X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/1d2f05c1a2fbdc662e0eb9ad8e2dd7f7e6f7986c..0a03cd809dd45e3645a54feffe364d8f2b33d71e:/src/xbt/graph.c

diff --git a/src/xbt/graph.c b/src/xbt/graph.c
index 71ee5b5963..b51fb15414 100644
--- a/src/xbt/graph.c
+++ b/src/xbt/graph.c
@@ -1,12 +1,7 @@
-
-
-/* 	$Id$	 */
-
-
 /* a generic graph library.                                                 */
 
-/* Copyright (c) 2006 Darina Dimitrova, Arnaud Legrand. 
-   All rights reserved.                  */
+/* Copyright (c) 2006 Darina Dimitrova, Arnaud Legrand.                     */
+/* All rights reserved.                                                     */
 
 /* This program is free software; you can redistribute it and/or modify it
  * under the terms of the license (GNU LGPL) which comes with this package. */
@@ -18,391 +13,710 @@
 #include "graph_private.h"
 #include "xbt/graphxml_parse.h"
 #include "xbt/dict.h"
+#include "xbt/heap.h"
+
+
+
+
+XBT_LOG_NEW_DEFAULT_SUBCATEGORY(xbt_graph, xbt, "Graph");
 
-XBT_LOG_NEW_DEFAULT_SUBCATEGORY(graph,xbt,"Graph");
 
-/** Constructor
- * \return a new graph
+
+/** @brief Constructor
+ *  @return a new graph
  */
 xbt_graph_t xbt_graph_new_graph(unsigned short int directed, void *data)
 {
-  xbt_graph_t graph=NULL;
-  graph=xbt_new0(struct xbt_graph,1);
-  graph->directed=directed;
-  graph->data=data;
-  graph->nodes= xbt_dynar_new(sizeof(xbt_node_t), free);
-  graph->edges= xbt_dynar_new(sizeof(xbt_edge_t), free);
+  xbt_graph_t graph = NULL;
+  graph = xbt_new0(struct xbt_graph, 1);
+  graph->directed = directed;
+  graph->data = data;
+  graph->nodes = xbt_dynar_new(sizeof(xbt_node_t), NULL);
+  graph->edges = xbt_dynar_new(sizeof(xbt_edge_t), NULL);
 
   return graph;
 }
 
+/** @brief add a node to the given graph */
 xbt_node_t xbt_graph_new_node(xbt_graph_t g, void *data)
 {
-  xbt_node_t node=NULL;
-  node=xbt_new0(struct xbt_node,1);
-  node->data=data;
-  node->in=xbt_dynar_new(sizeof(xbt_node_t), free);
-  node->out=xbt_dynar_new(sizeof(xbt_node_t), free);
-  xbt_dynar_push(g->nodes,&node);  
+  xbt_node_t node = NULL;
+  node = xbt_new0(struct xbt_node, 1);
+  node->data = data;
+  if (g->directed)
+    /* only the "out" field is used */
+    node->in = xbt_dynar_new(sizeof(xbt_edge_t), NULL);
+
+  node->out = xbt_dynar_new(sizeof(xbt_edge_t), NULL);
+  node->position_x = -1.0;
+  node->position_y = -1.0;
+
+  xbt_dynar_push(g->nodes, &node);
 
   return node;
 }
 
-
+/** @brief add an edge to the given graph */
 xbt_edge_t xbt_graph_new_edge(xbt_graph_t g,
-			     xbt_node_t src, xbt_node_t dst, void *data)
+                              xbt_node_t src, xbt_node_t dst, void *data)
 {
-  xbt_edge_t edge=NULL;
+  xbt_edge_t edge = NULL;
+
+  edge = xbt_new0(struct xbt_edge, 1);
+  xbt_dynar_push(src->out, &edge);
+  if (g->directed)
+    xbt_dynar_push(dst->in, &edge);
+  else                          /* only the "out" field is used */
+    xbt_dynar_push(dst->out, &edge);
 
-  edge=xbt_new0(struct xbt_edge,1);
-  xbt_dynar_push(src->out,&edge); 
-  xbt_dynar_push(dst->in,&edge); 
-  edge->data=data;
-  edge->src=src;
-  edge->dst=dst;
-  if(!g->directed) 
-   {
-     xbt_dynar_push(src->in,&edge); 
-     xbt_dynar_push(dst->out,&edge); 
-   }
+  edge->data = data;
+  edge->src = src;
+  edge->dst = dst;
 
- xbt_dynar_push(g->edges,&edge);
+  xbt_dynar_push(g->edges, &edge);
 
