ltlsynt: rework synthesis algorithms
ltlsynt now offers two algorithms: one where splitting occurs before determinization (the historical one) and one where determinization occurs before splitting. * bin/ltlsynt.cc: here * tests/core/ltlsynt.test: test it and refactor test file * NEWS: document it * spot/misc/game.hh, spot/misc/game.cc: remove Calude's algorithm
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Maximilien Colange
parent
516e9536df
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bd75ab5b39
5 changed files with 101 additions and 423 deletions
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@ -82,11 +82,6 @@ void parity_game::solve(region_t (&w)[2], strategy_t (&s)[2]) const
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solve_rec(states_, m, w, s);
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}
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bool parity_game::solve_qp() const
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{
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return reachability_game(*this).is_reachable();
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}
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parity_game::strategy_t
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parity_game::attractor(const region_t& subgame, region_t& set,
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unsigned max_parity, int p, bool attr_max) const
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@ -223,166 +218,4 @@ void parity_game::solve_rec(region_t& subgame, unsigned max_parity,
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subgame.insert(w0[!p].begin(), w0[!p].end());
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}
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int reachability_state::compare(const state* other) const
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{
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auto o = down_cast<const reachability_state*>(other);
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assert(o);
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if (num_ != o->num())
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return num_ - o->num();
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if (b_ < o->b())
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return -1;
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if (b_ > o->b())
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return 1;
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return 0;
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}
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bool reachability_state::operator<(const reachability_state& o) const
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{
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// Heuristic to process nodes with a higher chance of leading to a target
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// node first.
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assert(b_.size() == o.b().size());
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for (unsigned i = b_.size(); i > 0; --i)
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if (b_[i - 1] != o.b()[i - 1])
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return b_[i - 1] > o.b()[i - 1];
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return num_ < o.num();
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}
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const reachability_state* reachability_game_succ_iterator::dst() const
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{
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// NB: colors are indexed at 1 in Calude et al.'s paper and at 0 in spot
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// All acceptance sets are therefore incremented (which is already done by
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// max_set), so that 0 can be kept as a special value indicating that no
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// i-sequence is tracked at this index. Hence the parity switch in the
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// following implementation, compared to the paper.
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std::vector<unsigned> b = state_.b();
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unsigned a = it_->acc.max_set();
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assert(a);
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unsigned i = -1U;
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bool all_even = a % 2 == 0;
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for (unsigned j = 0; j < b.size(); ++j)
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{
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if ((b[j] % 2 == 1 || b[j] == 0) && all_even)
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i = j;
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else if (b[j] > 0 && a > b[j])
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i = j;
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all_even = all_even && b[j] > 0 && b[j] % 2 == 0;
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}
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if (i != -1U)
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{
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b[i] = a;
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for (unsigned j = 0; j < i; ++j)
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b[j] = 0;
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}
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return new reachability_state(it_->dst, b, !state_.anke());
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}
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const reachability_state* reachability_game::get_init_state() const
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{
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// b[ceil(log(n + 1))] != 0 implies there is an i-sequence of length
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// 2^(ceil(log(n + 1))) >= 2^log(n + 1) = n + 1, so it has to contain a
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// cycle.
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unsigned i = std::ceil(std::log2(pg_.num_states() + 1));
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return new reachability_state(pg_.get_init_state_number(),
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std::vector<unsigned>(i + 1),
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false);
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}
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reachability_game_succ_iterator*
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reachability_game::succ_iter(const state* s) const
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{
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auto state = down_cast<const reachability_state*>(s);
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return new reachability_game_succ_iterator(pg_, *state);
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}
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std::string reachability_game::format_state(const state* s) const
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{
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auto state = down_cast<const reachability_state*>(s);
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std::ostringstream fmt;
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bool first = true;
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fmt << state->num() << ", ";
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fmt << '[';
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for (unsigned b : state->b())
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{
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if (!first)
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fmt << ',';
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else
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first = false;
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fmt << b;
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}
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fmt << ']';
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return fmt.str();
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}
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bool reachability_game::is_reachable()
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{
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std::set<spot::reachability_state> todo{*init_state_};
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while (!todo.empty())
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{
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spot::reachability_state v = *todo.begin();
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todo.erase(todo.begin());
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std::vector<spot::const_reachability_state_ptr> succs;
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spot::reachability_game_succ_iterator* it = succ_iter(&v);
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for (it->first(); !it->done(); it->next())
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succs.push_back(spot::const_reachability_state_ptr(it->dst()));
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if (is_target(v))
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{
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c_[v] = 1;
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if (mark(v))
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return true;
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continue;
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}
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else if (v.anke())
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c_[v] = 1;
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else
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c_[v] = succs.size();
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for (auto succ: succs)
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{
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if (parents_[*succ].empty())
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{
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if (*succ != *init_state_)
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{
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todo.insert(*succ);
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parents_[*succ] = { v };
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c_[*succ] = -1U;
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}
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}
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else
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{
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parents_[*succ].push_back(v);
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if (c_[*succ] == 0 && mark(v))
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return true;
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}
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}
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}
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return false;
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}
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bool reachability_game::mark(const spot::reachability_state& s)
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{
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if (c_[s] > 0)
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{
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--c_[s];
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if (c_[s] == 0)
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{
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if (s == *init_state_)
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return true;
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for (auto& u: parents_[s])
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if (mark(u))
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return true;
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}
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}
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return false;
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}
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bool reachability_game::is_target(const reachability_state& v)
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{
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return v.b().back();
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}
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}
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@ -108,31 +108,6 @@ public:
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\endverbatim */
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void solve(region_t (&w)[2], strategy_t (&s)[2]) const;
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/// Whether player 1 has a winning strategy from the initial state.
