add exhaustive check of independent sets.

indset.py

@@ -1,8 +1,20 @@
 import networkx as nx
-import matplotlib.pyplot as plt
+#import matplotlib.pyplot as plt
+import itertools
 from random import choice
 
 
+#todo: see if there is a speed difference
+#between constructing a set of the neighbors and the nodes
+#then computing the intersection vs just using
+#list comprehension on the lists themselves.
+def isIndependent(graph, nodeSet):
+    #print nodeSet
+    for n in nodeSet:
+        if len(set(graph.neighbors(n)) & nodeSet) != 0:
+            return False
+
+    return True
 
 def setUtil(graph):
     if graph.number_of_nodes() == 0:#G is empty
@@ -20,11 +32,11 @@ def setUtil(graph):
     if len(v_one_degree) != 0:
         v = choice(v_one_degree)
         w = graph.copy().neighbors(v)[0]
-        w_neighborhood = graph.copy().neighbors(w) + [w]
+        w_neighborhood = graph.neighbors(w) + [w]
         withW = graph.copy()
         withW.remove_nodes_from(w_neighborhood)
 
-        v_neighborhood = graph.copy().neighbors(v) + [v]
+        v_neighborhood = graph.neighbors(v) + [v]
         withV = graph.copy()
         withV.remove_nodes_from(v_neighborhood)
 
@@ -35,7 +47,7 @@ def setUtil(graph):
     #G has a vertex degree >=3
     if len(v_three_or_more_degree) != 0:
         v = choice(v_three_or_more_degree)
-        neighborhood = graph.copy().neighbors(v) + [v]
+        neighborhood = graph.neighbors(v) + [v]
 
         withV = graph.copy()
         withV.remove_nodes_from(neighborhood)
@@ -50,9 +62,9 @@ def setUtil(graph):
         v = choice(graph.nodes())
         #should be exactly two of these
         u,w = graph.copy().neighbors(v)
-        u_neighborhood = graph.copy().neighbors(u) + [u]
-        v_neighborhood = graph.copy().neighbors(v) + [v]
-        w_neighborhood = graph.copy().neighbors(w) + [w]
+        u_neighborhood = graph.neighbors(u) + [u]
+        v_neighborhood = graph.neighbors(v) + [v]
+        w_neighborhood = graph.neighbors(w) + [w]
 
         withU = graph.copy()
         withU.remove_nodes_from(u_neighborhood)
@@ -66,10 +78,25 @@ def setUtil(graph):
 
         return max(1+setUtil(withU), 1+setUtil(withV), 1+setUtil(withW))
 
-G = nx.cycle_graph(5)
+G = nx.cycle_graph(7)
 S = nx.strong_product(G, G)
 
-G2 = nx.cycle_graph(7)
-S2 = nx.strong_product(G2, G2)
+# a = nx.convert.to_dict_of_lists(G)
+
+# print [r for r in a]
+
+for n in itertools.combinations(S.nodes(), setUtil(S)):
+    if isIndependent(S,set(n)):
+        print n
+
+
+
+#for s in c:
+#    print isIndependent(G, s)
+
+# G2 = nx.cycle_graph(7)
+# S2 = nx.strong_product(G2, G2)
+
+
 
-print setUtil(S)
+#print setUtil(S2)