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https://github.com/Z3Prover/z3
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v2 of dual maxres engine
Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner
parent
622d8b5cd1
commit
d429e72e92
6 changed files with 253 additions and 139 deletions
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@ -58,10 +58,10 @@ Notes:
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#include "maxres.h"
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#include "ast_pp.h"
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#include "mus.h"
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#include "mss.h"
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using namespace opt;
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class maxres : public maxsmt_solver_base {
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public:
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enum strategy_t {
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@ -75,8 +75,10 @@ private:
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obj_map<expr, rational> m_asm2weight;
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ptr_vector<expr> m_new_core;
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mus m_mus;
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mss m_mss;
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expr_ref_vector m_trail;
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strategy_t m_st;
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rational m_max_upper;
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public:
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maxres(ast_manager& m, opt_solver* s, params_ref& p,
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@ -85,6 +87,7 @@ public:
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maxsmt_solver_base(s, m, p, ws, soft),
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m_B(m), m_asms(m),
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m_mus(m_s, m),
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m_mss(m_s, m),
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m_trail(m),
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m_st(st)
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{
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@ -168,7 +171,6 @@ public:
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default:
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break;
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}
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IF_VERBOSE(1, verbose_stream() << "(opt.max_res [" << m_lower << ":" << m_upper << "])\n";);
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}
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return l_true;
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}
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@ -179,8 +181,7 @@ public:
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init_local();
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enable_bvsat();
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enable_sls();
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lbool was_sat = l_false;
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ptr_vector<expr> soft_compl;
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ptr_vector<expr> mcs;
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vector<ptr_vector<expr> > cores;
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while (m_lower < m_upper) {
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TRACE("opt",
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@ -189,37 +190,38 @@ public:
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tout << "\n";
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display(tout);
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);
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lbool is_sat = m_s->check_sat(0, 0);
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lbool is_sat = try_improve_bound(cores, mcs);
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if (m_cancel) {
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return l_undef;
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}
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if (is_sat == l_true) {
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was_sat = l_true;
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is_sat = extend_model(soft_compl);
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switch (is_sat) {
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case l_undef:
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break;
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case l_false:
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is_sat = process_unsat();
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break;
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case l_true:
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is_sat = process_sat(soft_compl);
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break;
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}
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}
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switch (is_sat) {
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case l_undef:
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return l_undef;
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case l_false:
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SASSERT(cores.empty() && mcs.empty());
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m_lower = m_upper;
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return was_sat;
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case l_true:
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return l_true;
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case l_true:
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SASSERT(cores.empty() || mcs.empty());
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SASSERT(!cores.empty() || !mcs.empty());
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for (unsigned i = 0; is_sat == l_true && i < cores.size(); ++i) {
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is_sat = process_unsat(cores[i]);
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}
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if (is_sat == l_true && !mcs.empty()) {
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is_sat = process_sat(mcs);
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}
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if (is_sat != l_true) {
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return is_sat;
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}
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break;
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}
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}
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return was_sat;
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m_lower = m_lower;
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return l_true;
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}
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lbool mss_solver() {
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NOT_IMPLEMENTED_YET();
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return l_undef;
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@ -314,6 +316,7 @@ public:
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fml = m.mk_not(m.mk_and(m_B.size(), m_B.c_ptr()));
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m_s->assert_expr(fml);
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m_lower += w;
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IF_VERBOSE(1, verbose_stream() << "(opt.maxres [" << m_lower << ":" << m_upper << "])\n";);
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return l_true;
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}
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@ -422,6 +425,7 @@ public:
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// cs is a correction set (a complement of a (maximal) satisfying assignment).
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void cs_max_resolve(ptr_vector<expr>& cs, rational const& w) {
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TRACE("opt", display_vec(tout << "correction set: ", cs.size(), cs.c_ptr()););
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SASSERT(!cs.empty());
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expr_ref fml(m), asum(m);
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app_ref cls(m), d(m), dd(m);
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@ -437,6 +441,7 @@ public:
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// asm => b_i
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// asm => d_{i-1} or b_{i-1}
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// d_i => d_{i-1} or b_{i-1}
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//
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for (unsigned i = 1; i < cs.size(); ++i) {
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expr* b_i = m_B[i-1].get();
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expr* b_i1 = m_B[i].get();
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@ -460,82 +465,89 @@ public:
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m_s->assert_expr(fml);
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}
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//
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// The hard constraints are satisfiable.
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// Extend the current model to satisfy as many
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// soft constraints as possible until either
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// hitting an unsatisfiable subset of size < 1/2*#assumptions,
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// or producing a maximal satisfying assignment exceeding
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// number of soft constraints >= 1/2*#assumptions.
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// In both cases, soft constraints that are not satisfied
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// is <= 1/2*#assumptions. In this way, the new modified assumptions
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// account for at most 1/2 of the current assumptions.
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// The core reduction algorithms also need to take into account
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// at most 1/2 of the assumptions for minimization.
