fix #1577

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/api/api_opt.cpp

@@ -124,10 +124,16 @@ extern "C" {
     }
 
 
-    Z3_lbool Z3_API Z3_optimize_check(Z3_context c, Z3_optimize o) {
+    Z3_lbool Z3_API Z3_optimize_check(Z3_context c, Z3_optimize o, unsigned num_assumptions, Z3_ast const assumptions[]) {
         Z3_TRY;
-        LOG_Z3_optimize_check(c, o);
+        LOG_Z3_optimize_check(c, o, num_assumptions, assumptions);
         RESET_ERROR_CODE();
+        for (unsigned i = 0; i < num_assumptions; i++) {
+            if (!is_expr(to_ast(assumptions[i]))) {
+                SET_ERROR_CODE(Z3_INVALID_ARG, "assumption is not an expression");
+                return Z3_L_UNDEF;
+            }
+        }
         lbool r = l_undef;
         cancel_eh<reslimit> eh(mk_c(c)->m().limit());
         unsigned timeout = to_optimize_ptr(o)->get_params().get_uint("timeout", mk_c(c)->get_timeout());
@@ -137,7 +143,9 @@ extern "C" {
             scoped_timer timer(timeout, &eh);
             scoped_rlimit _rlimit(mk_c(c)->m().limit(), rlimit);
             try {
-                r = to_optimize_ptr(o)->optimize();
+                expr_ref_vector asms(mk_c(c)->m());
+                asms.append(num_assumptions, to_exprs(assumptions));
+                r = to_optimize_ptr(o)->optimize(asms);
             }
             catch (z3_exception& ex) {
                 if (!mk_c(c)->m().canceled()) {
@@ -157,6 +165,22 @@ extern "C" {
         Z3_CATCH_RETURN(Z3_L_UNDEF);
     }
 
+    Z3_ast_vector Z3_API Z3_optimize_get_unsat_core(Z3_context c, Z3_optimize o) {
+        Z3_TRY;
+        LOG_Z3_optimize_get_unsat_core(c, o);
+        RESET_ERROR_CODE();
+        expr_ref_vector core(mk_c(c)->m());
+        to_optimize_ptr(o)->get_unsat_core(core);
+        Z3_ast_vector_ref * v = alloc(Z3_ast_vector_ref, *mk_c(c), mk_c(c)->m());
+        mk_c(c)->save_object(v);
+        for (expr* e : core) {
+            v->m_ast_vector.push_back(e);
+        }
+        RETURN_Z3(of_ast_vector(v));
+        Z3_CATCH_RETURN(nullptr);
+    }
+
+
     Z3_string Z3_API Z3_optimize_get_reason_unknown(Z3_context c, Z3_optimize o) {
         Z3_TRY;
         LOG_Z3_optimize_to_string(c, o);

src/api/c++/z3++.h

@@ -2455,8 +2455,19 @@ namespace z3 {
         void pop() {
             Z3_optimize_pop(ctx(), m_opt);
         }
-        check_result check() { Z3_lbool r = Z3_optimize_check(ctx(), m_opt); check_error(); return to_check_result(r); }
+        check_result check() { Z3_lbool r = Z3_optimize_check(ctx(), m_opt, 0, 0); check_error(); return to_check_result(r); }
+        check_result check(expr_vector const& asms) { 
+            array<Z3_ast> _asms(n);
+            for (unsigned i = 0; i < n; i++) {
+                check_context(*this, asms[i]);
+                _asms[i] = asms[i];
+            }
+            Z3_lbool r = Z3_optimize_check(ctx(), m_opt, n, _asms.ptr()); 
+            check_error(); 
+            return to_check_result(r); 
+        }
         model get_model() const { Z3_model m = Z3_optimize_get_model(ctx(), m_opt); check_error(); return model(ctx(), m); }
+        expr_vector unsat_core() const { Z3_ast_vector r = Z3_optimize_get_unsat_core(ctx(), m_solver); check_error(); return expr_vector(ctx(), r); }
         void set(params const & p) { Z3_optimize_set_params(ctx(), m_opt, p); check_error(); }
         expr lower(handle const& h) {
             Z3_ast r = Z3_optimize_get_lower(ctx(), m_opt, h.h());

