\resizebox{\textwidth}{!}{%
\begin{tabular}{@{}rrrrrr@{}}
\toprule Threads & Wall (s) & Group ops ($\times 10^6$) & Mops/s & Speed-up & Efficiency \\ \midrule
1 & 8.78 & 229.6 & 26 & 1.00 & 1.00 \\
2 & 3.04 & 155.5 & 51 & 1.96 & 0.98 \\
4 & 1.39 & 139.4 & 100 & 3.83 & 0.96 \\
8 & 0.81 & 158.9 & 195 & 7.46 & 0.93 \\
16 & 0.52 & 200.3 & 388 & 14.83 & 0.93 \\
28 & 0.41 & 235.3 & 578 & 22.11 & 0.79 \\
\bottomrule
\end{tabular}}