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https://github.com/Z3Prover/z3
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integrate v2 of lns
This commit is contained in:
Nikolaj Bjorner
parent
dfb7c87448
commit
0ec567fe15
18 changed files with 254 additions and 105 deletions
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@ -25,12 +25,12 @@ Author:
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namespace opt {
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lns::lns(solver& s, std::function<void(model_ref& mdl)>& update_model)
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lns::lns(solver& s, lns_context& ctx)
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: m(s.get_manager()),
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s(s),
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ctx(ctx),
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m_hardened(m),
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m_soft(m),
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m_update_model(update_model)
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m_unprocessed(m)
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{}
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void lns::set_lns_params() {
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@ -39,7 +39,7 @@ namespace opt {
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p.set_uint("restart.initial", 1000000);
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p.set_uint("max_conflicts", m_max_conflicts);
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p.set_uint("simplify.delay", 1000000);
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// p.set_bool("gc.burst", true);
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// p.set_bool("gc.burst", true);
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s.updt_params(p);
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}
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@ -52,17 +52,99 @@ namespace opt {
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p.set_uint("gc.burst", sp.gc_burst());
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}
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unsigned lns::climb(model_ref& mdl, expr_ref_vector const& asms) {
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unsigned lns::climb(model_ref& mdl) {
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IF_VERBOSE(1, verbose_stream() << "(opt.lns :climb)\n");
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m_num_improves = 0;
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params_ref old_p(s.get_params());
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save_defaults(old_p);
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set_lns_params();
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setup_assumptions(mdl, asms);
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unsigned num_improved = improve_linear(mdl);
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// num_improved += improve_rotate(mdl, asms);
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update_best_model(mdl);
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for (unsigned i = 0; i < 2; ++i)
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improve_bs();
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IF_VERBOSE(1, verbose_stream() << "(opt.lns :relax-cores " << m_cores.size() << ")\n");
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relax_cores();
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s.updt_params(old_p);
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IF_VERBOSE(1, verbose_stream() << "(opt.lns :num-improves " << m_num_improves << " :remaining-soft " << m_soft.size() << ")\n");
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return num_improved;
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IF_VERBOSE(1, verbose_stream() << "(opt.lns :num-improves " << m_num_improves << ")\n");
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return m_num_improves;
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}
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void lns::update_best_model(model_ref& mdl) {
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rational cost = ctx.cost(*mdl);
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if (m_best_cost.is_zero() || m_best_cost >= cost) {
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m_best_cost = cost;
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m_best_model = mdl;
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m_best_phase = s.get_phase();
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m_best_bound = 0;
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for (expr* e : ctx.soft())
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if (!mdl->is_true(e))
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m_best_bound += 1;
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}
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}
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void lns::apply_best_model() {
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s.set_phase(m_best_phase.get());
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for (expr* e : m_unprocessed) {
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s.move_to_front(e);
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s.set_phase(e);
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}
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}
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void lns::improve_bs() {
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m_unprocessed.reset();
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m_unprocessed.append(ctx.soft());
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m_hardened.reset();
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for (expr* a : ctx.soft())
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m_is_assumption.mark(a);
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shuffle(m_unprocessed.size(), m_unprocessed.c_ptr(), m_rand);
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model_ref mdl = m_best_model->copy();
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unsigned j = 0;
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for (unsigned i = 0; i < m_unprocessed.size(); ++i) {
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if (mdl->is_false(unprocessed(i))) {
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expr_ref tmp(m_unprocessed.get(j), m);
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m_unprocessed[j++] = m_unprocessed[i];
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m_unprocessed[i] = tmp;
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break;
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}
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}
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for (unsigned i = j; i < m_unprocessed.size(); ++i) {
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if (mdl->is_true(unprocessed(i))) {
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expr_ref tmp(m_unprocessed.get(j), m);
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m_unprocessed[j++] = m_unprocessed[i];
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m_unprocessed[i] = tmp;
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}
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}
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for (unsigned i = 0; i < 3 && !m_unprocessed.empty(); ++i)
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improve_bs1();
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}
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void lns::improve_bs1() {
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model_ref mdl = m_best_model->copy();
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unsigned j = 0;
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for (expr* e : m_unprocessed) {
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if (!m.inc())
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return;
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if (mdl->is_true(e))
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m_hardened.push_back(e);
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else {
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apply_best_model();
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switch (improve_step(mdl, e)) {
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case l_true:
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m_hardened.push_back(e);
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ctx.update_model(mdl);
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update_best_model(mdl);
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break;
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case l_false:
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m_hardened.push_back(m.mk_not(e));
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break;
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case l_undef:
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m_unprocessed[j++] = e;
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break;
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}
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}
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}
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m_unprocessed.shrink(j);
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}
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struct lns::scoped_bounding {
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@ -72,12 +154,13 @@ namespace opt {
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scoped_bounding(lns& l):m_lns(l) {
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if (!m_lns.m_enable_scoped_bounding)
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return;
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if (m_lns.m_best_bound == 0)
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return;
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m_cores_are_valid = m_lns.m_cores_are_valid;
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m_lns.m_cores_are_valid = false;
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m_lns.s.push();
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pb_util pb(m_lns.m);
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// TBD: bound should to be adjusted for current best solution, not number of soft constraints left.
