diff --git a/lib/pdr_context.cpp b/lib/pdr_context.cpp
index 552f8231e..a8def9a6f 100644
--- a/lib/pdr_context.cpp
+++ b/lib/pdr_context.cpp
@@ -382,16 +382,14 @@ namespace pdr {
     }
 
     lbool pred_transformer::is_reachable(model_node& n, expr_ref_vector* core) {
-        unsigned level = n.level();
-        expr* state = n.state();
-        model_ref model;
-        ensure_level(level);        
-        prop_solver::scoped_level _sl(m_solver, level);
-        TRACE("pdr", tout << "is-reachable: " << head()->get_name() << " level: " << level << "\n";
-              tout << mk_pp(state, m) << "\n";);
-
-        bool assumes_level;
-        lbool is_sat = m_solver.check_conjunction_as_assumptions(state, core, &model, assumes_level);
+        TRACE("pdr", 
+              tout << "is-reachable: " << head()->get_name() << " level: " << n.level() << "\n";
+              tout << mk_pp(n.state(), m) << "\n";);
+        ensure_level(n.level());        
+        prop_solver::scoped_level _sl(m_solver, n.level());
+        m_solver.set_core(core);
+        m_solver.set_model(&model);
+        lbool is_sat = m_solver.check_conjunction_as_assumptions(n.state());
         if (is_sat == l_true && core) {            
             core->reset();
             model2cube(*model, *core);
@@ -411,7 +409,31 @@ namespace pdr {
         }
         tmp = pm.mk_and(conj);
         prop_solver::scoped_level _sl(m_solver, level);
-        return m_solver.check_conjunction_as_assumptions(tmp, core, 0, assumes_level) == l_false;
+        m_solver.set_core(core);
+        lbool r = m_solver.check_conjunction_as_assumptions(tmp);
+        if (r == l_false) {
+            assumes_level = m_solver.assumes_level();
+        }
+        return r == l_false;
+    }
+
+    bool pred_transformer::check_inductive(unsigned level, expr_ref_vector& lits, bool& assumes_level) {
+        manager& pm = get_pdr_manager();
+        expr_ref_vector conj(m), core(m);
+        expr_ref fml(m), states(m);
+        states = m.mk_not(pm.mk_and(lits));
+        mk_assumptions(head(), states, conj);
+        fml = pm.mk_and(conj);
+        prop_solver::scoped_level _sl(m_solver, level);
+        m_solver.set_core(&core);
+        m_solver.set_subset_based_core(true);
+        lbool res = m_solver.check_assumptions_and_formula(lits, fml);
+        if (res == l_false) {
+            lits.reset();
+            lits.append(core);
+            assumes_level = m_solver.assumes_level();
+        }
+        return res == l_false;
     }
 
     void pred_transformer::mk_assumptions(func_decl* head, expr* fml, expr_ref_vector& result) {
@@ -425,7 +447,6 @@ namespace pdr {
             for (unsigned i = 0; i < m_predicates.size(); i++) {
                 func_decl* d = m_predicates[i];
                 if (d == head) {
-                    // tmp1 = (m_tag2rule.size() == 1)?fml:m.mk_implies(pred, fml);
                     tmp1 = m.mk_implies(pred, fml);
                     pm.formula_n2o(tmp1, tmp2, i);
                     result.push_back(tmp2);
@@ -883,10 +904,21 @@ namespace pdr {
         return result;
     }
 
