Neural Networks - Algorithms, Applications,and ... - Csbdu.in

1.3 ANS Simulation 37not know (or care) whether the connection list implements a fully interconnectednetwork or a sparsely connected network. It simply follows the list to the end,then moves on to the next unit and repeats the process.1.3.5 Extension of ANS Data StructuresNow that we have defined two possible structures for performing the inputcomputations at each node in the network, we can extend these basic structuresto implement an entire network. Since the array structure tends to be moreefficient for computing input values at run time on most computers, we willimplement the connection weights and node outputs as dynamically allocatedarrays. Similarly, any additional parameters required by the different networksand associated with individual connections will also be modeled as arrays thatcoexist with the connection-weights arrays.Now we must provide a higher-level structure to enable us to access thevarious instances of these arrays in a logical and efficient manner. We can easilycreate an adequate model for our integrated network structure if we adopt a fewassumptions about how information is processed in a "standard" neural network:• Units in the network can always be coerced into layers of units havingsimilar characteristics, even if there is only one unit in some layers.• All units in any layer must be processed completely before the CPU canbegin simulating units in any other layer.• The number of layers that our network simulator will support is indefinite,limited only by the amount of memory available.• The processing done at each layer will usually involve the input connectionsto a node, and will only rarely involve output connections from a node (seeChapter 3 for an exception to this assumption).Based on these assumptions, let us presume that the layer will be the networkstructure that binds the units together. Then, a layer will consist of arecord that contains pointers to the various arrays that store the informationabout the nodes on that layer. Such a layer model is presented in Figure 1.22.Notice that, whereas the layer record will locate the node output array directly,the connection arrays are accessed indirectly through an intermediate array ofpointers. The reason for this intermediate structure is again related to our desireto optimize the data structures for efficient computation of the net 4 value foreach node. Since each node on the layer will produce exactly one output, theoutputs for all the nodes on any layer can be stored in a single array. However,each node will also have many input connections, each with weights unique tothat node. We must therefore construct our data structures to allow input-weightarrays to be identified uniquely with specific nodes on the layer. The intermediateweight-pointer array satisfies the need to associate input weights withthe appropriate node (via the position of the pointer in the intermediate array),