49188715cd
Closes #405. This shows no difference on the test suite, but that is thanks to the previous patch: without it, an example in automata.ipynb would have an extra edge. * spot/twaalgos/cleanacc.cc (simplify_acceptance): Call unit_propagation() before simplify_complementary_marks_here() and fuse_marks_here(), because that is simpler to perform.
639 lines
22 KiB
C++
639 lines
22 KiB
C++
// -*- coding: utf-8 -*-
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// Copyright (C) 2015, 2017-2020 Laboratoire de Recherche et Développement
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// de l'Epita.
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//
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// This file is part of Spot, a model checking library.
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//
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// Spot is free software; you can redistribute it and/or modify it
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// under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3 of the License, or
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// (at your option) any later version.
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//
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// Spot is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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// or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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// License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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#include "config.h"
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#include <spot/twaalgos/cleanacc.hh>
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namespace spot
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{
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twa_graph_ptr cleanup_acceptance_here(twa_graph_ptr aut, bool strip)
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{
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auto& acc = aut->acc();
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if (acc.num_sets() == 0)
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return aut;
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auto c = aut->get_acceptance();
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acc_cond::mark_t used_in_cond = c.used_sets();
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acc_cond::mark_t used_in_aut = {};
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acc_cond::mark_t used_on_all_edges = used_in_cond;
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for (auto& t: aut->edges())
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{
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used_in_aut |= t.acc;
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used_on_all_edges &= t.acc;
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}
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auto useful = used_in_aut & used_in_cond;
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auto useless = strip ? acc.comp(useful) : (used_in_cond - used_in_aut);
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useless |= used_on_all_edges;
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if (!useless)
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return aut;
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// Remove useless marks from the automaton
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if (strip)
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for (auto& t: aut->edges())
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t.acc = t.acc.strip(useless);
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// if x appears on all edges, then
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// Fin(x) = false and Inf(x) = true
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if (used_on_all_edges)
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c = c.remove(used_on_all_edges, false);
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// Remove useless marks from the acceptance condition
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if (strip)
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aut->set_acceptance(useful.count(), c.strip(useless, true));
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else
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aut->set_acceptance(aut->num_sets(), c.remove(useless, true));
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// This may in turn cause even more set to be unused, because of
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// some simplifications in the acceptance condition, so do it again.
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return cleanup_acceptance_here(aut, strip);
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}
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twa_graph_ptr cleanup_acceptance(const_twa_graph_ptr aut, bool strip)
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{
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return cleanup_acceptance_here(make_twa_graph(aut, twa::prop_set::all()),
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strip);
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}
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namespace
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{
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twa_graph_ptr merge_identical_marks_here(twa_graph_ptr aut)
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{
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// /!\ This assumes that the acceptance condition has been
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// cleaned up first. If some mark appears in the acceptance
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// condition but not in the automaton, the result is undefined.
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auto& acc = aut->acc();
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auto& c = acc.get_acceptance();
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acc_cond::mark_t used_in_cond = c.used_sets();
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if (!used_in_cond)
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return aut;
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unsigned num_sets = acc.num_sets();
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std::vector<acc_cond::mark_t> always_together(num_sets);
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for (unsigned i = 0; i < num_sets; ++i)
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if (used_in_cond.has(i))
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always_together[i] = used_in_cond;
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else
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always_together[i] = acc_cond::mark_t({i});
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acc_cond::mark_t previous_a = {};
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for (auto& t: aut->edges())
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{
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acc_cond::mark_t a = t.acc & used_in_cond;
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if (a == previous_a)
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continue;
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previous_a = a;
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for (unsigned m: a.sets())
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{
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acc_cond::mark_t at = always_together[m];
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acc_cond::mark_t newm = at & a;
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for (unsigned rem: (at - newm).sets())
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always_together[rem] -= newm;
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always_together[m] = newm;
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}
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}
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acc_cond::mark_t to_remove = {};
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for (unsigned i = 0; i < num_sets; ++i)
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{
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auto oldm = always_together[i];
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if (oldm == acc_cond::mark_t({i}))
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continue;
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acc_cond::mark_t newm = oldm.lowest();
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to_remove |= oldm - newm;
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always_together[i] = newm;
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}
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for (auto& t: aut->edges())
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t.acc -= to_remove;
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// Replace the marks in the acceptance condition
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auto pos = &c.back();
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auto end = &c.front();
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while (pos > end)
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{
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switch (pos->sub.op)
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{
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case acc_cond::acc_op::And:
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case acc_cond::acc_op::Or:
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--pos;
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break;
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case acc_cond::acc_op::Fin:
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case acc_cond::acc_op::Inf:
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case acc_cond::acc_op::FinNeg:
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case acc_cond::acc_op::InfNeg:
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acc_cond::mark_t replace = pos[-1].mark & to_remove;
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pos[-1].mark -= replace;
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for (unsigned m: replace.sets())
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pos[-1].mark |= always_together[m];
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pos -= 2;
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break;
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}
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}
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return aut;
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}
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// Remove complementary marks from the acceptance condition.