+    bool model_search::is_repeated(model_node& n) const {
+        model_node* p = n.parent();
+        while (p) {
+            if (p->state() == n.state()) {
+                return true;
+            }
+            p = p->parent();
+        }
+        return false;
+    }
+
     void model_search::add_leaf(model_node& n) {
         unsigned& count = cache(n).insert_if_not_there2(n.state(), 0)->get_data().m_value;
         ++count;
-        if (count == 1) {
+        if (count == 1 || is_repeated(n)) {
             set_leaf(n);
         }
         else {
@@ -944,7 +976,6 @@ namespace pdr {
     }
 
     void model_search::erase_leaf(model_node& n) {
-
         if (n.children().empty() && n.is_open()) {
             std::deque<model_node*>::iterator 
                 it  = m_leaves.begin(), 
@@ -1619,7 +1650,7 @@ namespace pdr {
                 TRACE("pdr", tout << "invariant state: " << (uses_level?"":"(inductive) ") <<  mk_pp(ncube, m) << "\n";);
                 n.pt().add_property(ncube, uses_level?n.level():infty_level);
                 CASSERT("pdr",n.level() == 0 || check_invariant(n.level()-1));
-                m_search.backtrack_level(uses_level && m_params.get_bool(":flexible-trace",true), n);
+                m_search.backtrack_level(uses_level && m_params.get_bool(":flexible-trace", false), n);
                 break;
             }
             case l_undef: {
diff --git a/lib/pdr_context.h b/lib/pdr_context.h
index 42572bb1e..f849fdbcd 100644
--- a/lib/pdr_context.h
+++ b/lib/pdr_context.h
@@ -139,6 +139,7 @@ namespace pdr {
 
         lbool is_reachable(model_node& n, expr_ref_vector* core);
         bool is_invariant(unsigned level, expr* co_state, bool inductive, bool& assumes_level, expr_ref_vector* core = 0);
+        bool check_inductive(unsigned level, expr_ref_vector& state, bool& assumes_level);
 
         expr_ref get_formulas(unsigned level, bool add_axioms);
 
@@ -235,6 +236,8 @@ namespace pdr {
 
         model_node* next();
 
+        bool is_repeated(model_node& n) const;
+
         void add_leaf(model_node& n); // add fresh node.
 
         void set_leaf(model_node& n); // Set node as leaf, remove children.
diff --git a/lib/pdr_generalizers.cpp b/lib/pdr_generalizers.cpp
index 655a98967..cddc2eb37 100644
--- a/lib/pdr_generalizers.cpp
+++ b/lib/pdr_generalizers.cpp
@@ -99,31 +99,26 @@ namespace pdr {
         }
         ast_manager& m = core.get_manager();
         TRACE("pdr", for (unsigned i = 0; i < core.size(); ++i) { tout << mk_pp(core[i].get(), m) << "\n"; } "\n";);
-        unsigned num_failures = 0, i = 0, num_changes = 0;
+        unsigned num_failures = 0, i = 0, old_core_size = core.size();
+        ptr_vector<expr> processed;
+
         while (i < core.size() && 1 < core.size() && (!m_failure_limit || num_failures <= m_failure_limit)) {
-            expr_ref lit(m), state(m);
+            expr_ref lit(m);
             lit = core[i].get();
-            core[i] = m.mk_true();
-            state = m.mk_not(n.pt().get_pdr_manager().mk_and(core));
-            bool uses_level_tmp = false;
-            if (n.pt().is_invariant(n.level(), state, true, uses_level_tmp, 0)) {
+            core[i] = m.mk_true();            
+            if (n.pt().check_inductive(n.level(), core, uses_level)) {
                 num_failures = 0;
-                core[i] = core.back();
-                core.pop_back();
-                TRACE("pdr", tout << "Remove: " << mk_pp(lit, m) << "\n";);
-                IF_VERBOSE(3, verbose_stream() << "remove: " << mk_pp(lit, m) << "\n";);
-                ++num_changes;
-                uses_level = uses_level_tmp;
+                for (i = 0; i < core.size() && processed.contains(core[i].get()); ++i);
             }
             else {
-                IF_VERBOSE(3, verbose_stream() << "keep: " << mk_pp(lit, m) << "\n";);
                 core[i] = lit;
+                processed.push_back(lit);
                 ++num_failures;
                 ++i;
             }
         }
-        IF_VERBOSE(2, verbose_stream() << "changes: " << num_changes << " size: " << core.size() << "\n";);
-        TRACE("pdr", tout << "changes: " << num_changes << " index: " << i << " size: " << core.size() << "\n";);
+        IF_VERBOSE(2, verbose_stream() << "old size: " << old_core_size << " new size: " << core.size() << "\n";);
+        TRACE("pdr", tout << "old size: " << old_core_size << " new size: " << core.size() << "\n";);
     }
 
