def randomTree(G):
# assumption: nodes labelled 0 to n-1
n = len(G)
nodes = np.arange(n)
visited = np.zeros(n, dtype=np.bool)
hitTime = np.zeros(n, dtype=np.int)
x = [np.random.choice(nodes)]
visited[x[0]] = True
hitTime[x[0]] = 0
# random walk
i = 0
while (visited.sum() < n):
nbh = G.GetNeighbours(x[i])
r = np.random.choice(nbh)
if (not visited[r]):
hitTime[r] = i + 1
visited[r] = True
# end if
x = x + [r]
i = i + 1
# end random walk
T = Graph(n)
for i in range(n):
if (i == x[0]):
continue
p, q = hitTime[i] - 1, hitTime[i]
T.AddEdge(x[p], x[q])
return T
def Sample(self):
p = np.random.permutation(self._n)
T = Graph(self._n)
for i in range(self._n - 1):
T.AddEdge(p[i], p[i + 1])
return T