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acc_cond::acc_code remove_compl_rec(const acc_cond::acc_word* pos,
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const std::vector<acc_cond::mark_t>&
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complement)
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{
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auto start = pos - pos->sub.size;
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auto boolop =
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[&](acc_cond::acc_op opand, acc_cond::acc_op opfin,
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acc_cond::acc_op opinf,
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acc_cond::acc_code&& truecode,
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acc_cond::acc_code&& falsecode)
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{
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--pos;
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acc_cond::acc_code res = truecode;
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acc_cond::mark_t seen_fin = {};
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do
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{
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auto tmp = remove_compl_rec(pos, complement);
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if (!tmp.empty() && (tmp.back().sub.op == opfin
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&& tmp.front().mark.is_singleton()))
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seen_fin |= tmp.front().mark;
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if (opand == acc_cond::acc_op::And)
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tmp &= std::move(res);
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else
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tmp |= std::move(res);
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std::swap(tmp, res);
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pos -= pos->sub.size + 1;
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}
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while (pos > start);
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if (res.empty() || res.back().sub.op != opand)
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return res;
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// Locate the position of any Inf element.
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// A property of the &= operator is that there
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// is only one Inf in a conjunction.
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auto rbegin = &res.back();
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auto rend = rbegin - rbegin->sub.size;
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--rbegin;
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do
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{
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if (rbegin->sub.op == opinf)
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break;
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rbegin -= rbegin->sub.size + 1;
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}
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while (rbegin > rend);
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if (rbegin <= rend)
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return res;
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// Fin(i) & Inf(i) = f;
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if (rbegin[-1].mark & seen_fin)
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return std::move(falsecode);
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for (auto m: seen_fin.sets())
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{
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acc_cond::mark_t cm = complement[m];
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// Fin(i) & Fin(!i) = f;
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if (cm & seen_fin)
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return std::move(falsecode);
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// Inf({!i}) & Fin({i}) = Fin({i})
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rbegin[-1].mark -= complement[m];
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}
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if (rbegin[-1].mark)
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return res;
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// Inf(i) has been rewritten as t, we need to remove it. Sigh!
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acc_cond::acc_code res2 = std::move(truecode);
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rbegin = &res.back() - 1;
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do
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{
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acc_cond::acc_code tmp(rbegin);
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if (opand == acc_cond::acc_op::And)
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tmp &= std::move(res);
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else
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tmp |= std::move(res);
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std::swap(tmp, res2);
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rbegin -= rbegin->sub.size + 1;
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}
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while (rbegin > rend);
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return res2;
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};
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switch (pos->sub.op)
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{
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case acc_cond::acc_op::And:
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return boolop(acc_cond::acc_op::And,
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acc_cond::acc_op::Fin,
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acc_cond::acc_op::Inf,
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acc_cond::acc_code::t(),
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acc_cond::acc_code::f());
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case acc_cond::acc_op::Or:
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return boolop(acc_cond::acc_op::Or,
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acc_cond::acc_op::Inf,
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acc_cond::acc_op::Fin,
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acc_cond::acc_code::f(),
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acc_cond::acc_code::t());
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case acc_cond::acc_op::Fin:
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return acc_cond::acc_code::fin(pos[-1].mark);
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case acc_cond::acc_op::Inf:
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return acc_cond::acc_code::inf(pos[-1].mark);
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case acc_cond::acc_op::FinNeg:
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case acc_cond::acc_op::InfNeg:
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SPOT_UNREACHABLE();
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};
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SPOT_UNREACHABLE();
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return {};
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}
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// Always cleanup_acceptance_here with stripping after calling this function
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// As complementary marks might be simplified in the acceptance condition.
