title: weird behavior of numba guvectorize
body: <p>I write a function to test numba.guvectorize.  This function takes product of two numpy arrays and compute the sum after first axis, as following:</p>
  <pre><code>from numba import guvectorize, float64
  import numpy as np
  @guvectorize([(float64[:], float64[:], float64)], '(n),(n)-&gt;()')
  def g(x, y, res):
      res = np.sum(x * y)
  </code></pre>
  <p>However, the above guvectorize function returns wrong results as shown below:</p>
  <pre><code>&gt;&gt;&gt; a = np.random.randn(3,4)
  &gt;&gt;&gt; b = np.random.randn(3,4)
  &gt;&gt;&gt; np.sum(a * b, axis=1)
  array([-0.83053829, -0.15221319, -2.27825015])
  &gt;&gt;&gt; g(a, b)
  array([4.67406747e-310, 0.00000000e+000, 1.58101007e-322])
  </code></pre>
  <p>What might be causing this problem?</p>