[PPL-devel] mpz_addmul_ui with ui = 1
Paul.Zimmermann at loria.fr
Fri Jan 30 18:41:51 CET 2009
> (Not directly related)
> At some point I was wondering whether the special representation of 0
> (size==0) should be extended to represent instead small numbers that can
> fit in an integer at most as long as _mp_d. Hard to tell.
an alternate trick is to store in the mpz_t *pointer* a value of the form
p=2k+1, where k is a small integer. Since pointers are usually even, you
can easily distinguish between small integers and GMP integers,
and you obtain the value k = p >> 1. It is also more memory-efficient since
you don't allocate the mpz_t structure. A famous computer algebra system is
using that trick together with GMP.
It might make sense to have another layer on top of mpz with that trick.
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