gistfile1.py

#!/usr/bin/env python
# HITS (on memory)
# using von Neumann kernel

from numpy import *
from numpy import ones
from numpy.linalg import *

STEP = 500

class HITS():
    def __init__(self, adj_matrix):
        self._adj = adj_matrix

    def calc_vnk(self):
        cit_matrix = dot(self._adj.T, self._adj)
        sz = size(cit_matrix[0])
        beta = 1. / sorted( eigvals( cit_matrix ), reverse=True )[0] -0.001
        mul_tmp = beta * cit_matrix
        tmp = mul_tmp
        ret = ones( (sz,sz) ) + mul_tmp
        for i in range(STEP):
            tmp = dot(tmp, mul_tmp)
            ret += tmp
        return dot(cit_matrix, ret)


adj = array( ((0, 0, 1, 1),
              (0, 0, 1, 1),
              (1, 1, 0, 0),
              (0, 1, 1, 0)) )

hits = HITS(adj)
matrix = hits.calc_vnk()

print "matrix:"
print matrix
print "auth:", matrix[0,:]