An upper bound asymptotic to $2n\log _e n$ is established for the number of comparators required in a network that classifies $n$ values into two classes, each containing $n / 2$ values, with each value in one class less than or equal to each value in the other. (The best lower bound known for this problem is asymptotic to $(n / 2)\log _2 n$.)
© 1991 Society for Industrial and Applied Mathematics
Nicholas Pippenger. "Selection Networks", Society for Industrial and Applied Mathematics Journal on Computing, 20, 878 (1991).