
7.5 learning paradigMs 205
Where:
∂
∂
=−
()
−
()
E
w
OdOOw
ji
jjjjji
21
(11)
Furthermore, using Equation (7), we suppose that there are inputs u
k
into the neuron with v
ik
:
(12)
Similarly, more layers can be added. For practical reasons, ANNs imple-
menting the back-propagation algorithm do not have too many layers, since
the time for training the networks grows exponentially.
The back-propagation algorithm suffers from a typical problem when-
ever the gradient method is employed to minimize a target function. Nor-
mally, the error E starts with the large value and slowly decreases as iterations
proceed. If E is a smooth function, ...