>>> import numpy as np
>>> reliab = np.random.random((N,N))
>>> reliab = reliab < 0.6
>>> reliab.dtype = np.int8
>>> reliab
array([[0, 0, 0, ..., 1, 0, 1],
[0, 1, 1, ..., 0, 1, 0],
[1, 1, 0, ..., 1, 0, 1],
...,
[0, 1, 0, ..., 1, 1, 1],
[0, 0, 1, ..., 1, 1, 1],
[0, 1, 0, ..., 0, 0, 0]], dtype=int8)