]->is_marked()) {
@@ -45,9 +54,7 @@ maximal_planar_subgraph_finder::postOrderTraversal() {
 }
 
 
-// Determine the post-order-list by a DFS-traversal.
+//Determine the post-order-list by a DFS-traversal.
-// take in a post-order argument then traces the graph in the same order
-// return is by reference via _post_order_list
 void 
 maximal_planar_subgraph_finder::guidedPostOrderTraversal(vector<int> post_order) {
 	node::init_mark();
@@ -61,33 +68,31 @@ maximal_planar_subgraph_finder::guidedPostOrderTraversal(vector<int> post_order)
     int end_condition = _node_list.size();
     int start = rev_post_order[0];
     int i = start;
-    
-    int prev_node = INT_MAX;
     while (true)
     {
         if (((start > 0) && (i == (start - 1))) || ((start == 0 ) && (i == end_condition - 1)))
         {
             if (!_node_list[i]->is_marked())
             {
-                _node_list[i]->guided_DFS_visit(_post_order_list, _node_list, postOrderID, rev_post_order, prev_node);
+                _node_list[i]->guided_DFS_visit(_post_order_list, _node_list, postOrderID, rev_post_order);
             }
             break;
         }
+        // std::cout << _node_list[i]->node_id() << ", " << !_node_list[i]->is_marked() << std::endl;
         if (!_node_list[i]->is_marked())
         {
-            _node_list[i]->guided_DFS_visit(_post_order_list, _node_list, postOrderID, rev_post_order, prev_node);
+            _node_list[i]->guided_DFS_visit(_post_order_list, _node_list, postOrderID, rev_post_order);
         }
         i = (i + 1) % end_condition;
     }
 }
 
 //Determine the post-order-list by a DFS-traversal.
-// take in a post-order argument then traces the graph in the same order
-// return is by reference via _post_order_list
 void
-maximal_planar_subgraph_finder::mutatedPostOrderTraversal(vector<int> post_order) {
+maximal_planar_subgraph_finder::mutatedPostOrderTraversal(vector<int> post_order, int mutate_point) {
 	node::init_mark();
 
+    // reverse post_order because reversed post_order is the traversal of the DFS tree from the starting node
     vector<int> rev_post_order;
     for (int i = post_order.size() - 1; i >= 0; --i) {
         rev_post_order.push_back(post_order[i]);
@@ -96,30 +101,16 @@ maximal_planar_subgraph_finder::mutatedPostOrderTraversal(vector<int> post_order
     int traversal_index = 0;
 
     // introduce random selection
-    std::random_device rd;
-    std::mt19937 rng(rd());
     // Define the range [0, n]
     int n = _node_list.size() - 1;  // Change 'n' to your desired upper bound
-    // Create a uniform distribution for the range [0, n]
+    // assert(mutate_point < n);
-    std::uniform_int_distribution<int> distribution(0, n);
-    // Generate a random number between 0 and n (inclusive)
-    int mutate_point = distribution(rng);
-    // std::cout << "the mutate point: " << mutate_point << std::endl;
 
     // set loop variables
     int start = rev_post_order[0];
     int i = start;
 
-    // if mutate_point = 0
-    if (mutate_point == 0) {
-        // generate another point
-        start = distribution(rng); 
-    }
-
 
     int end_condition = _node_list.size();
-    // this loop assumes start is not from 0
-    // if starting index is not 0, it just increments and loops around until it encounters the element before it
     while (true)
     {
         if (((start > 0) && (i == (start - 1))) || ((start == 0 ) && (i == end_condition - 1)))
@@ -130,6 +121,7 @@ maximal_planar_subgraph_finder::mutatedPostOrderTraversal(vector<int> post_order
             }
             break;
         }
+        // std::cout << _node_list[i]->node_id() << ", " << !_node_list[i]->is_marked() << std::endl;
         if (!_node_list[i]->is_marked())
         {
             _node_list[i]->mutated_DFS_visit(_post_order_list, _node_list, postOrderID, traversal_index, rev_post_order, mutate_point);
@@ -138,25 +130,15 @@ maximal_planar_subgraph_finder::mutatedPostOrderTraversal(vector<int> post_order
     }
 }
 
-void
-maximal_planar_subgraph_finder::print_post_order() {
-    int current_index;
-    for (int i = 0; i < _post_order_list.size(); ++i) {
-        current_index = _post_order_list[i]->node_id();
-        std::cout << current_index << ",";
-    }
-    std::cout << std::endl;
-}
 
