diff --git a/src/api/api_datalog.cpp b/src/api/api_datalog.cpp
index c3fdeb94b..be9f5894f 100644
--- a/src/api/api_datalog.cpp
+++ b/src/api/api_datalog.cpp
@@ -130,12 +130,6 @@ namespace api {
             m_context.display_smt2(num_queries, queries, str);
             return str.str();
         }
-        void cancel() { 
-            m_context.cancel(); 
-        }
-        void reset_cancel() { 
-            m_context.reset_cancel(); 
-        }
         unsigned get_num_levels(func_decl* pred) {
             return m_context.get_num_levels(pred);
         }
@@ -285,13 +279,13 @@ extern "C" {
         LOG_Z3_fixedpoint_query(c, d, q);
         RESET_ERROR_CODE();
         lbool r = l_undef;
-        cancel_eh<api::fixedpoint_context> eh(*to_fixedpoint_ref(d));
         unsigned timeout = to_fixedpoint(d)->m_params.get_uint("timeout", mk_c(c)->get_timeout());
         unsigned rlimit  = to_fixedpoint(d)->m_params.get_uint("rlimit", mk_c(c)->get_rlimit());
-        api::context::set_interruptable si(*(mk_c(c)), eh);        
         {
-            scoped_timer timer(timeout, &eh);
             scoped_rlimit _rlimit(mk_c(c)->m().limit(), rlimit);
+            cancel_eh<reslimit> eh(mk_c(c)->m().limit());
+            api::context::set_interruptable si(*(mk_c(c)), eh);        
+            scoped_timer timer(timeout, &eh);
             try {
                 r = to_fixedpoint_ref(d)->ctx().query(to_expr(q));
             }
@@ -313,7 +307,7 @@ extern "C" {
         RESET_ERROR_CODE();
         lbool r = l_undef;
         unsigned timeout = to_fixedpoint(d)->m_params.get_uint("timeout", mk_c(c)->get_timeout());
-        cancel_eh<api::fixedpoint_context> eh(*to_fixedpoint_ref(d));
+        cancel_eh<reslimit> eh(mk_c(c)->m().limit());
         api::context::set_interruptable si(*(mk_c(c)), eh);
         {
             scoped_timer timer(timeout, &eh);
diff --git a/src/math/euclid/euclidean_solver.cpp b/src/math/euclid/euclidean_solver.cpp
index 9225a87ee..25419d7d1 100644
--- a/src/math/euclid/euclidean_solver.cpp
+++ b/src/math/euclid/euclidean_solver.cpp
@@ -98,7 +98,6 @@ struct euclidean_solver::imp {
 
     numeral_manager *  m_manager;
     bool               m_owns_m;
-    volatile bool      m_cancel;
 
     equations          m_equations;
     equations          m_solution;
@@ -517,7 +516,6 @@ struct euclidean_solver::imp {
         m_var_queue(16, elim_order_lt(m_solved)) {
         m_inconsistent       = null_eq_idx;
         m_next_justification = 0; 
-        m_cancel             = false;
         m_next_x             = null_var;
         m_next_eq            = null_eq_idx;
     }
@@ -779,9 +777,6 @@ struct euclidean_solver::imp {
         del_nums(m_norm_bs_vector);
     }
 
-    void set_cancel(bool f) {
-        m_cancel = f;
-    }
 
 };
 
@@ -842,12 +837,6 @@ void euclidean_solver::normalize(unsigned num, mpz const * as, var const * xs, m
     return m_imp->normalize(num, as, xs, c, a_prime, c_prime, js);
 }
 
-void euclidean_solver::set_cancel(bool f) {
-    #pragma omp critical (euclidean_solver)
-    {
-        m_imp->set_cancel(f);
-    }
-}
 
 void euclidean_solver::display(std::ostream & out) const {
     m_imp->display(out);
diff --git a/src/math/euclid/euclidean_solver.h b/src/math/euclid/euclidean_solver.h
index 839abc9f7..98a202e5e 100644
--- a/src/math/euclid/euclidean_solver.h
+++ b/src/math/euclid/euclidean_solver.h
@@ -95,10 +95,6 @@ public:
     */
     void normalize(unsigned num, mpz const * as, var const * xs, mpz const & c, mpz & a_prime, mpz & c_prime, justification_vector & js);
 
-    /**
-       \brief Set/Reset the cancel flag.
-    */
-    void set_cancel(bool f);
 
     void display(std::ostream & out) const;
 };
diff --git a/src/math/hilbert/hilbert_basis.cpp b/src/math/hilbert/hilbert_basis.cpp
index a2a3f4654..adac63e5c 100644
--- a/src/math/hilbert/hilbert_basis.cpp
+++ b/src/math/hilbert/hilbert_basis.cpp
@@ -647,8 +647,8 @@ private:
 };
 
