X-Git-Url: https://www.fleuret.org/cgi-bin/gitweb/gitweb.cgi?a=blobdiff_plain;f=mtp_graph.cc;h=fcdcfed00ebc0c82ee0c1ca37efef1016e8e7538;hb=e777319f3c213198e574dd3cac2de1aeac6bfbbf;hp=682dd808e830eb4f36d99a02695d240fc3da3f50;hpb=78b0bdef0b9a3479502c7598fd69a012c297e125;p=mtp.git

diff --git a/mtp_graph.cc b/mtp_graph.cc
index 682dd80..fcdcfed 100644
--- a/mtp_graph.cc
+++ b/mtp_graph.cc
@@ -24,6 +24,7 @@
 
 #include "mtp_graph.h"
 
+#include <cmath>
 #include <float.h>
 
 using namespace std;
@@ -43,9 +44,10 @@ public:
 
 class Vertex {
 public:
-  Edge *leaving_edges;
   scalar_t distance_from_source;
   Edge *pred_edge_toward_source;
+
+  Edge *leaving_edge_list_root;
   Vertex **heap_slot;
 
   Vertex();
@@ -69,19 +71,21 @@ void Edge::invert() {
 //////////////////////////////////////////////////////////////////////
 
 Vertex::Vertex() {
-  leaving_edges = 0;
+  leaving_edge_list_root = 0;
 }
 
 void Vertex::add_leaving_edge(Edge *e) {
-  e->next_leaving_edge = leaving_edges;
+  e->next_leaving_edge = leaving_edge_list_root;
   e->pred_leaving_edge = 0;
-  if(leaving_edges) { leaving_edges->pred_leaving_edge = e; }
-  leaving_edges = e;
+  if(leaving_edge_list_root) {
+    leaving_edge_list_root->pred_leaving_edge = e;
+  }
+  leaving_edge_list_root = e;
 }
 
 void Vertex::del_leaving_edge(Edge *e) {
-  if(e == leaving_edges) {
-    leaving_edges = e->next_leaving_edge;
+  if(e == leaving_edge_list_root) {
+    leaving_edge_list_root = e->next_leaving_edge;
   }
   if(e->pred_leaving_edge) {
     e->pred_leaving_edge->next_leaving_edge = e->next_leaving_edge;
@@ -129,7 +133,7 @@ void Vertex::increase_distance_in_heap(Vertex **heap, Vertex **heap_bottom) {
 
 //////////////////////////////////////////////////////////////////////
 
-static int compare_vertex(const void *v1, const void *v2) {
+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;
@@ -138,6 +142,8 @@ static int compare_vertex(const void *v1, const void *v2) {
   else return 0;
 }
 
+//////////////////////////////////////////////////////////////////////
+
 MTPGraph::MTPGraph(int nb_vertices, int nb_edges,
                    int *vertex_from, int *vertex_to,
                    int source, int sink) {
@@ -167,16 +173,9 @@ MTPGraph::MTPGraph(int nb_vertices, int nb_edges,
   paths = 0;
   nb_paths = 0;
 
-  if(compute_dp_ranks()) {
-    // Here the distance_from_source field of every vertex is the
-    // number of DP iterations needed to update it. Hence we only have
-    // to process the vertex in that order.
-    for(int v = 0; v < _nb_vertices; v++) { _dp_order[v] = &_vertices[v]; }
-    qsort(_dp_order, _nb_vertices, sizeof(Vertex *), compare_vertex);
-  } else {
-    cerr << __FILE__ << ": This graph is not a DAG." << endl;
-    abort();
-  }
+  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);
 }
 
 MTPGraph::~MTPGraph() {
@@ -188,9 +187,12 @@ MTPGraph::~MTPGraph() {
   delete[] paths;
 }
 
-int MTPGraph::compute_dp_ranks() {
+//////////////////////////////////////////////////////////////////////
+
+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
@@ -202,44 +204,61 @@ int MTPGraph::compute_dp_ranks() {
   // rank of a node is the iteration at which is it removed, and we
   // set the distance_from_source fields to this value.
 
-  Vertex **with_predecessor = new Vertex *[_nb_vertices];
+  int *nb_predecessors = new int[_nb_vertices];
+  int *without_predecessors = new int[_nb_vertices];
+  int *new_without_predecessors = new int[_nb_vertices];
+  int nb_without_predecessors, new_nb_without_predecessors;
 
-  // All the nodes are with_predecessor at first
   for(int k = 0; k < _nb_vertices; k++) {
-    _vertices[k].distance_from_source = 0;
-    with_predecessor[k] = &_vertices[k];
+    nb_predecessors[k] = 0;
   }
 
-  scalar_t rank = 1;
-  int nb_with_predecessor = _nb_vertices, pred_nb_with_predecessor;
-
-  do {
-    // We set the distance_from_source field of all the vertices with incoming
-    // edges to the current rank value
-    for(int f = 0; f < nb_with_predecessor; f++) {
-      v = with_predecessor[f];
-      for(e = v->leaving_edges; e; e = e->next_leaving_edge) {
-        e->terminal_vertex->distance_from_source = rank;
-      }
+  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]++;
     }
+  }
 