     //
diff --git a/lib/pdr_prop_solver.cpp b/lib/pdr_prop_solver.cpp
index 9f2466180..2908bf4f6 100644
--- a/lib/pdr_prop_solver.cpp
+++ b/lib/pdr_prop_solver.cpp
@@ -28,6 +28,7 @@ Revision History:
 #include "datatype_decl_plugin.h"
 #include "pdr_farkas_learner.h"
 #include "ast_smt2_pp.h"
+#include "expr_replacer.h"
 
 //
 // Auxiliary structure to introduce propositional names for assumptions that are not
@@ -42,36 +43,36 @@ namespace pdr {
         ast_manager&        m;
         expr_ref_vector     m_atoms;
         expr_ref_vector     m_assumptions;
-        obj_map<app,expr *> m_fresh2expr;
-        obj_map<expr, app*> m_expr2fresh;
-        obj_hashtable<expr> m_equivs;
-        unsigned            m_num_fresh;
+        obj_map<app,expr *> m_proxies2expr;
+        obj_map<expr, app*> m_expr2proxies;
+        obj_hashtable<expr> m_implies;
+        unsigned            m_num_proxies;
 
-        app * mk_fresh(expr* atom) {
+        app * mk_proxy(expr* literal) {
             app* res;
-            SASSERT(!is_var(atom)); //it doesn't make sense to introduce names to variables
-            if (m_expr2fresh.find(atom, res)) {
+            SASSERT(!is_var(literal)); //it doesn't make sense to introduce names to variables
+            if (m_expr2proxies.find(literal, res)) {
                 return res;
             }
-            SASSERT(s.m_fresh.size() >= m_num_fresh);
-            if (m_num_fresh == s.m_fresh.size()) {
+            SASSERT(s.m_proxies.size() >= m_num_proxies);
+            if (m_num_proxies == s.m_proxies.size()) {
                 std::stringstream name;
-                name << "pdr_proxy_" << s.m_fresh.size();
+                name << "pdr_proxy_" << s.m_proxies.size();
                 res = m.mk_const(symbol(name.str().c_str()), m.mk_bool_sort());
-                s.m_fresh.push_back(res);
+                s.m_proxies.push_back(res);
                 s.m_aux_symbols.insert(res->get_decl());
             }
             else {
-                res = s.m_fresh[m_num_fresh].get();
+                res = s.m_proxies[m_num_proxies].get();
             }
-            ++m_num_fresh;
-            m_expr2fresh.insert(atom, res);
-            m_fresh2expr.insert(res, atom);
-            expr_ref equiv(m.mk_or(atom, m.mk_not(res)), m);
-            s.m_ctx->assert_expr(equiv);
-            m_assumptions.push_back(equiv);
-            m_equivs.insert(equiv);
-            TRACE("pdr_verbose", tout << "name asserted " << mk_pp(equiv, m) << "\n";);    
+            ++m_num_proxies;
+            m_expr2proxies.insert(literal, res);
+            m_proxies2expr.insert(res, literal);
+            expr_ref implies(m.mk_or(m.mk_not(res), literal), m);
+            s.m_ctx->assert_expr(implies);
+            m_assumptions.push_back(implies);
+            m_implies.insert(implies);
+            TRACE("pdr_verbose", tout << "name asserted " << mk_pp(implies, m) << "\n";);    
             return res;
         }
 
