Thanks for you!
I draw a images more clearly.
In hypothesis 1/top image, the layer4_1 and layer4_2 share the same parameters, which is the same in layer4 in hypothesis 2/down image.
I update layer4_1 and layer4_2 alternatively in hypothesis 1/top image and I update layer4 in hypothesis 2/down image twice to get the the amount of updates compared to hypothesis 1.
And I promise the data are all the same.