 
-// this function is not used anywhere
 //Set the post-order-list via given list
-// void
+void
-// maximal_planar_subgraph_finder::set_post_order(vector<int> post_order) {
+maximal_planar_subgraph_finder::set_post_order(vector<int> post_order) {
-//     for (int i = 0; i < _node_list.size(); ++i) {
+    for (int i = 0; i < _node_list.size(); ++i) {
-//         _node_list[i]->set_post_order_index(post_order[i]);
+        _node_list[i]->set_post_order_index(post_order[i]);
-//     }
+    }
-// }
+}
 
 //Sort the adj-list of every node increasingly according to post-order-index.
 void
@@ -187,7 +169,7 @@ maximal_planar_subgraph_finder::determine_edges() {
 			if (_post_order_list[i]->adj(j)->post_order_index() > i) break;
 			if (_post_order_list[i]->adj(j)->get_1st_label() == i) continue;
 			_back_edge_list.push_back(pair<node*, node*> (_post_order_list[i], _post_order_list[i]->adj(j)));
-			_is_back_edge_eliminate.push_back(false);
+			_is_back_edge_eliminate.push_back(RETAINED);
 		}
 	}
 	for (int i = 0; i < _post_order_list.size(); ++i) {
@@ -198,13 +180,35 @@ maximal_planar_subgraph_finder::determine_edges() {
 //The main part of the whole algorithm: Back-edge-traversal
 void 
 maximal_planar_subgraph_finder::back_edge_traversal() {
-	node* i_node = 0;
+	node* i_node = nullptr;
-	node* current_node = 0;
+	node* current_node = nullptr;
+    int dfs_mutate_point = get_mutate_point();
+    int node_list_last_index = _node_list.size() - 1;
+    // dfs_mutate_point starts counting from the DFS head
+    // post_order starts from the last leaf of the DFS tree
+    // hence we start counting from the post_order last index
+    int post_order_mutate_point = node_list_last_index - dfs_mutate_point; 
+    // std::cout << "post_order_mutate_point: " << post_order_mutate_point << std::endl;
+    // back_edge first node is higher than the second
 	for (int i = 0; i < _back_edge_list.size(); ++i) {
+        // current node is the lower 
 		current_node = _back_edge_list[i].second;
 		i_node = _back_edge_list[i].first;
-		if (!back_edge_traversal(current_node, i_node->post_order_index())) _is_back_edge_eliminate[i] = true;
+        // back_edge_traversal returns true if it should be included
+        // false otherwise
+		if (!back_edge_traversal(current_node, i_node->post_order_index())) {
+            // if current_node is higher than post_order_mutate_point
+            // then it is the preserved section
+            if (current_node->post_order_index() > post_order_mutate_point) {
+                std::cout << "(" << current_node->node_id() << "[" << current_node->post_order_index() << "]"
+                << "," << i_node->node_id() << "[" << i_node->post_order_index() << "]" << ") ";
+                _is_back_edge_eliminate[i] = NON_MUTATED_REMOVE;
+            } else {
+                _is_back_edge_eliminate[i] = MUTATED_REMOVE;
+            }
+        } 
 	}
+    std::cout << std::endl;
 }
 
 //sub-function for the for-loop of back_edge_traversal().

deferred_planarity_test/src/mps_test.cpp

@@ -4,23 +4,29 @@
 
 #include "mps.h"
 #include <ogdf/fileformats/GraphIO.h>
+#include <algorithm>
+#include <vector>
 
-#define DEBUG
 
 //-----------------------------------------------------------------------------------
 // Finding MPS
 //-----------------------------------------------------------------------------------
 
-// programs to call from main:
+// functions to call from main:
 
 int find_mps(string input_file) {
 	maximal_planar_subgraph_finder m;
 	return m.find_mps(input_file);
 }
 
-int compute_removed_edge_size(string input_file, vector<int> post_order) {
+int compute_removed_edge_size(string input_file, vector<int> post_order, int mutate_point) {
     maximal_planar_subgraph_finder m;
-    return m.compute_removed_edge_size(input_file, post_order);
+    return m.compute_removed_edge_size(input_file, post_order, mutate_point);
+}
+
+void print_removed_edge_stats(string input_file, vector<int> post_order, int mutate_point) {
+    maximal_planar_subgraph_finder m;
+    m.print_removed_edge_stats(input_file, post_order, mutate_point);
 }
 
 vector<int> generate_post_order(string input_file) {
@@ -28,90 +34,78 @@ vector<int> generate_post_order(string input_file) {
     return m.generate_post_order(input_file);
 }
 