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expr_ref bound(pb.mk_at_most_k(m_lns.m_soft, m_lns.m_soft.size() - 1), m_lns.m);
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expr_ref bound(pb.mk_at_most_k(m_lns.ctx.soft(), m_lns.m_best_bound - 1), m_lns.m);
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m_lns.s.assert_expr(bound);
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}
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~scoped_bounding() {
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@ -89,7 +172,7 @@ namespace opt {
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};
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void lns::relax_cores() {
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if (!m_cores.empty() && m_relax_cores && m_cores_are_valid) {
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if (!m_cores.empty() && m_cores_are_valid) {
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std::sort(m_cores.begin(), m_cores.end(), [&](expr_ref_vector const& a, expr_ref_vector const& b) { return a.size() < b.size(); });
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unsigned num_disjoint = 0;
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vector<expr_ref_vector> new_cores;
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@ -104,43 +187,14 @@ namespace opt {
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new_cores.push_back(c);
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++num_disjoint;
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}
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m_relax_cores(new_cores);
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IF_VERBOSE(2, verbose_stream() << "num cores: " << m_cores.size() << " new cores: " << new_cores.size() << "\n");
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ctx.relax_cores(new_cores);
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}
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m_in_core.reset();
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m_is_assumption.reset();
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m_cores.reset();
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}
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void lns::setup_assumptions(model_ref& mdl, expr_ref_vector const& asms) {
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m_hardened.reset();
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m_soft.reset();
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for (expr* a : asms) {
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m_is_assumption.mark(a);
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if (mdl->is_true(a))
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m_hardened.push_back(a);
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else
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m_soft.push_back(a);
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}
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}
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unsigned lns::improve_rotate(model_ref& mdl, expr_ref_vector const& asms) {
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unsigned num_improved = 0;
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repeat:
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setup_assumptions(mdl, asms);
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unsigned sz = m_hardened.size();
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for (unsigned i = 0; i < sz; ++i) {
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expr_ref tmp(m_hardened.get(i), m);
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m_hardened[i] = m.mk_not(tmp);
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unsigned reward = improve_linear(mdl);
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if (reward > 1) {
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num_improved += (reward - 1);
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goto repeat;
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}
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setup_assumptions(mdl, asms);
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}
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return num_improved;
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}
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unsigned lns::improve_linear(model_ref& mdl) {
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scoped_bounding _scoped_bouding(*this);
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unsigned num_improved = 0;
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@ -156,43 +210,42 @@ namespace opt {
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set_lns_params();
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}
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m_max_conflicts = max_conflicts;
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relax_cores();
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return num_improved;
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}
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unsigned lns::improve_step(model_ref& mdl) {
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unsigned num_improved = 0;
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for (unsigned i = 0; m.inc() && i < m_soft.size(); ++i) {
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switch (improve_step(mdl, soft(i))) {
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for (unsigned i = 0; m.inc() && i < m_unprocessed.size(); ++i) {
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switch (improve_step(mdl, unprocessed(i))) {
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case l_undef:
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break;
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case l_false:
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TRACE("opt", tout << "pruned " << mk_bounded_pp(soft(i), m) << "\n";);
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m_hardened.push_back(m.mk_not(soft(i)));
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for (unsigned k = i; k + 1 < m_soft.size(); ++k)
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m_soft[k] = soft(k + 1);
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m_soft.pop_back();
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TRACE("opt", tout << "pruned " << mk_bounded_pp(unprocessed(i), m) << "\n";);
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m_hardened.push_back(m.mk_not(unprocessed(i)));
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for (unsigned k = i; k + 1 < m_unprocessed.size(); ++k)
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m_unprocessed[k] = unprocessed(k + 1);
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m_unprocessed.pop_back();
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--i;
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break;
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case l_true: {
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unsigned k = 0, offset = 0;
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for (unsigned j = 0; j < m_soft.size(); ++j) {
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if (mdl->is_true(soft(j))) {
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for (unsigned j = 0; j < m_unprocessed.size(); ++j) {
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if (mdl->is_true(unprocessed(j))) {
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if (j <= i)
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++offset;
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++m_num_improves;
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TRACE("opt", tout << "improved " << mk_bounded_pp(soft(j), m) << "\n";);
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m_hardened.push_back(soft(j));
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TRACE("opt", tout << "improved " << mk_bounded_pp(unprocessed(j), m) << "\n";);
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m_hardened.push_back(unprocessed(j));
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++num_improved;
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}
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else {
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m_soft[k++] = soft(j);
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m_unprocessed[k++] = unprocessed(j);
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}
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}
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m_soft.shrink(k);
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m_unprocessed.shrink(k);
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i -= offset;
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IF_VERBOSE(1, verbose_stream() << "(opt.lns :num-improves " << m_num_improves << " :remaining-soft " << m_soft.size() << ")\n");
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m_update_model(mdl);
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IF_VERBOSE(1, verbose_stream() << "(opt.lns :num-improves " << m_num_improves << " :remaining-soft " << m_unprocessed.size() << ")\n");
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ctx.update_model(mdl);
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break;
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}
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}
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@ -209,12 +262,12 @@ namespace opt {
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if (r == l_false) {
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expr_ref_vector core(m);
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s.get_unsat_core(core);
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bool all_assumed = true;
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bool all_assumed = true;
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for (expr* c : core)
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all_assumed &= m_is_assumption.is_marked(c);
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if (all_assumed) {
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m_cores.push_back(core);
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}
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IF_VERBOSE(2, verbose_stream() << "core " << all_assumed << " - " << core.size() << "\n");
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if (all_assumed)
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m_cores.push_back(core);
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}
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return r;
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}
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