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https://github.com/Z3Prover/z3
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use lookahead for simplification
Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner
parent
352f8b6cb9
commit
a3f4d58b00
11 changed files with 183 additions and 45 deletions
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@ -20,6 +20,8 @@ Notes:
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#ifndef _SAT_LOOKAHEAD_H_
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#define _SAT_LOOKAHEAD_H_
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#include "sat_elim_eqs.h"
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namespace sat {
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struct pp_prefix {
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@ -34,6 +36,9 @@ namespace sat {
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for (unsigned i = 0; i <= d; ++i) {
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if (0 != (p.m_prefix & (1ull << i))) out << "1"; else out << "0";
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}
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if (d < p.m_depth) {
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out << " d:" << p.m_depth;
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}
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return out;
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}
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@ -309,6 +314,7 @@ namespace sat {
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assign(u);
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return false;
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}
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IF_VERBOSE(3, verbose_stream() << "tc1: " << u << " " << w << "\n";);
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add_binary(u, w);
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}
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}
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@ -367,7 +373,8 @@ namespace sat {
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bool select(unsigned level) {
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init_pre_selection(level);
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unsigned max_num_cand = level == 0 ? m_freevars.size() : m_config.m_level_cand / level;
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unsigned level_cand = std::max(m_config.m_level_cand, m_freevars.size() / 50);
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unsigned max_num_cand = level == 0 ? m_freevars.size() : level_cand / level;
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max_num_cand = std::max(m_config.m_min_cutoff, max_num_cand);
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float sum = 0;
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@ -1010,7 +1017,8 @@ namespace sat {
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m_lits.push_back(lit_info());
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m_rating.push_back(0);
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m_vprefix.push_back(prefix());
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m_freevars.insert(v);
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if (!s.was_eliminated(v))
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m_freevars.insert(v);
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}
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void init() {
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@ -1040,11 +1048,31 @@ namespace sat {
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}
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}
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copy_clauses(s.m_clauses);
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copy_clauses(s.m_learned);
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// copy units
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unsigned trail_sz = s.init_trail_size();
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for (unsigned i = 0; i < trail_sz; ++i) {
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literal l = s.m_trail[i];
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if (!s.was_eliminated(l.var()))
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{
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if (s.m_config.m_drat) m_drat.add(l, false);
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assign(l);
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}
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}
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propagate();
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m_qhead = m_trail.size();
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TRACE("sat", s.display(tout); display(tout););
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}
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void copy_clauses(clause_vector const& clauses) {
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// copy clauses
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clause_vector::const_iterator it = s.m_clauses.begin();
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clause_vector::const_iterator end = s.m_clauses.end();
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for (; it != end; ++it) {
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clause_vector::const_iterator it = clauses.begin();
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clause_vector::const_iterator end = clauses.end();
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for (; it != end; ++it) {
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clause& c = *(*it);
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if (c.was_removed()) continue;
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clause* c1 = m_cls_allocator.mk_clause(c.size(), c.begin(), false);
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m_clauses.push_back(c1);
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attach_clause(*c1);
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@ -1053,17 +1081,6 @@ namespace sat {
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}
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if (s.m_config.m_drat) m_drat.add(c, false);
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}
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// copy units
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unsigned trail_sz = s.init_trail_size();
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for (unsigned i = 0; i < trail_sz; ++i) {
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literal l = s.m_trail[i];
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if (s.m_config.m_drat) m_drat.add(l, false);
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assign(l);
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}
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propagate();
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m_qhead = m_trail.size();
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TRACE("sat", s.display(tout); display(tout););
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}
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// ------------------------------------
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@ -1393,19 +1410,24 @@ namespace sat {
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TRACE("sat", display_lookahead(tout); );
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unsigned base = 2;
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bool change = true;
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bool first = true;
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while (change && !inconsistent()) {
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change = false;
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for (unsigned i = 0; !inconsistent() && i < m_lookahead.size(); ++i) {
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s.checkpoint();
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literal lit = m_lookahead[i].m_lit;
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if (is_fixed_at(lit, c_fixed_truth)) continue;
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unsigned level = base + m_lookahead[i].m_offset;
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if (m_stamp[lit.var()] >= level) {
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continue;
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}
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if (scope_lvl() == 1) {
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IF_VERBOSE(3, verbose_stream() << scope_lvl() << " " << lit << " binary: " << m_binary_trail.size() << " trail: " << m_trail_lim.back() << "\n";);
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}
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TRACE("sat", tout << "lookahead: " << lit << " @ " << m_lookahead[i].m_offset << "\n";);
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reset_wnb(lit);
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push_lookahead1(lit, level);
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do_double(lit, base);
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if (!first) do_double(lit, base);
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bool unsat = inconsistent();
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pop_lookahead1(lit);
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if (unsat) {
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@ -1424,7 +1446,13 @@ namespace sat {
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if (c_fixed_truth - 2 * m_lookahead.size() < base) {
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break;
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}
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base += 2 * m_lookahead.size();
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if (first && !change) {
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first = false;
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change = true;
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}
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reset_wnb();
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init_wnb();
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// base += 2 * m_lookahead.size();
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}
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reset_wnb();
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TRACE("sat", display_lookahead(tout); );
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@ -1487,6 +1515,7 @@ namespace sat {
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}
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bool check_autarky(literal l, unsigned level) {
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return false;
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// no propagations are allowed to reduce clauses.
