Torbjorn Granlund <t...@gmplib.org> writes:
> The quotient might need one more bit using this alternative convention.
> Right? We have no great place to return it.
I'd suggest the convention that
Q = -N D^{-1} (mod B^{nn - dn})
R B^{qn} = N + Q D
Then Q is qn = nn - dn limbs, no extra bit, and
0 <= R < B^dn + D
This is the same as for the current redc functions. But I'm leaning
towards putting the returned R at the high end rather than the low, and
with the loop organization you suggest it should then work fine to put Q
at the low end.
Maybe we don't even need bdiv_r then, if
bdiv_qr (up, up, un, dp, dn)
is cheap enough (storing the q limbs at the low end of U).
Ah, and notation. I suggest we write U for the numerator, rather than N,
like we have been doing in some other division work. To avoid confusion
with n used as a limb count (worse when talking than when writing).
Regards,
/Niels
--
Niels Möller. PGP-encrypted email is preferred. Keyid C0B98E26.
Internet email is subject to wholesale government surveillance.
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