matlabcentral/fileexchange/27076-shuffle 
% Shuffle> as it is both faster and more memory efficient than the built-in function. 
% Note that you need to enable this by setting |options.shuffle = true| in MISC 
% SETTINGS in RECONSTRUCTION PROPERTIES.
% 
% If you NEED to use implementation 1 WITHOUT precomputation (not  recommended), 
% then for Octave and MATLAB R2019b and EARLIER, it is  recommended to download 
% and build <https://github.com/stefanengblom/stenglib fsparse>. Note that you 
% need to enabl