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/// Implements Calude et al.'s quasipolynomial time algorithm.
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/** \verbatim
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@inproceedings{calude.17.stoc,
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author = {Calude, Cristian S. and Jain, Sanjay and Khoussainov,
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Bakhadyr and Li, Wei and Stephan, Frank},
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title = {Deciding Parity Games in Quasipolynomial Time},
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booktitle = {Proceedings of the 49th Annual ACM SIGACT Symposium on
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Theory of Computing},
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series = {STOC 2017},
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year = {2017},
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isbn = {978-1-4503-4528-6},
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location = {Montreal, Canada},
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pages = {252--263},
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numpages = {12},
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url = {http://doi.acm.org/10.1145/3055399.3055409},
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doi = {10.1145/3055399.3055409},
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acmid = {3055409},
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publisher = {ACM},
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address = {New York, NY, USA},
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keywords = {Muller Games, Parity Games, Quasipolynomial Time Algorithm},
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}
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\endverbatim */
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bool solve_qp() const;
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private:
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typedef twa_graph::graph_t::edge_storage_t edge_t;
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@ -149,159 +124,4 @@ private:
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region_t (&w)[2], strategy_t (&s)[2]) const;
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};
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class reachability_state: public state
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{
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private:
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unsigned num_;
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std::vector<unsigned> b_;
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bool anke_;
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public:
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reachability_state(unsigned state, const std::vector<unsigned>& b,
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bool anke)
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: num_(state), b_(b), anke_(anke)
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{
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}
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int compare(const state* other) const override;
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bool operator==(const reachability_state& o) const
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{
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return compare(&o) == 0;
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}
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bool operator!=(const reachability_state& o) const
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{
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return compare(&o) != 0;
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}
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bool operator<(const reachability_state& o) const;
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size_t hash() const override
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{
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size_t hash = wang32_hash(num_);
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for (unsigned i = 0; i < b_.size(); ++i)
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hash ^= wang32_hash(b_[i]) ^ wang32_hash(i);
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return hash;
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}
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reachability_state* clone() const override
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{
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return new reachability_state(*this);
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}
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std::vector<unsigned> b() const
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{
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return b_;
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}
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unsigned num() const
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{
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return num_;
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}
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bool anke() const
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{
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return anke_;
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}
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};
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typedef std::shared_ptr<const reachability_state>
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const_reachability_state_ptr;
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struct reachability_state_hash
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{
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size_t operator()(const reachability_state& state) const
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{
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return state.hash();
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}
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};
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class reachability_game_succ_iterator final: public twa_succ_iterator
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{
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private:
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const parity_game& pg_;
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const reachability_state& state_;
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internal::edge_iterator<const twa_graph::graph_t> it_;
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public:
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reachability_game_succ_iterator(const parity_game& pg,
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const reachability_state& s)
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: pg_(pg), state_(s)
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{
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}
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bool first() override
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{
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it_ = pg_.out(state_.num()).begin();
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return it_ != pg_.out(state_.num()).end();
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}
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bool next() override
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{
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++it_;
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return it_ != pg_.out(state_.num()).end();
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}
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bool done() const override
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{
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return it_ == pg_.out(state_.num()).end();
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}
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const reachability_state* dst() const override;
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bdd cond() const override
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{
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return bddtrue;
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}
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acc_cond::mark_t acc() const override
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{
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return {};
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}
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};
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// On-the-fly reachability game interface for a max even parity game such
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// that a target is reachable iff there is a memoryless winning strategy
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// in the parity game for player 1.
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class reachability_game final: public twa
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{
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private:
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typedef std::unordered_map<spot::reachability_state, unsigned,
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spot::reachability_state_hash> wincount_t;
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typedef std::unordered_map<spot::reachability_state,
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std::vector<spot::reachability_state>,
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spot::reachability_state_hash> parents_t;
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const parity_game& pg_;
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// number of successors that need to have a winning strategy in order for
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// a given node to have a winning strategy.
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wincount_t c_;
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parents_t parents_;
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const_reachability_state_ptr init_state_; // cache
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public:
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reachability_game(const parity_game& pg)
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: twa(std::make_shared<bdd_dict>()), pg_(pg)
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{
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init_state_ = std::shared_ptr<const reachability_state>(get_init_state());
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}
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const reachability_state* get_init_state() const override;
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reachability_game_succ_iterator* succ_iter(const state* s) const override;
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std::string format_state(const state* s) const override;
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bool is_reachable();
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private:
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bool mark(const spot::reachability_state& s);
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bool is_target(const reachability_state& s);
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};
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}
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