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twa_graph_ptr simplify_complementary_marks_here(twa_graph_ptr aut)
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{
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auto& acc = aut->acc();
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auto c = acc.get_acceptance();
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acc_cond::mark_t used_in_cond = c.used_sets();
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if (!used_in_cond)
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return aut;
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// complement[i] holds sets that appear when set #i does not.
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unsigned num_sets = acc.num_sets();
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std::vector<acc_cond::mark_t> complement(num_sets);
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for (unsigned i = 0; i < num_sets; ++i)
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if (used_in_cond.has(i))
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complement[i] = used_in_cond - acc_cond::mark_t({i});
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// Let's visit all edges to update complement[i]. To skip some
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// duplicated work, prev_acc remember the "acc" sets of the
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// previous edge, so we can skip consecutive edges with
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// identical "acc" sets. Note that there is no value of
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// prev_acc that would allow us to fail the comparison on the
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// first edge (this was issue #315), so we have to deal with
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// that first edge specifically.
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acc_cond::mark_t prev_acc = {};
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const auto& edges = aut->edges();
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auto b = edges.begin();
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auto e = edges.end();
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auto update = [&](acc_cond::mark_t tacc)
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{
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prev_acc = tacc;
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for (unsigned m: used_in_cond.sets())
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{
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if (tacc.has(m))
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complement[m] -= tacc;
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else
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complement[m] &= tacc;
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}
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};
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if (b != e)
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{
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update(b->acc);
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++b;
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while (b != e)
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{
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if (b->acc != prev_acc)
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update(b->acc);
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++b;
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}
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}
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aut->set_acceptance(num_sets,
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remove_compl_rec(&acc.get_acceptance().back(),
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complement));
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return aut;
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}
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acc_cond::acc_code acc_rewrite_rec(const acc_cond::acc_word* pos)
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{
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auto start = pos - pos->sub.size;
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switch (pos->sub.op)
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{
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case acc_cond::acc_op::And:
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{
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--pos;
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auto res = acc_cond::acc_code::t();
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do
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{
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auto tmp = acc_rewrite_rec(pos);
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tmp &= std::move(res);
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std::swap(tmp, res);
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pos -= pos->sub.size + 1;
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}
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while (pos > start);
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return res;
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}
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case acc_cond::acc_op::Or:
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{
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--pos;
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auto res = acc_cond::acc_code::f();
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do
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{
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auto tmp = acc_rewrite_rec(pos);
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tmp |= std::move(res);
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std::swap(tmp, res);
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pos -= pos->sub.size + 1;
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}
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while (pos > start);
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return res;
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}
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case acc_cond::acc_op::Fin:
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return acc_cond::acc_code::fin(pos[-1].mark);
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case acc_cond::acc_op::Inf:
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return acc_cond::acc_code::inf(pos[-1].mark);
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case acc_cond::acc_op::FinNeg:
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case acc_cond::acc_op::InfNeg:
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SPOT_UNREACHABLE();
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};
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SPOT_UNREACHABLE();
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return {};
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}
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acc_cond::mark_t find_interm_rec(const acc_cond::acc_word* pos)
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{
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acc_cond::acc_op wanted;
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auto topop = pos->sub.op;
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if (topop == acc_cond::acc_op::Or)
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{
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wanted = acc_cond::acc_op::Fin;
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}
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else
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{
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wanted = acc_cond::acc_op::Inf;
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assert(topop == acc_cond::acc_op::And);
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}
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acc_cond::mark_t res = {};
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const acc_cond::acc_word* rend = pos - (pos->sub.size + 1);
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--pos;
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do
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switch (auto op = pos->sub.op)
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{
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case acc_cond::acc_op::Inf:
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case acc_cond::acc_op::Fin:
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case acc_cond::acc_op::InfNeg:
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case acc_cond::acc_op::FinNeg:
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{
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auto m = pos[-1].mark;
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if (op == wanted)