- return edge; 
+  return edge;
 }
 
+xbt_edge_t xbt_graph_get_edge(xbt_graph_t g, xbt_node_t src, xbt_node_t dst)
+{
+  xbt_edge_t edge;
+  unsigned int cursor;
+
+  xbt_dynar_foreach(src->out, cursor, edge) {
+    DEBUG3("%p = %p--%p", edge, edge->src, edge->dst);
+    if ((edge->src == src) && (edge->dst == dst))
+      return edge;
+  }
+  if (!g->directed) {
+    xbt_dynar_foreach(src->out, cursor, edge) {
+      DEBUG3("%p = %p--%p", edge, edge->src, edge->dst);
+      if ((edge->dst == src) && (edge->src == dst))
+        return edge;
+    }
+  }
+  return NULL;
+}
+
+void *xbt_graph_node_get_data(xbt_node_t node)
+{
+  return node->data;
+}
 
-/** Destructor
- * \param l poor victim
+void xbt_graph_node_set_data(xbt_node_t node, void *data)
+{
+  node->data = data;
+}
+
+void *xbt_graph_edge_get_data(xbt_edge_t edge)
+{
+  return edge->data;
+}
+
+void xbt_graph_edge_set_data(xbt_edge_t edge, void *data)
+{
+  edge->data = data;
+}
+
+/** @brief Destructor
+ *  @param g: poor victim
+ *  @param node_free_function: function to use to free data associated to each node
+ *  @param edge_free_function: function to use to free data associated to each edge
+ *  @param graph_free_function: function to use to free data associated to g
  *
- * Free the graph structure. 
+ * Free the graph structure.
  */
 void xbt_graph_free_graph(xbt_graph_t g,
-			  void node_free_function(void * ptr),
-			  void edge_free_function(void * ptr),
-			  void graph_free_function(void * ptr))
-{ 
-  int cursor; 
-  xbt_node_t node=NULL; 
+                          void_f_pvoid_t node_free_function,
+                          void_f_pvoid_t edge_free_function,
+                          void_f_pvoid_t graph_free_function)
+{
+  unsigned int cursor = 0;
+  xbt_node_t node = NULL;
+  xbt_edge_t edge = NULL;
 
-  xbt_dynar_foreach(g->nodes,cursor,node)
-    xbt_graph_free_node(g,node,node_free_function);
 
-  xbt_assert0(!xbt_dynar_length(g->edges),
-	      "Damnit, there are some remaining edges!");
+  xbt_dynar_foreach(g->nodes, cursor, node) {
+    xbt_dynar_free(&(node->out));
+    xbt_dynar_free(&(node->in));
+    if (node_free_function)
+      (*node_free_function) (node->data);
+  }
 
+  xbt_dynar_foreach(g->edges, cursor, edge) {
+    if (edge_free_function)
+      (*edge_free_function) (edge->data);
+  }
+
+  xbt_dynar_foreach(g->nodes, cursor, node)
+    free(node);
   xbt_dynar_free(&(g->nodes));
-  xbt_dynar_free(&(g->edges));
-  fprintf(stderr,"%s","after free containers\n");    
 
+  xbt_dynar_foreach(g->edges, cursor, edge)
+    free(edge);
+  xbt_dynar_free(&(g->edges));
+  if (graph_free_function)
+    (*graph_free_function) (g->data);
+  free(g);
 
   return;
 }
 
-void xbt_graph_free_node(xbt_graph_t g, xbt_node_t n, void free_function(void * ptr))
-{ 
-  int cursor; 
-  xbt_node_t node=NULL;
 
-  if ((free_function)&&(n->data))
-    free_function(n->data);
+/** @brief remove the given node from the given graph */
+void xbt_graph_free_node(xbt_graph_t g, xbt_node_t n,
+                         void_f_pvoid_t node_free_function,
+                         void_f_pvoid_t edge_free_function)
+{
+  unsigned long nbr;
+  unsigned long i;
+  unsigned int cursor = 0;
+  xbt_node_t node = NULL;
+  xbt_edge_t edge = NULL;
+
+  nbr = xbt_dynar_length(g->edges);
+  cursor = 0;
+  for (i = 0; i < nbr; i++) {
+    xbt_dynar_get_cpy(g->edges, cursor, &edge);
 
