fcis_train_chain.py 文件源码

def _smooth_l1_loss(x, t, in_weight, sigma):
    sigma2 = sigma ** 2
    diff = in_weight * (x - t)
    abs_diff = F.absolute(diff)
    flag = (abs_diff.array < (1. / sigma2)).astype(np.float32)

    y = (flag * (sigma2 / 2.) * F.square(diff) +
         (1 - flag) * (abs_diff - 0.5 / sigma2))

    return F.sum(y)