@@ -84,7 +85,7 @@ namespace pdr {
                 m.is_not(lit, lit_core);
                 SASSERT(!m.is_true(lit));
                 if (!is_uninterp(lit_core) || to_app(lit_core)->get_num_args() != 0) {
-                    conjs[i] = mk_fresh(lit);
+                    conjs[i] = mk_proxy(lit);
                 }
             }
             m_assumptions.append(conjs);
@@ -122,38 +123,64 @@ namespace pdr {
 
     public:
         safe_assumptions(prop_solver& s, expr_ref_vector const& assumptions): 
-            s(s), m(s.m), m_atoms(assumptions), m_assumptions(m), m_num_fresh(0) {
+            s(s), m(s.m), m_atoms(assumptions), m_assumptions(m), m_num_proxies(0) {
               mk_safe(m_atoms);
-          }
+        }
+        
+        ~safe_assumptions() {
+        }    
+        
+        expr_ref_vector const& atoms() const { return m_atoms; }
+        
+        unsigned assumptions_size() const { return m_assumptions.size(); }
+        
+        expr* assumptions(unsigned i) const { return m_assumptions[i]; }
 
-          ~safe_assumptions() {
-          }    
+        void undo_proxies(expr_ref_vector& es) {
+            expr_ref e(m);
+            expr* r;
+            for (unsigned i = 0; i < es.size(); ++i) {
+                e = es[i].get();
+                if (is_app(e) && m_proxies2expr.find(to_app(e), r)) {
+                    es[i] = r;
+                }
+            }
+        }
+        
+        void elim_proxies(expr_ref_vector& es) {
+            expr_substitution sub(m, false, m.proofs_enabled());
+            proof_ref pr(m);
+            if (m.proofs_enabled()) {
+                pr = m.mk_asserted(m.mk_true());
+            }
+            obj_map<app,expr*>::iterator it = m_proxies2expr.begin(), end = m_proxies2expr.end();
+            for (; it != end; ++it) {
+                sub.insert(it->m_key, m.mk_true(), pr);
+            }
+            scoped_ptr<expr_replacer> rep = mk_default_expr_replacer(m);
+            rep->set_substitution(&sub);
+            replace_proxies(*rep, es);
+        }
+    private:
 
-          expr_ref_vector const& atoms() const { return m_atoms; }
-
-          unsigned assumptions_size() const { return m_assumptions.size(); }
-
-          expr* assumptions(unsigned i) const { return m_assumptions[i]; }
-
-          expr* undo_naming(expr* atom) {
-              if (m_equivs.contains(atom)) {
-                  return m.mk_true();
-              }
-              SASSERT(is_app(atom)); //only apps can be used in safe cubes
-              m_fresh2expr.find(to_app(atom), atom);
-              return atom;
-          }
-
-          void undo_naming(expr_ref_vector& literals) {
-              for (unsigned i = 0; i < literals.size(); ++i) {
-                  literals[i] = undo_naming(literals[i].get());
-                  if (m.is_true(literals[i].get())) {
-                      literals[i] = literals.back();
-                      literals.pop_back();
-                      --i;
-                  }
-              }        
-          }
+        void replace_proxies(expr_replacer& rep, expr_ref_vector& es) {
+            expr_ref e(m);
+            for (unsigned i = 0; i < es.size(); ++i) {
+                e = es[i].get();
+                if (m_implies.contains(e)) {
+                    e = m.mk_true();
+                }
+                else {
+                    rep(e);
+                }
+                es[i] = e;
+                if (m.is_true(e)) {
+                    es[i] = es.back();
+                    es.pop_back();
+                    --i;
+                }
+            }        
+        }
     };
 
