MATLAB: Fast way to retrieve nonzero entries of each row in a sparse matrix

sparse; nonzero-entries

I'm working with very large sparse matrices (10's of thousands to millions of entries) and I'd like to efficiently retrieve and store the unique nonzero entries of each row. For my application, the rows will have anywhere between 1 and 9 unique and nonzero entries.
I've decided to utilize "sprand" for an example – I'm fairly new to using sparse matrices and am not the best programmer so forgive my naivety – and I've tried to choose a density within the aforementioned range. My code is:
numrows = 1000000;
numcols = 1000000;
density = numrows^(-1.87);
num_entries_per_row  = numrows*numcols*density   %  This is an average.
rsm = sprand(numrows,numcols,density);           % random sparse matrix
tic
out = cell(numrows,1);                           % output.
for idx = 1:numrows
  [~,~,value] = find(rsm(idx,:));
  out{idx} = unique(value);
end
toc
I've had this running for a few minutes and still no result. Previously when the number of rows and columns were both 100,000 the result took about 32 seconds – way too slow for my purposes. Clearly not the fastest, but it is simple. Is there a better and more clever way to achieve this result in MATLAB?

Best Answer

[I,~,values]=find(rsm);
u=unique([I,values],'rows');
    N=size(u,1);
   tmp=diff([0;find(diff(u(:,1)));N]);
out=mat2cell(u(:,2),tmp);
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