Hessian computation issue (seems like there is a bug)

[MartinXPN]

The original implementation of DARTS seems to be dividing the (positive - negative) by (2 * eps): Code

return [(x-y).div_(2*R) for x, y in zip(grads_p, grads_n)]

In the implementation of pt.darts, seems like the braces for (2 * eps) are omitted. Which leads to wrong values of hessian and the final expression is evaluated as eps * (positive - negative) / 2:

pt.darts/architect.py

Line 108 in 48e7137

hessian = [(p-n) / 2.*eps for p, n in zip(dalpha_pos, dalpha_neg)]

Shouldn't the expression be (2 * eps) instead of 2 * eps?