usepackage{booktabs}
newcommand{ra}[1]{renewcommand{arraystretch}{#1}}
begin{table*}centering
ra{1.3}
begin{tabular}{@{}rrrrcrrrcrrr@{}}toprule
& multicolumn{3}{c}{$w = 8$} & phantom{abc}& multicolumn{3}{c}{$w = 16$} &
phantom{abc} & multicolumn{3}{c}{$w = 32$}\
cmidrule{2-4} cmidrule{6-8} cmidrule{10-12}
& $t=0$ & $t=1$ & $t=2$ && $t=0$ & $t=1$ & $t=2$ && $t=0$ & $t=1$ & $t=2$\ midrule
$dir=1$\
$c$ & 0.0790 & 0.1692 & 0.2945 && 0.3670 & 0.7187 & 3.1815 && -1.0032 & -1.7104 & -21.7969\
$c$ & -0.8651& 50.0476& 5.9384&& -9.0714& 297.0923& 46.2143&& 4.3590& 34.5809& 76.9167\
$c$ & 124.2756& -50.9612& -14.2721&& 128.2265& -630.5455& -381.0930&& -121.0518& -137.1210& -220.2500\
$dir=0$\
$c$ & 0.0357& 1.2473& 0.2119&& 0.3593& -0.2755& 2.1764&& -1.2998& -3.8202& -1.2784\
$c$ & -17.9048& -37.1111& 8.8591&& -30.7381& -9.5952& -3.0000&& -11.1631& -5.7108& -15.6728\
$c$ & 105.5518& 232.1160& -94.7351&& 100.2497& 141.2778& -259.7326&& 52.5745& 10.1098& -140.2130\
bottomrule
end{tabular}
caption{Caption}
end{table*}