src/api/dotnet/Optimize.cs

@@ -183,9 +183,9 @@ namespace Microsoft.Z3
         /// don't use strict inequalities) meets the objectives.
         /// </summary>
         ///
-        public Status Check()
+        public Status Check(params Expr[] assumptions)
         {
-            Z3_lbool r = (Z3_lbool)Native.Z3_optimize_check(Context.nCtx, NativeObject);
+            Z3_lbool r = (Z3_lbool)Native.Z3_optimize_check(Context.nCtx, NativeObject, (uint)assumptions.Length, AST.ArrayToNative(assumptions));
             switch (r)
             {
                 case Z3_lbool.Z3_L_TRUE:
@@ -236,6 +236,25 @@ namespace Microsoft.Z3
             }
         }
 
+        /// <summary>
+        /// The unsat core of the last <c>Check</c>.
+        /// </summary>
+        /// <remarks>
+        /// The unsat core is a subset of <c>assumptions</c>
+        /// The result is empty if <c>Check</c> was not invoked before,
+        /// if its results was not <c>UNSATISFIABLE</c>, or if core production is disabled.
+        /// </remarks>
+        public BoolExpr[] UnsatCore
+        {
+            get
+            {
+                Contract.Ensures(Contract.Result<Expr[]>() != null);
+
+                ASTVector core = new ASTVector(Context, Native.Z3_optimize_get_unsat_core(Context.nCtx, NativeObject));                
+                return core.ToBoolExprArray();
+            }
+        }
+
         /// <summary>
         /// Declare an arithmetical maximization objective.
         /// Return a handle to the objective. The handle is used as

src/api/java/Optimize.java

@@ -161,9 +161,23 @@ public class Optimize extends Z3Object {
      * Produce a model that (when the objectives are bounded and 
      * don't use strict inequalities) meets the objectives.
      **/
-    public Status Check()
+    public Status Check(Expr... assumptions)
     {
-        Z3_lbool r = Z3_lbool.fromInt(Native.optimizeCheck(getContext().nCtx(), getNativeObject()));
+        Z3_lbool r;
+        if (assumptions == null) {
+          r = Z3_lbool.fromInt(
+              Native.optimizeCheck(
+                  getContext().nCtx(), 
+                  getNativeObject(), 0, null);
+        }
+        else {
+          r = Z3_lbool.fromInt(
+              Native.optimizeCheck(
+                  getContext().nCtx(), 
+                  getNativeObject(), 
+                  assumptions.length, 
+                  AST.arrayToNative(assumptions)));
+        }
         switch (r) {
             case Z3_L_TRUE:
                 return Status.SATISFIABLE;
@@ -209,6 +223,21 @@ public class Optimize extends Z3Object {
         }
     }
 
+    /**
+     * The unsat core of the last {@code Check}.
+     * Remarks:  The unsat core
+     * is a subset of {@code Assumptions} The result is empty if
+     * {@code Check} was not invoked before, if its results was not
+     * {@code UNSATISFIABLE}, or if core production is disabled. 
+     * 
+     * @throws Z3Exception
+     **/
+    public BoolExpr[] getUnsatCore()
+    {
+        ASTVector core = new ASTVector(getContext(), Native.optimizeGetUnsatCore(getContext().nCtx(), getNativeObject()));        
+        return core.ToBoolExprArray();
+    }
+
     /**
      *  Declare an arithmetical maximization objective.
      *  Return a handle to the objective. The handle is used as

src/api/ml/z3.ml

@@ -1947,7 +1947,7 @@ struct
   let minimize (x:optimize) (e:Expr.expr) = mk_handle x (Z3native.optimize_minimize (gc x) x e)
 
