Advanced Data Analytics Using Python_ With Machine Learning, Deep Learning and NLP Examples ( 2023)

Chapter 5
Deep Learning and Neural Networks
Calculate the outputs.
o f o net
o
pk
=
k ( pk )
Calculate the error terms for the output units.
o
d pk
o’
( y o
pk
opk ) fk
( net
pk )
= -
Calculate the error terms for the hidden units.
d
h h ’ h o
pj
= fj
( netpj
)ådpk
k
w
o
kj
Update weights on the output layer.
( )= ()+
o
wkj
w o
o
t+
1
kj
t hd
pki pj
Update weights on the hidden layer.
( )= ()+
h
wji
w h
h
t+
1
ji
t hd
pj
x i
Backpropagation Algorithm
Let’s see some code:
class NeuralNetwork(object):
def backpropagate(self,x,y):
"""Return a tuple "(nabla_b, nabla_w)"
representing the
gradient for the cost function C_x. "nabla_b" and
"nabla_w" are layer-by-layer lists of numpy
arrays, similar
104