Re: flags in a bitmap

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.

-- Ruud