Soboleva modified hyperbolic tangent

The Soboleva modified hyperbolic tangent, also known as Soboleva modified hyperbolic tangent activation function, is a special S-shaped function based on the hyperbolic tangent, given by :\operatorname{mtanh}x = \rac {e^{ax} - e^{-bx}} {e^{cx} + e^{-dx}} This function was originally proposed as "modified hyperbolic tangent" by Elena V. Soboleva as a utility function for multi-objective optimization and choice modelling in decision-making.