Conversion to struct addrinfo is almost complete for this file.

[tinc] / src / graph.c

diff --git a/src/graph.c b/src/graph.c
index c7ca8af..aa1ec72 100644 (file)
--- a/src/graph.c
+++ b/src/graph.c
@@ -17,22 +17,24 @@
     along with this program; if not, write to the Free Software
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 
-    $Id: graph.c,v 1.1.2.2 2001/10/28 22:42:49 guus Exp $
+    $Id: graph.c,v 1.1.2.5 2001/10/31 12:50:24 guus Exp $
 */
 
 /* We need to generate two trees from the graph:
 
    1. A minimum spanning tree for broadcasts,
    2. A single-source shortest path tree for unicasts.
-   
+
    Actually, the first one alone would suffice but would make unicast packets
    take longer routes than necessary.
-   
+
    For the MST algorithm we can choose from Prim's or Kruskal's. I personally
    favour Kruskal's, because we make an extra AVL tree of edges sorted on
    weights (metric). That tree only has to be updated when an edge is added or
    removed, and during the MST algorithm we just have go linearly through that
-   tree, adding safe edges until #edges = #nodes - 1.
+   tree, adding safe edges until #edges = #nodes - 1. The implementation here
+   however is not so fast, because I tried to avoid having to make a forest and
+   merge trees.
 
    For the SSSP algorithm Dijkstra's seems to be a nice choice. Currently a
    simple breadth-first search is presented here.
@@ -40,6 +42,7 @@
 
 #include <syslog.h>
 #include "config.h"
+#include <string.h>
 
 #include <avl_tree.h>
 
@@ -50,20 +53,19 @@
 #include "system.h"
 
 /* Implementation of Kruskal's algorithm.
-   Running time: O(E)
+   Running time: O(EN)
    Please note that sorting on weight is already done by add_edge().
 */
 
 void mst_kruskal(void)
 {
-  avl_node_t *node;
+  avl_node_t *node, *next;
   edge_t *e;
   node_t *n;
   connection_t *c;
   int nodes = 0;
   int safe_edges = 0;
-  
-  syslog(LOG_DEBUG, _("Running Kruskal's algorithm:"));
+  int skipped;
 
   /* Clear visited status on nodes */
 
@@ -74,6 +76,10 @@ void mst_kruskal(void)
       nodes++;
     }
 
+  /* Starting point */
+  
+  ((edge_t *)edge_weight_tree->head->data)->from->status.visited = 1;
+
   /* Clear MST status on connections */
 
   for(node = connection_tree->head; node; node = node->next)
@@ -84,32 +90,29 @@ void mst_kruskal(void)
 
   /* Add safe edges */
 
-  for(node = edge_weight_tree->head; node; node = node->next)
+  for(skipped = 0, node = edge_weight_tree->head; node; node = next)
     {
-// Algorithm should work without this:
-//      if(safe_edges = nodes - 1)
-//        break;
-
+      next = node->next;
       e = (edge_t *)node->data;
-      
-      if(e->from->status.visited && e->to->status.visited)
-        continue;
+
+      if(e->from->status.visited == e->to->status.visited)
+        {
+          skipped = 1;
+          continue;
+        }
 
       e->from->status.visited = 1;
       e->to->status.visited = 1;
       if(e->connection)
         e->connection->status.mst = 1;
 
-      safe_edges++;      
-
-      syslog(LOG_DEBUG, _("Adding safe edge %s - %s weight %d"), e->from->name, e->to->name, e->weight);
-    }
-
-  syslog(LOG_DEBUG, _("Done."));
+      safe_edges++;
 
-  if(safe_edges != nodes - 1)
-    {
-      syslog(LOG_ERR, _("Implementation of Kruskal's algorithm is screwed: %d nodes, found %d safe edges"), nodes, safe_edges);
+      if(skipped)
+        {
+          next = edge_weight_tree->head;
+          continue;
+        }
     }
 }
 
@@ -117,16 +120,12 @@ void mst_kruskal(void)
    Running time: O(E)
 */
 
-void sssp_bfs(void)
+void sssp_bfs(int prune)
 {
   avl_node_t *node, *from, *next, *to;
   edge_t *e;
   node_t *n, *check;
-  int nodes = 0;
-  int visited = 0;
   avl_tree_t *todo_tree;
-  
-  syslog(LOG_DEBUG, _("Running BFS algorithm:"));
 
   todo_tree = avl_alloc_tree(NULL, NULL);
 
@@ -136,7 +135,6 @@ void sssp_bfs(void)
     {
       n = (node_t *)node->data;
       n->status.visited = 0;
-      nodes++;
     }
 
   /* Begin with myself */
@@ -147,7 +145,6 @@ void sssp_bfs(void)
   node = avl_alloc_node();
   node->data = myself;
   avl_insert_top(todo_tree, node);
-  visited++;
 
   /* Loop while todo_tree is filled */
 
@@ -157,7 +154,7 @@ void sssp_bfs(void)
         {
           next = from->next;
           n = (node_t *)from->data;
-          
+
           for(to = n->edge_tree->head; to; to = to->next)
             {
               e = (edge_t *)to->data;
@@ -170,10 +167,11 @@ void sssp_bfs(void)
               if(!check->status.visited)
                 {
                   check->status.visited = 1;
-                  check->nexthop = (n->nexthop == myself)?n:n->nexthop;
-                  check->via = check; /* FIXME: only if !(e->options & INDIRECT), otherwise use n->via */
-                  avl_insert_before(todo_tree, todo_tree->head, to);
-                  visited++;
+                  check->nexthop = (n->nexthop == myself) ? check : n->nexthop;
+                  check->via = (e->options & OPTION_INDIRECT || n->via != n) ? n->via : check;
+                  node = avl_alloc_node();
+                  node->data = check;
+                  avl_insert_before(todo_tree, from, node);
                 }
             }
 
@@ -181,10 +179,17 @@ void sssp_bfs(void)
         }
     }
 
-  syslog(LOG_DEBUG, _("Done."));
+  avl_free_tree(todo_tree);
+  
+  /* Nodes we haven't visited are unreachable, prune them. */
+
+  if(prune)
+    for(node = node_tree->head; node; node = next)
+      {
+        next = node->next;
+        n = (node_t *)node->data;
 
-  if(visited != nodes)
-    {
-      syslog(LOG_ERR, _("Implementation of BFS algorithm is screwed: %d nodes, visited %d"), nodes, visited);
-    }
+        if(n->status.visited == 0)
+          node_del(n);
+      }
 }