new conversion for Streett->GBA
* src/twaalgos/totgba.hh, src/twaalgos/totgba.cc: Implement the new function. * NEWS: Mention this new function. * src/bin/man/spot-x.x: Document SPOT_STREETT_CONV_MIN. * src/tests/ltl2dstar4.test: Add tests. * src/tests/Makefile.am: Add it. * src/bin/autfilt.cc: Do do call remove_fin explicitely when --tgba is used, let the postprocessor do it. * src/twa/acc.hh: Add shift operators for acceptance marks. * src/twaalgos/remfin.cc: Use the new algorithm. * src/twaalgos/sccinfo.cc, src/twaalgos/sccinfo.hh: Add a new method to supply the acceptance sets visited by an SCC.
This commit is contained in:
Alexandre Duret-Lutz
parent
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commit
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11 changed files with 419 additions and 11 deletions
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@ -20,12 +20,48 @@
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#include "totgba.hh"
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#include "remfin.hh"
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#include "cleanacc.hh"
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#include "sccinfo.hh"
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#include "twa/twagraph.hh"
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#include <deque>
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#include <tuple>
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namespace spot
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{
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namespace
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{
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struct st2gba_state
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{
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acc_cond::mark_t pend;
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unsigned s;
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st2gba_state(unsigned st, acc_cond::mark_t bv = -1U):
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pend(bv), s(st)
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{
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}
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};
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struct st2gba_state_hash
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{
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size_t
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operator()(const st2gba_state& s) const
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{
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std::hash<acc_cond::mark_t> h;
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return s.s ^ h(s.pend);
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}
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};
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struct st2gba_state_equal
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{
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bool
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operator()(const st2gba_state& left,
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const st2gba_state& right) const
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{
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if (left.s != right.s)
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return false;
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return left.pend == right.pend;
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}
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};
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typedef std::vector<acc_cond::mark_t> terms_t;
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terms_t cnf_terms(const acc_cond::acc_code& code)
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@ -55,12 +91,224 @@ namespace spot
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}
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// Specialized conversion for Streett -> TGBA
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// ============================================
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//
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// Christof Löding's Diploma Thesis: Methods for the
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// Transformation of ω-Automata: Complexity and Connection to
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// Second Order Logic. Section 3.4.3, gives a transition
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// from Streett with |Q| states to BA with |Q|*(4^n-3^n+2)
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// states, if n is the number of acceptance pairs.
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//
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// Duret-Lutz et al. (ATVA'2009): On-the-fly Emptiness Check of
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// Transition-based Streett Automata. Section 3.3 contains a
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// conversion from transition-based Streett Automata to TGBA using
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// the generalized Büchi acceptance to limit the explosion. It goes
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// from Streett with |Q| states to (T)GBA with |Q|*(2^n+1) states.
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// However the definition of the number of acceptance sets in that
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// paper is suboptimal: only n are needed, not 2^n.
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//
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// This implements this second version.
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twa_graph_ptr
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streett_to_generalized_buchi(const const_twa_graph_ptr& in)
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{
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// While "t" is Streett, it is also generalized Büchi, so
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// do not do anything.
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if (in->acc().is_generalized_buchi())
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return std::const_pointer_cast<twa_graph>(in);
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int p = in->acc().is_streett();
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if (p <= 0)
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throw std::runtime_error("streett_to_generalized_buchi() should only be"
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" called on automata with Streett acceptance");
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// In Streett acceptance, inf sets are odd, while fin sets are
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// even.
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acc_cond::mark_t inf;
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acc_cond::mark_t fin;
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std::tie(inf, fin) = in->get_acceptance().used_inf_fin_sets();
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assert((inf >> 1) == fin);
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scc_info si(in);
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// Compute the acceptance sets present in each SCC
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unsigned nscc = si.scc_count();
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std::vector<std::tuple<acc_cond::mark_t, acc_cond::mark_t, bool>> sccfi;
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sccfi.reserve(nscc);
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for (unsigned s = 0; s < nscc; ++s)
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{
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auto acc = si.acc_sets_of(s); // {0,1,2,3,4,6,7,9}
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auto acc_fin = acc & fin; // {0, 2, 4,6}
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auto acc_inf = acc & inf; // { 1, 3, 7,9}
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auto fin_wo_inf = acc_fin - (acc_inf >> 1); // {4}
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auto inf_wo_fin = acc_inf - (acc_fin << 1); // {9}
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sccfi.emplace_back(fin_wo_inf, inf_wo_fin, acc_fin == 0U);
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}
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auto out = make_twa_graph(in->get_dict());
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out->copy_ap_of(in);
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out->prop_copy(in, {false, false, false, true});
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out->set_generalized_buchi(p);
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acc_cond::mark_t outall = out->acc().all_sets();
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// Map st2gba pairs to the state numbers used in out.
