#endif
for(int n = 0; n < _nb_vertices; n++) {
for(Edge *e = _vertices[n].leaving_edges; e; e = e->next_leaving_edge) {
if(e->positivized_length < 0) {
#ifdef VERBOSE
residual_error -= e->positivized_length;
#endif
for(int n = 0; n < _nb_vertices; n++) {
for(Edge *e = _vertices[n].leaving_edges; e; e = e->next_leaving_edge) {
if(e->positivized_length < 0) {
#ifdef VERBOSE
residual_error -= e->positivized_length;