Source Code for Module datk.core.networks

 1  from distalgs import Network 
 2  import math 
 3  import random 
 4  import pdb 
 5   
 6 -class Unidirectional_Ring(Network): 
 7      """A Network of n Processes arranged in a ring. Each edge is directed 
 8          from a Process to its clockwise neighbor, that is, messages can 
 9          only be sent in a clockwise direction.""" 
10 -    def __init__(self, n, index_to_UID = None): 
11          Network.__init__(self, n, index_to_UID) 
12          for i in range(n): 
13              self[i].link_to(self[(i+1)%n]) 
14   
15 -class Bidirectional_Ring(Network): 
16      """A Network of n Processes arranged in a ring. Each edge between a Process 
17          and its neighbor is undirected, that is, messages can be sent in both 
18          the clockwise and the counterclockwise directions.""" 
19 -    def __init__(self, n, index_to_UID = None): 
20          Network.__init__(self, n, index_to_UID) 
21          for i in range(n): 
22              self[i].link_to(self[(i+1)%n]) 
23              self[i].link_to(self[(i-1)%n]) 
24   
25 -class Unidirectional_Line(Network): 
26      """A Network of n Processes arranged in a line. Each edge is directed 
27          from a Process to its clockwise neighbor, that is, messages can 
28          only be sent in a clockwise direction.""" 
29 -    def __init__(self, n, index_to_UID = None): 
30          Network.__init__(self, n, index_to_UID) 
31          for i in range(n-1): 
32              self[i].link_to(self[(i+1)]) 
33   
34 -class Bidirectional_Line(Network): 
35      """A Network of n Processes arranged in a line. Each edge between a Process 
36          and its neighbor is undirected, that is, messages can be sent in both 
37          the clockwise and the counterclockwise directions.""" 
38 -    def __init__(self, n, index_to_UID = None): 
39          Network.__init__(self, n, index_to_UID) 
40          for i in range(n-1): 
41              self[i].bi_link(self[(i+1)]) 
42   
43 -class Complete_Graph(Network): 
44      """A Network of n Processes arranged at the vertices of a Complete undirected 
45      graph of size n.""" 
46 -    def __init__(self, n, index_to_UID = None): 
47          Network.__init__(self, n, index_to_UID) 
48          for i in range(n-1): 
49              for j in range(i+1,n): 
50                  self[i].bi_link(self[j]) 
51   
52 -class Random_Line_Network(Network): 
53      """A Network of n processes arranged randomly at the vertices of a connected 
54      undirected line graph of size n. Additional pairs of vertices are connected 
55      at random with a probability that is inversely proportional to the difference 
56      in their positions on the line. 
57   
58      For example, the Process at index 3 is guaranteed to be connected to the Process 
59      at index 4, and is more likely to be connected to the Process at index 5 than to 
60      the Process at index 8. """ 
61 -    def __init__(self, n, sparsity = 1): 
62          """ 
63          sparsity = 0 --> a Complete_Graph(n) 
64          sparsity = infinity --> a Bidirectional_Line(n) 
65          """ 
66          Network.__init__(self, n) 
67          def sigmoid(t): 
68              if t > 100: return 1. 
69              if t < -100: return 0. 
70              return 1./(1.+math.exp(-t)) 
71   
72          for i in range(n-1): 
73              self[i].bi_link(self[(i+1)]) 
74              for j in range(i+2, n): 
75                  if random.random() < sigmoid( -((i-j)**2)/(float(n)**0.5)*sparsity)  *2.: 
76                      self[i].bi_link(self[j]) 
77