 
@@ -166,7 +193,9 @@ namespace pdr {
         m_ctx(pm.mk_fresh()),
         m_pos_level_atoms(m),
         m_neg_level_atoms(m),
-        m_fresh(m),
+        m_proxies(m),
+        m_core(0),
+        m_subset_based_core(false),
         m_in_level(false)
     {
         m_ctx->assert_expr(m_pm.get_background());
@@ -226,15 +255,11 @@ namespace pdr {
 
     lbool prop_solver::check_safe_assumptions(
         safe_assumptions& safe,
-        const expr_ref_vector& atoms, 
-        expr_ref_vector* core, 
-        model_ref * mdl, 
-        bool& assumes_level)
+        const expr_ref_vector& atoms)
     {
-        flet<bool> _model(m_fparams.m_model, mdl != 0);
+        flet<bool> _model(m_fparams.m_model, m_model != 0);
         expr_ref_vector expr_atoms(m);
         expr_atoms.append(atoms.size(), atoms.c_ptr());
-        assumes_level = false;
 
         if (m_in_level) {
             push_level_atoms(m_current_level, expr_atoms);
@@ -246,120 +271,106 @@ namespace pdr {
                tout << mk_pp(m_pm.mk_and(expr_atoms), m) << "\n";
                tout << result << "\n";);
 
-        if (result == l_true && mdl) {
-            m_ctx->get_model(*mdl);
-            TRACE("pdr_verbose", model_pp(tout, **mdl); );
+        if (result == l_true && m_model) {
+            m_ctx->get_model(*m_model);
+            TRACE("pdr_verbose", model_pp(tout, **m_model); );
         }
-
-        unsigned core_size = m_ctx->get_unsat_core_size(); 
-
-        if (result == l_false && !core) {            
+        
+        if (result == l_false) { 
+            unsigned core_size = m_ctx->get_unsat_core_size(); 
+            m_assumes_level = false;
             for (unsigned i = 0; i < core_size; ++i) {
                 if (m_level_atoms_set.contains(m_ctx->get_unsat_core_expr(i))) {
-                    assumes_level = true;
+                    m_assumes_level = true;
                     break;
                 }
             }
         }
 
-        if (result == l_false && core && m.proofs_enabled()) {
-            proof_ref pr(m);
-            pr = m_ctx->get_proof();
-            IF_VERBOSE(21, verbose_stream() << mk_ismt2_pp(pr, m) << "\n";);
-            farkas_learner fl(m_fparams, m);
-            expr_ref_vector lemmas(m);
-            obj_hashtable<expr> bs;
-            for (unsigned i = 0; i < safe.assumptions_size(); ++i) {
-                bs.insert(safe.assumptions(i));
-            }
-            fl.get_lemmas(pr, bs, lemmas);
-            safe.undo_naming(lemmas);
-            fl.simplify_lemmas(lemmas);
-
-            IF_VERBOSE(2, 
-                verbose_stream() << "Lemmas\n";            
-                for (unsigned i = 0; i < lemmas.size(); ++i) {
-                    verbose_stream() << mk_pp(lemmas[i].get(), m) << "\n";
-                });
-
-            core->reset();
-            core->append(lemmas);
-            return result;
+        if (result == l_false && m_core && m.proofs_enabled() && !m_subset_based_core) {
+            extract_theory_core(safe);
         }
-
-        if (result == l_false && core) {
-            core->reset();
-            for (unsigned i = 0; i < core_size; ++i) {
-                expr * core_expr = m_ctx->get_unsat_core_expr(i);
-                SASSERT(is_app(core_expr));
-
-                if (m_level_atoms_set.contains(core_expr)) {
-                    assumes_level = true;
-                    continue;
-                }
-                if (m_ctx->is_aux_predicate(core_expr)) {
-                    continue;
-                }
-                core->push_back(to_app(core_expr));
-            }
-            SASSERT(expr_atoms.size() >= core->size());
-
-            safe.undo_naming(*core);
-
-            TRACE("pdr", 
-                tout << mk_pp(m_pm.mk_and(expr_atoms), m) << "\n";
-                tout << "core_exprs: ";
-                for (unsigned i = 0; i < core_size; ++i) {
-                    tout << mk_pp(m_ctx->get_unsat_core_expr(i), m) << " ";
-                }
-                tout << "\n";
-                tout << "core: " << mk_pp(m_pm.mk_and(*core), m) << "\n";              
-                );
-            
+        else if (result == l_false && m_core) {
+            extract_subset_core(safe);    
+            SASSERT(expr_atoms.size() >= m_core->size());
         }
+        m_core = 0;
+        m_model = 0;
+        m_subset_based_core = false;
         return result;
     }
 