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//
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lbool extend_model(ptr_vector<expr>& soft_compl) {
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ptr_vector<expr> asms;
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model_ref mdl;
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expr_ref tmp(m);
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m_s->get_model(mdl);
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unsigned num_true = update_model(mdl, asms, soft_compl);
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for (unsigned j = 0; j < m_asms.size(); ++j) {
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expr* fml = m_asms[j].get();
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VERIFY(mdl->eval(fml, tmp));
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if (m.is_false(tmp)) {
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asms.push_back(fml);
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lbool is_sat = m_s->check_sat(asms.size(), asms.c_ptr());
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asms.pop_back();
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switch (is_sat) {
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case l_false:
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if (num_true*2 < m_asms.size()) {
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return l_false;
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}
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break;
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case l_true:
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m_s->get_model(mdl);
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num_true = update_model(mdl, asms, soft_compl);
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break;
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case l_undef:
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return l_undef;
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lbool try_improve_bound(vector<ptr_vector<expr> >& cores, ptr_vector<expr>& mcs) {
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cores.reset();
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mcs.reset();
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ptr_vector<expr> core;
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expr_ref_vector asms(m_asms);
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while (true) {
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rational upper = m_max_upper;
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unsigned sz = 0;
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for (unsigned i = 0; m_upper <= upper && i < asms.size(); ++i, ++sz) {
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upper -= get_weight(asms[i].get());
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}
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lbool is_sat = m_s->check_sat(sz, asms.c_ptr());
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switch (is_sat) {
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case l_true: {
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ptr_vector<expr> lits;
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lits.append(asms.size(), asms.c_ptr());
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set_mus(false);
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is_sat = m_mss(cores, lits);
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set_mus(true);
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if (is_sat != l_true) {
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return is_sat;
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}
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m_mss.get_model(m_model); // last model is best way to reduce search space.
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update_assignment();
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if (cores.empty() || asms.size() < cores.back().size()) {
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cores.reset();
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mcs.append(asms.size(), asms.c_ptr());
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}
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return l_true;
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}
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case l_undef:
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return l_undef;
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case l_false:
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core.reset();
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m_s->get_unsat_core(core);
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is_sat = minimize_core(core);
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if (is_sat != l_true) {
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break;
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}
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if (core.empty()) {
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cores.reset();
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mcs.reset();
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return l_false;
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}
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cores.push_back(core);
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if (core.size() >= 3) {
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return l_true;
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}
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//
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// check arithmetic: cannot improve upper bound
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//
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if (m_upper <= upper) {
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return l_true;
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}
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remove_soft(core, asms);
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break;
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}
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}
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return l_true;
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return l_undef;
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}
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unsigned update_model(model_ref& mdl, ptr_vector<expr>& asms, ptr_vector<expr>& soft_compl) {
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expr_ref tmp(m);
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asms.reset();
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soft_compl.reset();
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rational weight = m_lower;
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unsigned num_true = 0;
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for (unsigned i = 0; i < m_asms.size(); ++i) {
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expr* fml = m_asms[i].get();
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VERIFY(mdl->eval(fml, tmp));
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SASSERT(m.is_false(tmp) || m.is_true(tmp));
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if (m.is_false(tmp)) {
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weight += get_weight(fml);
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soft_compl.push_back(fml);
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}
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else {
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++num_true;
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asms.push_back(fml);
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void update_assignment() {
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rational upper(0);
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for (unsigned i = 0; i < m_soft.size(); ++i) {
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expr_ref tmp(m);
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expr* n = m_soft[i].get();
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VERIFY(m_model->eval(n, tmp));
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CTRACE("opt", !m.is_true(tmp) && !m.is_false(tmp),
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tout << mk_pp(n, m) << " |-> " << mk_pp(tmp, m) << "\n";);
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m_assignment[i] = m.is_true(tmp);
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if (!m_assignment[i]) {
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upper += m_weights[i];
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}
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}
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if (weight < m_upper) {
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m_upper = weight;
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m_model = mdl;
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for (unsigned i = 0; i < m_soft.size(); ++i) {
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expr_ref tmp(m);
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VERIFY(m_model->eval(m_soft[i].get(), tmp));
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m_assignment[i] = m.is_true(tmp);
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}
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IF_VERBOSE(1, verbose_stream() <<
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"(opt.mus-mss_max_res [" << m_lower << ":" << m_upper << "])\n";);
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}
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return num_true;
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SASSERT(upper <= m_upper);
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m_upper = upper;
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IF_VERBOSE(1, verbose_stream() <<
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"(opt.maxres [" << m_lower << ":" << m_upper << "])\n";);
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}
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void remove_soft(ptr_vector<expr> const& core, expr_ref_vector& asms) {
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@ -564,6 +576,7 @@ public:
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for (unsigned i = 0; i < m_soft.size(); ++i) {
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add_soft(m_soft[i].get(), m_weights[i]);
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}
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m_max_upper = m_upper;
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}
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};
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