RELIABILITY CHARACTERISTICS OF QUADRATIC HEBBIAN-TYPE ASSOCIATIVE MEMORIES IN OPTICAL AND ELECTRONIC NETWORK IMPLEMENTATIONS

The performance capability of quadratic Hebbian-type associative memor ies (QHAM's) in the presence of interconnection faults is examined, an d equations for predicting the probability of direct convergence P-dc given a fraction of interconnection butts are developed. The interconn ection faults considered are the equivalent of open-circuit and short- circuit synaptic interconnections in electronic implementations. Our r esults show that a network with open-circuit interconnection faults ha s a higher probability of direct convergence P-dc than a network with short-circuit interconnection faults, when the fraction of failed inte rconnections p is small and the short-circuit signal G is large. Certa in values of G are found to have only mild effects on network performa nce degradation. Network reliability characteristics taking the genera lization capability into account are also analyzed. All of these resul ts are compared with those of Hebbian-type associative memories (HAM's ), which have linear association network models. Our results indicate that QHAM's have much higher network capacity and fault-tolerance capa bility in the presence of interconnection faults. However, the fault t olerance to input errors in QHAM's is much less than that of HAM's.