On 12 Jun 2025, at 21:56, Joaquin M López Muñoz via Boost <boost@lists.boost.org <mailto:boost@lists.boost.org>> wrote:

For branchful lookup, a cost model for mixed lookup would be

P*M*(A*K) + (1-P)*M*C

where P is the percentange of successful lookups and M is an extra cost factor on top of the non-mixed approach due to branch mispredictions.

I agree this effect will affect measurements to the point that it will be decisive. Lets just agree on the obvious: an extra 64bit multiplication cannot affect the running time of any program on modern CPUs. The multiplier is from THE ART OF COMPUTER PROGRAMMING by D. Knuth, volume II, page 108. Regards, Kostas