feat: add graphutils to detect cyclical process dependencies

Author: Michael Hammann

supervisor/graphutils.py

@@ -0,0 +1,36 @@
+from collections import defaultdict
+ 
+class Graph():
+    def __init__(self,vertices):
+        self.graph = defaultdict(list)
+        self.V = vertices
+ 
+    def addEdge(self,u,v):
+        self.graph[u].append(v)
+
+    def cyclic(self):
+        """Return True if the directed graph has a cycle.
+        The graph must be represented as a dictionary mapping vertices to
+        iterables of neighbouring vertices. For example:
+
+        >>> cyclic({1: (2,), 2: (3,), 3: (1,)})
+        True
+        >>> cyclic({1: (2,), 2: (3,), 3: (4,)})
+        False
+
+        """
+        path = set()
+        visited = set()
+
+        def visit(vertex):
+            if vertex in visited:
+                return False
+            visited.add(vertex)
+            path.add(vertex)
+            for neighbour in self.graph.get(vertex, ()):
+                if neighbour in path or visit(neighbour):
+                    return True
+            path.remove(vertex)
+            return False
+
+        return any(visit(v) for v in self.graph)