wolffd@0: function [Gs, op, nodes] = mk_nbrs_of_dag(G0)
wolffd@0: % MK_NBRS_OF_DAG Make all DAGs that differ from G0 by a single edge deletion, addition or reversal
wolffd@0: % [Gs, op, nodes] = mk_nbrs_of_dag(G0)
wolffd@0: %
wolffd@0: % Gs{i} is the i'th neighbor.
wolffd@0: % op{i} = 'add', 'del', or 'rev' is the operation used to create the i'th neighbor.
wolffd@0: % nodes(i,1:2) are the head and tail of the operated-on arc.
wolffd@0: 
wolffd@0: Gs = {};
wolffd@0: op = {};
wolffd@0: nodes = [];
wolffd@0: 
wolffd@0: [I,J] = find(G0);
wolffd@0: nnbrs = 1;
wolffd@0: % all single edge deletions
wolffd@0: for e=1:length(I)
wolffd@0:   i = I(e); j = J(e);
wolffd@0:   G = G0;
wolffd@0:   G(i,j) = 0;
wolffd@0:   Gs{nnbrs} = G;
wolffd@0:   op{nnbrs} = 'del';
wolffd@0:   nodes(nnbrs, :) = [i j];
wolffd@0:   nnbrs = nnbrs + 1;
wolffd@0: end
wolffd@0: 
wolffd@0: % all single edge reversals
wolffd@0: for e=1:length(I)
wolffd@0:   i = I(e); j = J(e);
wolffd@0:   G = G0;
wolffd@0:   G(i,j) = 0;
wolffd@0:   G(j,i) = 1;
wolffd@0:   if acyclic(G)
wolffd@0:     Gs{nnbrs} = G;
wolffd@0:     op{nnbrs} = 'rev';
wolffd@0:     nodes(nnbrs, :) = [i j];
wolffd@0:     nnbrs = nnbrs + 1;
wolffd@0:   end
wolffd@0: end
wolffd@0: 
wolffd@0: [I,J] = find(~G0);
wolffd@0: % all single edge additions
wolffd@0: for e=1:length(I)
wolffd@0:   i = I(e); j = J(e);
wolffd@0:   if i ~= j % don't add self arcs
wolffd@0:     G = G0;
wolffd@0:     G(i,j) = 1;
wolffd@0:     if G(j,i)==0 % don't add i->j if j->i exists already
wolffd@0:       if acyclic(G)
wolffd@0: 	Gs{nnbrs} = G;
wolffd@0: 	op{nnbrs} = 'add';
wolffd@0: 	nodes(nnbrs, :) = [i j];
wolffd@0: 	nnbrs = nnbrs + 1;
wolffd@0:       end
wolffd@0:     end
wolffd@0:   end
wolffd@0: end
wolffd@0: 
wolffd@0: 
wolffd@0: 
wolffd@0: 
wolffd@0: 
wolffd@0: 
wolffd@0: 
wolffd@0: