Re: Implementation of forprime() and unextprime()

[Bill Allombert <Bill.Allombert@math.u-bordeaux.fr>]

On Sat, Jan 13, 2024 at 01:45:43AM -0800, Ilya Zakharevich wrote:
> On Sat, Jan 13, 2024 at 12:01:52AM +0100, Bill Allombert wrote:
> > If you like to look at the code, make sure to look at the git master branch,
> > otherwise this is a bit pointless.
> 
> This remark is also a tiny bit pointless without giving the HTTP url
> to browse…   ⅞ ;―]

I was quite sure you could find it yourself.
See README-git in the pari distribution.

> > In particular, we have changed primelimit to 2^20 in PARI 2.16.1.
> 
> Any reason why this particular value?

Yes, we store the product of all primes < 2^i for all i less than 20,
which we can then use for sieving (for factor(,0))

? for(i=1,1000,factor(random(2^1000),2^18))
With 2.15.4
  ***   last result computed in 1,865 ms.
With 2.16.1
  ***   last result computed in 124 ms.

Cheers,
Bill