+/** @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;
+ }
+
+ 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 ******************/