One real function is to find every set bit in vector A, then set the corresponding bit(s) in vector B

I deduce, therefore, that A is smaller than (or equal to) B.

I would expect you would observe a further siginificant increase in speed if you used the gmp library for that function - either accessing that library via Inline::C, or using one of the existing perl extensions (Math::GMP, Math::GMPz). Using the gmp library in C, the code to perform the above task would be something like: 
size = mpz_sizeinbase(A, 2);
for(i = 0; i < size; i++) {
   if(mpz_tstbit(A, i)) mpz_setbit(B,i);
}

[download]
(and the same approach when using the aforementioned perl modules.)

Of course, you might consider the involvement of the gmp library to be cheating - depending upon the extent to which you want to handle things yourself :-)

Cheers,
Rob

In reply to Re^7: Bit vector fiddling with Inline C by syphilis
in thread Bit vector fiddling with Inline C by oxone

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