diff --git a/src/api/api_solver.cpp b/src/api/api_solver.cpp
index ca15762f5..50b0c6e22 100644
--- a/src/api/api_solver.cpp
+++ b/src/api/api_solver.cpp
@@ -355,10 +355,7 @@ extern "C" {
         init_solver(c, s);
         Z3_stats_ref * st = alloc(Z3_stats_ref);
         to_solver_ref(s)->collect_statistics(st->m_stats);
-        unsigned long long max_mem = memory::get_max_used_memory();
-        unsigned long long mem = memory::get_allocation_size();
-        st->m_stats.update("max memory", static_cast<double>(max_mem)/(1024.0*1024.0));
-        st->m_stats.update("memory", static_cast<double>(mem)/(1024.0*1024.0));
+        get_memory_statistics(st->m_stats);
         mk_c(c)->save_object(st);
         Z3_stats r = of_stats(st);
         RETURN_Z3(r);
diff --git a/src/cmd_context/cmd_context.cpp b/src/cmd_context/cmd_context.cpp
index c8d5e8cab..3becba284 100644
--- a/src/cmd_context/cmd_context.cpp
+++ b/src/cmd_context/cmd_context.cpp
@@ -1624,11 +1624,10 @@ void cmd_context::set_solver_factory(solver_factory * f) {
 
 void cmd_context::display_statistics(bool show_total_time, double total_time) {
     statistics st;
-    unsigned long long mem = memory::get_max_used_memory();
     if (show_total_time)
         st.update("total time", total_time);
     st.update("time", get_seconds());
-    st.update("memory", static_cast<double>(mem)/static_cast<double>(1024*1024));
+    get_memory_statistics(st);
     if (m_check_sat_result) {
         m_check_sat_result->collect_statistics(st);
     }
diff --git a/src/cmd_context/tactic_cmds.cpp b/src/cmd_context/tactic_cmds.cpp
index 75d56928e..9d4c18262 100644
--- a/src/cmd_context/tactic_cmds.cpp
+++ b/src/cmd_context/tactic_cmds.cpp
@@ -157,11 +157,8 @@ public:
     
     void display_statistics(cmd_context & ctx, tactic * t) {
         statistics stats;
-        unsigned long long max_mem = memory::get_max_used_memory();
-        unsigned long long mem = memory::get_allocation_size();
+        get_memory_statistics(stats);
         stats.update("time", ctx.get_seconds());
-        stats.update("memory", static_cast<double>(mem)/static_cast<double>(1024*1024));
-        stats.update("max memory", static_cast<double>(max_mem)/static_cast<double>(1024*1024));
         t->collect_statistics(stats);
         stats.display_smt2(ctx.regular_stream());
     }
diff --git a/src/muz/base/dl_context.cpp b/src/muz/base/dl_context.cpp
index 3555e5bdc..9fb597600 100644
--- a/src/muz/base/dl_context.cpp
+++ b/src/muz/base/dl_context.cpp
@@ -945,10 +945,7 @@ namespace datalog {
         if (m_engine) {
             m_engine->collect_statistics(st);
         }
-        unsigned long long max_mem = memory::get_max_used_memory();
-        unsigned long long mem = memory::get_allocation_size();
-        st.update("max memory", static_cast<double>(max_mem)/(1024.0*1024.0));
-        st.update("memory", static_cast<double>(mem)/(1024.0*1024.0));        
+        get_memory_statistics(st);
     }
 
