Mauch MIREX 2010

function [edge_id, nedges] = assignEdgeNums(adj_mat)

% give each edge a unique number

% we number (i,j) for j>i first, in row, column order.

% Then we number the reverse links

nnodes = length(adj_mat);

edge_id = zeros(nnodes);

e = 1;

for i=1:nnodes

  for j=i+1:nnodes

    if adj_mat(i,j)

      edge_id(i,j) = e;

      e = e+1;

    end

  end

end

nedges = e-1;

tmp = edge_id;

ndx = find(tmp);

tmp(ndx) = tmp(ndx)+nedges;

edge_id = edge_id + triu(tmp)';

if 0

ndx = find(adj_mat);

nedges = length(ndx);

nnodes = length(adj_mat);

edge_id = zeros(1, nnodes*nnodes);

edge_id(ndx) = 1:nedges; 

edge_id = reshape(edge_id, nnodes, nnodes);

end