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Add TA minimization: merge bisimulating states

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* src/taalgos/minimize.hh, src/taalgos/minimize.cc: implements a
minimization of TA by merging bisimular states.
* src/taalgos/statessetbuilder.hh, src/taalgos/statessetbuilder.cc:
returns the set of reachable states of a TA (used in minimize.cc).
* src/taalgos/Makefile.am: add them.
* src/tgbatest/ltl2tgba.cc: add commands to test TA minimization
This commit is contained in:
Ala Eddine 2011-03-08 15:06:56 +01:00 • committed by Alexandre Duret-Lutz
parent 81e80e6069
commit cd04d9acf3
6 changed files with 605 additions and 3 deletions
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src/taalgos/minimize.cc Normal file
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// Copyright (C) 2010, 2011 Laboratoire de Recherche et Développement
// de l'Epita (LRDE).
//
// 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.
//#define TRACE
#ifdef TRACE
# define trace std::cerr
#else
# define trace while (0) std::cerr
#endif
#include <set>
#include <list>
#include <sstream>
#include "minimize.hh"
#include "ltlast/allnodes.hh"
#include "misc/hash.hh"
#include "misc/bddlt.hh"
#include "ta/taproduct.hh"
#include "taalgos/statessetbuilder.hh"
#include "tgba/tgbaexplicit.hh"
namespace spot
{
typedef Sgi::hash_set<const state*, state_ptr_hash, state_ptr_equal> hash_set;
typedef Sgi::hash_map<const state*, unsigned, state_ptr_hash, state_ptr_equal>
hash_map;
namespace
{
static std::ostream&
dump_hash_set(const hash_set* hs, const ta* aut, std::ostream& out)
{
out << "{";
const char* sep = "";
for (hash_set::const_iterator i = hs->begin(); i != hs->end(); ++i)
{
out << sep << aut->format_state(*i);
sep = ", ";
}
out << "}";
return out;
}
static std::string
format_hash_set(const hash_set* hs, const ta* aut)
{
std::ostringstream s;
dump_hash_set(hs, aut, s);
return s.str();
}
}
// From the base automaton and the list of sets, build the minimal
// tgbaulting automaton
ta*
build_result(const ta* a, std::list<hash_set*>& sets)
{
tgba_explicit_number* tgba = new tgba_explicit_number(a->get_dict());
ta_explicit* ta = new ta_explicit(tgba);
// For each set, create a state in the tgbaulting automaton.
// For a state s, state_num[s] is the number of the state in the minimal
// automaton.
hash_map state_num;
std::list<hash_set*>::iterator sit;
unsigned num = 0;
for (sit = sets.begin(); sit != sets.end(); ++sit)
{
hash_set::iterator hit;
hash_set* h = *sit;
for (hit = h->begin(); hit != h->end(); ++hit)
state_num[*hit] = num;
++num;
}
// For each transition in the initial automaton, add the corresponding
// transition in ta.
for (sit = sets.begin(); sit != sets.end(); ++sit)
{
hash_set::iterator hit;
hash_set* h = *sit;
hit = h->begin();
const state* src = *hit;
unsigned src_num = state_num[src];
state* tgba_state = new state_explicit(tgba->add_state(src_num));
bdd tgba_condition = bddtrue;
bool is_initial_state = a->is_initial_state(src);
if (is_initial_state)
tgba_condition = a->get_state_condition(src);
bool is_accepting_state = a->is_accepting_state(src);
bool is_livelock_accepting_state = a->is_livelock_accepting_state(src);
state_ta_explicit* new_src = new state_ta_explicit(tgba_state,
tgba_condition, is_initial_state, is_accepting_state,
is_livelock_accepting_state);
state_ta_explicit* ta_src = ta->add_state(new_src);
if (ta_src != new_src)
{
delete new_src;
delete tgba_state;
}
else if (is_initial_state)
ta->add_to_initial_states_set(new_src);
ta_succ_iterator* succit = a->succ_iter(src);
for (succit->first(); !succit->done(); succit->next())
{
const state* dst = succit->current_state();
hash_map::const_iterator i = state_num.find(dst);
if (i == state_num.end()) // Ignore useless destinations.
continue;
state* tgba_state = new state_explicit(tgba->add_state(i->second));
bdd tgba_condition = bddtrue;
is_initial_state = a->is_initial_state(dst);
if (is_initial_state)
tgba_condition = a->get_state_condition(dst);
bool is_accepting_state = a->is_accepting_state(dst);
bool is_livelock_accepting_state = a->is_livelock_accepting_state(
dst);
state_ta_explicit* new_dst = new state_ta_explicit(tgba_state,
tgba_condition, is_initial_state, is_accepting_state,
is_livelock_accepting_state);
state_ta_explicit* ta_dst = ta->add_state(new_dst);
if (ta_dst != new_dst) {
delete new_dst;
delete tgba_state;
}
else if (is_initial_state)
ta->add_to_initial_states_set(new_dst);
ta->create_transition(ta_src, succit->current_condition(), ta_dst);
}
delete succit;
}
return ta;
}
ta*
minimize_ta(const ta* ta_)
{
typedef std::list<hash_set*> partition_t;
partition_t cur_run;
partition_t next_run;
// The list of equivalent states.
partition_t done;
std::set<const state*> states_set = get_states_set(ta_);
// livelock acceptance states
hash_set* G = new hash_set;
// Buchi acceptance states
hash_set* F = new hash_set;
// Buchi and livelock acceptance states
hash_set* G_F = new hash_set;
// the other states (non initial and not in G, F and G_F)
hash_set* S = new hash_set;
std::set<const state*>::iterator it;
for (it = states_set.begin(); it != states_set.end(); it++)
{
const state* s = (*it);
if (ta_->is_initial_state(s))
{
hash_set* i = new hash_set;
i->insert(s);
done.push_back(i);
}
else if (ta_->is_livelock_accepting_state(s)
&& ta_->is_accepting_state(s))
{
G_F->insert(s);
}
else if (ta_->is_accepting_state(s))
{
F->insert(s);
}
else if (ta_->is_livelock_accepting_state(s))
{
G->insert(s);
}
else
{
S->insert(s);
}
}
hash_map state_set_map;
// Size of ta_
unsigned size = states_set.size();
// Use bdd variables to number sets. set_num is the first variable
// available.
unsigned set_num = ta_->get_dict()->register_anonymous_variables(size, ta_);
std::set<int> free_var;
for (unsigned i = set_num; i < set_num + size; ++i)
free_var.insert(i);
std::map<int, int> used_var;
if (!G->empty())
{
unsigned s = G->size();
used_var[set_num] = s;
free_var.erase(set_num);
if (s > 1)
cur_run.push_back(G);
else
done.push_back(G);
for (hash_set::const_iterator i = G->begin(); i != G->end(); ++i)
state_set_map[*i] = set_num;
}
else
delete G;
if (!F->empty())
{
unsigned s = F->size();
unsigned num = set_num + 1;
used_var[num] = s;
free_var.erase(num);
if (s > 1)
cur_run.push_back(F);
else
done.push_back(F);
for (hash_set::const_iterator i = F->begin(); i != F->end(); ++i)
state_set_map[*i] = num;
}
else
delete F;
if (!G_F->empty())
{
unsigned s = G_F->size();
unsigned num = set_num + 2;
used_var[num] = s;
free_var.erase(num);
if (s > 1)
cur_run.push_back(G_F);
else
done.push_back(G_F);
for (hash_set::const_iterator i = G_F->begin(); i != G_F->end(); ++i)
state_set_map[*i] = num;
}
else
delete G_F;
if (!S->empty())
{
unsigned s = S->size();
unsigned num = set_num + 3;
used_var[num] = s;
free_var.erase(num);
if (s > 1)
cur_run.push_back(S);
else
done.push_back(S);
for (hash_set::const_iterator i = S->begin(); i != S->end(); ++i)
state_set_map[*i] = num;
}
else
delete S;
// A bdd_states_map is a list of formulae (in a BDD form) associated with a
// destination set of states.
