void Vertex::decrease_distance_in_heap(Vertex **heap) {
Vertex **p, **h;
- // There is some beauty in that
h = heap_slot;
- while(h > heap &&
- (p = heap + (h - heap + 1) / 2 - 1,
- (*p)->distance_from_source > (*h)->distance_from_source)) {
+ while(1) {
+ if(h <= heap) break;
+ p = heap + ((h - heap + 1) >> 1) - 1;
+ if((*p)->distance_from_source <= distance_from_source) break;
+ swap((*p)->heap_slot, heap_slot);
swap(*p, *h);
- swap((*p)->heap_slot, (*h)->heap_slot);
h = p;
}
}
void Vertex::increase_distance_in_heap(Vertex **heap, Vertex **heap_bottom) {
Vertex **c1, **c2, **h;
- // omg, that's beautiful
h = heap_slot;
- while(c1 = heap + 2 * (h - heap) + 1,
- c1 < heap_bottom &&
- (c2 = c1 + 1,
- (*c1)->distance_from_source < (*h)->distance_from_source
- ||
- (c2 < heap_bottom && (*c2)->distance_from_source < (*h)->distance_from_source)
- )) {
- if(c2 < heap_bottom && (*c2)->distance_from_source <= (*c1)->distance_from_source) {
- swap(*c2, *h);
- swap((*c2)->heap_slot, (*h)->heap_slot);
- h = c2;
+ while(1) {
+ c1 = heap + 2 * (h - heap) + 1;
+ if(c1 >= heap_bottom) break;
+ c2 = c1 + 1;
+ if((*c1)->distance_from_source < distance_from_source) {
+ if(c2 < heap_bottom && (*c2)->distance_from_source < (*c1)->distance_from_source) {
+ swap((*c2)->heap_slot, heap_slot);
+ swap(*c2, *h);
+ h = c2;
+ } else {
+ swap((*c1)->heap_slot, heap_slot);
+ swap(*c1, *h);
+ h = c1;
+ }
} else {
- swap(*c1, *h);
- swap((*c1)->heap_slot, (*h)->heap_slot);
- h = c1;
+ if(c2 < heap_bottom && (*c2)->distance_from_source < distance_from_source) {
+ swap((*c2)->heap_slot, heap_slot);
+ swap(*c2, *h);
+ h = c2;
+ } else break;
}
}
}
//////////////////////////////////////////////////////////////////////
-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];
}
}
#ifdef VERBOSE
- cerr << __FILE__ << ": residual_error " << residual_error << " max_error " << residual_error << endl;
+ cerr << __FILE__ << ": residual_error " << residual_error << " max_error " << max_error << endl;
#endif
}
// pred_edge_toward_source.
void MTPGraph::find_shortest_path() {
+ int heap_size;
Vertex *v, *tv, **last_slot;
Edge *e;
scalar_t d;
_vertices[k].pred_edge_toward_source = 0;
}
- _heap_size = _nb_vertices;
+ heap_size = _nb_vertices;
_source->distance_from_source = 0;
_source->decrease_distance_in_heap(_heap);
- do {
+ while(heap_size > 1) {
// Get the closest to the source
v = _heap[0];
// Remove it from the heap (swap it with the last_slot in the heap, and
// update the distance of that one)
- _heap_size--;
- last_slot = _heap + _heap_size;
+ heap_size--;
+ last_slot = _heap + heap_size;
swap(*_heap, *last_slot); swap((*_heap)->heap_slot, (*last_slot)->heap_slot);
- _heap[0]->increase_distance_in_heap(_heap, _heap + _heap_size);
+ (*_heap)->increase_distance_in_heap(_heap, last_slot);
// Now update the neighbors of the node currently closest to the
// source
d = v->distance_from_source + e->positivized_length;
tv = e->terminal_vertex;
if(d < tv->distance_from_source) {
- ASSERT(tv->heap_slot - _heap < _heap_size);
+ ASSERT(tv->heap_slot < last_slot);
tv->distance_from_source = d;
tv->pred_edge_toward_source = e;
tv->decrease_distance_in_heap(_heap);
}
}
- } while(_heap_size > 0);
+ }
}
void MTPGraph::find_best_paths(scalar_t *lengths) {
}
}
-int MTPGraph::retrieve_one_path(Edge *e, Path *path) {
+int MTPGraph::retrieve_one_path(Edge *e, Path *path, int *used_edges) {
Edge *f, *next = 0;
int l = 0, nb_occupied_next;
nb_occupied_next = 0;
for(f = e->terminal_vertex->leaving_edge_list_root; f; f = f->next_leaving_edge) {
- if(f->occupied) { nb_occupied_next++; next = f; }
+ if(f->occupied && !used_edges[f - _edges]) {
+ nb_occupied_next++; next = f;
+ }
}
#ifdef DEBUG
cerr << __FILE__ << ": retrieve_one_path: Non-sink end point." << endl;
abort();
}
-
- else if(nb_occupied_next > 1) {
- cerr << __FILE__ << ": retrieve_one_path: Non node-disjoint paths." << endl;
- abort();
- }
#endif
+ if(path) { used_edges[next - _edges] = 1; }
+
e = next;
}
return l;
}
+//////////////////////////////////////////////////////////////////////
+
+void MTPGraph::compute_dp_ordering() {
+ Vertex *v;
+ Edge *e;
+ int ntv;
+
+ // This method orders the nodes by putting first the ones with no
+ // predecessors, then going on adding nodes whose predecessors have
+ // all been already added. Computing the distances from the source
+ // by visiting nodes in that order is equivalent to DP.
+
+ 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;
+ }
+ }
+
+ while(already_processed < front) {
+ // Here, nodes before already_processed can be ignored, nodes
+ // before front were set to 0 predecessors during the previous
+ // iteration. During this new iteration, we have to visit the
+ // successors of these ones only, since they are the only ones
+ // which may end up with no predecessors.
+ new_front = front;
+ while(already_processed < front) {
+ v = *(already_processed++);
+ 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;
+ }
+
+ if(already_processed < _dp_order + _nb_vertices) {
+ cerr << __FILE__ << ": The graph is not a DAG." << endl;
+ abort();
+ }
+
+ delete[] nb_predecessors;
+}
+
+//////////////////////////////////////////////////////////////////////
+
void MTPGraph::retrieve_disjoint_paths() {
Edge *e;
int p, l;
+ int *used_edges;
for(int p = 0; p < nb_paths; p++) delete paths[p];
delete[] paths;
}
paths = new Path *[nb_paths];
+ used_edges = new int[_nb_edges];
+ for(int e = 0; e < _nb_edges; e++) {
+ used_edges[e] = 0;
+ }
p = 0;
for(e = _source->leaving_edge_list_root; e; e = e->next_leaving_edge) {
- if(e->occupied) {
- l = retrieve_one_path(e, 0);
+ if(e->occupied && !used_edges[e - _edges]) {
+ l = retrieve_one_path(e, 0, used_edges);
paths[p] = new Path(l);
- retrieve_one_path(e, paths[p]);
+ retrieve_one_path(e, paths[p], used_edges);
+ used_edges[e - _edges] = 1;
p++;
}
}
+
+ delete[] used_edges;
}
projects / mtp.git / blobdiff