sample_z for DCGAN

#should be normal distribution
def sample_z(dim_z, num_batch):
    mu = 0
    sigma = 1
#    s = np.random.normal(mu, sigma, num_batch*dim_z)
    s = np.random.normal(loc=0.0, scale=1.0, size=(num_batch, dim_z)).astype(np.float32)
    samples = s.reshape(num_batch, 1, 1, dim_z)

    return samples