\begin{table}%t3
%\centering
\par
\caption{\label{CPU_memory_with_res}Variation in CPU time and memory requirements with resolution
 to simulate CMB maps (unlensed and lensed, oversampling
 factor $\sigma=2$, convolution length $K=4$) using NFFT.}
\begin{tabular}{cccc}
\hline\hline  
nside&
$l_{\max}$&
CPU&
Memory
\\
&
&
time&
requirement
\\
\hline
256&
512&
1 min 12 s&
491 MB
\\
%\hline 
512&
1024&
6 min 8 s&
1.9 GB
\\
%\hline 
1024&
2048&
32 min &
7.6 GB
\\
\hline
\end{tabular}
\end{table}