/// @@prerequisite opérations élémentaires 
A=sprand(100,100,0.1); /// \sleftarrow {\begin{minipage}[t]{6cm}{\nf{}a \verb-(100,100)- sparse matrix with \verb+10%+ of\\ nonzero values} \end{minipage}}
whos('-type','sparse') /// \sleftarrow{\normalfont check used memory}
B=full(A);
whos('-name','B'); /// \sleftarrow {\begin{minipage}[t]{6cm}{\nf{}used memory {for} the same matrix with a\\ full implementation} \end{minipage}} 
timer();inv(B);timer()/// \sleftarrow{\normalfont CPU time {for} full matrix inversion}
timer();inv(A);timer()/// \sleftarrow{\normalfont CPU time {for} sparse matrix inversion}