   let check (x:optimize) =
-    let r = lbool_of_int (Z3native.optimize_check (gc x) x) in
+    let r = lbool_of_int (Z3native.optimize_check (gc x) x) 0 [] in
     match r with
     | L_TRUE -> Solver.SATISFIABLE
     | L_FALSE -> Solver.UNSATISFIABLE

src/api/python/z3/z3.py

@@ -7311,10 +7311,15 @@ class Optimize(Z3PPObject):
         """restore to previously created backtracking point"""
         Z3_optimize_pop(self.ctx.ref(), self.optimize)
 
-    def check(self):
+    def check(self, *assumptions):
         """Check satisfiability while optimizing objective functions."""
-        return CheckSatResult(Z3_optimize_check(self.ctx.ref(), self.optimize))
+        assumptions = _get_args(assumptions)
-
+        num = len(assumptions)
+        _assumptions = (Ast * num)()
+        for i in range(num):
+            _assumptions[i] = assumptions[i].as_ast()
+        return CheckSatResult(Z3_optimize_check(self.ctx.ref(), self.optimize, num, _assumptions))
+    
     def reason_unknown(self):
         """Return a string that describes why the last `check()` returned `unknown`."""
         return Z3_optimize_get_reason_unknown(self.ctx.ref(), self.optimize)
@@ -7326,6 +7331,9 @@ class Optimize(Z3PPObject):
         except Z3Exception:
             raise Z3Exception("model is not available")
 
+    def unsat_core(self):
+        return AstVector(Z3_optimize_get_unsat_core(self.ctx.ref(), self.optimize), self.ctx)
+
     def lower(self, obj):
         if not isinstance(obj, OptimizeObjective):
             raise Z3Exception("Expecting objective handle returned by maximize/minimize")

src/api/z3_optimization.h

@@ -117,10 +117,12 @@ extern "C" {
        \brief Check consistency and produce optimal values.
        \param c - context
        \param o - optimization context
+       \param num_assumptions - number of additional assumptions
+       \param assumptions - the additional assumptions
 
-       def_API('Z3_optimize_check', INT, (_in(CONTEXT), _in(OPTIMIZE)))
+       def_API('Z3_optimize_check', INT, (_in(CONTEXT), _in(OPTIMIZE), _in(UINT), _in_array(2, AST)))
     */
-    Z3_lbool Z3_API Z3_optimize_check(Z3_context c, Z3_optimize o);
+    Z3_lbool Z3_API Z3_optimize_check(Z3_context c, Z3_optimize o, unsigned num_assumptions, Z3_ast const assumptions[]);
 
 
     /**
@@ -143,6 +145,14 @@ extern "C" {
     */
     Z3_model Z3_API Z3_optimize_get_model(Z3_context c, Z3_optimize o);
 
+    /**
+       \brief Retrieve the unsat core for the last #Z3_optimize_chec
+       The unsat core is a subset of the assumptions \c a.
+
+       def_API('Z3_optimize_get_unsat_core', AST_VECTOR, (_in(CONTEXT), _in(OPTIMIZE)))       
+     */
+    Z3_ast_vector Z3_API Z3_optimize_get_unsat_core(Z3_context c, Z3_optimize o);
+
     /**
        \brief Set parameters on optimization context.
 