-  xbt_dynar_free_container(&(n->in));
+    if ((edge->dst == n) || (edge->src == n)) {
+      xbt_graph_free_edge(g, edge, edge_free_function);
+    } else
+      cursor++;
+  }
+
+  if ((node_free_function) && (n->data))
+    (*node_free_function) (n->data);
+
+  cursor = 0;
+  xbt_dynar_foreach(g->nodes, cursor, node)
+    if (node == n)
+    xbt_dynar_cursor_rm(g->nodes, &cursor);
+
+  xbt_dynar_free(&(n->in));
+  xbt_dynar_free(&(n->out));
+
+  free(n);
 
-  xbt_dynar_free_container(&(n->out));
-  xbt_dynar_foreach(g->nodes,cursor,node)
-    {
-      if (node==n)
-	xbt_dynar_cursor_rm(g->nodes,&cursor);   
-      
-    }
   return;
-   
-}
-void xbt_graph_free_edge(xbt_graph_t g, xbt_edge_t e, void free_function(void * ptr))
-{
-   int cursor=0; 
-   xbt_edge_t edge=NULL;
-   xbt_node_t node=NULL;
-   xbt_node_t temp=NULL;
-   
-   if ((free_function)&&(e->data))
-     free_function(e->data);
-   xbt_dynar_foreach(g->nodes,cursor,node)
-     {
-       if (node==e->src)
-	 xbt_dynar_pop(node->out,temp);
-       if (g->directed)
-	 xbt_dynar_pop(node->in,temp);
-        
-     }
-   node=NULL;
-   cursor=0;
-   xbt_dynar_foreach(g->nodes,cursor,node)
-     {
-        if (node==e->dst)
-	  xbt_dynar_pop(node->in,temp);
-	if (g->directed)
-	  xbt_dynar_pop(node->out,temp);
-        
-     }
-   cursor=0;
-   xbt_dynar_foreach(g->edges,cursor,edge)
-     if (edge==e) 
-       {
-	 xbt_dynar_cursor_rm(g->edges,&cursor);
-	 break;
-       }
-   
 }
 
+/** @brief remove the given edge from the given graph */
+void xbt_graph_free_edge(xbt_graph_t g, xbt_edge_t e,
+                         void_f_pvoid_t free_function)
+{
+  int idx;
+  unsigned int cursor = 0;
+  xbt_edge_t edge = NULL;
+
+  if ((free_function) && (e->data))
+    (*free_function) (e->data);
+
+  xbt_dynar_foreach(g->edges, cursor, edge) {
+    if (edge == e) {
+      if (g->directed) {
+        idx = __xbt_find_in_dynar(edge->dst->in, edge);
+        xbt_dynar_remove_at(edge->dst->in, idx, NULL);
+      } else {                  /* only the out field is used */
+        idx = __xbt_find_in_dynar(edge->dst->out, edge);
+        xbt_dynar_remove_at(edge->dst->out, idx, NULL);
+      }
+
+      idx = __xbt_find_in_dynar(edge->src->out, edge);
+      xbt_dynar_remove_at(edge->src->out, idx, NULL);
+
+      xbt_dynar_cursor_rm(g->edges, &cursor);
+      free(edge);
+      break;
+    }
+  }
+}
+
+int __xbt_find_in_dynar(xbt_dynar_t dynar, void *p)
+{
+
+  unsigned int cursor = 0;
+  void *tmp = NULL;
+
+  xbt_dynar_foreach(dynar, cursor, tmp) {
+    if (tmp == p)
+      return cursor;
+  }
+  return -1;
+}
+
+/** @brief Retrieve the graph's nodes as a dynar */
 xbt_dynar_t xbt_graph_get_nodes(xbt_graph_t g)
 {
   return g->nodes;
 }
+
+/** @brief Retrieve the graph's edges as a dynar */
 xbt_dynar_t xbt_graph_get_edges(xbt_graph_t g)
 {
   return g->edges;
 }
 
+/** @brief Retrieve the node at the source of the given edge */
 xbt_node_t xbt_graph_edge_get_source(xbt_edge_t e)
 {
-  
   return e->src;
 }
+
+/** @brief Retrieve the node being the target of the given edge */
 xbt_node_t xbt_graph_edge_get_target(xbt_edge_t e)
 {
   return e->dst;
 }
-int xbt_get_node_index(xbt_graph_t g, xbt_node_t n)
-{
 
-  int cursor=0;
-  xbt_node_t tmp;
-  xbt_dynar_foreach(g->nodes,cursor,tmp)
-    {
-      if (tmp==n)
-	break;
-    }
-  return (cursor-1);
+/** @brief Retrieve the outgoing edges of the given node */
+xbt_dynar_t xbt_graph_node_get_outedges(xbt_node_t n)
+{
+  return n->out;
 }
 