 
-hilbert_basis::hilbert_basis(): 
-    m_cancel(false),
+hilbert_basis::hilbert_basis(reslimit& lim):
+    m_limit(lim),
     m_use_support(true),
     m_use_ordered_support(true),
     m_use_ordered_subsumption(true)
@@ -804,7 +804,7 @@ void hilbert_basis::add_unit_vector(unsigned i, numeral const& e) {
 lbool hilbert_basis::saturate() {
     init_basis();
     m_current_ineq = 0;
-    while (!m_cancel && m_current_ineq < m_ineqs.size()) {
+    while (checkpoint() && m_current_ineq < m_ineqs.size()) {
         select_inequality();
         stopwatch sw;
         sw.start();
@@ -823,7 +823,7 @@ lbool hilbert_basis::saturate() {
         }        
         ++m_current_ineq;
     }
-    if (m_cancel) {
+    if (!checkpoint()) {
         return l_undef;
     }
     return l_true;
@@ -853,7 +853,7 @@ lbool hilbert_basis::saturate_orig(num_vector const& ineq, bool is_eq) {
     // resolve passive into active
     offset_t j = alloc_vector();
     while (!m_passive->empty()) {
-        if (m_cancel) {
+        if (!checkpoint()) {
             return l_undef;
         }
         offset_t idx = m_passive->pop();
@@ -862,7 +862,7 @@ lbool hilbert_basis::saturate_orig(num_vector const& ineq, bool is_eq) {
             recycle(idx);
             continue;
         }
-        for (unsigned i = 0; !m_cancel && i < m_active.size(); ++i) {
+        for (unsigned i = 0; checkpoint() && i < m_active.size(); ++i) {
             if ((!m_use_support || support.contains(m_active[i].m_offset)) && can_resolve(idx, m_active[i], true)) {
                 resolve(idx, m_active[i], j);
                 if (add_goal(j)) {
@@ -942,7 +942,7 @@ lbool hilbert_basis::saturate(num_vector const& ineq, bool is_eq) {
     TRACE("hilbert_basis", display(tout););
     // resolve passive into active
     offset_t idx = alloc_vector();
-    while (!m_cancel && !m_passive2->empty()) {
+    while (checkpoint() && !m_passive2->empty()) {
         offset_t sos, pas;
         TRACE("hilbert_basis", display(tout); );
         unsigned offset = m_passive2->pop(sos, pas);
@@ -967,7 +967,7 @@ lbool hilbert_basis::saturate(num_vector const& ineq, bool is_eq) {
         }
         idx = alloc_vector();
     }
-    if (m_cancel) {
+    if (!checkpoint()) {
         return l_undef;
     }
 
@@ -1112,6 +1112,10 @@ hilbert_basis::offset_t hilbert_basis::alloc_vector() {
     }
 }
 
+bool hilbert_basis::checkpoint() {
+    return m_limit.inc();
+}
+
 bool hilbert_basis::add_goal(offset_t idx) {
     TRACE("hilbert_basis", display(tout, idx););
     values v = vec(idx);
diff --git a/src/math/hilbert/hilbert_basis.h b/src/math/hilbert/hilbert_basis.h
index 4969b2c61..2cfb4e36f 100644
--- a/src/math/hilbert/hilbert_basis.h
+++ b/src/math/hilbert/hilbert_basis.h
@@ -32,6 +32,7 @@ Revision History:
 #include "lbool.h"
 #include "statistics.h"
 #include "checked_int64.h"
+#include "rlimit.h"
 
 typedef vector<rational> rational_vector;
 
@@ -85,6 +86,7 @@ class hilbert_basis {
         numeral const* operator()() const { return m_values; }
     };
 
+    reslimit&          m_limit;
     vector<num_vector> m_ineqs;      // set of asserted inequalities
     svector<bool>      m_iseq;       // inequalities that are equalities
     num_vector         m_store;      // store of vectors
@@ -95,7 +97,6 @@ class hilbert_basis {
     svector<offset_t>  m_zero;       // zeros
     passive*           m_passive;    // passive set
     passive2*          m_passive2;   // passive set
-    volatile bool      m_cancel;     
     stats              m_stats;
     index*             m_index;      // index of generated vectors
     unsigned_vector    m_ints;       // indices that can be both positive and negative
@@ -105,6 +106,7 @@ class hilbert_basis {
     bool               m_use_ordered_support;     // parameter: (commutativity) resolve in order
     bool               m_use_ordered_subsumption; // parameter
 
+
     class iterator {
         hilbert_basis const& hb;
         unsigned             m_idx;
@@ -138,6 +140,8 @@ class hilbert_basis {
     bool can_resolve(offset_t i, offset_t j, bool check_sign) const;
     sign_t get_sign(offset_t idx) const;
     bool add_goal(offset_t idx);
+    bool checkpoint();
+
     offset_t alloc_vector();
     void resolve(offset_t i, offset_t j, offset_t r);
     iterator begin() const { return iterator(*this,0); }
@@ -154,7 +158,7 @@ class hilbert_basis {
 
 public:
         
-    hilbert_basis();
+    hilbert_basis(reslimit& rl);
     ~hilbert_basis();
 
     void reset();
@@ -188,8 +192,6 @@ public:
     unsigned get_num_ineqs() const { return m_ineqs.size(); }
     void get_ge(unsigned i, rational_vector& v, rational& b, bool& is_eq);    
 
-    void set_cancel(bool f) { m_cancel = f; }
-
     void display(std::ostream& out) const;
 
     void collect_statistics(statistics& st) const;
diff --git a/src/math/simplex/simplex.h b/src/math/simplex/simplex.h
index 2d0fc4443..06fcd54ec 100644
--- a/src/math/simplex/simplex.h
+++ b/src/math/simplex/simplex.h
@@ -92,6 +92,7 @@ namespace simplex {
         };
 
         static const var_t null_var;
+        reslimit&                   m_limit;
         mutable manager             m;
         mutable eps_manager         em;
         mutable matrix              M;
@@ -109,10 +110,10 @@ namespace simplex {
         stats                       m_stats;
 