 
diff --git a/src/muz/fp/dl_cmds.cpp b/src/muz/fp/dl_cmds.cpp
index 66f1c6d38..a583d7a26 100644
--- a/src/muz/fp/dl_cmds.cpp
+++ b/src/muz/fp/dl_cmds.cpp
@@ -338,12 +338,8 @@ private:
         if (m_dl_ctx->get_params().print_statistics()) {
             statistics st;
             datalog::context& dlctx = m_dl_ctx->dlctx();
-            unsigned long long max_mem = memory::get_max_used_memory();
-            unsigned long long mem = memory::get_allocation_size();
             dlctx.collect_statistics(st);
             st.update("time", ctx.get_seconds());            
-            st.update("memory", static_cast<double>(mem)/static_cast<double>(1024*1024));
-            st.update("max-memory", static_cast<double>(max_mem)/static_cast<double>(1024*1024));
             st.display_smt2(ctx.regular_stream());            
         }
     }
diff --git a/src/opt/opt_context.cpp b/src/opt/opt_context.cpp
index 6fb4ef542..2a6265fc4 100644
--- a/src/opt/opt_context.cpp
+++ b/src/opt/opt_context.cpp
@@ -1188,10 +1188,7 @@ namespace opt {
         for (; it != end; ++it) {
             it->m_value->collect_statistics(stats);
         }        
-        unsigned long long max_mem = memory::get_max_used_memory();
-        unsigned long long mem = memory::get_allocation_size();
-        stats.update("memory", static_cast<double>(mem)/static_cast<double>(1024*1024));
-        stats.update("max memory", static_cast<double>(max_mem)/static_cast<double>(1024*1024));
+        get_memory_statistics(stats);
     }
 
     void context::collect_param_descrs(param_descrs & r) {
diff --git a/src/tactic/nlsat_smt/nl_purify_tactic.cpp b/src/tactic/nlsat_smt/nl_purify_tactic.cpp
index 91c462486..be52bb477 100644
--- a/src/tactic/nlsat_smt/nl_purify_tactic.cpp
+++ b/src/tactic/nlsat_smt/nl_purify_tactic.cpp
@@ -203,22 +203,32 @@ public:
             return BR_FAILED;            
         }
 
+        // (+ (f x) y)
+        // (f (+ x y))
+        // 
+        bool is_arith_op(expr* e) {
+            return is_app(e) && to_app(e)->get_family_id() == u().get_family_id();
+        }
         br_status reduce_app_real(func_decl * f, unsigned num, expr* const* args, expr_ref& result, proof_ref & pr) {
             bool has_interface = false;
+            bool is_arith = false;
             if (f->get_family_id() == u().get_family_id()) {
                 switch (f->get_decl_kind()) {
                 case OP_NUM: case OP_IRRATIONAL_ALGEBRAIC_NUM:
-                case OP_ADD: case OP_MUL: case OP_SUB: 
-                case OP_UMINUS: case OP_ABS: case OP_POWER: 
                     return BR_FAILED;
                 default:
+                    is_arith = true;
                     break;
                 }
             }
             m_args.reset();
             for (unsigned i = 0; i < num; ++i) {
                 expr* arg = args[i];
-                if (u().is_real(arg)) {
+                if (is_arith && !is_arith_op(arg)) {
+                    has_interface = true;
+                    m_args.push_back(mk_interface_var(arg));
+                }
+                else if (!is_arith && u().is_real(arg)) {
                     has_interface = true;
                     m_args.push_back(mk_interface_var(arg));
                 }
diff --git a/src/util/env_params.cpp b/src/util/env_params.cpp
index b01a1c250..6748598bf 100644
--- a/src/util/env_params.cpp
+++ b/src/util/env_params.cpp
@@ -27,6 +27,7 @@ void env_params::updt_params() {
     set_verbosity_level(p.get_uint("verbose", get_verbosity_level()));
     enable_warning_messages(p.get_bool("warning", true));
     memory::set_max_size(megabytes_to_bytes(p.get_uint("memory_max_size", 0)));
+    memory::set_max_alloc_count(p.get_uint("memory_max_alloc_count", 0));
     memory::set_high_watermark(p.get_uint("memory_high_watermark", 0));
 }
 
