mpz_trial_div

[Paul Leyland]

> From: Torbjorn Granlund [mailto:tege@swox.com]=20
> "Paul Leyland" <pleyland@microsoft.com> writes:
>=20
>   > Possible , although I think it is unneccessairy (as we have=20
>   > the mpz fn mpz_remove_ui) , consider
>   >=20
>   > d=3Dmpz_trial_div(N,1,10000);
>   > m=3Dmpz_remove_ui(N,N,d);
>   >=20
>   > to cover the multiplicity case
>  =20
>   Fair point.  Thanks.
>=20
> Not sure that would work.  Assume our number has the factor 3^2*5.
> mpz_trial_div might find 3*5 and return that.  mpz_remove_ui
> would then typically leave one factor 3.
>=20
> Since some usages of mpz_trial_div will only care if any factor is
> found, we don't want to slow it down by having it figure out any
> factor multiplicity.

I thought we'd agreed, wrongly it appears, that mpz_trial_div would =
return only prime factors and would always return the smallest such =
(perhaps in the range start--end if those arguments are present).


Paul