Changeset 8734:d84d24c8d5bb for sage/graphs/graph_generators.py

Timestamp:

02/06/08 17:48:21 (5 years ago)

Author:

Emily Kirkman

Branch:

default

Message:

genus improvements and bm planarity

File:

• sage/graphs/graph_generators.py (modified) (1 diff)

sage/graphs/graph_generators.py

@@ -211 +211 @@
     \end{verbatim}
     """
-
+    
+################################################################################
+#   TODO
+#   New -- still needs docstrings / position dictionary
+#   mod?
+################################################################################
+
+    def HoffmanSingletonGraph(self):
+        Q = graph.Graph({'q00':['q01'], 'q01':['q02'], 'q02':['q03'], \
+                                        'q03':['q04'], 'q04':['q00'], \
+                        'q10':['q11'], 'q11':['q12'], 'q12':['q13'], \
+                                        'q13':['q14'], 'q14':['q10'], \
+                        'q20':['q21'], 'q21':['q22'], 'q22':['q23'], \
+                                        'q23':['q24'], 'q24':['q20'], \
+                        'q30':['q31'], 'q31':['q32'], 'q32':['q33'], \
+                                        'q33':['q34'], 'q34':['q30'], \
+                        'q40':['q41'], 'q41':['q42'], 'q42':['q43'], \
+                                        'q43':['q44'], 'q44':['q40'], \
+                        'p00':['p02'], 'p02':['p04'], 'p04':['p01'], \
+                                        'p01':['p03'], 'p03':['p00'], \
+                        'p10':['p12'], 'p12':['p14'], 'p14':['p11'], \
+                                        'p11':['p13'], 'p13':['p10'], \
+                        'p20':['p22'], 'p22':['p24'], 'p24':['p21'], \
+                                        'p21':['p23'], 'p23':['p20'], \
+                        'p30':['p32'], 'p32':['p34'], 'p34':['p31'], \
+                                        'p31':['p33'], 'p33':['p30'], \
+                        'p40':['p42'], 'p42':['p44'], 'p44':['p41'], \
+                                        'p41':['p43'], 'p43':['p40']})
+
+        for j in range(5):
+            for i in range(5):
+                for k in range(5):
+                    con = mod(i+j*k,5)
+                    Q.add_edge(('q%d%d'%(k,con),'p%d%d'%(j,i)))
+                    
+        return Q
+                    
+    
 ################################################################################
 #   Basic Structures