Cleanup the DFA minimization algorithm.
* src/tgbaalgos/minimize.cc (minimize): Move the minimization code into... (minimize_dfa): ... this new function, and fix the condition under which a partition is considered to be minimal. Also use a map instead of a list to lookup known formulae.
This commit is contained in:
Alexandre Duret-Lutz
parent
ef317685c8
commit
92126a6cf9
2 changed files with 247 additions and 155 deletions
10
ChangeLog
10
ChangeLog
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@ -1,3 +1,13 @@
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2011-01-05 Alexandre Duret-Lutz <adl@lrde.epita.fr>
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Cleanup the DFA minimization algorithm.
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* src/tgbaalgos/minimize.cc (minimize): Move the minimization
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code into...
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(minimize_dfa): ... this new function, and fix the condition
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under which a partition is considered to be minimal. Also
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use a map instead of a list to lookup known formulae.
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2011-01-05 Alexandre Duret-Lutz <adl@lrde.epita.fr>
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Speed up the obligation test.
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@ -18,14 +18,25 @@
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// Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
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// 02111-1307, USA.
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//#define TRACE
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#ifdef TRACE
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# define trace std::cerr
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#else
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# define trace while (0) std::cerr
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#endif
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#include <queue>
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#include <deque>
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#include <set>
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#include <list>
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#include <vector>
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#include <sstream>
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#include "minimize.hh"
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#include "ltlast/allnodes.hh"
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#include "misc/hash.hh"
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#include "misc/bddlt.hh"
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#include "tgba/tgbaproduct.hh"
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#include "tgba/tgbatba.hh"
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#include "tgbaalgos/powerset.hh"
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@ -43,6 +54,31 @@ namespace spot
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typedef Sgi::hash_map<const state*, unsigned,
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state_ptr_hash, state_ptr_equal> hash_map;
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namespace
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{
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static std::ostream&
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dump_hash_set(const hash_set* hs, const tgba* aut, std::ostream& out)
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{
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out << "{";
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const char* sep = "";
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for (hash_set::const_iterator i = hs->begin(); i != hs->end(); ++i)
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{
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out << sep << aut->format_state(*i);
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sep = ", ";
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}
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out << "}";
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return out;
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}
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static std::string
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format_hash_set(const hash_set* hs, const tgba* aut)
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{
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std::ostringstream s;
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dump_hash_set(hs, aut, s);
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return s.str();
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}
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}
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// Given an automaton a, find all states that are not in "final" and add
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// them to the set "non_final".
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void init_sets(const tgba_explicit* a,
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@ -269,22 +305,216 @@ namespace spot
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}
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tgba_explicit_number* minimize_dfa(const tgba_explicit_number* det_a,
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hash_set* final)
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{
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typedef std::list<hash_set*> partition_t;
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partition_t cur_run;
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partition_t next_run;
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// The list of equivalent states.
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partition_t done;
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hash_map state_set_map;
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hash_set* non_final = new hash_set;
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init_sets(det_a, *final, *non_final);
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// Size of det_a
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unsigned size = final->size() + non_final->size();
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// Use bdd variables to number sets. set_num is the first variable
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// available.
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unsigned set_num =
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det_a->get_dict()->register_anonymous_variables(size, det_a);
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std::set<int> free_var;
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for (unsigned i = set_num; i < set_num + size; ++i)
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free_var.insert(i);
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std::map<int, int> used_var;
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hash_set* final_copy;
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if (!final->empty())
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{
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unsigned s = final->size();
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used_var[set_num] = s;
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free_var.erase(set_num);
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if (s > 1)
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cur_run.push_back(final);
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else
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done.push_back(final);
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for (hash_set::const_iterator i = final->begin();
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i != final->end(); ++i)
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state_set_map[*i] = set_num;
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final_copy = new hash_set(*final);
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}
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else
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{
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final_copy = final;
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}
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if (!non_final->empty())
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{
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unsigned s = non_final->size();
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unsigned num = set_num + 1;
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used_var[num] = s;
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free_var.erase(num);
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if (s > 1)
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cur_run.push_back(non_final);
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else
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done.push_back(non_final);
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for (hash_set::const_iterator i = non_final->begin();
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i != non_final->end(); ++i)
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state_set_map[*i] = num;
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}
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else
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{
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delete non_final;
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}
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// A bdd_states_map is a list of formulae (in a BDD form) associated with a
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// destination set of states.