-void  xbt_graph_edge_set_length(xbt_edge_t e, double length)
+/** @brief Set the weight of the given edge */
+void xbt_graph_edge_set_length(xbt_edge_t e, double length)
 {
-  e->length=length;
-  
+  e->length = length;
+
 }
+
 double xbt_graph_edge_get_length(xbt_edge_t e)
 {
   return e->length;
 }
 
 
-/*construct the adjacency matrix corresponding to a graph,
-  the weights are the distances between nodes
+/** @brief construct the adjacency matrix corresponding to the given graph
+ *
+ * The weights are the distances between nodes
  */
-double* xbt_graph_get_length_matrix(xbt_graph_t g)
+double *xbt_graph_get_length_matrix(xbt_graph_t g)
 {
- fprintf(stderr,"%s","START GET LENGTHS\n" );
- int cursor = 0;
-  int in_cursor = 0;
-  int idx,i;
+  unsigned int cursor = 0;
+  unsigned int in_cursor = 0;
+  unsigned long idx, i;
   unsigned long n;
   xbt_edge_t edge = NULL;
-  xbt_node_t node;
-  double* d=NULL;
+  xbt_node_t node = NULL;
+  double *d = NULL;
 
- # define D(u,v) d[(u)*n+(v)] 
- n = xbt_dynar_length(g->nodes);
+# define D(u,v) d[(u)*n+(v)]
+  n = xbt_dynar_length(g->nodes);
 
-  d = (double*)xbt_malloc(n*n*(sizeof(double)));
+  d = (double *) xbt_new0(double, n * n);
 
-  for (i=0;i<n*n;i++)
-    {
-	  d[i]=-1.0;
-    }
+  for (i = 0; i < n * n; i++) {
+    d[i] = -1.0;
+  }
 
+  xbt_dynar_foreach(g->nodes, cursor, node) {
+    in_cursor = 0;
+    D(cursor, cursor) = 0;
 
-  xbt_dynar_foreach(g->nodes,cursor,node)
-    {fprintf(stderr,"CURSOR:      %d\n",cursor );
-      in_cursor=0;
-      D(cursor-1,cursor-1)=0;
-      xbt_dynar_foreach(node->in,in_cursor,edge)
-	{fprintf(stderr,"EDGE IN:      %s\n",(char*)edge->data );
-fprintf(stderr,"EDGE DST:      %s\n",(char*)edge->dst->data );
-	  idx = xbt_get_node_index(g,edge->dst);
- fprintf(stderr,"IDX: %d\n",idx );
-fprintf(stderr,"EDGE ADR: %x\n",(int)edge );
-fprintf(stderr,"EDGE LENGTH: %le\n", edge->length );
-	  D(cursor-1,idx) = edge->length;
-	}
+    xbt_dynar_foreach(node->out, in_cursor, edge) {
+      if (edge->dst == node)
+        idx = __xbt_find_in_dynar(g->nodes, edge->src);
+      else                      /*case of  undirected graphs */
+        idx = __xbt_find_in_dynar(g->nodes, edge->dst);
+      D(cursor, idx) = edge->length;
     }
- fprintf(stderr,"BEFORE RETURN\n" );
- 
+  }
+
 # undef D
 
-return d; 
+  return d;
 }
 
- /*  calculate all-pairs shortest paths */
-/*   the shortest distance between node  i and j are stocked in  distances[i][j] */
-void xbt_floyd_algorithm(xbt_graph_t g, double* adj,double* d,  xbt_node_t* p)
+/** @brief Floyd-Warshall algorithm for shortest path finding
+ *
+ * From wikipedia:
+ *
+ * The Floyd–Warshall algorithm takes as input an adjacency matrix
+ * representation of a weighted, directed graph (V, E). The weight of a
+ * path between two vertices is the sum of the weights of the edges along
+ * that path. The edges E of the graph may have negative weights, but the
+ * graph must not have any negative weight cycles. The algorithm computes,
+ * for each pair of vertices, the minimum weight among all paths between
+ * the two vertices. The running time complexity is Θ(|V|3).
+ */
+void xbt_floyd_algorithm(xbt_graph_t g, double *adj, double *d,
+                         xbt_node_t * p)
 {
-  int i,j,k;
- unsigned long n;
- n = xbt_dynar_length(g->nodes);
+  unsigned long i, j, k;
+  unsigned long n;
+  n = xbt_dynar_length(g->nodes);
 
