You need to reduce the \linewidth before using \lstinputlisting, otherwise it uses the full normal line width.
You can do this using \parbox or minipage environment. For example the following code places the listing in a paragraph box with 48% of the normal line width. (Some people use \textwidth which is mostly the same.)
\parbox{.48\linewidth}{\lstinputlisting{file.c}}
The reason why your first example doesn't work is that lstlisting is a verbatim environment and therefore not allowed in arguments of other macros. This is because the code is read as part of the argument before \begin{lstlisting} is processed and tells LaTeX to thread the code verbatim!
If you want to have the code in the main file, you could store the listings in a box which is then used in the \subfloat. This requires minipage because \parbox would also read the listing as macro argument.
\documentclass{article}
\usepackage{xcolor}
\usepackage{subfig}
\usepackage{listings}
\lstset{%
language=C,
frame=single,
numbers=left,
numberstyle=\footnotesize,
tabsize=2,
keepspaces=true,
columns=fullflexible,
basicstyle=\ttfamily\scriptsize,
keywordstyle=\color{blue}
}
\newsavebox{\mylistingbox}
\begin{document}
\begin{figure}
\begin{lrbox}{\mylistingbox}%
\begin{minipage}{.45\linewidth}%
\begin{lstlisting}
for(int i = 0 ; i < N ; i++)
for(int j = 0 ; j < N ; j++)
for(int k = 0 ; k < N ; k++)
c[i][j] += a[i][k] * b[k][j];
\end{lstlisting}%
\end{minipage}%
\end{lrbox}%
%
\subfloat[small code]{\usebox{\mylistingbox}}%
%
\hfill
%
\begin{lrbox}{\mylistingbox}%
\begin{minipage}{.45\linewidth}%
\begin{lstlisting}
for(int ii = 0 ; ii < N ; ii+=B) {
for(int jj = 0 ; jj < N ; jj+=B) {
for(int kk = 0 ; kk < N ; kk+=B) {
for(int i = ii ; i < ii + B ; i++) {
for(int k = kk ; k < kk + B ; k++){
c_i = c[i];
a_ik = a[i][k];
b_k = b[k];
for(int j = jj ; j < jj + B ; j+=2){
c_i[j] += a_ik * b_k[j];
c_i[j+1] += a_ik * b_k[j+1];
}
}
}
}
}
}
\end{lstlisting}%
\end{minipage}%
\end{lrbox}%
%
\subfloat[Larger code]{\usebox{\mylistingbox}}%
\end{figure}
\end{document}
I reduces the font size here to fit both on the normal text width. For figures you could also extend it in the margin using the technique shown be me in Center figure that is wider than \textwidth and Place figures side by side, spill into outer margin.
In your case either use two box registers and then:
\makebox[1.2\textwidth]{\subfloat[Shorter code]{\usebox{\mylistingboxa}}\hfill\subfloat[Larger code]{\usebox{\mylistingboxb}}}
or add the following equivalent lines before and after the whole subfloat related code:
\hbox to 1.2\textwidth\bgroup\hss
% the whole box saving and \subfloat code above
\hss\egroup
If you enclose your text in \shortstack{...}, you'll get the line breaks:
\documentclass{article}
\usepackage{subfig}
\begin{document}
\begin{figure}[h]
\centering
\subfloat[a]{\shortstack{A\\\texttt{This is a test}}}
\subfloat[b]{B}
\end{figure}
\end{document}
The alignment can be adjusted using the optional argument. \shortstack[l]{...} will align your text on the left, \shortstack[r]{...} on the right.
Best Answer
This is not really an answer - I don't know what the problem you are having is! It is really hard to help with this sort of thing! It's very strange that you can plot them when not in the
subfloat- it implies there is no package missing for rendering graphics generally.I thought it might be useful for me to send you some code that works for me so you can see if there is a difference in what you are doing or how you are loading the packages. Obviously replace my
.epsfiles with your own!If this doesn't point you in the right direction, please change your question to include a minimal working example - i.e. something that can be compiled by someone else, as it may help someone to spot some incompatibility somewhere in your preamble.