there is no copy in my code and

```
In [1]: X = np.random.randn(500, 1000)

In [2]: %timeit np.var(X, axis=0).sum()
1000 loops, best of 3: 1.61 ms per loop

In [3]: %timeit np.sum(X.ravel() * X.ravel())
1000 loops, best of 3: 962 µs per loop
```