-    lbool prop_solver::check_assumptions(
-        const expr_ref_vector & atoms, 
-        expr_ref_vector * core, 
-        model_ref * mdl, 
-        bool& assumes_level)
-    {
-        return check_assumptions_and_formula(atoms, m.mk_true(), core, mdl, assumes_level);
+    void prop_solver::extract_subset_core(safe_assumptions& safe) {
+        unsigned core_size = m_ctx->get_unsat_core_size(); 
+        m_core->reset();
+        for (unsigned i = 0; i < core_size; ++i) {
+            expr * core_expr = m_ctx->get_unsat_core_expr(i);
+            SASSERT(is_app(core_expr));
+
+            if (m_level_atoms_set.contains(core_expr)) {
+                continue;
+            }
+            if (m_ctx->is_aux_predicate(core_expr)) {
+                continue;
+            }
+            m_core->push_back(to_app(core_expr));
+        }        
+
+        safe.undo_proxies(*m_core);
+
+        TRACE("pdr", 
+            tout << "core_exprs: ";
+                for (unsigned i = 0; i < core_size; ++i) {
+                tout << mk_pp(m_ctx->get_unsat_core_expr(i), m) << " ";
+            }
+            tout << "\n";
+            tout << "core: " << mk_pp(m_pm.mk_and(*m_core), m) << "\n";              
+        );
     }
 
-    lbool prop_solver::check_conjunction_as_assumptions(
-        expr * conj, 
-        expr_ref_vector * core, 
-        model_ref * mdl, 
-        bool& assumes_level) {
+
+    void prop_solver::extract_theory_core(safe_assumptions& safe) {
+        proof_ref pr(m);
+        pr = m_ctx->get_proof();
+        IF_VERBOSE(21, verbose_stream() << mk_ismt2_pp(pr, m) << "\n";);
+        farkas_learner fl(m_fparams, m);
+        expr_ref_vector lemmas(m);
+        obj_hashtable<expr> bs;
+        for (unsigned i = 0; i < safe.assumptions_size(); ++i) {
+            bs.insert(safe.assumptions(i));
+        }
+        fl.get_lemmas(pr, bs, lemmas);
+        safe.elim_proxies(lemmas);
+        fl.simplify_lemmas(lemmas); // redundant
+
+        IF_VERBOSE(2, 
+            verbose_stream() << "Lemmas\n";            
+        for (unsigned i = 0; i < lemmas.size(); ++i) {
+            verbose_stream() << mk_pp(lemmas[i].get(), m) << "\n";
+        });
+
+        m_core->reset();
+        m_core->append(lemmas);
+    }
+
+    lbool prop_solver::check_assumptions(const expr_ref_vector & atoms)
+    {
+        return check_assumptions_and_formula(atoms, m.mk_true());
+    }
+
+    lbool prop_solver::check_conjunction_as_assumptions(expr * conj) {
         expr_ref_vector asmp(m);
         asmp.push_back(conj);
-        return check_assumptions(asmp, core, mdl, assumes_level);
+        return check_assumptions(asmp);
     }
 