-    pred_nb_with_predecessor = nb_with_predecessor;
-    nb_with_predecessor = 0;
+  nb_without_predecessors = 0;
+  for(int k = 0; k < _nb_vertices; k++) {
+    if(nb_predecessors[k] == 0) {
+      without_predecessors[nb_without_predecessors++] = k;
+    }
+  }
 
-    // We keep all the vertices with incoming nodes
-    for(int f = 0; f < pred_nb_with_predecessor; f++) {
-      v = with_predecessor[f];
-      if(v->distance_from_source == rank) {
-        with_predecessor[nb_with_predecessor++] = v;
+  scalar_t rank = 1;
+  while(nb_without_predecessors > 0) {
+    new_nb_without_predecessors = 0;
+    for(int l = 0; l < nb_without_predecessors; l++) {
+      v = _vertices + without_predecessors[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_predecessors[new_nb_without_predecessors++] = tv;
+        }
       }
     }
 
+    swap(without_predecessors, new_without_predecessors);
+    nb_without_predecessors = new_nb_without_predecessors;
     rank++;
-  } while(nb_with_predecessor < pred_nb_with_predecessor);
+  }
 
-  delete[] with_predecessor;
+  for(int k = 0; k < _nb_vertices; k++) {
+    if(nb_predecessors[k] > 0) {
+      cerr << __FILE__ << ": The graph is not a DAG." << endl;
+      abort();
+    }
+  }
 
-  return nb_with_predecessor == 0;
+  delete[] nb_predecessors;
+  delete[] without_predecessors;
+  delete[] new_without_predecessors;
 }
 
 //////////////////////////////////////////////////////////////////////
@@ -248,13 +267,10 @@ void MTPGraph::print(ostream *os) {
   for(int k = 0; k < _nb_edges; k++) {
     Edge *e = _edges + k;
     (*os) << e->origin_vertex - _vertices
-         << " -> "
-         << e->terminal_vertex - _vertices
-         << " "
-         << e->length;
-    if(e->occupied) {
-      (*os) << " *";
-    }
+          << " -> "
+          << e->terminal_vertex - _vertices
+          << " (" << e->length << ")";
+    if(e->occupied) { (*os) << " *"; }
     (*os) << endl;
   }
 }
@@ -326,7 +342,7 @@ void MTPGraph::dp_compute_distances() {
 
   for(int k = 0; k < _nb_vertices; k++) {
     v = _dp_order[k];
-    for(e = v->leaving_edges; e; e = e->next_leaving_edge) {
+    for(e = v->leaving_edge_list_root; e; e = e->next_leaving_edge) {
       d = v->distance_from_source + e->positivized_length;
       tv = e->terminal_vertex;
       if(d < tv->distance_from_source) {
@@ -368,7 +384,7 @@ void MTPGraph::find_shortest_path() {
 
     // Now update the neighbors of the node currently closest to the
     // source
-    for(e = v->leaving_edges; e; e = e->next_leaving_edge) {
+    for(e = v->leaving_edge_list_root; e; e = e->next_leaving_edge) {
       d = v->distance_from_source + e->positivized_length;
       tv = e->terminal_vertex;
       if(d < tv->distance_from_source) {
@@ -450,18 +466,18 @@ int MTPGraph::retrieve_one_path(Edge *e, Path *path) {
   int l = 0, nb_occupied_next;
 
   if(path) {
-    path->nodes[l++] = e->origin_vertex - _vertices;
+    path->nodes[l++] = int(e->origin_vertex - _vertices);
     path->length = e->length;
   } else l++;
 
   while(e->terminal_vertex != _sink) {
     if(path) {
-      path->nodes[l++] = e->terminal_vertex - _vertices;
+      path->nodes[l++] = int(e->terminal_vertex - _vertices);
       path->length += e->length;
     } else l++;
 
     nb_occupied_next = 0;
-    for(f = e->terminal_vertex->leaving_edges; f; f = f->next_leaving_edge) {
+    for(f = e->terminal_vertex->leaving_edge_list_root; f; f = f->next_leaving_edge) {
       if(f->occupied) { nb_occupied_next++; next = f; }
     }
 
@@ -481,7 +497,7 @@ int MTPGraph::retrieve_one_path(Edge *e, Path *path) {
   }
 
   if(path) {
-    path->nodes[l++] = e->terminal_vertex - _vertices;
+    path->nodes[l++] = int(e->terminal_vertex - _vertices);
     path->length += e->length;
   } else l++;
 
@@ -496,14 +512,14 @@ void MTPGraph::retrieve_disjoint_paths() {
   delete[] paths;
 
   nb_paths = 0;
-  for(e = _source->leaving_edges; e; e = e->next_leaving_edge) {
+  for(e = _source->leaving_edge_list_root; e; e = e->next_leaving_edge) {
     if(e->occupied) { nb_paths++; }
   }
 
   paths = new Path *[nb_paths];
 
   p = 0;
-  for(e = _source->leaving_edges; e; e = e->next_leaving_edge) {
+  for(e = _source->leaving_edge_list_root; e; e = e->next_leaving_edge) {
     if(e->occupied) {
       l = retrieve_one_path(e, 0);
       paths[p] = new Path(l);