typedef std::map<bdd, hash_set*, bdd_less_than> bdd_states_map;
bool did_split = true;
while (did_split)
{
did_split = false;
while (!cur_run.empty())
{
// Get a set to process.
hash_set* cur = cur_run.front();
cur_run.pop_front();
trace
<< "processing " << format_hash_set(cur, ta_) << std::endl;
hash_set::iterator hi;
bdd_states_map bdd_map;
for (hi = cur->begin(); hi != cur->end(); ++hi)
{
const state* src = *hi;
bdd f = bddfalse;
ta_succ_iterator* si = ta_->succ_iter(src);
for (si->first(); !si->done(); si->next())
{
const state* dst = si->current_state();
hash_map::const_iterator i = state_set_map.find(dst);
if (i == state_set_map.end())
// The destination state is not in our
// partition. This can happen if the initial
// FINAL and NON_FINAL supplied to the algorithm
// do not cover the whole automaton (because we
// want to ignore some useless states). Simply
// ignore these states here.
continue;
f |= (bdd_ithvar(i->second) & si->current_condition());
}
delete si;
// Have we already seen this formula ?
bdd_states_map::iterator bsi = bdd_map.find(f);
if (bsi == bdd_map.end())
{
// No, create a new set.
hash_set* new_set = new hash_set;
new_set->insert(src);
bdd_map[f] = new_set;
}
else
{
// Yes, add the current state to the set.
bsi->second->insert(src);
}
}
bdd_states_map::iterator bsi = bdd_map.begin();
if (bdd_map.size() == 1)
{
// The set was not split.
trace
<< "set " << format_hash_set(bsi->second, ta_)
<< " was not split" << std::endl;
next_run.push_back(bsi->second);
}
else
{
for (; bsi != bdd_map.end(); ++bsi)
{
hash_set* set = bsi->second;
// Free the number associated to these states.
unsigned num = state_set_map[*set->begin()];
assert(used_var.find(num) != used_var.end());
unsigned left = (used_var[num] -= set->size());
// Make sure LEFT does not become negative (hence bigger
// than SIZE when read as unsigned)
assert(left < size);
if (left == 0)
{
used_var.erase(num);
free_var.insert(num);
}
// Pick a free number
assert(!free_var.empty());
num = *free_var.begin();
free_var.erase(free_var.begin());
used_var[num] = set->size();
for (hash_set::iterator hit = set->begin(); hit
!= set->end(); ++hit)
state_set_map[*hit] = num;
// Trivial sets can't be splitted any further.
if (set->size() == 1)
{
trace
<< "set " << format_hash_set(set, ta_)
<< " is minimal" << std::endl;
done.push_back(set);
}
else
{
did_split = true;
trace
<< "set " << format_hash_set(set, ta_)
<< " should be processed further" << std::endl;
next_run.push_back(set);
}
}
}
delete cur;
}
if (did_split)
trace
<< "splitting did occur during this pass." << std::endl;
//elsetrace << "splitting did not occur during this pass." << std::endl;
std::swap(cur_run, next_run);
}
done.splice(done.end(), cur_run);
#ifdef TRACE
trace << "Final partition: ";
for (partition_t::const_iterator i = done.begin(); i != done.end(); ++i)
trace << format_hash_set(*i, ta_) << " ";
trace << std::endl;
#endif
// Build the tgbault.
ta* res = build_result(ta_, done);
// Free all the allocated memory.
std::list<hash_set*>::iterator itdone;
for (itdone = done.begin(); itdone != done.end(); ++itdone)
delete *itdone;
delete ta_;
return res;
}
}