Complex numbers product using only three multiplications

Question

We do complex number multiplication as follows:

(a + i * b) * (c + i * d) = (a * c - b * d) + i * (a * d + b * c)

The real and imaginary pa

Answer 1

Winograd is practically correct if you want to do a mixture of adds and multiplies. But if you only want to do complex multiplies, work in logpolar representation that multiplication is just adding logamplitudes and angles; but of course logpolar adds are hard! Logpolar can be nice for limited precision FFTs on e.g. 8 bit logamplitude +j8 bit phase on microprocessors.