mirror of
https://github.com/Z3Prover/z3
synced 2025-07-19 10:52:02 +00:00
added pareto utility
Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner
parent
55863b4bb5
commit
20cb8a3092
8 changed files with 477 additions and 104 deletions
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@ -152,7 +152,7 @@ namespace opt {
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IF_VERBOSE(1, verbose_stream() << "(optimize:sat)\n";);
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s.get_model(m_model);
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m_optsmt.setup(s);
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update_lower();
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update_lower(true);
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switch (m_objectives.size()) {
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case 0:
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return is_sat;
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@ -234,91 +234,147 @@ namespace opt {
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return r;
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}
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class context::pareto : public pareto_callback {
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context& ctx;
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ast_manager& m;
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expr_ref mk_ge(expr* t, expr* s) {
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expr_ref result(m);
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if (ctx.m_bv.is_bv(t)) {
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result = ctx.m_bv.mk_ule(s, t);
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}
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else {
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result = ctx.m_arith.mk_ge(t, s);
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}
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return result;
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}
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public:
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pareto(context& ctx):ctx(ctx),m(ctx.m) {}
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virtual void yield(model_ref& mdl) {
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ctx.m_model = mdl;
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ctx.update_lower(true);
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for (unsigned i = 0; i < ctx.m_objectives.size(); ++i) {
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objective const& obj = ctx.m_objectives[i];
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switch(obj.m_type) {
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case O_MINIMIZE:
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case O_MAXIMIZE:
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ctx.m_optsmt.update_upper(obj.m_index, ctx.m_optsmt.get_lower(obj.m_index), true);
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break;
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case O_MAXSMT: {
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rational r = ctx.m_maxsmts.find(obj.m_id)->get_lower();
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ctx.m_maxsmts.find(obj.m_id)->update_upper(r, true);
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break;
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}
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}
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}
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IF_VERBOSE(1, ctx.display_assignment(verbose_stream()););
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}
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virtual unsigned num_objectives() {
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return ctx.m_objectives.size();
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}
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virtual expr_ref mk_le(unsigned i, model_ref& mdl) {
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objective const& obj = ctx.m_objectives[i];
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expr_ref val(m), result(m), term(m);
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mk_term_val(mdl, obj, term, val);
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switch (obj.m_type) {
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case O_MINIMIZE:
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result = mk_ge(term, val);
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break;
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case O_MAXSMT:
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result = mk_ge(term, val);
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break;
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case O_MAXIMIZE:
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result = mk_ge(val, term);
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break;
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}
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return result;
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}
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virtual expr_ref mk_ge(unsigned i, model_ref& mdl) {
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objective const& obj = ctx.m_objectives[i];
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expr_ref val(m), result(m), term(m);
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mk_term_val(mdl, obj, term, val);
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switch (obj.m_type) {
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case O_MINIMIZE:
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result = mk_ge(val, term);
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break;
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case O_MAXSMT:
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result = mk_ge(val, term);
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break;
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case O_MAXIMIZE:
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result = mk_ge(term, val);
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break;
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}
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return result;
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}
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virtual expr_ref mk_gt(unsigned i, model_ref& mdl) {
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expr_ref result = mk_le(i, mdl);
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result = m.mk_not(result);
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return result;
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}
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private:
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void mk_term_val(model_ref& mdl, objective const& obj, expr_ref& term, expr_ref& val) {
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rational r;
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switch (obj.m_type) {
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case O_MINIMIZE:
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case O_MAXIMIZE:
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term = obj.m_term;
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break;
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case O_MAXSMT: {
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unsigned sz = obj.m_terms.size();
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expr_ref_vector sum(m);
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expr_ref zero(m);
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zero = ctx.m_arith.mk_numeral(rational(0), false);
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for (unsigned i = 0; i < sz; ++i) {
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expr* t = obj.m_terms[i];
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rational const& w = obj.m_weights[i];
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sum.push_back(m.mk_ite(t, ctx.m_arith.mk_numeral(w, false), zero));
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}
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if (sum.empty()) {
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term = zero;
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}
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else {
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term = ctx.m_arith.mk_add(sum.size(), sum.c_ptr());
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}
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break;
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}
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}
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VERIFY(mdl->eval(term, val) && ctx.is_numeral(val, r));
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}
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#if 0
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// use PB
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expr_ref mk_pb_cmp(objective const& obj, model_ref& mdl, bool is_ge) {
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rational r, sum(0);
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expr_ref val(m), result(m);
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unsigned sz = obj.m_terms.size();
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pb_util pb(m);
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for (unsigned i = 0; i < sz; ++i) {
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expr* t = obj.m_terms[i];
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VERIFY(mdl->eval(t, val));
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if (m.is_true(val)) {
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sum += r;
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}
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}
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if (is_ge) {
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result = pb.mk_ge(obj.m_terms.size(), obj.m_weights.c_ptr(), obj.m_terms.c_ptr(), r);
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}
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else {
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result = pb.mk_le(obj.m_terms.size(), obj.m_weights.c_ptr(), obj.m_terms.c_ptr(), r);
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}
