From cc9473d8c6467e9eaa82fe8a639d8edba232ee76 Mon Sep 17 00:00:00 2001 From: Guus Sliepen Date: Mon, 29 Oct 2001 13:14:57 +0000 Subject: [PATCH] Working version of Kruskal's algorithm. The running time is very bad though. --- src/graph.c | 46 ++++++++++++++++++++++++++++++++-------------- src/graph.h | 25 +++++++++++++++++++++++++ 2 files changed, 57 insertions(+), 14 deletions(-) create mode 100644 src/graph.h diff --git a/src/graph.c b/src/graph.c index c7ca8af..7b8880d 100644 --- 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. - $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. - + 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 @@ -40,6 +40,7 @@ #include #include "config.h" +#include #include @@ -50,7 +51,7 @@ #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(). */ @@ -62,7 +63,8 @@ void mst_kruskal(void) connection_t *c; int nodes = 0; int safe_edges = 0; - + int skipped; + syslog(LOG_DEBUG, _("Running Kruskal's algorithm:")); /* 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) @@ -84,25 +90,32 @@ void mst_kruskal(void) /* 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; - - 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++; + safe_edges++; 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.")); @@ -125,7 +138,7 @@ void sssp_bfs(void) int nodes = 0; int visited = 0; avl_tree_t *todo_tree; - + 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; - + 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; - 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 */ - avl_insert_before(todo_tree, todo_tree->head, to); + node = avl_alloc_node(); + node->data = check; + avl_insert_before(todo_tree, from, node); 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.")); + avl_free_tree(todo_tree); + if(visited != nodes) { syslog(LOG_ERR, _("Implementation of BFS algorithm is screwed: %d nodes, visited %d"), nodes, visited); diff --git a/src/graph.h b/src/graph.h new file mode 100644 index 0000000..c69fc98 --- /dev/null +++ b/src/graph.h @@ -0,0 +1,25 @@ +/* + graph.h -- header for graph.c + Copyright (C) 2001 Guus Sliepen , + 2001 Ivo Timmermans + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + + $Id: graph.h,v 1.1.2.1 2001/10/29 13:14:57 guus Exp $ +*/ + +extern void mst_kruskal(void); +extern void mst_prim(void); +extern void sssp_bfs(void); -- 2.25.1