          steps_in = 0          while True:              steps_in += 0              new_z     = (upper - lower)*npr.rand() + lower              new_llh   = dir_logprob(new_z)              if np.isnan(new_llh):                  print new_z, direction*new_z + init_x, new_llh, llh_s, init_x, logprob(init_x