src/cmd_context/cmd_context.cpp

@@ -1488,13 +1488,13 @@ void cmd_context::check_sat(unsigned num_assumptions, expr * const * assumptions
         scoped_ctrl_c ctrlc(eh);
         scoped_timer timer(timeout, &eh);
         scoped_rlimit _rlimit(m().limit(), rlimit);
+        expr_ref_vector asms(m());
+        asms.append(num_assumptions, assumptions);
         if (!m_processing_pareto) {
-            ptr_vector<expr> cnstr(m_assertions);
+            get_opt()->set_hard_constraints(m_assertions);
-            cnstr.append(num_assumptions, assumptions);
-            get_opt()->set_hard_constraints(cnstr);
         }
         try {
-            r = get_opt()->optimize();
+            r = get_opt()->optimize(asms);
             if (r == l_true && get_opt()->is_pareto()) {
                 m_processing_pareto = true;
             }

src/cmd_context/cmd_context.h

@@ -148,7 +148,7 @@ public:
     virtual bool empty() = 0;
     virtual void push() = 0;
     virtual void pop(unsigned n) = 0;
-    virtual lbool optimize() = 0;
+    virtual lbool optimize(expr_ref_vector const& asms) = 0;
     virtual void set_hard_constraints(ptr_vector<expr> & hard) = 0;
     virtual void display_assignment(std::ostream& out) = 0;
     virtual bool is_pareto() = 0;

src/opt/opt_context.cpp

@@ -130,6 +130,7 @@ namespace opt {
         m_fm(alloc(generic_model_converter, m, "opt")),
         m_model_fixed(),
         m_objective_refs(m),
+        m_core(m),
         m_enable_sat(false),
         m_is_clausal(false),
         m_pp_neat(false),
@@ -173,10 +174,9 @@ namespace opt {
     }
 
     void context::get_unsat_core(expr_ref_vector & r) { 
-        throw default_exception("Unsat cores are not supported with optimization"); 
+        r.append(m_core);
     }
 
-
     void context::set_hard_constraints(ptr_vector<expr>& fmls) {
         if (m_scoped_state.set(fmls)) {
             clear_state();
@@ -253,7 +253,7 @@ namespace opt {
         m_hard_constraints.append(s.m_hard);
     }
 
-    lbool context::optimize() {
+    lbool context::optimize(expr_ref_vector const& asms) {
         if (m_pareto) {
             return execute_pareto();
         }
@@ -263,7 +263,10 @@ namespace opt {
         clear_state();
         init_solver(); 
         import_scoped_state(); 
-        normalize();
+        normalize(asms);
+        if (m_hard_constraints.size() == 1 && m.is_false(m_hard_constraints.get(0))) {
+            return l_false;
+        }
         internalize();
         update_solver();
         if (contains_quantifiers()) {
@@ -281,7 +284,7 @@ namespace opt {
         symbol pri = optp.priority();
 
         IF_VERBOSE(1, verbose_stream() << "(optimize:check-sat)\n");
-        lbool is_sat = s.check_sat(0,nullptr);
+        lbool is_sat = s.check_sat(asms.size(),asms.c_ptr());
         TRACE("opt", s.display(tout << "initial search result: " << is_sat << "\n");); 
         if (is_sat != l_false) {
             s.get_model(m_model);
@@ -290,6 +293,9 @@ namespace opt {
         }
         if (is_sat != l_true) {
             TRACE("opt", tout << m_hard_constraints << "\n";);            
+            if (!asms.empty()) {
+                s.get_unsat_core(m_core);
+            }
             return is_sat;
         }
         IF_VERBOSE(1, verbose_stream() << "(optimize:sat)\n");
@@ -751,22 +757,25 @@ namespace opt {
         return m_arith.is_numeral(e, n) || m_bv.is_numeral(e, n, sz);
     }
 
-    void context::normalize() {
+    void context::normalize(expr_ref_vector const& asms) {
         expr_ref_vector fmls(m);
         to_fmls(fmls);
-        simplify_fmls(fmls);
+        simplify_fmls(fmls, asms);
         from_fmls(fmls);
     }
 
-    void context::simplify_fmls(expr_ref_vector& fmls) {
+    void context::simplify_fmls(expr_ref_vector& fmls, expr_ref_vector const& asms) {
         if (m_is_clausal) {
             return;
         }
 