     public:
-        simplex():
+        simplex(reslimit& lim):
+            m_limit(lim),
             M(m),
             m_max_iterations(UINT_MAX),
-            m_cancel(false),
             m_to_patch(1024),
             m_bland(false),
             m_blands_rule_threshold(1000) {}
@@ -140,7 +141,6 @@ namespace simplex {
         void  unset_lower(var_t var);
         void  unset_upper(var_t var); 
         void  set_value(var_t var, eps_numeral const& b);        
-        void  set_cancel(bool f) { m_cancel = f; }
         void  set_max_iterations(unsigned n) { m_max_iterations = n; }
         void  reset();
         lbool make_feasible();
diff --git a/src/math/simplex/simplex_def.h b/src/math/simplex/simplex_def.h
index 7a3ca01be..6ca4048ad 100644
--- a/src/math/simplex/simplex_def.h
+++ b/src/math/simplex/simplex_def.h
@@ -332,7 +332,7 @@ namespace simplex {
         SASSERT(well_formed());
         while ((v = select_var_to_fix()) != null_var) {
             TRACE("simplex", display(tout << "v" << v << "\n"););
-            if (m_cancel || num_iterations > m_max_iterations) {
+            if (!m_limit.inc() || num_iterations > m_max_iterations) {
                 return l_undef;
             }
             check_blands_rule(v, num_repeated);
@@ -670,7 +670,7 @@ namespace simplex {
         bool inc_x_i, inc_x_j;
 
         while (true) {
-            if (m_cancel) {
+            if (!m_limit.inc()) {
                 return l_undef;
             }
             select_pivot_primal(v, x_i, x_j, a_ij, inc_x_i, inc_x_j);
diff --git a/src/muz/base/dl_context.cpp b/src/muz/base/dl_context.cpp
index 210173f8c..36e46d125 100644
--- a/src/muz/base/dl_context.cpp
+++ b/src/muz/base/dl_context.cpp
@@ -230,8 +230,7 @@ namespace datalog {
         m_enable_bind_variables(true),
         m_last_status(OK),
         m_last_answer(m),
-        m_engine_type(LAST_ENGINE),
-        m_cancel(false) {
+        m_engine_type(LAST_ENGINE) {
         re.set_context(this);
         updt_params(pa);
     }
@@ -751,15 +750,16 @@ namespace datalog {
     }
 
 
+#if 0
     void context::cancel() {
         m_cancel = true;
         m_last_status = CANCELED;
         m_transf.cancel();
         if (m_engine) m_engine->cancel();
     }
+#endif
 
     void context::cleanup() {
-        m_cancel = false;
         m_last_status = OK;
         if (m_engine) m_engine->cleanup();
     }
diff --git a/src/muz/base/dl_context.h b/src/muz/base/dl_context.h
index 3b8b9d067..92ff429a3 100644
--- a/src/muz/base/dl_context.h
+++ b/src/muz/base/dl_context.h
@@ -487,11 +487,13 @@ namespace datalog {
         //
         // -----------------------------------
 
-        void cancel();
-        bool canceled() const { return m_cancel; }
+        bool canceled() {
+            if (m.limit().inc()) return true;
+            m_last_status = CANCELED;
+            return false;
+        }
 
         void cleanup();
-        void reset_cancel() { cleanup(); }
 
         /**
            \brief check if query 'q' is satisfied under asserted rules and background.
diff --git a/src/muz/base/hnf.cpp b/src/muz/base/hnf.cpp
index 54bd727d6..2355e32fd 100644
--- a/src/muz/base/hnf.cpp
+++ b/src/muz/base/hnf.cpp
@@ -74,7 +74,6 @@ class hnf::imp {
 
     ast_manager&          m;
     bool                  m_produce_proofs;
-    volatile bool         m_cancel;
     expr_ref_vector       m_todo;
     proof_ref_vector      m_proofs;
     expr_ref_vector       m_refs;
@@ -96,7 +95,6 @@ public:
     imp(ast_manager & m):
         m(m),
         m_produce_proofs(false),
-        m_cancel(false),
         m_todo(m),
         m_proofs(m),
         m_refs(m), 
@@ -156,7 +154,7 @@ public:
         m_todo.push_back(n);
         m_proofs.push_back(p);
         m_produce_proofs = p != 0;
-        while (!m_todo.empty() && !m_cancel) {
+        while (!m_todo.empty() && checkpoint()) {
             fml = m_todo.back();
             pr = m_proofs.back();
             m_todo.pop_back();
@@ -174,8 +172,8 @@ public:
               });
     }
 
-    void set_cancel(bool f) {
-        m_cancel = f;
+    bool checkpoint() {
+        return m.limit().inc();
     }
 
     void set_name(symbol const& n) {
@@ -192,7 +190,6 @@ public:
     }
 
     void reset() {
-        m_cancel = false;
         m_todo.reset();
         m_proofs.reset();
         m_refs.reset();
@@ -524,9 +521,6 @@ void hnf::operator()(expr * n, proof* p, expr_ref_vector & rs, proof_ref_vector&
           );
 }
 
-void hnf::set_cancel(bool f) {
-    m_imp->set_cancel(f);
-}
 
 void hnf::set_name(symbol const& n) {
     m_imp->set_name(n);
diff --git a/src/muz/base/hnf.h b/src/muz/base/hnf.h
index 35fc5fafc..23b379d4d 100644
--- a/src/muz/base/hnf.h
+++ b/src/muz/base/hnf.h
@@ -43,9 +43,6 @@ class hnf {
                     proof_ref_vector& ps               // [OUT] proofs of rs
                     );
 
