\begin{table}%tB.1
%\centering
\par
\caption{Benchmarking results}\label{table:benchmark}
\begin{tabular}{ccccr}
\hline\hline
\multicolumn{3}{c}{parameters of the 2D~grid} & 1D grid & CPU time\\
extension & $N_{\rm r}$ & $N_{\rm s}$ & extension & of process\\
\hline
0.35--3.0     & 165 & 320 & none & 6167 s.\\
0.35--3.0     & 165 & 320 & \ 0.1167 - 20 & 6008 s.\\
0.1167--5.0 & 294 & 320 & none & 99494 s.\\
\hline
\end{tabular}
\end{table}