-        goal_ref g(alloc(goal, m, true, false));
+        goal_ref g(alloc(goal, m, true, !asms.empty()));
         for (expr* fml : fmls) {
             g->assert_expr(fml);
         }
+        for (expr * a : asms) {
+            g->assert_expr(a, a);
+        }
         tactic_ref tac0 = 
             and_then(mk_simplify_tactic(m, m_params), 
                      mk_propagate_values_tactic(m),
@@ -788,6 +797,7 @@ namespace opt {
             set_simplify(tac0.get());
         }
         goal_ref_buffer result;
+        TRACE("opt", g->display(tout););
         (*m_simplify)(g, result); 
         SASSERT(result.size() == 1);
         goal* r = result[0];
@@ -797,6 +807,12 @@ namespace opt {
         for (unsigned i = 0; i < r->size(); ++i) {
             fmls.push_back(r->form(i));
         }        
+        if (r->inconsistent()) {
+            ptr_vector<expr> core_elems;
+            expr_dependency_ref core(r->dep(0), m);
+            m.linearize(core, core_elems);
+            m_core.append(core_elems.size(), core_elems.c_ptr());
+        }
     }
 
     bool context::is_maximize(expr* fml, app_ref& term, expr_ref& orig_term, unsigned& index) {
@@ -1395,6 +1411,7 @@ namespace opt {
         m_box_index = UINT_MAX;
         m_model.reset();
         m_model_fixed.reset();
+        m_core.reset();
     }
 
     void context::set_pareto(pareto_base* p) {

src/opt/opt_context.h

@@ -164,6 +164,7 @@ namespace opt {
         obj_map<func_decl, unsigned> m_objective_fns;
         obj_map<func_decl, expr*>    m_objective_orig;
         func_decl_ref_vector         m_objective_refs;
+        expr_ref_vector              m_core;
         tactic_ref                   m_simplify;
         bool                         m_enable_sat;
         bool                         m_enable_sls;
@@ -187,7 +188,7 @@ namespace opt {
         void pop(unsigned n) override;
         bool empty() override { return m_scoped_state.m_objectives.empty(); }
         void set_hard_constraints(ptr_vector<expr> & hard) override;
-        lbool optimize() override;
+        lbool optimize(expr_ref_vector const& asms) override;
         void set_model(model_ref& _m) override { m_model = _m; }
         void get_model_core(model_ref& _m) override;
         void get_box_model(model_ref& _m, unsigned index) override;
@@ -254,7 +255,7 @@ namespace opt {
 
         void reset_maxsmts();
         void import_scoped_state();
-        void normalize();
+        void normalize(expr_ref_vector const& asms);
         void internalize();
         bool is_maximize(expr* fml, app_ref& term, expr_ref& orig_term, unsigned& index);
         bool is_minimize(expr* fml, app_ref& term, expr_ref& orig_term, unsigned& index);
@@ -270,7 +271,7 @@ namespace opt {
         expr* mk_objective_fn(unsigned index, objective_t ty, unsigned sz, expr*const* args);
         void to_fmls(expr_ref_vector& fmls);
         void from_fmls(expr_ref_vector const& fmls);
-        void simplify_fmls(expr_ref_vector& fmls);
+        void simplify_fmls(expr_ref_vector& fmls, expr_ref_vector const& asms);
         void mk_atomic(expr_ref_vector& terms);
 
         void update_lower() { update_bound(true); }

src/shell/opt_frontend.cpp

@@ -108,7 +108,8 @@ static unsigned parse_opt(std::istream& in, opt_format f) {
         unsigned rlimit = std::stoi(gparams::get_value("rlimit"));
         scoped_timer timer(timeout, &eh);
         scoped_rlimit _rlimit(m.limit(), rlimit);
-        lbool r = opt.optimize();
+        expr_ref_vector asms(m);
+        lbool r = opt.optimize(asms);
         switch (r) {
         case l_true:  std::cout << "sat\n"; break;
         case l_false: std::cout << "unsat\n"; break;