Re: checking against signed integer overflow

[Paul Eggert]

On 12/5/20 7:36 PM, Bruno Haible wrote:

> (*) The function did a Montgomery multiplication mod p, where p > 2^128; this
> is the workhorse of the arithmetic on an elliptic curve.
Small world. I worked with the late Peter Montgomery circa 1980; he was down the 
hall from me at System Development Corporation in Santa Monica, and was 
developing what led to Montgomery multiplication, though due to security 
regulations I never really knew what he was up to at the time. He was such a 
nice guy, with a great attitude, and was a pleasure to be around.

Peter was famous for his mastery of the CDC 7600, the fastest computer in the 
world in the early 1970s. If you wanted fast math code, he was *the guy*. And 
the CDC 7600 used 60-bit ones'-complement integer arithmetic, so this email 
isn't *entirely* a digression.