I knew counting bits individually was slow, but it never really mattered
until now. However, I didn't expect such a dramatic boost just by going
to mapping bytes to bit counts. 16-bit words would be faster still, but
the 64kB lookup table would probably start hurting cache performance,
and 32-bit words (4GB table) definitely would ruin the cache. The
universe isn't big enough for 64-bits :)
Having set_expand exposed is useful for loading data into a set.
However, it turns out there was a bug in its size calculation in that
when the requested set size was a multiple of SET_BITS (and greater than
the current set size), the new set size one be SET_BITS larger than
requested. There's now some tests for this :)
set_bits_t is now 64 bits for x86_64 machines (in linux, anyway). This gave
qfvis a huge speed boost: from ~815s to ~720s.
Also, expose some of the set internals so custom set operators can be
created.
Getting everything right with an enum proved to be too difficult if not
impossible. Also use better tests for equivalence and intersection.
Many more tests have been added. All pass :)
