Classic programming

[Mouse]

> 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.

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