-    void cancel() { set_cancel(true); }
-    void reset_cancel() { set_cancel(false); }
-    void set_cancel(bool f);
     void set_name(symbol const& name);    
     void reset();
     func_decl_ref_vector const& get_fresh_predicates();
diff --git a/src/muz/ddnf/ddnf.cpp b/src/muz/ddnf/ddnf.cpp
index 6545d4282..e7babc719 100644
--- a/src/muz/ddnf/ddnf.cpp
+++ b/src/muz/ddnf/ddnf.cpp
@@ -470,7 +470,6 @@ namespace datalog {
         ast_manager&           m;
         rule_manager&          rm;
         bv_util                bv;
-        volatile bool          m_cancel;
         ptr_vector<expr>       m_todo;
         ast_mark               m_visited1, m_visited2;
         ddnfs                  m_ddnfs;
@@ -486,7 +485,6 @@ namespace datalog {
             m(ctx.get_manager()),
             rm(ctx.get_rule_manager()),
             bv(m),
-            m_cancel(false),
             m_trail(m),
             m_inner_ctx(m, m_ctx.get_register_engine(), m_ctx.get_fparams())
         {
@@ -518,15 +516,7 @@ namespace datalog {
             // return execute_rules(new_rules);
         }
     
-        void cancel() {
-            m_cancel = true;
-            m_inner_ctx.cancel();
-        }
-        
-        void cleanup() {
-            m_cancel = false;
-        }
-
+       
         void reset_statistics() {
             m_stats.reset();
         }
@@ -884,12 +874,6 @@ namespace datalog {
     lbool ddnf::query(expr* query) {
         return m_imp->query(query);
     }
-    void ddnf::cancel() {
-        m_imp->cancel();
-    }
-    void ddnf::cleanup() {
-        m_imp->cleanup();
-    }
     void ddnf::reset_statistics() {
         m_imp->reset_statistics();
     }
diff --git a/src/muz/ddnf/ddnf.h b/src/muz/ddnf/ddnf.h
index 7e1e83e52..997009026 100644
--- a/src/muz/ddnf/ddnf.h
+++ b/src/muz/ddnf/ddnf.h
@@ -37,8 +37,6 @@ namespace datalog {
         ddnf(context& ctx);
         ~ddnf();
         virtual lbool query(expr* query);
-        virtual void cancel();
-        virtual void cleanup();
         virtual void reset_statistics();
         virtual void collect_statistics(statistics& st) const;
         virtual void display_certificate(std::ostream& out) const;        
diff --git a/src/muz/fp/dl_cmds.cpp b/src/muz/fp/dl_cmds.cpp
index a583d7a26..2ce96c15e 100644
--- a/src/muz/fp/dl_cmds.cpp
+++ b/src/muz/fp/dl_cmds.cpp
@@ -230,7 +230,7 @@ public:
         set_background(ctx);        
         dlctx.updt_params(m_params);
         unsigned timeout   = m_dl_ctx->get_params().timeout(); 
-        cancel_eh<datalog::context> eh(dlctx);
+        cancel_eh<reslimit> eh(ctx.m().limit());
         bool query_exn = false;
         lbool status = l_undef;
         {
diff --git a/src/muz/fp/horn_tactic.cpp b/src/muz/fp/horn_tactic.cpp
index ee1b773cc..a77c97f3f 100644
--- a/src/muz/fp/horn_tactic.cpp
+++ b/src/muz/fp/horn_tactic.cpp
@@ -64,9 +64,6 @@ class horn_tactic : public tactic {
         }
 
         void set_cancel(bool f) {
-            if (f) {
-                m_ctx.cancel();
-            }
         }
 
         void normalize(expr_ref& f) {
diff --git a/src/muz/rel/dl_base.h b/src/muz/rel/dl_base.h
index 7b6210850..781c8539d 100644
--- a/src/muz/rel/dl_base.h
+++ b/src/muz/rel/dl_base.h
@@ -270,8 +270,6 @@ namespace datalog {
 
             symbol const& get_name() const { return m_name; }
 
-            virtual void set_cancel(bool f) {}
-
             relation_manager & get_manager() const { return m_manager; }
             ast_manager& get_ast_manager() const { return datalog::get_ast_manager_from_rel_manager(m_manager); }
             context& get_context() const { return datalog::get_context_from_rel_manager(m_manager); }
diff --git a/src/muz/rel/dl_lazy_table.h b/src/muz/rel/dl_lazy_table.h
index 25870ac1e..28360c95f 100644
--- a/src/muz/rel/dl_lazy_table.h
+++ b/src/muz/rel/dl_lazy_table.h
@@ -54,8 +54,6 @@ namespace datalog {
         
         virtual table_base * mk_empty(const table_signature & s);
                 
-        virtual void set_cancel(bool f) { m_plugin.set_cancel(f); }
-
         static table_plugin* mk_sparse(relation_manager& rm);
         
     protected:
diff --git a/src/muz/rel/dl_relation_manager.cpp b/src/muz/rel/dl_relation_manager.cpp
index ddcdf7ae2..1127dbb31 100644
--- a/src/muz/rel/dl_relation_manager.cpp
+++ b/src/muz/rel/dl_relation_manager.cpp
@@ -463,12 +463,6 @@ namespace datalog {
             }
     }
 
