Working version of Kruskal's algorithm. The running time is very bad though.

[tinc] / src / graph.c

diff --git a/src/graph.c b/src/graph.c
index c7ca8af..7b8880d 100644 (file)
--- a/src/graph.c
+++ b/src/graph.c
@@ -17,17 +17,17 @@
     along with this program; if not, write to the Free Software
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 
     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 1.1.2.3 2001/10/29 13:14:57 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.
 */
 
 /* 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.
    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
    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


@@ -40,6 +40,7 @@
 
 #include <syslog.h>
 #include "config.h"
 
 #include <syslog.h>
 #include "config.h"

+#include <string.h>

 
 #include <avl_tree.h>
 
 
 #include <avl_tree.h>
 


@@ -50,7 +51,7 @@
 #include "system.h"
 
 /* Implementation of Kruskal's algorithm.
 #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().
 */
 
    Please note that sorting on weight is already done by add_edge().
 */
 


@@ -62,7 +63,8 @@ void mst_kruskal(void)
   connection_t *c;
   int nodes = 0;
   int safe_edges = 0;
   connection_t *c;
   int nodes = 0;
   int safe_edges = 0;

-  
+  int skipped;
+

   syslog(LOG_DEBUG, _("Running Kruskal's algorithm:"));
 
   /* Clear visited status on nodes */
   syslog(LOG_DEBUG, _("Running Kruskal's algorithm:"));
 
   /* Clear visited status on nodes */


@@ -74,6 +76,10 @@ void mst_kruskal(void)
       nodes++;
     }
 
       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)
   /* Clear MST status on connections */
 
   for(node = connection_tree->head; node; node = node->next)


@@ -84,25 +90,32 @@ void mst_kruskal(void)
 
   /* Add safe edges */
 
 
   /* Add safe edges */
 

-  for(node = edge_weight_tree->head; node; node = node->next)
+  while(safe_edges < nodes - 1)
+  for(skipped = 0, node = edge_weight_tree->head; node; node = node->next)

     {
 // Algorithm should work without this:
 //      if(safe_edges = nodes - 1)
 //        break;
 
       e = (edge_t *)node->data;
     {
 // Algorithm should work without this:
 //      if(safe_edges = nodes - 1)
 //        break;
 
       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;
 
 
       e->from->status.visited = 1;
       e->to->status.visited = 1;
       if(e->connection)
         e->connection->status.mst = 1;
 

-      safe_edges++;      
+      safe_edges++;

 
       syslog(LOG_DEBUG, _("Adding safe edge %s - %s weight %d"), e->from->name, e->to->name, e->weight);
 
       syslog(LOG_DEBUG, _("Adding safe edge %s - %s weight %d"), e->from->name, e->to->name, e->weight);

+
+      if(skipped)
+        break;

     }
 
   syslog(LOG_DEBUG, _("Done."));
     }
 
   syslog(LOG_DEBUG, _("Done."));


@@ -125,7 +138,7 @@ void sssp_bfs(void)
   int nodes = 0;
   int visited = 0;
   avl_tree_t *todo_tree;
   int nodes = 0;
   int visited = 0;
   avl_tree_t *todo_tree;

-  
+

   syslog(LOG_DEBUG, _("Running BFS algorithm:"));
 
   todo_tree = avl_alloc_tree(NULL, NULL);
   syslog(LOG_DEBUG, _("Running BFS algorithm:"));
 
   todo_tree = avl_alloc_tree(NULL, NULL);


@@ -157,7 +170,7 @@ void sssp_bfs(void)
         {
           next = from->next;
           n = (node_t *)from->data;
         {
           next = from->next;
           n = (node_t *)from->data;

-          
+

           for(to = n->edge_tree->head; to; to = to->next)
             {
               e = (edge_t *)to->data;
           for(to = n->edge_tree->head; to; to = to->next)
             {
               e = (edge_t *)to->data;


@@ -170,10 +183,13 @@ void sssp_bfs(void)
               if(!check->status.visited)
                 {
                   check->status.visited = 1;
               if(!check->status.visited)
                 {
                   check->status.visited = 1;

-                  check->nexthop = (n->nexthop == myself)?n:n->nexthop;
+                  check->nexthop = (n->nexthop == myself) ? n : n->nexthop;

                   check->via = check; /* FIXME: only if !(e->options & INDIRECT), otherwise use n->via */
                   check->via = check; /* FIXME: only if !(e->options & INDIRECT), otherwise use n->via */

-                  avl_insert_before(todo_tree, todo_tree->head, to);
+                  node = avl_alloc_node();
+                  node->data = check;
+                  avl_insert_before(todo_tree, from, node);

                   visited++;
                   visited++;

+                  syslog(LOG_DEBUG, _("Node %s nexthop %s via %s"), check->name, check->nexthop->name, check->via->name);

                 }
             }
 
                 }
             }
 


@@ -183,6 +199,8 @@ void sssp_bfs(void)
 
   syslog(LOG_DEBUG, _("Done."));
 
 
   syslog(LOG_DEBUG, _("Done."));
 

+  avl_free_tree(todo_tree);
+

   if(visited != nodes)
     {
       syslog(LOG_ERR, _("Implementation of BFS algorithm is screwed: %d nodes, visited %d"), nodes, visited);
   if(visited != nodes)
     {
       syslog(LOG_ERR, _("Implementation of BFS algorithm is screwed: %d nodes, visited %d"), nodes, visited);