-vector<int> generate_mutated_post_order(string input_file, vector<int> post_order) {
-    maximal_planar_subgraph_finder m;
-    return m.generate_mutated_post_order(input_file, post_order);
-}
-
 vector<int> generate_guided_post_order(string input_file, vector<int> post_order) {
     maximal_planar_subgraph_finder m;
     return m.generate_guided_post_order(input_file, post_order);
 }
 
+vector<int> generate_mutated_post_order_at_x(string input_file, vector<int> post_order, int mutate_point) {
+    maximal_planar_subgraph_finder m;
+    return m.generate_mutated_post_order(input_file, post_order, mutate_point);
+}
 
-// ---------
+
+// immediate functions called by functions called from main
 
 int maximal_planar_subgraph_finder::find_mps(string input_file) {
 	read_from_gml(input_file);
 	postOrderTraversal();
-
-    #ifdef DEBUG
-    print_post_order();
-    #endif
-
 	sort_adj_list();
 	determine_edges();
 	back_edge_traversal();
-	return output_removed_edge_size();
+	return output_int_removed_edge_size();
 }
 
 vector<int> maximal_planar_subgraph_finder::generate_post_order(string input_file) {
     read_from_gml(input_file);
+    set_mutate_point(INT_MAX); // essentially removed mutate_point
     postOrderTraversal();
-
-    #ifdef DEBUG
-    std::cout << "standard post order traversal" << std::endl;
-    print_post_order();
-    #endif
-
     return return_post_order();
 }
 
-// result of this will be used as input to "compute_removed_edge_size"
-vector<int> maximal_planar_subgraph_finder::generate_mutated_post_order(string input_file, vector<int> post_order) {
-    read_from_gml(input_file);
-    mutatedPostOrderTraversal(post_order);
-
-    #ifdef DEBUG
-    std::cout << "mutated post order traversal" << std::endl;
-    print_post_order();
-    #endif
-
-    return return_post_order();
-}
-
-// result of this will be used as input to "compute_removed_edge_size"
 vector<int> maximal_planar_subgraph_finder::generate_guided_post_order(string input_file, vector<int> post_order) {
     read_from_gml(input_file);
+    set_mutate_point(INT_MAX); // essentially remove mutate point
     guidedPostOrderTraversal(post_order);
-
-    #ifdef DEBUG
-    std::cout << "guided post order traversal" << std::endl;
-    print_post_order();
-    #endif
-
     return return_post_order();
 }
 
 
+vector<int> maximal_planar_subgraph_finder::generate_mutated_post_order(string input_file, vector<int> post_order, int mutate_point) {
+    read_from_gml(input_file);
+    set_mutate_point(INT_MAX);
+    mutatedPostOrderTraversal(post_order, mutate_point);
+    return return_post_order();
+}
 
-int maximal_planar_subgraph_finder::compute_removed_edge_size(string input_file, vector<int> post_order) {
+
+int maximal_planar_subgraph_finder::compute_removed_edge_size(string input_file, vector<int> post_order, int mutate_point) {
 	read_from_gml(input_file);
+    set_mutate_point(mutate_point);
     guidedPostOrderTraversal(post_order);
-    
-    #ifdef DEBUG
-    std::cout << "guided post order traversal" << std::endl;
-    print_post_order();
-    #endif
 
 	sort_adj_list();
 	determine_edges();
 	back_edge_traversal();
-	return output_removed_edge_size();
+	return output_int_removed_edge_size();
 }
 
+void maximal_planar_subgraph_finder::print_removed_edge_stats(string input_file, vector<int> post_order, int mutate_point) {
+	read_from_gml(input_file);
+    set_mutate_point(mutate_point);
+    guidedPostOrderTraversal(post_order);
+
+	sort_adj_list();
+	determine_edges();
+	back_edge_traversal();
+	output_print_removed_edge_stats();
+}
+
+
+
+
 //-----------------------------------------------------------------------------------
-// Imput, output
+// Input, output
 //-----------------------------------------------------------------------------------
 
 
@@ -130,6 +124,14 @@ void maximal_planar_subgraph_finder::read_from_gml(string input_file) {
 		_node_list[i]->set_id(i);
 	}
 
+    // vector<ogdf::edge> unique_edges;
+    // // we want to get unique edge only
+    // for (ogdf::edge e : G.edges) {
+    //     // Check if the edge is already in the array
+    //     if (std::find(unique_edges.begin(), unique_edges.end(), e) == unique_edges.end())
+    //         unique_edges.push_back(e);
+    // }
+
     // create edges
     for (ogdf::edge e : G.edges) {
         ogdf::node source = e->source();
@@ -142,10 +144,47 @@ void maximal_planar_subgraph_finder::read_from_gml(string input_file) {
 
