Re: nonprime(n)

[Jean-Luc Arnaud <jean-luc@filmsons.com>]

Le 05/02/2024 à 18:47, Bill Allombert a écrit :
> On Mon, Feb 05, 2024 at 06:41:35PM +0100, Jean-Luc Arnaud wrote:
> > Le 03/02/2024 à 18:33, Ruud H.G. van Tol a écrit :
> > > for(n=1,2^18, prime(n));
> > Hi Ruud,
> >
> > What kind of PC or Mac Monster do you own, which is able to calculate:
> >
> >      ? for(n=1,2^18, prime(n));
> >      cpu time = 1,516 ms, real time = 1,521 ms.
> >
> > in 1.5 s, where my iMac does it in ... close to 4min? 😭😭
> >
> >      cpu time = 3min, 38,881 ms, real time = 3min, 56,939 ms.
> The trick is to start GP with -p257M so you already have the
> prime number availabkle
>
> %gp -q -p 257M
> ? for(n=1,2^18, prime(n));
> ? ##
>    ***   last result: cpu time 1,198 ms, real time 1,198 ms.
>
> Cheers,
> Bill.
Ok, with -q -p257M, I got:

    ? for(n=1,2^18, prime(n));
    cpu time = 1,157 ms, real time = 1,158 ms.

    ? for(n=1,2^18, nonprime(n));
    cpu time = 1,792 ms, real time = 1,794 ms.


    ? for(n=1,2^19, prime(n));
    cpu time = 6,690 ms, real time = 6,695 ms.

    ? for(n=1,2^19, nonprime(n));
    cpu time = 4,087 ms, real time = 4,090 ms.


Note that parfor works, too, without -q -p257M:

    ? parfor(n=1,2^19, prime(n));
    cpu time = 38min, 46,353 ms, real time = 2min, 27,849 ms.

    ? export(nonprime);parfor(n=1,2^19, nonprime(n));
    cpu time = 8,607 ms, real time = 1,009 ms.


and with -q -p257M:

    ? parfor(n=1,2^19, prime(n));
    cpu time = 12,721 ms, real time = 1,290 ms.

    ? export(nonprime);parfor(n=1,2^19, nonprime(n));
    cpu time = 8,653 ms, real time = 1,011 ms.


In addition, gp -q -p257M needs almost 1 GB RAM, whereas gp needs 7.2 MB.

If of any interest...

Jean-Luc