C++ Neural Networks and Fuzzy Logic: Preface

Asynchronous Update

The Hopfield network is a recurrent network. This means that outputs from the network are fed back as

inputs. This is not apparent from Figure 1.3, but is clearly seen from Figure 1.4.

Figure 1.4

  Feedback in the Hopfield network.

The Hopfield network always stabilizes to a fixed point. There is a very important detail regarding the

Hopfield network to achieve this stability. In the examples thus far, we have not had a problem getting a

stable output from the network, so we have not presented this detail of network operation. This detail is the

need to update the network asynchronously. This means that changes do not occur simultaneously to outputs

that are fed back as inputs, but rather occur for one vector component at a time. The true operation of the

Hopfield network follows the procedure below for input vector Invec and output vector Outvec: