//////////////////////////////////////////////////////////////////////
-static int compare_vertices_on_distance(const void *v1, const void *v2) {
- scalar_t delta =
- (*((Vertex **) v1))->distance_from_source -
- (*((Vertex **) v2))->distance_from_source;
- if(delta < 0) return -1;
- else if(delta > 0) return 1;
- else return 0;
-}
-
-//////////////////////////////////////////////////////////////////////
-
MTPGraph::MTPGraph(int nb_vertices, int nb_edges,
int *vertex_from, int *vertex_to,
int source, int sink) {
paths = 0;
nb_paths = 0;
- compute_dp_ranks();
- for(int v = 0; v < _nb_vertices; v++) { _dp_order[v] = &_vertices[v]; }
- qsort(_dp_order, _nb_vertices, sizeof(Vertex *), compare_vertices_on_distance);
+ compute_dp_ordering();
}
MTPGraph::~MTPGraph() {
//////////////////////////////////////////////////////////////////////
-void MTPGraph::compute_dp_ranks() {
- Vertex *v;
- Edge *e;
- int tv;
-
- // This procedure computes for each node the longest link from the
- // source and abort if the graph is not a DAG. It works by removing
- // successively nodes without predecessor: At the first iteration it
- // removes the source, then the nodes with incoming edge only from
- // the source, etc. If it can remove all the nodes that way, the
- // graph is a DAG. If at some point it can not remove node anymore
- // and there are some remaining nodes, the graph is not a DAG. The
- // rank of a node is the iteration at which is it removed, and we
- // set the distance_from_source fields to this value.
-
- int *nb_predecessors = new int[_nb_vertices];
- int *without_predecessor = new int[_nb_vertices];
- int *new_without_predecessor = new int[_nb_vertices];
- int nb_without_predecessor, new_nb_without_predecessor;
-
- for(int k = 0; k < _nb_vertices; k++) {
- nb_predecessors[k] = 0;
- }
-
- for(int k = 0; k < _nb_vertices; k++) {
- v = &_vertices[k];
- for(e = v->leaving_edge_list_root; e; e = e->next_leaving_edge) {
- tv = int(e->terminal_vertex - _vertices);
- nb_predecessors[tv]++;
- }
- }
-
- nb_without_predecessor = 0;
- for(int k = 0; k < _nb_vertices; k++) {
- if(nb_predecessors[k] == 0) {
- without_predecessor[nb_without_predecessor++] = k;
- }
- }
-
- scalar_t rank = 1;
- while(nb_without_predecessor > 0) {
- new_nb_without_predecessor = 0;
- for(int l = 0; l < nb_without_predecessor; l++) {
- v = &_vertices[without_predecessor[l]];
- v->distance_from_source = rank;
- for(e = v->leaving_edge_list_root; e; e = e->next_leaving_edge) {
- tv = int(e->terminal_vertex - _vertices);
- nb_predecessors[tv]--;
- ASSERT(nb_predecessors[tv] >= 0);
- if(nb_predecessors[tv] == 0) {
- new_without_predecessor[new_nb_without_predecessor++] = tv;
- }
- }
- }
-
- swap(without_predecessor, new_without_predecessor);
- nb_without_predecessor = new_nb_without_predecessor;
- rank++;
- }
-
- for(int k = 0; k < _nb_vertices; k++) {
- if(nb_predecessors[k] > 0) {
- cerr << __FILE__ << ": The graph is not a DAG." << endl;
- abort();
- }
- }
-
- delete[] nb_predecessors;
- delete[] without_predecessor;
- delete[] new_without_predecessor;
-}
-
-//////////////////////////////////////////////////////////////////////
-
void MTPGraph::print(ostream *os) {
for(int k = 0; k < _nb_edges; k++) {
Edge *e = &_edges[k];
return l;
}
+//////////////////////////////////////////////////////////////////////
+
+static int compare_vertices_on_distance(const void *v1, const void *v2) {
+ scalar_t delta =
+ (*((Vertex **) v1))->distance_from_source -
+ (*((Vertex **) v2))->distance_from_source;
+ if(delta < 0) return -1;
+ else if(delta > 0) return 1;
+ else return 0;
+}
+
+void MTPGraph::compute_dp_ordering() {
+ Vertex *v;
+ Edge *e;
+ int ntv;
+
+ // This method computes for each node the length of the longest link
+ // from the source, and orders the node in _dp_order according to
+ // it. It aborts if the graph is not a DAG.
+
+ int *nb_predecessors = new int[_nb_vertices];
+
+ Vertex **already_processed = _dp_order, **front = _dp_order, **new_front = _dp_order;
+
+ for(int k = 0; k < _nb_vertices; k++) {
+ nb_predecessors[k] = 0;
+ }
+
+ for(int k = 0; k < _nb_vertices; k++) {
+ v = &_vertices[k];
+ for(e = v->leaving_edge_list_root; e; e = e->next_leaving_edge) {
+ ntv = int(e->terminal_vertex - _vertices);
+ nb_predecessors[ntv]++;
+ }
+ }
+
+ for(int k = 0; k < _nb_vertices; k++) {
+ if(nb_predecessors[k] == 0) {
+ *(front++) = _vertices + k;
+ }
+ }
+
+ scalar_t rank = 1;
+ while(already_processed < front) {
+ new_front = front;
+ while(already_processed < front) {
+ v = *(already_processed++);
+ v->distance_from_source = rank;
+ for(e = v->leaving_edge_list_root; e; e = e->next_leaving_edge) {
+ ntv = int(e->terminal_vertex - _vertices);
+ nb_predecessors[ntv]--;
+ ASSERT(nb_predecessors[ntv] >= 0);
+ if(nb_predecessors[ntv] == 0) {
+ *(new_front++) = e->terminal_vertex;
+ }
+ }
+ }
+ front = new_front;
+ rank++;
+ }
+
+ if(already_processed < _dp_order + _nb_vertices) {
+ cerr << __FILE__ << ": The graph is not a DAG." << endl;
+ abort();
+ }
+
+ delete[] nb_predecessors;
+
+ for(int v = 0; v < _nb_vertices; v++) { _dp_order[v] = &_vertices[v]; }
+ qsort(_dp_order, _nb_vertices, sizeof(Vertex *), compare_vertices_on_distance);
+}
+
+//////////////////////////////////////////////////////////////////////
+
void MTPGraph::retrieve_disjoint_paths() {
Edge *e;
int p, l;
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