 # define D(u,v) d[(u)*n+(v)]
 # define P(u,v) p[(u)*n+(v)]
 
+  for (i = 0; i < n * n; i++) {
+    d[i] = adj[i];
+  }
 
- 
-  for(i=0;i<n*n;i++)
-    {
-      d[i]=adj[i];
-    }
-  for(i=0;i<n;i++)
-    {
-      for(j=0;j<n;j++)
-	{
-	  if(D(i,j)!=-1) P(i,j)=xbt_dynar_get_ptr (g->nodes,i) ;
-	}
+
+  for (i = 0; i < n; i++) {
+    for (j = 0; j < n; j++) {
+      if (D(i, j) != -1) {
+        P(i, j) = *((xbt_node_t *) xbt_dynar_get_ptr(g->nodes, i));
+      }
     }
-	
-  for(k=0;k<n;k++)
-    {
-      for(i=0;i<n;i++)
-	{
-	  for(j=0;j<n;j++)
-	    {
-	      if((D(i,k)!=-1) && (D(k,j)!=-1))
-		{
-		  if((D(i,j)==-1) || (D(i,j) > D(i,k)+D(k,j)))
-		    {
-		      D(i,j) = D(i,k)+D(k,j) ;
-		      P(i,j) = P(k,j);
-		    }
-		}
-	    }
-	}
+  }
+
+  for (k = 0; k < n; k++) {
+    for (i = 0; i < n; i++) {
+      for (j = 0; j < n; j++) {
+        if ((D(i, k) != -1) && (D(k, j) != -1)) {
+          if ((D(i, j) == -1) || (D(i, j) > D(i, k) + D(k, j))) {
+            D(i, j) = D(i, k) + D(k, j);
+            P(i, j) = P(k, j);
+          }
+        }
+      }
     }
+  }
+
+
+
 # undef P
 # undef D
 }
 
-/*computes all-pairs shortest paths*/
-xbt_node_t* xbt_graph_shortest_paths(xbt_graph_t g)
+/** @brief computes all-pairs shortest paths */
+xbt_node_t *xbt_graph_shortest_paths(xbt_graph_t g)
 {
-  xbt_node_t* p;
- xbt_node_t* r;
- int i,j,k;
- unsigned long  n; 
- 
-  double* adj=NULL;
- double* d=NULL;
+  xbt_node_t *p;
+  xbt_node_t *r;
+  unsigned long i, j, k;
+  unsigned long n;
+
+  double *adj = NULL;
+  double *d = NULL;
 
 # define P(u,v) p[(u)*n+(v)]
 # define R(u,v) r[(u)*n+(v)]
 
- n = xbt_dynar_length(g->nodes);
- adj= xbt_graph_get_length_matrix(g); 
- xbt_floyd_algorithm(g,adj,d,p);
-
- for(i=0;i<n;i++)
-   {
-     for(j=0;j<n;j++)
-       {
-	 k=j;
-	 while((P(i,k))&&( xbt_get_node_index(g,P(i,k))!=i))
-	   { 
-	     k =  xbt_get_node_index(g,P(i,k));
-	   }
-	 if(P(i,j)) 
-	   {
-	     R(i,j)=(xbt_node_t)xbt_dynar_get_ptr(g->nodes,k);
-	   }
-       }
-   }
+  n = xbt_dynar_length(g->nodes);
+  adj = xbt_graph_get_length_matrix(g);
+  d = xbt_new0(double, n * n);
+  p = xbt_new0(xbt_node_t, n * n);
+  r = xbt_new0(xbt_node_t, n * n);
+
+  xbt_floyd_algorithm(g, adj, d, p);
+
+  for (i = 0; i < n; i++) {
+    for (j = 0; j < n; j++) {
+      k = j;
+
+      while ((P(i, k)) && (__xbt_find_in_dynar(g->nodes, P(i, k)) != i)) {
+        k = __xbt_find_in_dynar(g->nodes, P(i, k));
+      }
+
+      if (P(i, j)) {
+        R(i, j) = *((xbt_node_t *) xbt_dynar_get_ptr(g->nodes, k));
+      }
+    }
+  }
 # undef R
 # undef P
 
-   xbt_free(d);
-   xbt_free(p);
- return r;
+  free(d);
+  free(p);
+  free(adj);
+  return r;
 }
 
