Added graph creation and functions in base class and lower level modules.

compiler/characterizer/graph_util.py

@@ -0,0 +1,69 @@
+import os
+from collections import defaultdict
+
+import gdsMill
+import tech
+import math
+import globals
+import debug
+from vector import vector
+from pin_layout import pin_layout
+
+class graph():
+    """Implements a directed graph"""
+    
+    def __init__(self):
+        self.graph = defaultdict(list)
+
+    def add_edge(self, u, v):
+        """Adds edge to graph. Nodes added as well if they do not exist."""
+        if v not in self.graph[u]:
+            self.graph[u].append(v)
+
+    def add_node(self, u):
+        """Add node to graph with no edges"""
+        if not u in self.graph:
+            self.graph[u] = []
+            
+    def remove_edges(self, node):
+        """Helper function to remove edges, useful for removing vdd/gnd"""
+        self.graph[node] = []    
+            
+    def printAllPaths(self,s, d): 
+  
+        # Mark all the vertices as not visited 
+        visited = set()
+  
+        # Create an array to store paths 
+        path = [] 
+        self.path_count = 0
+  
+        # Call the recursive helper function to print all paths 
+        self.printAllPathsUtil(s, d,visited, path)     
+        debug.info(1, "Paths found={}".format(self.path_count))
+            
+    def printAllPathsUtil(self, u, d, visited, path): 
+  
+        # Mark the current node as visited and store in path 
+        visited.add(u)
+        path.append(u) 
+  
+        # If current vertex is same as destination, then print 
+        # current path[] 
+        if u == d: 
+            debug.info(1,"{}".format(path)) 
+            self.path_count+=1
+        else: 
+            # If current vertex is not destination 
+            #Recur for all the vertices adjacent to this vertex 
+            for i in self.graph[u]: 
+                if i not in visited: 
+                    self.printAllPathsUtil(i, d, visited, path) 
+                      
+        # Remove current vertex from path[] and mark it as unvisited 
+        path.pop() 
+        visited.remove(u)        
+            
+    def __str__(self):
+        """ override print function output """
+        return "Nodes: {}\nEdges:{} ".format(list(self.graph), self.graph)