of f(un+1.sup.(1), . . . , un+1.sup.(k)) when said fourth storage means stores a coordinate value un+1.sup.(i) (1???i???k) into said fourth storage means; means for controlling said expanding, scanning, reading, storing and calculating means so as to accumulate a value of generated f(un+1.sup.(1), . . . , un+1.sup.(k)) from n=1 to n=N, wherein said N is a predetermined integer greater than 1; and