@@ -34,5 +35,6 @@ void env_params::collect_param_descrs(param_descrs & d) {
     d.insert("verbose", CPK_UINT, "be verbose, where the value is the verbosity level", "0");
     d.insert("warning", CPK_BOOL, "enable/disable warning messages", "true");
     d.insert("memory_max_size", CPK_UINT, "set hard upper limit for memory consumption (in megabytes), if 0 then there is no limit", "0");
+    d.insert("memory_max_alloc_count", CPK_UINT, "set hard upper limit for memory allocations, if 0 then there is no limit", "0");
     d.insert("memory_high_watermark", CPK_UINT, "set high watermark for memory consumption (in megabytes), if 0 then there is no limit", "0");
 }
diff --git a/src/util/error_codes.h b/src/util/error_codes.h
index 4afc9a38d..32d760470 100644
--- a/src/util/error_codes.h
+++ b/src/util/error_codes.h
@@ -32,6 +32,7 @@ Revision History:
 #define ERR_INTERNAL_FATAL      110
 #define ERR_TYPE_CHECK          111
 #define ERR_UNKNOWN_RESULT      112
+#define ERR_ALLOC_EXCEEDED      113
 
 #endif /* _ERROR_CODES_H_ */
 
diff --git a/src/util/memory_manager.cpp b/src/util/memory_manager.cpp
index 7539e7ba3..88bd6b92e 100644
--- a/src/util/memory_manager.cpp
+++ b/src/util/memory_manager.cpp
@@ -33,12 +33,17 @@ void mem_finalize();
 out_of_memory_error::out_of_memory_error():z3_error(ERR_MEMOUT) {
 }
 
+exceeded_memory_allocations::exceeded_memory_allocations():z3_error(ERR_ALLOC_EXCEEDED) {
+}
+
 static volatile bool g_memory_out_of_memory  = false;
 static bool       g_memory_initialized       = false;
 static long long  g_memory_alloc_size        = 0;
 static long long  g_memory_max_size          = 0;
 static long long  g_memory_max_used_size     = 0;
 static long long  g_memory_watermark         = 0;
+static long long  g_memory_alloc_count       = 0;
+static long long  g_memory_max_alloc_count   = 0;
 static bool       g_exit_when_out_of_memory  = false;
 static char const * g_out_of_memory_msg      = "ERROR: out of memory";
 static volatile bool g_memory_fully_initialized = false;
@@ -52,9 +57,7 @@ void memory::exit_when_out_of_memory(bool flag, char const * msg) {
 static void throw_out_of_memory() {
     #pragma omp critical (z3_memory_manager) 
     {
-        if (!g_memory_out_of_memory) {
-            g_memory_out_of_memory = true;
-        }
+        g_memory_out_of_memory = true;
     }
     if (g_exit_when_out_of_memory) {
         std::cerr << g_out_of_memory_msg << "\n";
@@ -65,12 +68,18 @@ static void throw_out_of_memory() {
     }
 }
 
+static void throw_alloc_counts_exceeded() {
+    throw exceeded_memory_allocations();
+}
+
+
 #ifdef PROFILE_MEMORY
 static unsigned g_synch_counter = 0;
 class mem_usage_report {
 public:
     ~mem_usage_report() { 
         std::cerr << "(memory :max " << g_memory_max_used_size 
+                  << " :allocs " << g_memory_alloc_count
                   << " :final " << g_memory_alloc_size 
                   << " :synch " << g_synch_counter << ")" << std::endl; 
     }
@@ -129,11 +138,17 @@ bool memory::above_high_watermark() {
     return r;
 }
 
+// The following methods are only safe to invoke at 
+// initialization time, that is, before threads are created.
+
 void memory::set_max_size(size_t max_size) {
-    // This method is only safe to invoke at initialization time, that is, before the threads are created.
     g_memory_max_size = max_size;
 }
 
+void memory::set_max_alloc_count(size_t max_count) {
+    g_memory_max_alloc_count = max_count;
+}
+
 static bool g_finalizing = false;
 
 void memory::finalize() {
@@ -165,6 +180,11 @@ unsigned long long memory::get_max_used_memory() {
     return r;
 }
 