-static xbt_graph_t parsed_graph=NULL;
-static xbt_dict_t parsed_nodes=NULL;
-static xbt_dict_t parsed_edges=NULL; 
-     
+/** @brief Extract a spanning tree of the given graph */
+xbt_edge_t *xbt_graph_spanning_tree_prim(xbt_graph_t g)
+{
+  int tree_size = 0;
+  int tree_size_max = xbt_dynar_length(g->nodes) - 1;
+  xbt_edge_t *tree = xbt_new0(xbt_edge_t, tree_size_max);
+  xbt_edge_t e, edge;
+  xbt_node_t node = NULL;
+  xbt_dynar_t edge_list = NULL;
+  xbt_heap_t heap = xbt_heap_new(10, NULL);
+  unsigned int cursor;
+
+  xbt_assert0(!(g->directed),
+              "Spanning trees do not make sense on directed graphs");
+
+  xbt_dynar_foreach(g->nodes, cursor, node) {
+    node->xbtdata = NULL;
+  }
+
+  node = xbt_dynar_getfirst_as(g->nodes, xbt_node_t);
+  node->xbtdata = (void *) 1;
+  edge_list = node->out;
+  xbt_dynar_foreach(edge_list, cursor, e)
+    xbt_heap_push(heap, e, -(e->length));
+
+  while ((edge = xbt_heap_pop(heap))) {
+    if ((edge->src->xbtdata) && (edge->dst->xbtdata))
+      continue;
+    tree[tree_size++] = edge;
+    if (!(edge->src->xbtdata)) {
+      edge->src->xbtdata = (void *) 1;
+      edge_list = edge->src->out;
+      xbt_dynar_foreach(edge_list, cursor, e) {
+        xbt_heap_push(heap, e, -(e->length));
+      }
+    } else {
+      edge->dst->xbtdata = (void *) 1;
+      edge_list = edge->dst->out;
+      xbt_dynar_foreach(edge_list, cursor, e) {
+        xbt_heap_push(heap, e, -(e->length));
+      }
+    }
+    if (tree_size == tree_size_max)
+      break;
+  }
 
-static void  __parse_graph_begin(void)
+  xbt_heap_free(heap);
+
+  return tree;
+}
+
+/** @brief Topological sort on the given graph
+ *
+ *  From wikipedia:
+ *
+ * In graph theory, a topological sort of a directed acyclic graph (DAG) is
+ * a linear ordering of its nodes which is compatible with the partial
+ * order R induced on the nodes where x comes before y (xRy) if there's a
+ * directed path from x to y in the DAG. An equivalent definition is that
+ * each node comes before all nodes to which it has edges. Every DAG has at
+ * least one topological sort, and may have many.
+ */
+xbt_node_t *xbt_graph_topo_sort(xbt_graph_t g)
+{
+
+  xbt_node_t *sorted;
+  unsigned int cursor;
+  int idx;
+  xbt_node_t node;
+  unsigned long n;
+
+  n = xbt_dynar_length(g->nodes);
+  idx = n - 1;
+
+  sorted = xbt_malloc(n * sizeof(xbt_node_t));
+
+  xbt_dynar_foreach(g->nodes, cursor, node)
+    node->xbtdata = xbt_new0(int, 1);
+
+  xbt_dynar_foreach(g->nodes, cursor, node)
+    xbt_graph_depth_visit(g, node, sorted, &idx);
+
+  xbt_dynar_foreach(g->nodes, cursor, node) {
+    free(node->xbtdata);
+    node->xbtdata = NULL;
+  }
+
+  return sorted;
+}
+
+/** @brief First-depth graph traversal */
+void xbt_graph_depth_visit(xbt_graph_t g, xbt_node_t n,
+                           xbt_node_t * sorted, int *idx)
+{
+  unsigned int cursor;
+  xbt_edge_t edge;
+
+  if (*((int *) (n->xbtdata)) == ALREADY_EXPLORED)
+    return;
+  else if (*((int *) (n->xbtdata)) == CURRENTLY_EXPLORING)
+    THROW0(0, 0, "There is a cycle");
+  else {
+    *((int *) (n->xbtdata)) = CURRENTLY_EXPLORING;
+
+    xbt_dynar_foreach(n->out, cursor, edge) {
+      xbt_graph_depth_visit(g, edge->dst, sorted, idx);
+    }
+
+    *((int *) (n->xbtdata)) = ALREADY_EXPLORED;
+    sorted[(*idx)--] = n;
+  }
+}
+
+/********************* Import and Export ******************/
+static xbt_graph_t parsed_graph = NULL;
+static xbt_dict_t parsed_nodes = NULL;
+
+static void *(*__parse_node_label_and_data) (xbt_node_t, const char *,
+                                             const char *) = NULL;
+static void *(*__parse_edge_label_and_data) (xbt_edge_t, const char *,
+                                             const char *) = NULL;
+
+static void __parse_graph_begin(void)
 {
   DEBUG0("<graph>");
+  if (A_graphxml_graph_isDirected == A_graphxml_graph_isDirected_true)
+    parsed_graph = xbt_graph_new_graph(1, NULL);
+  else
+    parsed_graph = xbt_graph_new_graph(0, NULL);
+
+  parsed_nodes = xbt_dict_new();
 }
-static void  __parse_graph_end(void)
+
+static void __parse_graph_end(void)
 {
+  xbt_dict_free(&parsed_nodes);
   DEBUG0("</graph>");
 }
 
