Work done on knot-detection. Still figuring out how to best organize the data to look for loops.

src/knotted.cpp

@@ -1,17 +1,120 @@
+/* +----------------+---------+--------------------------+
+   | Michael Laymon | mal0420 | MichaelLaymon@my.unt.edu |
+   +----------------+---------+--------------------------+
+   |    Created 2022-04-17    |    Updated 2022-04-27    |
+   +--------------------------+--------------------------+  */
+
 #include <cstdlib>
 #include <string>
 #include <vector>
 #include "graph.hpp"
 
-/* knotted:
-      Perform the knot detection algorithm on the adjacency matrix to detect deadlocks
-      (!THIS MODIFIES THE GRAPH!)
-   @params: none, uses class-internal data
-   @returns:
-      int:
-         true if graph is knotted (deadlock)
-         false if graph is not (no deadlock)
-*/
-bool graph::knotted()  {
-   return false;
+
+
+// goal is to create an group of objects that point to each other the same way the graph does and then detect loops
+/*
+enum class resourcetype { P, R };
+
+struct PR {
+    int value;
+	resourcetype type; // {P,R}
+	resourcenum index;
+    vector<struct PR*> in;
+	vector<struct PR*> out;
+	bool visited;
+};
+
+void insertPR( struct PR** head,) {
+	struct PR* new_node = new PR; // neclare a new resource
+	new_node->value = new_data; 
+    new_node->in.push_back(); 
+	new_node->out.push_back(); 
+	new_node->visited  = false;
+}
+
+void checkKnots () {
+
+	//
+	// convert graph to a list where each item is a resource and has a list of connected resources
+	// ex:  	0 (P1)	:	0 (P1), 4 (R2)
+	// 		 	1 (P2)	:	1 (P2), 3 (R1), 5 (R3)
+	//
+	
+}*/
+
+
+/* convert adjaceny matrix to adjaceny list */
+std::vector<std::vector<int>> convert(std::vector<std::vector<int>> x) {
+	std::vector<std::vector<int>> adjacencyList(x.size());
+	for ( int ii = 0; ii < x.size(); ii++ )
+		for ( int jj = 0; jj < x[ii].size(); jj++ )
+			if (x[ii][jj] == 1)
+				adjacencyList[ii].push_back(jj);
+    return adjacencyList;
+}
+
+
+
+/* linked list data structure */
+struct Vertex {
+    int data; // contents of node
+    struct Vertex* next; // point to next node
+	struct Vertex* prev; // point to prev node
+	bool visited; // flag used to signal visited
+};
+ 
+void pushLL(struct Vertex** list_head, int new_data) {
+    struct Vertex* new_node = new Vertex; // declare a new vertex
+    new_node->data = new_data; // populate the data for the new node
+    new_node->next = (*list_head); // link back to the old list from the new node
+	new_node->prev = (*list_head); // link back to the old list from the new node
+	new_node->visited  = false;
+    (*list_head) = new_node; // point list head to the new node
+}
+
+bool checkKnot(struct Vertex* v) {
+	
+	//vector<vector<int>> a;
+	//vector<vector<int>> AdjacencyList = convert(m);
+	
+    std::vector<Vertex*> visited; // set to store the visited nodes
+    while ( v != NULL ) { // loop over the nodes in the linked list if the linked list is not empty
+		/* detect if node has been visited; if has, then there is a knot (and a loop) */
+        if ( v->visited ) // find if this node is visited
+            return true; // immediate return
+        /* if node not visited, visit it and then continue */
+        v->visited = true; // mark node as visited
+        v = v->next; // increment linked list position
+    }
+    return false;
+}
+
+
+/* knotted:
+	Perform the knot detection algorithm on the adjacency matrix to detect deadlocks
+	@params:
+		none, uses class-internal data
+	@returns:
+		bool:
+			true iff graph is knotted (deadlock)
+			false if graph is not knotted (no deadlock)
+*/
+bool graph::knotted() {
+	/* Matrix sequel (copy) to preserve original */
+	matrix revolutions = m;
+	struct Vertex* neo = NULL; // neo is the head of the linked list
+	
+	for ( int matrix_row = 0; matrix_row < num_processes + num_resources; matrix_row++ ) {
+		for ( int matrix_col = 0; matrix_col < num_processes + num_resources; matrix_col++ ) {
+			if ( matrix_row == matrix_col ) continue; // do not connect processes and resources to themselves
+			if ( m[matrix_row][matrix_col] == 1 ) {
+				pushLL(&neo,matrix_row);
+			}
+			else {
+				continue;
+			}
+		}
+	}
+	
+	return false;
 }