+unsigned long long memory::get_allocation_count() {
+    return g_memory_alloc_count;
+}
+
+
 void memory::display_max_usage(std::ostream & os) {
     unsigned long long mem = get_max_used_memory();
     os << "max. heap size:     " 
@@ -207,9 +227,11 @@ void * memory::allocate(char const* file, int line, char const* obj, size_t s) {
 #ifdef _WINDOWS
 // Actually this is VS specific instead of Windows specific.
 __declspec(thread) long long g_memory_thread_alloc_size    = 0;
+__declspec(thread) long long g_memory_thread_alloc_count   = 0;
 #else
 // GCC style
 __thread long long g_memory_thread_alloc_size    = 0;
+__thread long long g_memory_thread_alloc_count  = 0;
 #endif
 
 static void synchronize_counters(bool allocating) {
@@ -218,18 +240,25 @@ static void synchronize_counters(bool allocating) {
 #endif
 
     bool out_of_mem = false;
+    bool counts_exceeded = false;
     #pragma omp critical (z3_memory_manager) 
     {
         g_memory_alloc_size += g_memory_thread_alloc_size;
+        g_memory_alloc_count += g_memory_thread_alloc_count;
         if (g_memory_alloc_size > g_memory_max_used_size)
             g_memory_max_used_size = g_memory_alloc_size;
         if (g_memory_max_size != 0 && g_memory_alloc_size > g_memory_max_size)
             out_of_mem = true;
+        if (g_memory_max_alloc_count != 0 && g_memory_alloc_count > g_memory_max_alloc_count)
+            counts_exceeded = true;
     }
     g_memory_thread_alloc_size = 0;
     if (out_of_mem && allocating) {
         throw_out_of_memory();
     }
+    if (counts_exceeded && allocating) {
+        throw_alloc_counts_exceeded();
+    }
 }
 
 void memory::deallocate(void * p) {
@@ -252,6 +281,7 @@ void * memory::allocate(size_t s) {
         throw_out_of_memory();
     *(static_cast<size_t*>(r)) = s;
     g_memory_thread_alloc_size += s;
+    g_memory_thread_alloc_count += 1;
     if (g_memory_thread_alloc_size > SYNCH_THRESHOLD) {
         synchronize_counters(true);
     }
@@ -265,6 +295,7 @@ void* memory::reallocate(void *p, size_t s) {
     s = s + sizeof(size_t); // we allocate an extra field!
 
     g_memory_thread_alloc_size += s - sz;
+    g_memory_thread_alloc_count += 1;
     if (g_memory_thread_alloc_size > SYNCH_THRESHOLD) {
         synchronize_counters(true);
     }
@@ -299,17 +330,22 @@ void * memory::allocate(size_t s) {
     if (s == 0) 
         return 0;
     s = s + sizeof(size_t); // we allocate an extra field!
-    bool out_of_mem = false;
+    bool out_of_mem = false, counts_exceeded = false;
     #pragma omp critical (z3_memory_manager) 
     {
         g_memory_alloc_size += s;
+        g_memory_alloc_count += 1;
         if (g_memory_alloc_size > g_memory_max_used_size)
             g_memory_max_used_size = g_memory_alloc_size;
         if (g_memory_max_size != 0 && g_memory_alloc_size > g_memory_max_size)
             out_of_mem = true;
+        if (g_memory_max_alloc_count != 0 && g_memory_alloc_count > g_memory_max_alloc_count)
+            counts_exceeded = true;
     }
     if (out_of_mem)
         throw_out_of_memory();
+    if (counts_exceeded)
+        throw_alloc_counts_exceeded();
     void * r = malloc(s);
     if (r == 0)
         throw_out_of_memory();
@@ -322,18 +358,22 @@ void* memory::reallocate(void *p, size_t s) {
     size_t sz      = *sz_p;
     void * real_p  = reinterpret_cast<void*>(sz_p);
     s = s + sizeof(size_t); // we allocate an extra field!
-    bool out_of_mem = false;
+    bool out_of_mem = false, counts_exceeded = false;
     #pragma omp critical (z3_memory_manager)
     {
         g_memory_alloc_size += s - sz;
+        g_memory_alloc_count += 1;
         if (g_memory_alloc_size > g_memory_max_used_size)
             g_memory_max_used_size = g_memory_alloc_size;
         if (g_memory_max_size != 0 && g_memory_alloc_size > g_memory_max_size)
             out_of_mem = true;
+        if (g_memory_max_alloc_count != 0 && g_memory_alloc_count > g_memory_max_alloc_count)
+            counts_exceeded = true;
     }
     if (out_of_mem)
         throw_out_of_memory();
-
+    if (counts_exceeded)
+        throw_alloc_counts_exceeded();
     void *r = realloc(real_p, s);
     if (r == 0)
         throw_out_of_memory();
diff --git a/src/util/memory_manager.h b/src/util/memory_manager.h
index bd912828e..94865fa90 100644
--- a/src/util/memory_manager.h
+++ b/src/util/memory_manager.h
@@ -46,6 +46,11 @@ public:
     out_of_memory_error();
 };
 