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{
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res |= m;
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}
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else
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{
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return {};
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}
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pos -= 2;
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break;
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}
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case acc_cond::acc_op::And:
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case acc_cond::acc_op::Or:
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if (op == topop)
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{
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if (auto m = find_interm_rec(pos))
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res |= m;
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else
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return {};
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pos -= pos->sub.size + 1;
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}
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else
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{
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auto posend = pos - (pos->sub.size + 1);
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--pos;
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bool seen = false;
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do
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{
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switch (auto op = pos->sub.op)
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{
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case acc_cond::acc_op::Inf:
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case acc_cond::acc_op::Fin:
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case acc_cond::acc_op::InfNeg:
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case acc_cond::acc_op::FinNeg:
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if (op == wanted)
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{
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auto m = pos[-1].mark;
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if (!seen)
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{
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seen = true;
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res |= m;
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}
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else
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{
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return {};
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}
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}
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pos -= 2;
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break;
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case acc_cond::acc_op::And:
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case acc_cond::acc_op::Or:
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return {};
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}
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}
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while (pos > posend);
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}
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break;
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}
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while (pos > rend);
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return res;
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}
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// Replace Inf(i)|Inf(j) by Inf(k)
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// or Fin(i)&Fin(j) by Fin(k)
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// For this to work, k must be one of i or j,
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// k must be used only once in the acceptance
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// the transitions have to be updated: every transition marked
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// by i or j should be marked by k.
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void fuse_marks_here(twa_graph_ptr aut)
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{
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acc_cond::acc_code acccopy = aut->get_acceptance();
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acc_cond::mark_t once = acccopy.used_once_sets();
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if (!once)
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return;
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acc_cond::acc_word* pos = &acccopy.back();
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const acc_cond::acc_word* front = &acccopy.front();
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// a list of pairs ({i}, {j, k, l, ...}) where i is a set
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// occurring once that can be removed if all transitions in set
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// i are added to sets j,k,l, ...
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std::vector<std::pair<acc_cond::mark_t, acc_cond::mark_t>> to_fuse;
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auto find_fusable = [&](acc_cond::acc_word* pos)
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{
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acc_cond::acc_op wanted;
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auto topop = pos->sub.op;
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if (topop == acc_cond::acc_op::And)
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{
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wanted = acc_cond::acc_op::Fin;
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}
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else
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{
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wanted = acc_cond::acc_op::Inf;
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assert(topop == acc_cond::acc_op::Or);
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}
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// Build a vector of "singleton-sets" of
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// the wanted type in the operand of the
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// pointed Or/And operator. For instance,
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// assuming wanted=Inf and pos points to
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//
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// Inf({1})|Inf({2,3})|Fin({4})
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// |Inf({5})|Inf({5,6})
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//
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// This returns [({1}, Inf({1})),
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// ({5}, Inf({5}))]].
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std::vector<std::pair<acc_cond::mark_t,
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acc_cond::acc_word*>>
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singletons;
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const acc_cond::acc_word* rend =
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pos - (pos->sub.size + 1);
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--pos;
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do
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{
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switch (auto op = pos->sub.op)
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{
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case acc_cond::acc_op::InfNeg:
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case acc_cond::acc_op::FinNeg:
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case acc_cond::acc_op::Inf:
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case acc_cond::acc_op::Fin:
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{
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if (op == wanted)
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singletons.emplace_back(pos[-1].mark,
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pos);
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pos -= 2;
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}
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break;
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case acc_cond::acc_op::And:
|
|
case acc_cond::acc_op::Or:
|
|
// On Fin(a)&(Fin(b)&Inf(c)|Fin(d))
|
|
// we'd like to build [({a},...),
|
|
// ({b,d},...)] and decide later that
|
|
// {b,d} can receive {a} if they
|
|
// (b and d) are both used once.