 static void __parse_node(void)
 {
- xbt_node_t node= xbt_graph_new_node(parsed_graph,(void*)A_graphxml_node_name);
+  xbt_node_t node = xbt_graph_new_node(parsed_graph, NULL);
+
+  DEBUG1("<node name=\"%s\"/>", A_graphxml_node_name);
+  if (__parse_node_label_and_data)
+    node->data = __parse_node_label_and_data(node, A_graphxml_node_label,
+                                             A_graphxml_node_data);
+  xbt_graph_parse_get_double(&(node->position_x), A_graphxml_node_position_x);
+  xbt_graph_parse_get_double(&(node->position_y), A_graphxml_node_position_y);
 
- xbt_dict_set( parsed_nodes,A_graphxml_node_name, (void *)node, free); 
-  
- DEBUG1("<node label=\"%s\"/>",(char*)(node->data));
+  xbt_dict_set(parsed_nodes, A_graphxml_node_name, (void *) node, NULL);
 }
+
 static void __parse_edge(void)
 {
-   xbt_edge_t edge= xbt_graph_new_edge(parsed_graph,
-				       xbt_dict_get(parsed_nodes,
-				       A_graphxml_edge_source),
-				       xbt_dict_get(parsed_nodes,
-				       A_graphxml_edge_target),
-				       (void*) A_graphxml_edge_name);
-
- xbt_dict_set( parsed_edges,A_graphxml_edge_name, (void *)edge, free);
- xbt_graph_edge_set_length(edge,atof(A_graphxml_edge_length));
- 
-  DEBUG4("<edge name=\"%s\"  source=\"%s\" target=\"%s\" length=\"%f\"/>",
-	 (char*)edge->data,
-	 (char*)(edge->src)->data,
-	 (char*)(edge->dst)->data,
-	 xbt_graph_edge_get_length(edge));
+  xbt_edge_t edge = xbt_graph_new_edge(parsed_graph,
+                                       xbt_dict_get(parsed_nodes,
+                                                    A_graphxml_edge_source),
+                                       xbt_dict_get(parsed_nodes,
+                                                    A_graphxml_edge_target),
+                                       NULL);
+
+  if (__parse_edge_label_and_data)
+    edge->data = __parse_edge_label_and_data(edge, A_graphxml_edge_label,
+                                             A_graphxml_edge_data);
+
+  xbt_graph_parse_get_double(&(edge->length), A_graphxml_edge_length);
+
+  DEBUG3("<edge  source=\"%s\" target=\"%s\" length=\"%f\"/>",
+         (char *) (edge->src)->data,
+         (char *) (edge->dst)->data, xbt_graph_edge_get_length(edge));
 }
 
-xbt_graph_t xbt_graph_read(const char *filename)
-{ 
-  xbt_graph_t graph = xbt_graph_new_graph(1,NULL);
+/** @brief Import a graph from a file following the GraphXML format */
+xbt_graph_t xbt_graph_read(const char *filename,
+                           void *(*node_label_and_data) (xbt_node_t,
+                                                         const char *,
+                                                         const char *),
+                           void *(*edge_label_and_data) (xbt_edge_t,
+                                                         const char *,
+                                                         const char *))
+{
 
-  parsed_graph = graph;
-  parsed_nodes= xbt_dict_new();
-  parsed_edges= xbt_dict_new();
+  xbt_graph_t graph = NULL;
 
+  __parse_node_label_and_data = node_label_and_data;
+  __parse_edge_label_and_data = edge_label_and_data;
 
   xbt_graph_parse_reset_parser();
-  
+
   STag_graphxml_graph_fun = __parse_graph_begin;
   ETag_graphxml_graph_fun = __parse_graph_end;
   ETag_graphxml_node_fun = __parse_node;
   ETag_graphxml_edge_fun = __parse_edge;
 