-    void relation_manager::set_cancel(bool f) {
-        for (unsigned i = 0; i < m_relation_plugins.size(); ++i) {
-            m_relation_plugins[i]->set_cancel(f);
-        }
-    }
-
     std::string relation_manager::to_nice_string(const relation_element & el) const {
         uint64 val;
         std::stringstream stm;
diff --git a/src/muz/rel/dl_relation_manager.h b/src/muz/rel/dl_relation_manager.h
index 6e1b5737e..a641a5fd2 100644
--- a/src/muz/rel/dl_relation_manager.h
+++ b/src/muz/rel/dl_relation_manager.h
@@ -225,8 +225,6 @@ namespace datalog {
             relation_fact & to);
 
 
-        void set_cancel(bool f);
-
 
         // -----------------------------------
         //
diff --git a/src/muz/rel/karr_relation.cpp b/src/muz/rel/karr_relation.cpp
index d7ea7de6b..7be271b3e 100644
--- a/src/muz/rel/karr_relation.cpp
+++ b/src/muz/rel/karr_relation.cpp
@@ -499,7 +499,6 @@ namespace datalog {
     }  
 
     void karr_relation_plugin::set_cancel(bool f) {
-        m_hb.set_cancel(f);
     }
 
     relation_base * karr_relation_plugin::mk_empty(const relation_signature & s) {
diff --git a/src/muz/rel/karr_relation.h b/src/muz/rel/karr_relation.h
index 90c9abbd4..f4fd5312c 100644
--- a/src/muz/rel/karr_relation.h
+++ b/src/muz/rel/karr_relation.h
@@ -41,6 +41,7 @@ namespace datalog {
     public:
         karr_relation_plugin(relation_manager& rm):
             relation_plugin(karr_relation_plugin::get_name(), rm),
+            m_hb(get_ast_manager().limit()),
             a(get_ast_manager())
         {}            
         
diff --git a/src/muz/rel/rel_context.cpp b/src/muz/rel/rel_context.cpp
index 52dd10202..25af7d798 100644
--- a/src/muz/rel/rel_context.cpp
+++ b/src/muz/rel/rel_context.cpp
@@ -512,9 +512,6 @@ namespace datalog {
         get_rmanager().set_predicate_kind(pred, target_kind);
     }
 
-    void rel_context::set_cancel(bool f) {
-        get_rmanager().set_cancel(f);        
-    }
 
     void rel_context::setup_default_relation() {
         if (m_context.default_relation() == symbol("doc")) {
diff --git a/src/muz/rel/rel_context.h b/src/muz/rel/rel_context.h
index 5d85a1e7c..c263ddc03 100644
--- a/src/muz/rel/rel_context.h
+++ b/src/muz/rel/rel_context.h
@@ -51,8 +51,6 @@ namespace datalog {
         
         lbool saturate(scoped_query& sq);
 
-        void set_cancel(bool f);
-
         void setup_default_relation();
 
     public:
@@ -82,8 +80,6 @@ namespace datalog {
 
         virtual void collect_statistics(statistics& st) const;
 
-        virtual void cancel() { set_cancel(true); }
-        virtual void cleanup() { set_cancel(false);}
         virtual void updt_params();
 
         /**
diff --git a/src/muz/tab/tab_context.cpp b/src/muz/tab/tab_context.cpp
index 472b28292..72171d227 100644
--- a/src/muz/tab/tab_context.cpp
+++ b/src/muz/tab/tab_context.cpp
@@ -509,7 +509,6 @@ namespace tb {
         bool_rewriter          m_rw;
         smt_params             m_fparams;
         smt::kernel            m_solver;
-        volatile bool          m_cancel;
         
     public:
         index(ast_manager& m):
@@ -523,8 +522,7 @@ namespace tb {
             m_subst(m),
             m_qe(m),
             m_rw(m),
-            m_solver(m, m_fparams),
-            m_cancel(false) {}
+            m_solver(m, m_fparams) {}
 
         void insert(ref<clause>& g) {
             m_index.push_back(g);
@@ -540,17 +538,6 @@ namespace tb {
             return found;
         }
 
-        void cancel() {
-            m_cancel = true;
-            m_solver.cancel();
-            m_qe.set_cancel(true);
-        }
-
-        void cleanup() {
-            m_solver.reset_cancel();
-            m_qe.set_cancel(false);
-            m_cancel = false;
-        }
 
         void reset() {
             m_index.reset();
@@ -594,7 +581,7 @@ namespace tb {
 
         // extract pre_cond => post_cond validation obligation from match.
         bool find_match(unsigned& subsumer) {
-            for (unsigned i = 0; !m_cancel && i < m_index.size(); ++i) {
+            for (unsigned i = 0; m.limit().inc() && i < m_index.size(); ++i) {
                 if (match_rule(i)) {
                     subsumer = m_index[i]->get_seqno();
                     return true;
@@ -631,7 +618,7 @@ namespace tb {
 
             app* q = g.get_predicate(predicate_index);
 
-            for (unsigned i = 0; !m_cancel && i < m_preds.size(); ++i) {
+            for (unsigned i = 0; m.limit().inc() && i < m_preds.size(); ++i) {
                 app* p = m_preds[i].get();
                 m_subst.push_scope();
                 unsigned limit = m_sideconds.size();
@@ -660,7 +647,7 @@ namespace tb {
             expr_ref_vector fmls(m_sideconds);
             m_subst.reset_cache();
             