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typedef std::map<bdd, hash_set*, bdd_less_than> bdd_states_map;
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bool did_split = true;
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while (did_split)
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{
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did_split = false;
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while (!cur_run.empty())
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{
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// Get a set to process.
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hash_set* cur = cur_run.front();
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cur_run.pop_front();
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trace << "processing " << format_hash_set(cur, det_a) << std::endl;
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hash_set::iterator hi;
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bdd_states_map bdd_map;
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for (hi = cur->begin(); hi != cur->end(); ++hi)
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{
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const state* src = *hi;
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bdd f = bddfalse;
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tgba_succ_iterator* si = det_a->succ_iter(src);
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for (si->first(); !si->done(); si->next())
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{
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const state* dst = si->current_state();
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unsigned dst_set = state_set_map[dst];
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delete dst;
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f |= (bdd_ithvar(dst_set) & si->current_condition());
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}
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delete si;
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// Have we already seen this formula ?
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bdd_states_map::iterator bsi = bdd_map.find(f);
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if (bsi == bdd_map.end())
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{
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// No, create a new set.
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hash_set* new_set = new hash_set;
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new_set->insert(src);
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bdd_map[f] = new_set;
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}
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else
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{
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// Yes, add the current state to the set.
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bsi->second->insert(src);
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}
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}
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bdd_states_map::iterator bsi = bdd_map.begin();
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if (bdd_map.size() == 1)
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{
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// The set was not split.
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trace << "set " << format_hash_set(bsi->second, det_a)
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<< " was not split" << std::endl;
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next_run.push_back(bsi->second);
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}
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else
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{
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for (; bsi != bdd_map.end(); ++bsi)
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{
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hash_set* set = bsi->second;
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// Free the number associated to these states.
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unsigned num = state_set_map[*set->begin()];
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assert(used_var.find(num) != used_var.end());
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unsigned left = (used_var[num] -= set->size());
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// Make sure LEFT does not become negative (hence bigger
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// than SIZE when read as unsigned)
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assert(left < size);
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if (left == 0)
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{
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used_var.erase(num);
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free_var.insert(num);
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}
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// Pick a free number
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assert(!free_var.empty());
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num = *free_var.begin();
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free_var.erase(free_var.begin());
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used_var[num] = set->size();
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for (hash_set::iterator hit = set->begin();
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hit != set->end(); ++hit)
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state_set_map[*hit] = num;
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// Trivial sets can't be splitted any further.
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if (set->size() == 1)
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{
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trace << "set " << format_hash_set(set, det_a)
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<< " is minimal" << std::endl;
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done.push_back(set);
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}
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else
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{
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did_split = true;
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trace << "set " << format_hash_set(set, det_a)
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<< " should be processed further" << std::endl;
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next_run.push_back(set);
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}
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}
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}
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delete cur;
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}
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if (did_split)
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trace << "splitting did occur during this pass." << std::endl;
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else
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trace << "splitting did not occur during this pass." << std::endl;
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std::swap(cur_run, next_run);
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}
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done.splice(done.end(), cur_run);
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#ifdef TRACE
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trace << "Final partition: ";
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for (partition_t::const_iterator i = done.begin(); i != done.end(); ++i)
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trace << format_hash_set(*i, det_a) << " ";
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trace << std::endl;
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#endif
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// Build the result.
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tgba_explicit_number* res = build_result(det_a, done, final_copy);
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// Free all the allocated memory.
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delete final_copy;
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hash_map::iterator hit;
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for (hit = state_set_map.begin(); hit != state_set_map.end(); ++hit)
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delete hit->first;
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std::list<hash_set*>::iterator it;
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for (it = done.begin(); it != done.end(); ++it)
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delete *it;
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delete det_a;
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return res;
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}
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tgba_explicit_number* minimize(const tgba* a, bool monitor)
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{
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std::queue<hash_set*> todo;
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// The list of equivalent states.
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std::list<hash_set*> done;
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hash_set* final = new hash_set;
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hash_set* non_final = new hash_set;
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hash_map state_set_map;
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tgba_explicit_number* det_a;
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{
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power_map pm;
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det_a = tgba_powerset(a, pm);
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if (!monitor)
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{
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// For each SCC of the deterministic automaton, determine if
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}
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}
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init_sets(det_a, *final, *non_final);
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// Size of det_a
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unsigned size = final->size() + non_final->size();
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// Use bdd variables to number sets. set_num is the first variable
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// available.
