Re: void mpz_set_GEN(mpz_ptr z, GEN x) and GEN mpz_get_GEN(mpz_srcptr z)

[hermann@stamm-wilbrandt.de]

On 2023-06-19 21:56, hermann@stamm-wilbrandt.de wrote:
> On 2023-06-19 10:04, Andreas Enge wrote:
> > you may be interested in the PariTwine project:
> >    https://www.multiprecision.org/paritwine/home.html
> > which provides a link to GMP, but also MPFR, MPC, FLINT/ARB and CMH.
> > There are conversion functions and helpers to call functions of the
> > other libraries from GP scripts.
> Thanks, that code looks like the posting I pointed to.
> ...
> The basic difference of pointed to posting and paritwine conversion 
> code
> https://github.com/Hermann-SW/RSA_numbers_factored/blob/main/c%2B%2B/sqrtm1.smallest_known_1million_digit_prime.cc
>
> to new version of based on Karim's code is that the first two create a
> copy using realloc2(), while Karim's code does a shallow copy:
> https://github.com/Hermann-SW/RSA_numbers_factored/blob/main/c%2B%2B/sqrtm1.smallest_known_1million_digit_prime.cc#L30
Today I found another small difference, this time in Karim's 
mpz2GEN(mpz_t X).
That function had a bug in processing X being 0.
I noticed this today when working with cgal4gp repo, this is the fix 
commit:
https://github.com/Hermann-SW/cgal4gp/commit/3b519d4e6e245188f3319059fec6f4602cd86d79


While working with cgal4gp "get_all_build_directions()"
https://github.com/Hermann-SW/cgal4gp?tab=readme-ov-file#ternary-quadratic-form-width

I noticed that too many directions might get returned and created new 
issue:
https://github.com/CGAL/cgal/issues/8358

Nice how easy this can be corrected in GP with "Set(...)" workaround:

        print("optimal solutions: ",get_number_of_optimal_solutions());
        get_all_build_directions(dir);
        print("workaround(all build directions): ", 
Set([d/gcd(d)*if(d[1]<0,-1,1) | d<-dir]));

The output shows discrepancy between CGAL 
"get_number_of_optimal_solutions()"
and "Set([d/gcd(d)*if(d[1]<0,-1,1) | d<-dir])" workaround for unique 
directions:

optimal solutions: 8
workaround(all build directions): [[10, 112, -5]]


Regards,

Hermann.