Transitive Reduction

% This function performs 'Transitive Reduction' on the input path matrix 'm', which is a directed acyclic graph (DAG),
% and returns the reduced 'redec_m', using Hsu (1975)'s algorithm
% See Harry Hsu. "An algorithm for finding a minimal equivalent graph of a digraph.", Journal of the ACM, 22(1):11-16, January 1975.
% Example:
% input: m = [ 0 1 1;
% 0 0 1;
% 0 0 0];
% output: reduc_m = [ 0 1 0;
% 0 0 1;
% 0 0 0];