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typedef std::unordered_map<st2gba_state, unsigned,
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st2gba_state_hash,
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st2gba_state_equal> bs2num_map;
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bs2num_map bs2num;
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// Queue of states to be processed.
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typedef std::deque<st2gba_state> queue_t;
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queue_t todo;
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st2gba_state s(in->get_init_state_number());
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bs2num[s] = out->new_state();
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todo.push_back(s);
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bool sbacc = in->has_state_based_acc();
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while (!todo.empty())
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{
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s = todo.front();
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todo.pop_front();
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unsigned src = bs2num[s];
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unsigned scc_src = si.scc_of(s.s);
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bool maybe_acc_scc = !si.is_rejecting_scc(scc_src);
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acc_cond::mark_t scc_fin_wo_inf;
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acc_cond::mark_t scc_inf_wo_fin;
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bool no_fin;
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std::tie(scc_fin_wo_inf, scc_inf_wo_fin, no_fin) = sccfi[scc_src];
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for (auto& t: in->out(s.s))
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{
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acc_cond::mark_t pend = s.pend;
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acc_cond::mark_t acc = 0U;
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bool maybe_acc = maybe_acc_scc && (scc_src == si.scc_of(t.dst));
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if (pend != -1U)
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{
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if (!maybe_acc)
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continue;
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// No point going to some place we will never leave
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if (t.acc & scc_fin_wo_inf)
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continue;
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// For any Fin set we see, we want to see the
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// corresponding Inf set.
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pend |= (t.acc & fin) << 1;
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pend -= t.acc & inf;
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// Label this transition with all non-pending
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// inf sets. The strip will shift everything
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// to the correct numbers in the targets.
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acc = (inf - pend).strip(fin) & outall;
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// Adjust the pending sets to what will be necessary
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// required on the destination state.
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if (sbacc)
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{
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auto a = in->state_acc_sets(t.dst);
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if (a & scc_fin_wo_inf)
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continue;
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pend |= (a & fin) << 1;
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pend -= a & inf;
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}
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pend |= scc_inf_wo_fin;
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}
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else if (no_fin && maybe_acc)
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{
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assert(maybe_acc);
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acc = outall;
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}
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st2gba_state d(t.dst, pend);
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// Have we already seen this destination?
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unsigned dest;
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auto dres = bs2num.emplace(d, 0);
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if (!dres.second)
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{
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dest = dres.first->second;
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}
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else // No, this is a new state
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{
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dest = dres.first->second = out->new_state();
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todo.push_back(d);
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}
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out->new_edge(src, dest, t.cond, acc);
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// Nondeterministically jump to level ∅. We need to do
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// that only once per cycle. As an approximation, we
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// only to that for transition where t.src >= t.dst as
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// this has to occur at least once per cycle.
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if (pend == -1U && (t.src >= t.dst) && maybe_acc && !no_fin)
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{
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acc_cond::mark_t pend = 0U;
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if (sbacc)
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{
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auto a = in->state_acc_sets(t.dst);
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if (a & scc_fin_wo_inf)
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continue;
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pend = (a & fin) << 1;
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pend -= a & inf;
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}
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st2gba_state d(t.dst, pend | scc_inf_wo_fin);
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// Have we already seen this destination?
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unsigned dest;
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auto dres = bs2num.emplace(d, 0);
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if (!dres.second)
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{
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dest = dres.first->second;
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}
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else // No, this is a new state
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{
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dest = dres.first->second = out->new_state();
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todo.push_back(d);
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}
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out->new_edge(src, dest, t.cond);
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}
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}
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}
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// for (auto s: bs2num)
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// {
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// std::cerr << s.second << " ("
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// << s.first.s << ", ";
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// if (s.first.pend == -1U)
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// std::cerr << "-)\n";
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// else
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// std::cerr << s.first.pend << ")\n";
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// }
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return out;
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}
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twa_graph_ptr
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streett_to_generalized_buchi_maybe(const const_twa_graph_ptr& in)
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{
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static int min = [&]() {
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const char* c = getenv("SPOT_STREETT_CONV_MIN");
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if (!c)
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return 3;
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errno = 0;
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int val = strtol(c, nullptr, 10);
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if (val < 0 || errno != 0)
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throw std::runtime_error("unexpected value for SPOT_STREETT_CONV_MIN");
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return val;
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}();
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if (min == 0 || min > in->acc().is_streett())
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return nullptr;
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else
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return streett_to_generalized_buchi(in);
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}
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/// \brief Take an automaton with any acceptance condition and return
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/// an equivalent Generalized Büchi automaton.
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twa_graph_ptr
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to_generalized_buchi(const const_twa_graph_ptr& aut)
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{
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auto maybe = streett_to_generalized_buchi_maybe(aut);
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if (maybe)
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return maybe;
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auto res = remove_fin(cleanup_acceptance(aut));
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if (res->acc().is_generalized_buchi())
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return res;
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