-            for (unsigned i = 0; !m_cancel && i < fmls.size(); ++i) {
+            for (unsigned i = 0; m.limit().inc() && i < fmls.size(); ++i) {
                 m_subst.apply(2, deltas, expr_offset(fmls[i].get(), 0), q);
                 fmls[i] = q;
             }
@@ -677,7 +664,7 @@ namespace tb {
                 }
             }
             m_rw.mk_and(fmls.size(), fmls.c_ptr(), postcond);
-            if (m_cancel) {
+            if (!m.limit().inc()) {
                 return false;
             }
             if (m.is_false(postcond)) {
@@ -1350,7 +1337,6 @@ namespace datalog {
         unsigned               m_seqno;
         tb::instruction        m_instruction;
         lbool                  m_status;
-        volatile bool          m_cancel;
         stats                  m_stats;
         uint_set               m_displayed_rules;
     public:
@@ -1365,8 +1351,7 @@ namespace datalog {
             m_rules(),
             m_seqno(0),
             m_instruction(tb::SELECT_PREDICATE),
-            m_status(l_undef),
-            m_cancel(false)
+            m_status(l_undef)
         {
             // m_fparams.m_relevancy_lvl = 0;
             m_fparams.m_mbqi = false;
@@ -1393,18 +1378,9 @@ namespace datalog {
             IF_VERBOSE(1, display_clause(*get_clause(), verbose_stream() << "g" << get_clause()->get_seqno() << " "););
             return run();
         }
-    
-        void cancel() {
-            m_cancel = true;
-            m_index.cleanup();
-            m_solver.cancel();
-        }
-        
+            
         void cleanup() {
-            m_cancel = false;
             m_clauses.reset();
-            m_index.cleanup();
-            m_solver.reset_cancel();
         }
 
         void reset_statistics() {
@@ -1519,7 +1495,7 @@ namespace datalog {
             m_status      = l_undef;
             while (true) {
                 IF_VERBOSE(2, verbose_stream() << m_instruction << "\n";);
-                if (m_cancel) {
+                if (!m.limit().inc()) {
                     cleanup();
                     return l_undef;
                 }
@@ -1671,9 +1647,6 @@ namespace datalog {
     lbool tab::query(expr* query) {
         return m_imp->query(query);
     }
-    void tab::cancel() {
-        m_imp->cancel();
-    }
     void tab::cleanup() {
         m_imp->cleanup();
     }
diff --git a/src/muz/tab/tab_context.h b/src/muz/tab/tab_context.h
index f9b22a418..703109475 100644
--- a/src/muz/tab/tab_context.h
+++ b/src/muz/tab/tab_context.h
@@ -34,7 +34,6 @@ namespace datalog {
         tab(context& ctx);
         ~tab();
         virtual lbool query(expr* query);
-        virtual void cancel();
         virtual void cleanup();
         virtual void reset_statistics();
         virtual void collect_statistics(statistics& st) const;
diff --git a/src/muz/transforms/dl_mk_karr_invariants.cpp b/src/muz/transforms/dl_mk_karr_invariants.cpp
index ced0d39f4..3c4d04aeb 100644
--- a/src/muz/transforms/dl_mk_karr_invariants.cpp
+++ b/src/muz/transforms/dl_mk_karr_invariants.cpp
@@ -50,8 +50,7 @@ namespace datalog {
         rm(ctx.get_rule_manager()),
         m_inner_ctx(m, ctx.get_register_engine(), ctx.get_fparams()),
         a(m),
-        m_pinned(m),
-        m_cancel(false) {
+        m_pinned(m) {
             params_ref params;
             params.set_sym("default_relation", symbol("karr_relation"));
             params.set_sym("engine", symbol("datalog"));
@@ -189,11 +188,6 @@ namespace datalog {
             }
         }
     };
-
-    void mk_karr_invariants::cancel() {
-        m_cancel = true;
-        m_inner_ctx.cancel();
-    }
     
     rule_set * mk_karr_invariants::operator()(rule_set const & source) {
         if (!m_ctx.karr()) {
@@ -214,7 +208,7 @@ namespace datalog {
 
         get_invariants(*src_loop);
 
-        if (m_cancel) {
+        if (!m.limit().inc()) {
             return 0;
         }
 
diff --git a/src/muz/transforms/dl_mk_karr_invariants.h b/src/muz/transforms/dl_mk_karr_invariants.h
index ed43e550b..bf0ba9021 100644
--- a/src/muz/transforms/dl_mk_karr_invariants.h
+++ b/src/muz/transforms/dl_mk_karr_invariants.h
@@ -57,7 +57,6 @@ namespace datalog {
         arith_util      a;
         obj_map<func_decl, expr*>      m_fun2inv;
         ast_ref_vector m_pinned;
-        volatile bool  m_cancel;
 
         void get_invariants(rule_set const& src);
 
@@ -67,8 +66,6 @@ namespace datalog {
         mk_karr_invariants(context & ctx, unsigned priority);
 
         virtual ~mk_karr_invariants();
-
-        virtual void cancel();
         
         rule_set * operator()(rule_set const & source);
 
diff --git a/src/opt/hitting_sets.cpp b/src/opt/hitting_sets.cpp
index 54ecaf35b..8bbad6683 100644
--- a/src/opt/hitting_sets.cpp
+++ b/src/opt/hitting_sets.cpp
@@ -88,7 +88,7 @@ namespace opt {
             bool empty() const { return 0 == size(); }
         };
 
-        volatile bool           m_cancel;
+        reslimit&               m_limit;
         rational                m_lower;
         rational                m_upper;
         vector<rational>        m_weights;
@@ -144,8 +144,8 @@ namespace opt {
 
         static unsigned const null_idx = UINT_MAX;
 
