zeroDivisionError using cg_solve

[duncan]

here's the error

ERROR: test_expand_search3 (__main__.Test_Least_Squares)
----------------------------------------------------------------------

Traceback (most recent call last):
  File "I:\inundation\fit_interpolate\benchmark_least_squares.py", lin
e 147, in test_expand_search3
    calc = interp.fit_points(point_atts )
  File "I:\inundation\pyvolution\least_squares.py", line 881, in fit_p
oints
    return self.fit(z)
  File "I:\inundation\pyvolution\least_squares.py", line 869, in fit
    return conjugate_gradient(self.B, Atz, Atz, imax=2*len(Atz) )
  File "I:\inundation\pyvolution\cg_solve.py", line 55, in conjugate_g
radient
    alpha = rTr/dot(d,q)
ZeroDivisionError: float division

see show_cg_bug.py (changeset:1959)