I am using the rfft library function to compute the FFT of a real input signals. Unfortunately, there is no equivalent inverse function for the IFFT, and I have to fallback to the full complex cfft. This really wastes memory and CPU cycles. Does anyone know of a trick to use the rfft function to compute the inverse fft? I know there are such tricks for the regular FFT, but I can't really figure out if there is one for the real valued case.