diff --git a/src/ast/ast.cpp b/src/ast/ast.cpp
index bdf1c18db..b000201b7 100644
--- a/src/ast/ast.cpp
+++ b/src/ast/ast.cpp
@@ -3161,3 +3161,6 @@ void prexpr(expr_ref &e){
   std::cout << mk_pp(e.get(), e.get_manager()) << std::endl;
 }
 
+void ast_manager::show_id_gen(){
+  std::cout << "id_gen: " << m_expr_id_gen.show_hash() << " " << m_decl_id_gen.show_hash() << "\n";
+}
diff --git a/src/ast/ast.h b/src/ast/ast.h
index 2c3843587..68f08e1ac 100644
--- a/src/ast/ast.h
+++ b/src/ast/ast.h
@@ -1418,6 +1418,8 @@ protected:
 public:
     typedef expr_dependency_array_manager::ref expr_dependency_array;
 
+    void show_id_gen();
+
 protected:
     small_object_allocator    m_alloc;
     family_manager            m_family_manager;
diff --git a/src/duality/duality_wrapper.cpp b/src/duality/duality_wrapper.cpp
index 0b1c688b9..08c5d1f8a 100644
--- a/src/duality/duality_wrapper.cpp
+++ b/src/duality/duality_wrapper.cpp
@@ -513,7 +513,6 @@ expr context::make_quant(decl_kind op, const std::vector<sort> &_sorts, const st
 	opts.set("weak","1"); 
       
       ::ast *proof = m_solver->get_proof();
-      show_assertion_ids();
       iz3interpolate(m(),proof,_assumptions,_parents,_interpolants,_theory,&opts);
       
       std::vector<expr> linearized_interpolants(_interpolants.size());
@@ -604,6 +603,14 @@ expr context::make_quant(decl_kind op, const std::vector<sort> &_sorts, const st
     std::cout << std::endl;
   }
   
+  void model::show_hash() const {
+    std::ostringstream ss;
+    model_smt2_pp(ss, m(), *m_model, 0);
+    std::hash<std::string> hasher;
+    unsigned h = hasher(ss.str());
+    std::cout << "model hash: " << h << "\n";
+  }
+
   void solver::show() {
     unsigned n = m_solver->get_num_assertions();
     if(!n)
@@ -615,11 +622,20 @@ expr context::make_quant(decl_kind op, const std::vector<sort> &_sorts, const st
   }
 
   void solver::show_assertion_ids() {
+#if 0
     unsigned n = m_solver->get_num_assertions();
     std::cerr << "assertion ids: ";
     for (unsigned i = 0; i < n-1; ++i)
       std::cerr << " " << m_solver->get_assertion(i)->get_id();
     std::cerr << "\n";
+#else
+    unsigned n = m_solver->get_num_assertions();
+    std::cerr << "assertion ids hash: ";
+    unsigned h = 0;
+    for (unsigned i = 0; i < n-1; ++i)
+      h += m_solver->get_assertion(i)->get_id();
+    std::cerr << h << "\n";
+#endif
   }
 
   void include_ast_show(ast &a){
diff --git a/src/duality/duality_wrapper.h b/src/duality/duality_wrapper.h
index f0988013d..256560d02 100755
--- a/src/duality/duality_wrapper.h
+++ b/src/duality/duality_wrapper.h
@@ -727,6 +727,7 @@ namespace Duality {
         }
         
         void show() const;
+	void show_hash() const;
 
         unsigned num_consts() const {return m_model.get()->get_num_constants();}
         unsigned num_funcs() const {return m_model.get()->get_num_functions();}
@@ -1386,7 +1387,8 @@ namespace std {
     class less<Duality::ast> {
   public:
     bool operator()(const Duality::ast &s, const Duality::ast &t) const {
-      return s.raw() < t.raw(); // s.raw()->get_id() < t.raw()->get_id();
+      // return s.raw() < t.raw();
+      return s.raw()->get_id() < t.raw()->get_id();
     }
   };
 }
diff --git a/src/interp/iz3interp.cpp b/src/interp/iz3interp.cpp
index 9196e24d9..56dc1ccec 100755
--- a/src/interp/iz3interp.cpp
+++ b/src/interp/iz3interp.cpp
@@ -213,6 +213,7 @@ public:
     test_secondary(cnsts,parents,interps);
     return;
 #endif
+
     profiling::timer_start("Interpolation prep");
 
     // get rid of frames not used in proof
diff --git a/src/interp/iz3mgr.h b/src/interp/iz3mgr.h
index 7bdc2ecce..39c14c724 100644
--- a/src/interp/iz3mgr.h
+++ b/src/interp/iz3mgr.h
@@ -140,7 +140,8 @@ namespace std {
     class less<ast_r> {
   public:
     bool operator()(const ast_r &s, const ast_r &t) const {
-      return s.raw() < t.raw(); // s.raw()->get_id() < t.raw()->get_id();
+      // return s.raw() < t.raw(); 
+      return s.raw()->get_id() < t.raw()->get_id();
     }
   };
 }
diff --git a/src/util/id_gen.h b/src/util/id_gen.h
index b1713b524..c6d22246d 100644
--- a/src/util/id_gen.h
+++ b/src/util/id_gen.h
@@ -57,6 +57,11 @@ public:
         m_free_ids.finalize();
     }
     
+    unsigned show_hash(){
+      unsigned h = string_hash((char *)&m_free_ids[0],m_free_ids.size()*sizeof(unsigned),17);
+      return hash_u_u(h,m_next_id);
+    }
+
     /**
        \brief Return N if the range of ids generated by this module is in the set [0..N)
     */