Method and apparatus for affine CPMV or ALF refinement are mentioned. According to this method, statistical data associated with the affine CPMV or ALF refinement are collected over a picture area. Updated parameters for the affine CPMV refinement or the ALF refinement are then derived based on the statistical data, where a process to derive the updated parameters includes performing multiplication using a reduced-precision multiplier for the statistical data. The reduced-precision multiplier truncates at least one bit of the mantissa part. In another embodiment, the process to derive the updated parameters includes performing reciprocal for the statistical data using a lookup table with (m−k)-bit input by truncating k bits from the m-bit mantissa part, and contents of the lookup table includes m-bit outputs. m and k are positive integers.