|
|
if (auto m = find_interm_rec(pos))
|
|
singletons.emplace_back(m, pos);
|
|
pos -= pos->sub.size + 1;
|
|
break;
|
|
}
|
|
}
|
|
while (pos > rend);
|
|
|
|
// sort the singletons vector: we want
|
|
// those that are not really singleton to
|
|
// be first to they can become recipient
|
|
std::partition(singletons.begin(), singletons.end(),
|
|
[&] (auto s)
|
|
{ return !s.first.is_singleton(); });
|
|
|
|
acc_cond::mark_t can_receive = {};
|
|
for (auto p: singletons)
|
|
if ((p.first & once) == p.first)
|
|
{
|
|
can_receive = p.first;
|
|
break;
|
|
}
|
|
if (!can_receive)
|
|
return;
|
|
for (auto p: singletons)
|
|
if (p.first != can_receive
|
|
&& p.first.is_singleton())
|
|
{
|
|
// Mark fused singletons as false,
|
|
// so that a future call to
|
|
// find_fusable() ignores them.
|
|
if (p.second->sub.op == acc_cond::acc_op::Fin)
|
|
p.second->sub.op = acc_cond::acc_op::Inf;
|
|
else if (p.second->sub.op ==
|
|
acc_cond::acc_op::Inf)
|
|
p.second->sub.op = acc_cond::acc_op::Fin;
|
|
else
|
|
continue;
|
|
p.second[-1].mark = {};
|
|
to_fuse.emplace_back(p.first, can_receive);
|
|
}
|
|
};
|
|
|
|
do
|
|
{
|
|
switch (pos->sub.op)
|
|
{
|
|
case acc_cond::acc_op::And:
|
|
case acc_cond::acc_op::Or:
|
|
find_fusable(pos);
|
|
// Don't skip to entire operands, as we might find
|
|
// fusable sub-parts.
|
|
--pos;
|
|
break;
|
|
case acc_cond::acc_op::Inf:
|
|
case acc_cond::acc_op::InfNeg:
|
|
case acc_cond::acc_op::FinNeg:
|
|
case acc_cond::acc_op::Fin:
|
|
pos -= 2;
|
|
break;
|
|
}
|
|
}
|
|
while (pos >= front);
|
|
|
|
if (to_fuse.empty())
|
|
return;
|
|
|
|
// Update the transition according to to_fuse.
|
|
for (auto pair: to_fuse)
|
|
if (pair.first & once) // can we remove pair.first?
|
|
{
|
|
assert(pair.first.is_singleton());
|
|
for (auto& e: aut->edges())
|
|
if (e.acc & pair.first)
|
|
e.acc = (e.acc - pair.first) | pair.second;
|
|
}
|
|
else
|
|
{
|
|
for (auto& e: aut->edges())
|
|
if (e.acc & pair.first)
|
|
e.acc |= pair.second;
|
|
}
|
|
|
|
// Now rewrite the acceptance condition, removing all the "to_kill" terms.
|
|
aut->set_acceptance(aut->num_sets(), acc_rewrite_rec(&acccopy.back()));
|
|
}
|
|
}
|
|
|
|
twa_graph_ptr simplify_acceptance_here(twa_graph_ptr aut)
|
|
{
|
|
for (;;)
|
|
{
|
|
cleanup_acceptance_here(aut, false);
|
|
merge_identical_marks_here(aut);
|
|
if (aut->acc().is_generalized_buchi())
|
|
break;
|
|
acc_cond::acc_code old = aut->get_acceptance();
|
|
aut->set_acceptance(aut->acc().unit_propagation());
|
|
simplify_complementary_marks_here(aut);
|
|
fuse_marks_here(aut);
|
|
if (old == aut->get_acceptance())
|
|
break;
|
|
}
|
|
cleanup_acceptance_here(aut, true);
|
|
return aut;
|
|
}
|
|
|
|
twa_graph_ptr simplify_acceptance(const_twa_graph_ptr aut)
|
|
{
|
|
return simplify_acceptance_here(make_twa_graph(aut, twa::prop_set::all()));
|
|
}
|
|
}
|