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Re: Suggestion For mpz_sizeinbase() Function

From: Kevin Ryde
Subject: Re: Suggestion For mpz_sizeinbase() Function
Date: 17 Jul 2001 11:20:34 +1000
User-agent: Gnus/5.0808 (Gnus v5.8.8) Emacs/20.5

"David T. Ashley" <address@hidden> writes:
> It depends on the assumptions about the platforms.  Can they all divide
> integers?  And the least capable platform--what sizes of integers can it
> divide?

Alas division as such is usually slow, and sometimes doesn't exist at
all natively (alpha, itanium).

A multiply-by-inverse is often best if an inverse can be
pre-calculated (as in this case), or will be used a few times.  It
ends up roughly equivalent to 2 muls, and finds good use in
mpn_divrem_1 in particular.  See "Division by Invariant Integers"
paper in the references in the manual, and udiv_qrnnd_preinv in

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