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unsigned set_num =
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det_a->get_dict()->register_anonymous_variables(size, det_a);
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std::set<int> free_var;
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for (unsigned i = set_num; i < set_num + size; ++i)
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free_var.insert(i);
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std::map<int, int> used_var;
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hash_set* final_copy;
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if (!final->empty())
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{
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unsigned s = final->size();
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used_var[set_num] = s;
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free_var.erase(set_num);
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if (s > 1)
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todo.push(final);
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else
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done.push_back(final);
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for (hash_set::const_iterator i = final->begin();
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i != final->end(); ++i)
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state_set_map[*i] = set_num;
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final_copy = new hash_set(*final);
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}
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else
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{
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final_copy = final;
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}
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if (!non_final->empty())
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{
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unsigned s = non_final->size();
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unsigned num = set_num + 1;
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used_var[num] = s;
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free_var.erase(num);
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if (s > 1)
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todo.push(non_final);
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else
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done.push_back(non_final);
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for (hash_set::const_iterator i = non_final->begin();
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i != non_final->end(); ++i)
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state_set_map[*i] = num;
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}
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else
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{
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delete non_final;
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}
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// A bdd_states_map is a list of formulae (in a BDD form) associated with a
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// destination set of states.
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typedef std::list<std::pair<bdd, hash_set*> > bdd_states_map;
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// While we have unprocessed sets.
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while (!todo.empty())
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{
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// Get a set to process.
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hash_set* cur = todo.front();
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todo.pop();
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hash_set::iterator hi;
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bdd_states_map bdd_map;
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for (hi = cur->begin(); hi != cur->end(); ++hi)
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{
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const state* src = *hi;
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bdd f = bddfalse;
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tgba_succ_iterator* si = det_a->succ_iter(src);
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for (si->first(); !si->done(); si->next())
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{
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const state* dst = si->current_state();
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unsigned dst_set = state_set_map[dst];
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delete dst;
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f |= (bdd_ithvar(dst_set) & si->current_condition());
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}
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delete si;
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bdd_states_map::iterator bsi;
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// Have we already seen this formula ?
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for (bsi = bdd_map.begin(); bsi != bdd_map.end() && bsi->first != f;
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++bsi)
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continue;
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if (bsi == bdd_map.end())
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{
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// No, create a new set.
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hash_set* new_set = new hash_set;
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new_set->insert(src);
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bdd_map.push_back(std::make_pair<bdd, hash_set*>(f, new_set));
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}
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else
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{
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// Yes, add the current state to the set.
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hash_set* set = bsi->second;
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set->insert(src);
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}
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}
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bdd_states_map::iterator bsi = bdd_map.begin();
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// The set is minimal.
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if (bdd_map.size() == 1)
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done.push_back(bsi->second);
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else
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{
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for (; bsi != bdd_map.end(); ++bsi)
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{
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hash_set* set = bsi->second;
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// Free the number associated to these states.
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unsigned num = state_set_map[*set->begin()];
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assert(used_var.find(num) != used_var.end());
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unsigned left = (used_var[num] -= set->size());
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// Make sure LEFT does not become negative (hence bigger
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// than SIZE when read as unsigned)
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assert(left < size);
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if (left == 0)
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{
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used_var.erase(num);
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free_var.insert(num);
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}
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// Pick a free number
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assert(!free_var.empty());
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num = *free_var.begin();
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free_var.erase(free_var.begin());
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used_var[num] = set->size();
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for (hash_set::iterator hit = set->begin(); hit != set->end(); ++hit)
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state_set_map[*hit] = num;
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// Trivial sets can't be splitted any further.
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if (set->size() == 1)
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done.push_back(set);
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else
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todo.push(set);
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}
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}
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delete cur;
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}
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// Build the result.
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tgba_explicit_number* res = build_result(det_a, done, final_copy);
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// Free all the allocated memory.
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delete final_copy;
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hash_map::iterator hit;
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for (hit = state_set_map.begin(); hit != state_set_map.end(); ++hit)
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delete hit->first;
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std::list<hash_set*>::iterator it;
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for (it = done.begin(); it != done.end(); ++it)
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delete *it;
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delete det_a;
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return res;
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return minimize_dfa(det_a, final);
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}
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const tgba*
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