16-bit kogge-stone adder Verilog implementation.

In computing, the Kogge–Stone adder is a parallel prefix form carry look-ahead adder. 

The Kogge–Stone adder takes more area to implement than the Brent–Kung adder, but has a lower fan-out at each stage, which increases performance for typical CMOS process nodes. However, wiring congestion is often a problem for Kogge–Stone adders. 

source : https://en.wikipedia.org/wiki/Kogge%E2%80%93Stone_adder