Re: flags in a bitmap

["Ruud H.G. van Tol" <rvtol@isolution.nl>]

On 2025-07-05 15:40, Ruud H.G. van Tol wrote:
> On 2025-07-04 16:04, Ruud H.G. van Tol wrote:
> > On 2025-07-04 10:06, Bill Allombert wrote:
> > > I can do a git branch if you want to test:
> > >
> > > ? install(bitset,vWL)
> > > ? x=2^(2^20);
> > > ? forprime(p=2,2^20,bitset(~x,p))
> > >   ***   last result computed in 8 ms.
> > > ? my(S=0);for(i=0,2^20-1,S+=bittest(x,i));S
> > > %16 = 82025
> > >   ***   last result computed in 159 ms.
> >
> > To set a base, first a pure-pari test:
> >
> > ? { my( bitset(~v,p)=v[1]=bitor(v[1],2^p), L=2^20, x=[2^L], s=0 );
> >     forprime(p=2,L-1, bitset(~x,p));
> >     for(i=0,L-1, s+=bittest(x[1],i));
> >     print(s);
> > }
> >
> > 82025
> > cpu time = 1,857 ms, real time = 1,861 ms.
>
> Now similar on the freshly patched gp:
>
> ? { my( L=2^20, x=2^L, s=0 );
>     forprime(p=2,L-1, bitset(~x,p));
>     for(i=0,L-1, s+=bittest(x,i));
>     print(s);
> }
>
> 82025
> time = 135 ms.

On the latest code:

{ my( bitset(~v,p)=v[1]=bitor(v[1],2^p), L=2^20, x=[2^L], s=0 );
    forprime(p=2,L-1, bitset(~x,p));
    for(i=0,L-1, s+=bittest(x[1],i));
    print(s);
}

82025
time = 1,005 ms.


{ my( L=2^20, x=2^L, s=0 );
    forprime(p=2,L-1, bitset(~x,p));
    for(i=0,L-1, s+=bittest(x,i));
    print(s);
}
82025
time = 128 ms.

-- Ruud (without gmp)