\begin{table}%t4
%\centering
\par
\caption{\label{CPU_memory_with_conv}Variation in the CPU time and memory requirements with the
 convolution length $K$ to simulate a CMB map (both unlensed and lensed,
 with nside = 1024, $l_{\max}=2048$) using NFFT.}
\begin{tabular}{cccc}
\hline\hline 
Oversampling&
Convolution&
CPU&
Memory
\\
factor&
length&
time&
requirement
\\
$\left(\sigma\right)$&
$\left(K\right)$&
&
\\
\hline
2&
4&
32 min&
7.6 GB
\\
%\hline 
2&
6&
45 min&
8.4 GB
\\
%\hline 
2&
8&
60 min&
9.1 GB
\\
\hline
\end{tabular}
\end{table}