Modified Cascade-2 Algorithm with Adaptive Slope Sigmoidal Function

Cascade-2 algorithm is a variant of well-known cascade-correlation algorithm that is widely investigated constructive training algorithm for designing cascade feed forward neural networks. This paper proposes a modified Cascade-2 algorithm with adaptive slope sigmoid function (MC2AASF). The algorithm emphasizes on architectural adaptation and functional adaptation during learning. This algorithm is a constructive approach of designing cascade architecture. To achieve functional adaptation, the slope of the sigmoid function is adapted during training. One simple variant is derived from MC2AASF is where the slope parameter of sigmoid function used at the hidden layers’ nodes is fixed to unity. Both the variants are compared to each other on five function approximation tasks. Simulation results show that adaptive slope sigmoid function presents several advantages over standard fixed shape sigmoid function, resulting in increasing flexibility, smoother learning, better generalization performance and better convergence.