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clause_vector::const_iterator it = m_full_watches[l.index()].begin();
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clause_vector::const_iterator end = m_full_watches[l.index()].end();
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@ -1568,7 +1597,7 @@ namespace sat {
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}
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void do_double(literal l, unsigned& base) {
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if (!inconsistent() && scope_lvl() > 0 && dl_enabled(l)) {
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if (!inconsistent() && scope_lvl() > 1 && dl_enabled(l)) {
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if (get_wnb(l) > m_delta_trigger) {
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if (dl_no_overflow(base)) {
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++m_stats.m_double_lookahead_rounds;
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@ -1588,6 +1617,7 @@ namespace sat {
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SASSERT(dl_no_overflow(base));
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unsigned dl_truth = base + 2 * m_lookahead.size() * (m_config.m_dl_max_iterations + 1);
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scoped_level _sl(*this, dl_truth);
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IF_VERBOSE(2, verbose_stream() << "double: " << l << "\n";);
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init_wnb();
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assign(l);
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propagate();
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@ -1769,9 +1799,6 @@ namespace sat {
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m_drat(s),
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m_level(2),
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m_prefix(0) {
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m_search_mode = lookahead_mode::searching;
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scoped_level _sl(*this, c_fixed_truth);
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init();
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}
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~lookahead() {
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@ -1779,9 +1806,73 @@ namespace sat {
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}
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lbool check() {
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{
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m_search_mode = lookahead_mode::searching;
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scoped_level _sl(*this, c_fixed_truth);
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init();
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}
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return search();
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}
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void simplify() {
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SASSERT(m_prefix == 0);
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SASSERT(m_watches.empty());
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m_search_mode = lookahead_mode::searching;
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scoped_level _sl(*this, c_fixed_truth);
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init();
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if (inconsistent()) return;
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inc_istamp();
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literal l = choose();
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if (inconsistent()) return;
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SASSERT(m_trail_lim.empty());
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unsigned num_units = 0;
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for (unsigned i = 0; i < m_trail.size(); ++i) {
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literal lit = m_trail[i];
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if (s.value(lit) == l_undef && !s.was_eliminated(lit.var())) {
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s.m_simplifier.propagate_unit(lit);
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++num_units;
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}
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}
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IF_VERBOSE(1, verbose_stream() << "units found: " << num_units << "\n";);
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s.m_simplifier.subsume();
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m_lookahead.reset();
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}
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void scc() {
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SASSERT(m_prefix == 0);
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SASSERT(m_watches.empty());
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m_search_mode = lookahead_mode::searching;
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scoped_level _sl(*this, c_fixed_truth);
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init();
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if (inconsistent()) return;
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inc_istamp();
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m_lookahead.reset();
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if (select(0)) {
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// extract equivalences
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get_scc();
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if (inconsistent()) return;
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literal_vector roots;
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bool_var_vector to_elim;
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for (unsigned i = 0; i < s.num_vars(); ++i) {
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roots.push_back(literal(i, false));
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}
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for (unsigned i = 0; i < m_candidates.size(); ++i) {
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bool_var v = m_candidates[i].m_var;
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literal lit = literal(v, false);
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literal p = get_parent(lit);
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if (p != null_literal && p.var() != v && !s.is_external(v) && !s.was_eliminated(v) && !s.was_eliminated(p.var())) {
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to_elim.push_back(v);
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roots[v] = p;
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}
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}
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IF_VERBOSE(1, verbose_stream() << "eliminate " << to_elim.size() << " variables\n";);
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elim_eqs elim(s);
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elim(roots, to_elim);
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}
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m_lookahead.reset();
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}
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std::ostream& display(std::ostream& out) const {
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out << "Prefix: " << pp_prefix(m_prefix, m_trail_lim.size()) << "\n";
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out << "Level: " << m_level << "\n";
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