-        imp():
-            m_cancel(false), 
+        imp(reslimit& lim):
+            m_limit(lim),
             m_max_weight(0), 
             m_denominator(1),
             m_alloc("hitting-sets"),
@@ -155,6 +155,7 @@ namespace opt {
             m_scope_lvl(0),
             m_compare_scores(),
             m_heap(0, m_compare_scores),
+            m_simplex(lim),
             m_weights_var(0) {
             m_enable_simplex = true;
             m_compare_scores.m_imp = this;
@@ -298,11 +299,6 @@ namespace opt {
                 m_model[idx] == l_true;
         }
 
-        void set_cancel(bool f) {
-            m_cancel = f;
-            m_simplex.set_cancel(f);
-        }
-
         void collect_statistics(::statistics& st) const {
             m_simplex.collect_statistics(st);
         }
@@ -641,7 +637,7 @@ namespace opt {
 
         inline unsigned scope_lvl() const { return m_scope_lvl; }
         inline bool inconsistent() const { return m_inconsistent; }
-        inline bool canceled() const { return m_cancel; }
+        inline bool canceled() const { return !m_limit.inc(); }
         inline unsigned lvl(unsigned idx) const { return m_level[idx]; }
         inline lbool value(unsigned idx) const { return m_value[idx]; }
 
@@ -1073,7 +1069,7 @@ namespace opt {
     };
 
 
-    hitting_sets::hitting_sets() { m_imp = alloc(imp); }
+    hitting_sets::hitting_sets(reslimit& lim) { m_imp = alloc(imp, lim); }
     hitting_sets::~hitting_sets() { dealloc(m_imp); }
     void hitting_sets::add_weight(rational const& w) { m_imp->add_weight(w); }
     void hitting_sets::add_exists_true(unsigned sz, unsigned const* elems) { m_imp->add_exists_true(sz, elems); }
@@ -1084,7 +1080,6 @@ namespace opt {
     rational hitting_sets::get_upper() { return m_imp->get_upper(); }
     void hitting_sets::set_upper(rational const& r) { return m_imp->set_upper(r); }
     bool hitting_sets::get_value(unsigned idx) { return m_imp->get_value(idx); }
-    void hitting_sets::set_cancel(bool f) { m_imp->set_cancel(f); }
     void hitting_sets::collect_statistics(::statistics& st) const { m_imp->collect_statistics(st); }
     void hitting_sets::reset() { m_imp->reset(); }
 
diff --git a/src/opt/hitting_sets.h b/src/opt/hitting_sets.h
index 718616a9e..c9708710f 100644
--- a/src/opt/hitting_sets.h
+++ b/src/opt/hitting_sets.h
@@ -22,6 +22,7 @@ Notes:
 #include "rational.h"
 #include "statistics.h"
 #include "lbool.h"
+#include "rlimit.h"
 
 namespace opt {
 
@@ -29,7 +30,7 @@ namespace opt {
         struct imp;
         imp* m_imp;
     public:        
-        hitting_sets();
+        hitting_sets(reslimit& lim);
         ~hitting_sets();
         void add_weight(rational const& w);
         void add_exists_true(unsigned sz, unsigned const* elems);
diff --git a/src/opt/maxhs.cpp b/src/opt/maxhs.cpp
index 9ce9844b5..6c67dcbb5 100644
--- a/src/opt/maxhs.cpp
+++ b/src/opt/maxhs.cpp
@@ -77,6 +77,7 @@ namespace opt {
     public:
         maxhs(maxsat_context& c, weights_t& ws, expr_ref_vector const& soft):
             maxsmt_solver_base(c, ws, soft), 
+            m_hs(m.limit()), 
             m_aux(m), 
             m_at_lower_bound(false) {
         }
@@ -84,7 +85,6 @@ namespace opt {
 
         virtual void set_cancel(bool f) { 
             maxsmt_solver_base::set_cancel(f); 
-            m_hs.set_cancel(f);
         }
 
         virtual void collect_statistics(statistics& st) const {
diff --git a/src/smt/theory_dense_diff_logic_def.h b/src/smt/theory_dense_diff_logic_def.h
index 7702a1ef2..28ee4b025 100644
--- a/src/smt/theory_dense_diff_logic_def.h
+++ b/src/smt/theory_dense_diff_logic_def.h
@@ -896,8 +896,8 @@ namespace smt {
     template<typename Ext>
     inf_eps_rational<inf_rational> theory_dense_diff_logic<Ext>::maximize(theory_var v, expr_ref& blocker, bool& has_shared) {
         typedef simplex::simplex<simplex::mpq_ext> Simplex;
-        Simplex S;
         ast_manager& m = get_manager();
+        Simplex S(m.limit());
         objective_term const& objective = m_objectives[v];
         has_shared = false;
         
diff --git a/src/smt/theory_diff_logic.h b/src/smt/theory_diff_logic.h
index 390bd271d..6fb9e6454 100644
--- a/src/smt/theory_diff_logic.h
+++ b/src/smt/theory_diff_logic.h
@@ -236,6 +236,7 @@ namespace smt {
             m_non_diff_logic_exprs(false),
             m_factory(0),
             m_nc_functor(*this),
+            m_S(m.limit()),
             m_num_simplex_edges(0) {
         }            
 
