(push using geometric pre-reserve) vs ((exact-per-element growth + concat) x N times) vs (exact reserve and then add the elements) . Being the third case analog

(push using geometric pre-reserve) vs ((exact-per-element growth + concat) x N times) vs (exact reserve and then add the elements) . Being the third case analogous to the "builder" concatenation technique (resize the element to receive the concatenation for the final size, and copy the N strings into the resized space). The concat privitive not doing geometric pre-reserve is not a bad thing, in my opinion, even if in this case is slower, because of memory saving for the most frequent case. Of course, the concat operation should be always efficient when destination container has enough space.