 
 // count the number of removed edges
-int maximal_planar_subgraph_finder::output_removed_edge_size() {
+void maximal_planar_subgraph_finder::output_print_removed_edge_stats() {
+    int mutated_sum = 0;
+    int preserved_sum = 0;
+
+    vector<pair<node*, node*>> mutated_removed_edges;
+    vector<pair<node*, node*>> preserved_removed_edges;
+    
+    for (int i = 0; i < _back_edge_list.size(); ++i) {
+		if (_is_back_edge_eliminate[i] == MUTATED_REMOVE) {
+            mutated_removed_edges.push_back(_back_edge_list[i]);
+            ++mutated_sum; 
+        }
+		if (_is_back_edge_eliminate[i] == NON_MUTATED_REMOVE) {
+            preserved_removed_edges.push_back(_back_edge_list[i]);
+            ++preserved_sum; 
+        }
+    }
+
+    // print the edges
+    // std::cout << "mutated removed edges: " << std::endl;
+    // for (int i = 0; i < mutated_removed_edges.size(); ++i) {
+    //     std::cout << mutated_removed_edges[i].first->node_id() << ", " <<
+    //     mutated_removed_edges[i].second->node_id() << std::endl;
+    // }
+
+    // std::cout << "preserved removed edges: " << std::endl;
+    // for (int i = 0; i < preserved_removed_edges.size(); ++i) {
+    //     std::cout << preserved_removed_edges[i].first->node_id() << ", " <<
+    //     preserved_removed_edges[i].second->node_id() << std::endl;
+    // }
+
+    std::cout << "<- sum of removed edges -> " << std::endl;
+    std::cout << "mutated portion: " << mutated_sum << std::endl;
+    std::cout << "preserved portion: " << preserved_sum << std::endl;
+}
+
+int maximal_planar_subgraph_finder::output_int_removed_edge_size() {
     int sum = 0;
     for (int i = 0; i < _back_edge_list.size(); ++i) {
-		if (_is_back_edge_eliminate[i]) ++sum; 
+		if (_is_back_edge_eliminate[i] != RETAINED) ++sum; 
     }
+
     return sum;
 }

deferred_planarity_test/src/node.cpp

@@ -4,8 +4,6 @@
 
 #include "mps.h"
 
-// #define DEBUG
-
 //-----------------------------------------------------------------------------------
 // CONSTRUCTOR
 //-----------------------------------------------------------------------------------
@@ -55,6 +53,8 @@ node* node::adj(int i) {return _adj_list[i];}
 
 void node::set_adj_list(vector<node*> vec) {_adj_list = vec;}
 
+// original DFS visit implementation
+// it just uses _adj_list directly as list of neighbors
 void node::DFS_visit(vector<node*> &dfsList, int &index) {
 	mark();
 	for (int i = 0; i < _adj_list.size(); ++i) {
@@ -63,78 +63,19 @@ void node::DFS_visit(vector<node*> &dfsList, int &index) {
 			_adj_list[i]->DFS_visit(dfsList, index);
 		}
 	}
+    // head recursion: function call before returning result
 	set_post_order_index(index);
 	dfsList.push_back(this);
 	++index;
 }
 
-
 void node::guided_DFS_visit(vector<node *> &dfsList, 
                             vector<node *> &node_list, 
                             int &return_index, 
-                            vector<int> rev_post_order,
+                            vector<int> rev_post_order)
-                            int prev_node)
 {
+    mark();
 
