mpn_gcd[ext] interface details (was: Re: Cofactor canonicalisation of mpn_gcdext)
nisse at lysator.liu.se
Tue May 10 16:39:01 CEST 2011
nisse at lysator.liu.se (Niels Möller) writes:
> I've tried to clarify the mpz_gcdext documentation now. Feel free to
> double check that the conditions on S and T make sense (including the
> borderline cases where one or both inputs are zero). I also edited the
> description of mpz_gcd, to document that we define gcd(0,0) = 0.
And what about normalization of the inputs? The mpn_gcdext documentation
says nothing about normalization. The documentation for mpn_gcd says
that both inputs must be normalized.
I think the actual requirements for both functions are something like
* an < bn is not allowed
* if an == bn, then at least one of a or b must be normalized.
* if an > bn, then b must be normalized
In particular, a > b seems not to be necessary in all cases.
What should the documented requirements be?
Niels Möller. PGP-encrypted email is preferred. Keyid C0B98E26.
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