Fix random_graph() not to generate dead states.

This is actually the third time I fix random_graph().  On
2007-02-06 I changed the function not to generated dead states,
but in a way that made it non-deterministic.  On 2010-01-20 I made
the function deterministic again, but it started to generate dead
states as a side effect.  This time, I'm making sure that dead
states won't come again with a test-case that we should have had
from the beginning.

* src/tgbaalgos/randomgraph.cc (random_graph): Add an extra
indirection array, state_randomizer[], so that we can reorder
states indices after a random selection without actually changing
the value of the indices used by unreachable_states and
nodes_to_process.
* src/tgbatest/randtgba.test: New file.
* src/tgbatest/Makefile.am: Add randtgba.test.

ChangeLog

@@ -1,3 +1,23 @@
+2010-02-23  Alexandre Duret-Lutz  <adl@lrde.epita.fr>
+
+	Fix random_graph() not to generate dead states.
+
+	This is actually the third time I fix random_graph().  On
+	2007-02-06 I changed the function not to generated dead states,
+	but in a way that made it non-deterministic.  On 2010-01-20 I made
+	the function deterministic again, but it started to generate dead
+	states as a side effect.  This time, I'm making sure that dead
+	states won't come again with a test-case that we should have had
+	from the beginning.
+
+	* src/tgbaalgos/randomgraph.cc (random_graph): Add an extra
+	indirection array, state_randomizer[], so that we can reorder
+	states indices after a random selection without actually changing
+	the value of the indices used by unreachable_states and
+	nodes_to_process.
+	* src/tgbatest/randtgba.test: New file.
+	* src/tgbatest/Makefile.am: Add randtgba.test.
+
 2010-02-17  Alexandre Duret-Lutz  <adl@lrde.epita.fr>
 
 	ltl2tgba cgi updates.

src/tgbaalgos/randomgraph.cc

@@ -108,6 +108,8 @@ namespace spot
       props[pi++] = dict->register_proposition(*i, res);
 
     std::vector<tgba_explicit::state*> states(n);
+    // Indirect access to state[] to help random selection of successors.
+    std::vector<int> state_randomizer(n);
 
     std::list<bdd> accs;
     bdd allneg = bddtrue;
@@ -134,11 +136,13 @@ namespace spot
     node_set unreachable_nodes;
 
     states[0] = res->add_state(st(0));
+    state_randomizer[0] = 0;
     nodes_to_process.insert(0);
 
     for (int i = 1; i < n; ++i)
       {
 	states[i] = res->add_state(st(i));
+	state_randomizer[i] = i;
 	unreachable_nodes.insert(i);
       }
 
@@ -163,6 +167,8 @@ namespace spot
 	int possibilities = n;
 	while (nsucc--)
 	  {
+	    // No connection to unreachable successors so far.  This
+	    // is our last chance, so force it now.
 	    if (nsucc == 0
 		&& !saw_unreachable
 		&& !unreachable_nodes.empty())
@@ -180,21 +186,23 @@ namespace spot
 	      }
 	    else
 	      {
-		// Pick a random node.
+		// Pick the index of a random node.
 		int index = mrand(possibilities--);
-		tgba_explicit::state* dest = states[index];
 
-		// Permute the state with states[possibilities], so we
+		// Permute it with state_randomizer[possibilities], so
-		// cannot pick it again.
+		// we cannot pick it again.
-		states[index] = states[possibilities];
+		int x = state_randomizer[index];
-		states[possibilities] = dest;
+		state_randomizer[index] = state_randomizer[possibilities];
+		state_randomizer[possibilities] = x;
+
+		tgba_explicit::state* dest = states[x];
 
 		random_labels(res, src, dest, props, props_n, t, accs, a);
 
-		node_set::iterator j = unreachable_nodes.find(possibilities);
+		node_set::iterator j = unreachable_nodes.find(x);
 		if (j != unreachable_nodes.end())
 		  {
-		    nodes_to_process.insert(possibilities);
+		    nodes_to_process.insert(x);
 		    unreachable_nodes.erase(j);
 		    saw_unreachable = true;
 		  }

src/tgbatest/Makefile.am

@@ -1,4 +1,4 @@
-## Copyright (C) 2009 Laboratoire de Recherche et Développement
+## Copyright (C) 2009, 2010 Laboratoire de Recherche et Développement
 ## de l'Epita (LRDE).
 ## Copyright (C) 2003, 2004, 2005, 2006 Laboratoire d'Informatique de
 ## Paris 6 (LIP6), département Systèmes Répartis Coopératifs (SRC),
@@ -91,6 +91,7 @@ TESTS = \
   reduccmp.test \
   reductgba.test \
   scc.test \
+  randtgba.test \
   emptchk.test \
   emptchke.test \
   dfs.test \

src/tgbatest/randtgba.test

@@ -0,0 +1,34 @@
+#!/bin/sh
+# Copyright (C) 2010  Laboratoire de Recherche et Development de l'EPITA.
+#
+# This file is part of Spot, a model checking library.
+#
+# Spot 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.
+#
+# Spot 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 Spot; see the file COPYING.  If not, write to the Free
+# Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+# 02111-1307, USA.
+
+. ./defs
+
+set -e
+
+for n in 10 20 30 40 50 60 70 80 90 100 200 500 1000; do
+  # Make sure graph generated by randtgba have successors for each
+  # of their $n nodes.
+  r=`../randtgba -n $n a b c | sed -n 's/^"S\([0-9]*\)".*/\1/p' |
+     sort -u | wc -l`
+  if test "$r" -eq "$n"; then :; else
+     echo "test failed for n=$n"
+     exit 1
+  fi
+done