-	mark();
-
-    // purpose of this block: create list of neighbors ordered in the order they appear in rev_post_order
-    // we want to select neighbors that match the rev_post_order at the specific traversal_index
-
-    // create an unordered set to efficiently check for presence of an element
-    std::unordered_set<int> neighbor_set; 
-    for (int i = 0; i < _adj_list.size(); ++i) {
-        neighbor_set.insert(_adj_list[i]->node_id());
-    }
-    // when an element in rev_post_order is found in neighbor_set, we add that to neighbor_list
-    // this produces a neighbor_list that follows the order by which they occur in the rev_post_order
-    // it is ok if the neighbor was already visited before, 
-    // it would've been marked and will be subsequently ignored
-    vector<node *> neighbor_list;
-    for (int i = 0; i < rev_post_order.size(); ++i) {
-        if (neighbor_set.find(rev_post_order[i]) != neighbor_set.end()) {
-            // only add if newly encountered
-            if (!node_list[rev_post_order[i]]->is_marked()) {
-                neighbor_list.push_back(node_list[rev_post_order[i]]);
-            }
-        }
-    }
-
-    #ifdef DEBUG
-    std::cout << "current node:" << this->node_id() << std::endl;
-    std::cout << "prev node:" << prev_node << std::endl;
-    for (int i = 0; i < neighbor_list.size(); ++i) {
-        std::cout << neighbor_list[i]->node_id() << "(" << neighbor_list[i]->is_marked() << ")" << ",";
-    }
-    std::cout << std::endl;
-    #endif
-
-
-	
-	for (int i = 0; i < neighbor_list.size(); ++i) {
-		if (!neighbor_list[i]->is_marked()) {
-			neighbor_list[i]->_parent = this;
-			neighbor_list[i]->guided_DFS_visit(dfsList, node_list, return_index, rev_post_order, this->node_id());
-		}
-	}
-
-    set_post_order_index(return_index);
-	dfsList.push_back(this);
-	++return_index;
-}
-
-
-void node::mutated_DFS_visit(vector<node*> &dfsList, 
-                             vector<node*> &node_list, 
-                             int &return_index, 
-                             int &traversal_index, 
-                             vector<int> rev_post_order, 
-                             int mutate_point)
-{
-
-    // mark current node
-	mark();
-    
     // purpose of this block: create list of neighbors ordered in the order they appear in rev_post_order
     // we want to select neighbors that match the rev_post_order at the specific traversal_index
 
@@ -154,18 +95,57 @@ void node::mutated_DFS_visit(vector<node*> &dfsList,
         }
     }
 
+	for (int i = 0; i < neighbor_list.size(); ++i) {
+		if (!neighbor_list[i]->is_marked()) {
+			neighbor_list[i]->_parent = this;
+			neighbor_list[i]->guided_DFS_visit(dfsList, node_list, return_index, rev_post_order);
+		}
+	}
+
+    // head recursion
+	set_post_order_index(return_index);
+	dfsList.push_back(this);
+	++return_index;
+}
+
+void node::mutated_DFS_visit(vector<node*> &dfsList, 
+                             vector<node*> &node_list, 
+                             int &return_index, 
+                             int &traversal_index, 
+                             vector<int> rev_post_order, 
+                             int mutate_point) {
+	mark();
+
+    // purpose of this block: create list of neighbors ordered in the order they appear in rev_post_order
+    // we want to select neighbors that match the rev_post_order at the specific traversal_index
+
+    // create an unordered set to efficiently check for presence of an element
+    std::unordered_set<int> neighbor_set; 
+    for (int i = 0; i < _adj_list.size(); ++i) {
+        neighbor_set.insert(_adj_list[i]->node_id());
+    }
+    // when an element in rev_post_order is found in neighbor_set, we add that to neighbor_list
+    // this produces a neighbor_list that follows the order by which they occur in the rev_post_order
+    // it is ok if the neighbor was already visited before, 
+    // it would've been marked and will be subsequently ignored
+    vector<node *> neighbor_list;
+    for (int i = 0; i < rev_post_order.size(); ++i) {
+        if (neighbor_set.find(rev_post_order[i]) != neighbor_set.end()) {
+            neighbor_list.push_back(node_list[rev_post_order[i]]);
+        }
+    }
     
 
-    // since we increment the index before this line, the current index is "index - 1"
+    // introduce mutation at mutate_point
-    // if the current index matches the mutate_point, then we know this is the cycle to mutate
     if (traversal_index == mutate_point) {
         // Create a random number generator and seed it
         // std::cout << "mutated at index: " << index - 1<< "and at mutate point: " << mutate_point << std::endl;
         std::random_device rd;
         std::mt19937 rng(rd());
+
         // Use std::shuffle to shuffle the elements in the vector
         std::shuffle(neighbor_list.begin(), neighbor_list.end(), rng);
-    } 
+    }
 
     // increment traversal index after checking
     // next node will receive incremented index
@@ -180,11 +160,14 @@ void node::mutated_DFS_visit(vector<node*> &dfsList,
         }
     }
 
-	set_post_order_index(return_index);
+    // head recursion like the initial dfs visit implementation
+    set_post_order_index(return_index);
 	dfsList.push_back(this);
 	++return_index;
 }
 
+
+
 //-----------------------------------------------------------------------------------
 // PARENT-CHILDREN
 //-----------------------------------------------------------------------------------