-    lbool prop_solver::check_assumptions_and_formula(
-        const expr_ref_vector & atoms, 
-        expr * form, 
-        expr_ref_vector * core, 
-        model_ref * mdl, 
-        bool& assumes_level) 
+    lbool prop_solver::check_assumptions_and_formula(const expr_ref_vector & atoms, expr * form) 
     {
         pdr::smt_context::scoped _scoped(*m_ctx);
         safe_assumptions safe(*this, atoms);
         m_ctx->assert_expr(form);    
         CTRACE("pdr", !m.is_true(form), tout << "check with formula: " << mk_pp(form, m) << "\n";);
-        lbool res = check_safe_assumptions(safe, safe.atoms(), core, mdl, assumes_level);
-        if (res == l_false && core && m_try_minimize_core) {
-            unsigned sz = core->size();
-            bool assumes_level1 = false;
-            lbool res2 = check_safe_assumptions(safe, *core, core, mdl, assumes_level1);
-            if (res2 == l_false && sz > core->size()) {
-                assumes_level = assumes_level1;
-                IF_VERBOSE(1, verbose_stream() << "reduced core size from " << sz << " to " << core->size() << "\n";);
-            }
-        }
+        lbool res = check_safe_assumptions(safe, safe.atoms());
 
         //
         // we don't have to undo model naming, as from the model 
diff --git a/lib/pdr_prop_solver.h b/lib/pdr_prop_solver.h
index 76e65fca6..2b7c1af6d 100644
--- a/lib/pdr_prop_solver.h
+++ b/lib/pdr_prop_solver.h
@@ -33,6 +33,7 @@ Revision History:
 
 namespace pdr {
     class prop_solver {
+    
     private:
         front_end_params&   m_fparams;        
         ast_manager&        m;
@@ -44,7 +45,11 @@ namespace pdr {
         app_ref_vector      m_pos_level_atoms;  // atoms used to identify level
         app_ref_vector      m_neg_level_atoms;  // 
         obj_hashtable<expr> m_level_atoms_set;
-        app_ref_vector      m_fresh;            // predicates for assumptions
+        app_ref_vector      m_proxies;          // predicates for assumptions
+        expr_ref_vector*    m_core; 
+        model_ref*          m_model;
+        bool                m_subset_based_core;
+        bool                m_assumes_level;
         func_decl_set       m_aux_symbols;      
         bool                m_in_level;         
         unsigned            m_current_level;    // set when m_in_level
@@ -55,13 +60,14 @@ namespace pdr {
         void ensure_level(unsigned lvl);
 
         class safe_assumptions;
+
+        void extract_theory_core(safe_assumptions& assumptions);
+
+        void extract_subset_core(safe_assumptions& assumptions);
         
         lbool check_safe_assumptions(
             safe_assumptions& assumptions,
-            expr_ref_vector const& atoms,
-            expr_ref_vector * core, 
-            model_ref * mdl, 
-            bool& assumes_level);
+            expr_ref_vector const& atoms);
         
         
     public:
@@ -73,6 +79,11 @@ namespace pdr {
                 m_aux_symbols.contains(s) ||
                 m_ctx->is_aux_predicate(s); 
         }
+
+        void set_core(expr_ref_vector* core) { m_core = core; }
+        void set_model(model_ref* mdl) { m_model = mdl; }
+        void set_subset_based_core(bool f) { m_subset_based_core = f; }
+        bool assumes_level() const { return m_assumes_level; }
         
         void add_level();
         unsigned level_cnt() const;
@@ -99,24 +110,16 @@ namespace pdr {
          * If the conjunction of atoms is consistent with the solver state and o_model is non-zero,
          * o_model will contain the "o" literals true in the assignment.
          */
-        lbool check_assumptions(
-            const expr_ref_vector & atoms, 
-            expr_ref_vector * core, model_ref * mdl, 
-            bool& assumes_level);
+        lbool check_assumptions(const expr_ref_vector & atoms);
         
-        lbool check_conjunction_as_assumptions(
-            expr * conj, expr_ref_vector * core, 
-            model_ref * mdl, bool& assumes_level);
+        lbool check_conjunction_as_assumptions(expr * conj);
         
         /**
          * Like check_assumptions, except it also asserts an extra formula
          */
         lbool check_assumptions_and_formula(
             const expr_ref_vector & atoms, 
-            expr * form, 
-            expr_ref_vector * core, 
-            model_ref * mdl, 
-            bool& assumes_level);
+            expr * form);
         
         void collect_statistics(statistics& st) const;