-
   xbt_graph_parse_open(filename);
-  xbt_assert1((!xbt_graph_parse()),"Parse error in %s",filename);
+  xbt_assert1((!(*xbt_graph_parse) ()), "Parse error in %s", filename);
   xbt_graph_parse_close();
 
+  graph = parsed_graph;
   parsed_graph = NULL;
+
   return graph;
 }
-void xbt_graph_export_surfxml(xbt_graph_t g,
-			      const char *filename,
-			      const char *(node_name)(xbt_node_t),
-			      const char *(edge_name)(xbt_edge_t)
-			      )
+
+/** @brief Export the given graph in the GraphViz formatting for visualization */
+void xbt_graph_export_graphviz(xbt_graph_t g, const char *filename,
+                               const char *(node_name) (xbt_node_t),
+                               const char *(edge_name) (xbt_edge_t))
 {
-  
+  unsigned int cursor = 0;
+  xbt_node_t node = NULL;
+  xbt_edge_t edge = NULL;
+  FILE *file = NULL;
+  const char *name = NULL;
+
+  file = fopen(filename, "w");
+  xbt_assert1(file, "Failed to open %s \n", filename);
+
+  if (g->directed)
+    fprintf(file, "digraph test {\n");
+  else
+    fprintf(file, "graph test {\n");
+
+  fprintf(file, "  graph [overlap=scale]\n");
+
+  fprintf(file, "  node [shape=box, style=filled]\n");
+  fprintf(file,
+          "  node [width=.3, height=.3, style=filled, color=skyblue]\n\n");
+
+  xbt_dynar_foreach(g->nodes, cursor, node) {
+    fprintf(file, "  \"%p\" ", node);
+    if ((node_name) && ((name = node_name(node))))
+      fprintf(file, "[label=\"%s\"]", name);
+    fprintf(file, ";\n");
+  }
+  xbt_dynar_foreach(g->edges, cursor, edge) {
+    if (g->directed)
+      fprintf(file, "  \"%p\" -> \"%p\"", edge->src, edge->dst);
+    else
+      fprintf(file, "  \"%p\" -- \"%p\"", edge->src, edge->dst);
+    if ((edge_name) && ((name = edge_name(edge))))
+      fprintf(file, "[label=\"%s\"]", name);
+    fprintf(file, ";\n");
+  }
+  fprintf(file, "}\n");
+  fclose(file);
 }
 
-/* ./xbt/graphxml_usage xbt/graph.xml --xbt-log=graph.thres=debug */
+/** @brief Export the given graph in the GraphXML format */
+void xbt_graph_export_graphxml(xbt_graph_t g, const char *filename,
+                               const char *(node_name) (xbt_node_t),
+                               const char *(edge_name) (xbt_edge_t),
+                               const char *(node_data_print) (void *),
+                               const char *(edge_data_print) (void *))
+{
+  unsigned int cursor = 0;
+  xbt_node_t node = NULL;
+  xbt_edge_t edge = NULL;
+  FILE *file = NULL;
+  const char *name = NULL;
+
+  file = fopen(filename, "w");
+  xbt_assert1(file, "Failed to open %s \n", filename);
+
+  fprintf(file, "<?xml version='1.0'?>\n");
+  fprintf(file, "<!DOCTYPE graph SYSTEM \"graphxml.dtd\">\n");
+  if (g->directed)
+    fprintf(file, "<graph isDirected=\"true\">\n");
+  else
+    fprintf(file, "<graph isDirected=\"false\">\n");
+  xbt_dynar_foreach(g->nodes, cursor, node) {
+    fprintf(file, "  <node name=\"%p\" ", node);
+    if ((node_name) && ((name = node_name(node))))
+      fprintf(file, "label=\"%s\" ", name);
+    if ((node_data_print) && ((name = node_data_print(node->data))))
+      fprintf(file, "data=\"%s\" ", name);
+    fprintf(file, ">\n");
+  }
+  xbt_dynar_foreach(g->edges, cursor, edge) {
+    fprintf(file, "  <edge source=\"%p\" target =\"%p\" ",
+            edge->src, edge->dst);
+    if ((edge_name) && ((name = edge_name(edge))))
+      fprintf(file, "label=\"%s\" ", name);
+    if (edge->length >= 0.0)
+      fprintf(file, "length=\"%g\" ", edge->length);
+    if ((edge_data_print) && ((name = edge_data_print(edge->data))))
+      fprintf(file, "data=\"%s\" ", name);
+    fprintf(file, ">\n");
+  }
+  fprintf(file, "</graph>\n");
+  fclose(file);
+}