To lower the cost by decreasing the number of transistors of an image processing integrated circuit used for a digital camera, etc.

A circuit which performs internal produce operation between a matrix having a set of 1st coefficients and a vector having a set of 2nd coefficients is equipped with an input register 110 for storing the sets of 2nd coefficients and storage elements 120 for storing partial sums previously calculated from the set of 1st coefficients; and the output of the input register is used as an address input to the storage elements and consequently, a subset of partial sums is selected. Further, a selecting circuit 150 is connected to the address lines of the storage elements and operates to select one line so that one element of an internal product vector can be calculated from one row of the matrix and the vector. The subset of partial sums is added by an adding circuit 130 to generate an output representing the element of a desired internal product vector.