introduce spot::simplify_acceptance()
Simplify some automata where some marks are identical, or complementary to another. Fixes #216. * NEWS: mention the new function. * spot/twaalgos/cleanacc.cc, spot/twaalgos/cleanacc.hh: Implement the function. * tests/Makefile.am, tests/python/merge.py: Test this implementation.
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Thomas Medioni
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5 changed files with 884 additions and 0 deletions
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@ -73,5 +73,224 @@ namespace spot
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twa::prop_set::all()));
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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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// always cleanup before proceeding, otherwise if some mark appears in the
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// acceptance condition, but not in the automaton the result is undefined.
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cleanup_acceptance_here(aut, false);
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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 = 0U;
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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 = 0U;
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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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// Eventually 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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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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acc_cond::mark_t seen_fin = 0U;
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auto inf = acc_cond::acc_code::inf(0U);
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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.back().sub.op == acc_cond::acc_op::Fin
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&& tmp.front().mark.count() == 1)
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seen_fin |= tmp.front().mark;
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if (tmp.back().sub.op == acc_cond::acc_op::Inf)
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{
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inf &= std::move(tmp);
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pos -= pos->sub.size + 1;
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continue;
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}
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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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for (auto m: seen_fin.sets())
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inf.front().mark -= complement[m];
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res &= inf;
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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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acc_cond::mark_t seen_inf = 0U;
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auto fin = acc_cond::acc_code::f();
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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.back().sub.op == acc_cond::acc_op::Inf
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&& tmp.front().mark.count() == 1)
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seen_inf |= tmp.front().mark;
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if (tmp.back().sub.op == acc_cond::acc_op::Fin)
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{
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fin |= std::move(tmp);
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pos -= pos->sub.size + 1;
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continue;
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}
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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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for (auto m: seen_inf.sets())
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fin.front().mark -= complement[m];
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res |= fin;
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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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// 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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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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acc_cond::mark_t previous_a = 0U;
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for (auto& t: aut->edges())
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{
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if (t.acc == previous_a)
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continue;
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previous_a = t.acc;
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for (unsigned m: used_in_cond.sets())
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{
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if (t.acc.has(m))
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complement[m] -= t.acc;
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else
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complement[m] &= t.acc;
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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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}
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twa_graph_ptr simplify_acceptance_here(twa_graph_ptr aut)
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{
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cleanup_acceptance_here(aut, false);
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merge_identical_marks_here(aut);
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simplify_complementary_marks_here(aut);
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cleanup_acceptance_here(aut, true);
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return aut;
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}
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twa_graph_ptr simplify_acceptance(const_twa_graph_ptr aut)
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{
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return simplify_acceptance_here(make_twa_graph(aut, twa::prop_set::all()));
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}
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}
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@ -34,4 +34,17 @@ namespace spot
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/// \brief Remove useless acceptance sets
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SPOT_API twa_graph_ptr
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cleanup_acceptance(const_twa_graph_ptr aut);
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/// \brief Simplify an acceptance condition
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///
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/// Remove useless acceptance sets.
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/// Merge identical sets.
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/// If some sets are complement to each other, might result in the
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/// simplification of some clause in the acceptance condition.
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SPOT_API twa_graph_ptr
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simplify_acceptance_here(twa_graph_ptr aut);
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/// \brief Simplify an acceptance condition
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SPOT_API twa_graph_ptr
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simplify_acceptance(const_twa_graph_ptr aut);
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}
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