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}
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#endif
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};
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lbool context::execute_pareto() {
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opt_solver& s = get_solver();
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expr_ref val(m);
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rational r;
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lbool is_sat = l_true;
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vector<bounds_t> bounds;
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for (unsigned i = 0; i < m_objectives.size(); ++i) {
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objective const& obj = m_objectives[i];
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if (obj.m_type == O_MAXSMT) {
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IF_VERBOSE(0, verbose_stream() << "Pareto optimization is not supported for MAXSMT\n";);
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return l_undef;
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}
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solver::scoped_push _sp(s);
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is_sat = m_optsmt.pareto(obj.m_index);
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if (is_sat != l_true) {
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return is_sat;
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}
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if (!m_optsmt.get_upper(obj.m_index).is_finite()) {
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return l_undef;
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}
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bounds_t bound;
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for (unsigned j = 0; j < m_objectives.size(); ++j) {
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objective const& obj_j = m_objectives[j];
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inf_eps lo = m_optsmt.get_lower(obj_j.m_index);
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inf_eps hi = m_optsmt.get_upper(obj_j.m_index);
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bound.push_back(std::make_pair(lo, hi));
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}
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bounds.push_back(bound);
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}
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for (unsigned i = 0; i < bounds.size(); ++i) {
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for (unsigned j = 0; j < bounds.size(); ++j) {
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objective const& obj = m_objectives[j];
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bounds[i][j].second = bounds[j][j].second;
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}
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IF_VERBOSE(0, display_bounds(verbose_stream() << "new bound\n", bounds[i]););
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}
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for (unsigned i = 0; i < bounds.size(); ++i) {
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bounds_t b = bounds[i];
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vector<inf_eps> mids;
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solver::scoped_push _sp(s);
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for (unsigned j = 0; j < b.size(); ++j) {
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objective const& obj = m_objectives[j];
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inf_eps mid = (b[j].second - b[j].first)/rational(2);
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mids.push_back(mid);
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expr_ref ge = s.mk_ge(obj.m_index, mid);
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s.assert_expr(ge);
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}
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is_sat = execute_box();
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switch(is_sat) {
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case l_undef:
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return is_sat;
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case l_true: {
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bool at_bound = true;
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for (unsigned j = 0; j < b.size(); ++j) {
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objective const& obj = m_objectives[j];
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if (m_model->eval(obj.m_term, val) && is_numeral(val, r)) {
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mids[j] = inf_eps(r);
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}
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at_bound = at_bound && mids[j] == b[j].second;
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b[j].second = mids[j];
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}
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IF_VERBOSE(0, display_bounds(verbose_stream() << "new bound\n", b););
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if (!at_bound) {
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bounds.push_back(b);
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}
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break;
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}
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case l_false: {
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bounds_t b2(b);
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for (unsigned j = 0; j < b.size(); ++j) {
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b2[j].second = mids[j];
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if (j > 0) {
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b2[j-1].second = b[j-1].second;
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}
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IF_VERBOSE(0, display_bounds(verbose_stream() << "refined bound\n", b2););
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bounds.push_back(b2);
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}
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break;
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}
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}
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}
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return is_sat;
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pareto cb(*this);
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m_pareto = alloc(gia_pareto, m, cb, m_solver.get(), m_params);
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return (*(m_pareto.get()))();
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// NB. stack reference cb is out of scope after return.
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// NB. fix race condition for set_cancel
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}
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void context::display_bounds(std::ostream& out, bounds_t const& b) const {
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@ -652,7 +708,7 @@ namespace opt {
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}
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}
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void context::update_lower() {
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void context::update_lower(bool override) {
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expr_ref val(m);
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rational r(0);
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for (unsigned i = 0; i < m_objectives.size(); ++i) {
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@ -660,12 +716,12 @@ namespace opt {
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switch(obj.m_type) {
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case O_MINIMIZE:
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if (m_model->eval(obj.m_term, val) && is_numeral(val, r)) {
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m_optsmt.update_lower(obj.m_index, -r);
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m_optsmt.update_lower(obj.m_index, inf_eps(-r), override);
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}
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break;
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case O_MAXIMIZE:
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if (m_model->eval(obj.m_term, val) && is_numeral(val, r)) {
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m_optsmt.update_lower(obj.m_index, r);
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m_optsmt.update_lower(obj.m_index, inf_eps(r), override);
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}
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break;
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case O_MAXSMT: {
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@ -681,7 +737,7 @@ namespace opt {
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}
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}
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if (ok) {
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m_maxsmts.find(obj.m_id)->update_lower(r);
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m_maxsmts.find(obj.m_id)->update_lower(r, override);
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}
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break;
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}
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@ -816,6 +872,9 @@ namespace opt {
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if (m_simplify) {
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m_simplify->set_cancel(f);
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}
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if (m_pareto) {
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m_pareto->set_cancel(f);
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}
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m_optsmt.set_cancel(f);
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map_t::iterator it = m_maxsmts.begin(), end = m_maxsmts.end();
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for (; it != end; ++it) {
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