-\item Reduction circuit sums the numbers in a row of a (sparse) matrix
-\item Nice speed considering we don't optimize for it
+\item Reduction circuit sums the numbers in a row, of different length
+\item It uses a pipelined adder: multiple rows in pipeline, rows longer than pipeline
+\item We hope you see this is not a trivial problem
+\item Nice speed considering we don't optimize for it (only single example!)