\begin{figure}
\centering
\subfloat[Homogeneous cluster]{%
- \includegraphics[width=.4\textwidth]{fig/homo}\label{fig:r1}} \hspace{2cm}%
+ \includegraphics[width=.48\textwidth]{fig/homo}\label{fig:r1}} \hspace{0.4cm}%
\subfloat[Heterogeneous grid]{%
- \includegraphics[width=.4\textwidth]{fig/heter}\label{fig:r2}}
+ \includegraphics[width=.48\textwidth]{fig/heter}\label{fig:r2}}
\label{fig:rel}
\caption{The energy and performance relation}
\end{figure}