diff --git a/src/smt/theory_pb.cpp b/src/smt/theory_pb.cpp
index c82076e87..a1aebf3e1 100644
--- a/src/smt/theory_pb.cpp
+++ b/src/smt/theory_pb.cpp
@@ -231,6 +231,7 @@ namespace smt {
     theory_pb::theory_pb(ast_manager& m, theory_pb_params& p):
         theory(m.mk_family_id("pb")),
         m_params(p),
+        m_simplex(m.limit()),
         m_util(m),
         m_max_compiled_coeff(rational(8))
     {        
diff --git a/src/tactic/tactical.cpp b/src/tactic/tactical.cpp
index 9786ccc8d..d92ef4c36 100644
--- a/src/tactic/tactical.cpp
+++ b/src/tactic/tactical.cpp
@@ -98,14 +98,6 @@ public:
     }
 
 protected:
-    /**
-       \brief Reset cancel flag of t if this was not canceled.
-    */
-    void parent_reset_cancel(tactic & t) {
-        if (!m_cancel) {
-            t.reset_cancel();
-        }
-    }
 
     virtual void set_cancel(bool f) {
         m_cancel = f;
@@ -390,14 +382,6 @@ public:
     }
 
 protected:
-    /**
-       \brief Reset cancel flag of st if this was not canceled.
-    */
-    void parent_reset_cancel(tactic & t) {
-        if (!m_cancel) {
-            t.reset_cancel();
-        }
-    }
 
     virtual void set_cancel(bool f) {
         m_cancel = f;
@@ -583,8 +567,10 @@ public:
                 }                
                 if (first) {
                     for (unsigned j = 0; j < sz; j++) {
-                        if (static_cast<unsigned>(i) != j)
+                        if (static_cast<unsigned>(i) != j) {
                             ts.get(j)->cancel();
+                            managers[j]->limit().cancel();
+                        }
                     }
                     ast_translation translator(*(managers[i]), m, false);
                     for (unsigned k = 0; k < _result.size(); k++) {
@@ -784,8 +770,10 @@ public:
 
                 if (curr_failed) {
                     for (unsigned j = 0; j < r1_size; j++) {
-                        if (static_cast<unsigned>(i) != j)
+                        if (static_cast<unsigned>(i) != j) {
                             ts2.get(j)->cancel();
+                            managers[j]->limit().cancel();
+                        }
                     }
                 }
                 else {
@@ -804,8 +792,10 @@ public:
                             }
                             if (first) {
                                 for (unsigned j = 0; j < r1_size; j++) {
-                                    if (static_cast<unsigned>(i) != j)
+                                    if (static_cast<unsigned>(i) != j) {
                                         ts2.get(j)->cancel();
+                                        managers[j]->limit().cancel();
+                                    }
                                 }
                                 ast_translation translator(new_m, m, false);
                                 SASSERT(r2.size() == 1);
diff --git a/src/util/rlimit.cpp b/src/util/rlimit.cpp
index 0e5c65b3e..495dce620 100644
--- a/src/util/rlimit.cpp
+++ b/src/util/rlimit.cpp
@@ -19,35 +19,36 @@ Revision History:
 #include "rlimit.h"
 
 reslimit::reslimit():
+    m_cancel(false),
     m_count(0),
-    m_limit(UINT_MAX) {
+    m_limit(0) {
 }
 
-unsigned reslimit::count() const {
+uint64 reslimit::count() const {
     return m_count;
 }
 
 bool reslimit::inc() {
     ++m_count;
-    return m_count <= m_limit;
+    return !m_cancel && (m_limit == 0 || m_count <= m_limit);
 }
 
 bool reslimit::inc(unsigned offset) {
     m_count += offset;
-    return m_count <= m_limit;
+    return !m_cancel && (m_limit == 0 || m_count <= m_limit);
 }
 
 void reslimit::push(unsigned delta_limit) {
-    unsigned new_limit = delta_limit + m_count;
+    uint64 new_limit = delta_limit + m_count;
     if (new_limit <= m_count) {
-        new_limit = UINT_MAX;
+        new_limit = 0;
     }
     m_limits.push_back(m_limit);
-    m_limit = std::min(new_limit, m_limit);
+    m_limit = m_limit==0?new_limit:std::min(new_limit, m_limit);
 }
 
 void reslimit::pop() {
-    if (m_count > m_limit) {
+    if (m_count > m_limit && m_limit > 0) {
         m_count = m_limit;
     }
     m_limit = m_limits.back();
diff --git a/src/util/rlimit.h b/src/util/rlimit.h
index 36912de40..f120fe433 100644
--- a/src/util/rlimit.h
+++ b/src/util/rlimit.h
@@ -22,16 +22,21 @@ Revision History:
 #include "vector.h"
 
 class reslimit {
-    unsigned        m_count;
-    unsigned        m_limit;
-    unsigned_vector m_limits;
+    volatile bool   m_cancel;
+    uint64          m_count;
+    uint64          m_limit;
+    svector<uint64> m_limits;
+
 public:    
     reslimit();
-    bool inc();
-    bool inc(unsigned offset);
     void push(unsigned delta_limit);
     void pop();
-    unsigned count() const; 
+    bool inc();
+    bool inc(unsigned offset);
+    uint64 count() const; 
+
+    void cancel() { m_cancel = true; }
+    void reset_cancel() { m_cancel = false; }
 };
 
 class scoped_rlimit {
diff --git a/src/util/statistics.cpp b/src/util/statistics.cpp
index 685a8abcc..38be32c8b 100644
--- a/src/util/statistics.cpp
+++ b/src/util/statistics.cpp
@@ -238,5 +238,5 @@ void get_memory_statistics(statistics& st) {
 }
 
 void get_rlimit_statistics(reslimit& l, statistics& st) {
-    st.update("rlimit count",     l.count());
+    st.update("rlimit count",     static_cast<double>(l.count()));
 }