Removing parameter q and bitcount?

[ksahlin]

Posting from discussion in #350 (comment)

Should we remove q and Bitcount() in the randstrobe linking function? Bitcount() uses popcount which seems computationally expensive compared to other link methods (I can show you some results from another study offline). q and Bitcount() were initially introduced to skew the sampling towards shorter seeds, which positively affected the shortest reads (=< 100ish), but with above settings, read lengths 50-100 does not even need this computation.

Note: For read lengths were a proper window is used (150 and up) this may affect the recent parameter optimisations.

[marcelm]

The std::bitset<64>::count() method compiles down to a single POPCNT machine instruction, so it should be quite fast (with the proper compiler options). I can measure it, though.