There is provided an information processing apparatus. A multidimensional input vector is input. For each dimension of the input vector, a function value of a single-variable function with an element of the dimension as a variable is derived, by referring to a lookup table indicating a correspondence between a variable and a function value of the single-variable function. A product of the single-variable functions approximates a function value of a multiple-variable function. For each dimension of the input vector, a product of the function value derived by the derivation unit and a predetermined coefficient corresponding to the dimension is calculated. A value calculated using the total of the products calculated by the product calculation unit for each dimension of the input vector is output as a classification index indicating a class of the input vector.