$n$ (millions) 1 2 4 8 16 32
Average time (s) $6.1 \pm 0.3$ $12.2 \pm 0.6$ $25.4 \pm 1.1$ $51.4 \pm 2.0$ $117.3 \pm 4.4$ $262.2 \pm 8.7$
SD (s) $2.6$ $5.4$ $9.8$ $17.6$ $37.3$ $76.3$