+class exceeded_memory_allocations : public z3_error {
+public:
+    exceeded_memory_allocations();
+};
+
 class memory {
 public:
     static bool is_out_of_memory();
@@ -53,6 +58,7 @@ public:
     static void set_high_watermark(size_t watermak);
     static bool above_high_watermark();
     static void set_max_size(size_t max_size);
+    static void set_max_alloc_count(size_t max_count);
     static void finalize();
     static void display_max_usage(std::ostream& os);
     static void display_i_max_usage(std::ostream& os);
@@ -65,6 +71,7 @@ public:
 #endif
     static unsigned long long get_allocation_size();
     static unsigned long long get_max_used_memory();
+    static unsigned long long get_allocation_count();
     // temporary hack to avoid out-of-memory crash in z3.exe
     static void exit_when_out_of_memory(bool flag, char const * msg);
 };
diff --git a/src/util/statistics.cpp b/src/util/statistics.cpp
index 24d17ddfa..6e50fd4a8 100644
--- a/src/util/statistics.cpp
+++ b/src/util/statistics.cpp
@@ -226,3 +226,13 @@ double statistics::get_double_value(unsigned idx) const {
     SASSERT(!is_uint(idx));
     return m_d_stats[idx - m_stats.size()].second;
 }
+
+void get_memory_statistics(statistics& st) {
+    unsigned long long max_mem = memory::get_max_used_memory();
+    unsigned long long mem = memory::get_allocation_size();
+    max_mem = (100*max_mem)/(1024*1024);
+    mem = (100*mem)/(1024*1024);
+    st.update("max memory",  static_cast<double>(max_mem)/100.0);
+    st.update("memory",      static_cast<double>(mem)/100.0);
+    st.update("num allocs",  static_cast<double>(memory::get_allocation_count()));
+}
diff --git a/src/util/statistics.h b/src/util/statistics.h
index a1a155df9..676c6b744 100644
--- a/src/util/statistics.h
+++ b/src/util/statistics.h
@@ -42,4 +42,6 @@ public:
     double get_double_value(unsigned idx) const;
 };
 
+void get_memory_statistics(statistics& st);
+
 #endif
diff --git a/src/util/z3_exception.cpp b/src/util/z3_exception.cpp
index 0e791ad92..52d42d27a 100644
--- a/src/util/z3_exception.cpp
+++ b/src/util/z3_exception.cpp
@@ -49,6 +49,7 @@ char const * z3_error::msg() const {
     case ERR_CMD_LINE: return "invalid command line";
     case ERR_INTERNAL_FATAL: return "internal error";
     case ERR_TYPE_CHECK: return "type error";
+    case ERR_ALLOC_EXCEEDED: return "number of configured allocations exceeded";
     default: return "unknown error";
     }
 }