> Quite recently, I have a requirement to square very large unsigned > integers up to one billion bits [...]
Are you aware of faster-than-n^2 multiplication algorithms like Karatsuba, Toom-Cook, or Schönhage-Strassen? If not, you might want to look into them; if you're working with numbers that large, such things can make the difference between "practical" and "might finish before the heat-death of the universe if we're lucky"...though, admittedly, for just simple squaring it's probably not all _that_ bad. /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTML mo...@rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B