diff --git a/src/sat/sat_clause.cpp b/src/sat/sat_clause.cpp
index f9caffe94..78d62bac0 100644
--- a/src/sat/sat_clause.cpp
+++ b/src/sat/sat_clause.cpp
@@ -95,7 +95,6 @@ namespace sat {
         } 
     }
 
-
     bool clause::satisfied_by(model const & m) const {
         for (literal l : *this) {
             if (l.sign()) {
@@ -110,6 +109,23 @@ namespace sat {
         return false;
     }
 
+    clause_offset clause::get_new_offset() const {
+        unsigned o1 = m_lits[0].index();
+        if (sizeof(clause_offset) == 8) {
+            unsigned o2 = m_lits[1].index();
+            return (clause_offset)o1 + (((clause_offset)o2) << 32);
+        }        
+        return (clause_offset)o1;
+    }
+
+    void clause::set_new_offset(clause_offset offset) {
+        m_lits[0] = to_literal(static_cast<unsigned>(offset));
+        if (sizeof(offset) == 8) {
+            m_lits[1] = to_literal(static_cast<unsigned>(offset >> 32));
+        }
+    }
+
+
     void tmp_clause::set(unsigned num_lits, literal const * lits, bool learned) {
         if (m_clause && m_clause->m_capacity < num_lits) {
             dealloc_svect(m_clause);
diff --git a/src/sat/sat_clause.h b/src/sat/sat_clause.h
index c42427afb..8b2d113c8 100644
--- a/src/sat/sat_clause.h
+++ b/src/sat/sat_clause.h
@@ -98,6 +98,8 @@ namespace sat {
         unsigned glue() const { return m_glue; }
         void set_psm(unsigned psm) { m_psm = psm > 255 ? 255 : psm; }
         unsigned psm() const { return m_psm; }
+        clause_offset get_new_offset() const;
+        void set_new_offset(clause_offset off); 
 
         bool on_reinit_stack() const { return m_reinit_stack; }
         void set_reinit_stack(bool f) { m_reinit_stack = f; }
diff --git a/src/sat/sat_local_search.cpp b/src/sat/sat_local_search.cpp
index 35e371a9c..e02560e5f 100644
--- a/src/sat/sat_local_search.cpp
+++ b/src/sat/sat_local_search.cpp
@@ -79,11 +79,13 @@ namespace sat {
     void local_search::init_cur_solution() {
         for (var_info& vi : m_vars) {
             // use bias with a small probability
-            if (m_rand() % 10 < 5 || m_config.phase_sticky()) {
-                vi.m_value = ((unsigned)(m_rand() % 100) < vi.m_bias);
-            }
-            else {
-                vi.m_value = (m_rand() % 2) == 0;
+            if (!vi.m_unit) {
+                if (m_rand() % 10 < 5 || m_config.phase_sticky()) {
+                    vi.m_value = ((unsigned)(m_rand() % 100) < vi.m_bias);
+                }
+                else {
+                    vi.m_value = (m_rand() % 2) == 0;
+                }
             }
         }
     }
@@ -149,7 +151,7 @@ namespace sat {
 
     void local_search::reinit() {
 
-        IF_VERBOSE(0, verbose_stream() << "(sat-local-search reinit)\n";);
+        IF_VERBOSE(1, verbose_stream() << "(sat-local-search reinit)\n";);
         if (true || !m_is_pb) {
             //
             // the following methods does NOT converge for pseudo-boolean
@@ -216,13 +218,15 @@ namespace sat {
         for (unsigned i = 0; i < m_prop_queue.size() && i < m_vars.size(); ++i) {
             literal lit2 = m_prop_queue[i];
             if (!is_true(lit2)) {
-                if (is_unit(lit2)) return false;
+                if (is_unit(lit2)) {
+                    return false;
+                }
                 flip_walksat(lit2.var());
                 add_propagation(lit2);
             }
         }
         if (m_prop_queue.size() >= m_vars.size()) {
-            IF_VERBOSE(0, verbose_stream() << "failed literal\n");
+            IF_VERBOSE(0, verbose_stream() << "propagation loop\n");
             return false;
         }
         if (unit) {
@@ -328,6 +332,7 @@ namespace sat {
             return;
         }
         if (k == 1 && sz == 2) {
+            // IF_VERBOSE(0, verbose_stream() << "bin: " << ~c[0] << " + " << ~c[1] << " <= 1\n");
             for (unsigned i = 0; i < 2; ++i) {
                 literal t(c[i]), s(c[1-i]);
                 m_vars.reserve(t.var() + 1);
@@ -750,11 +755,12 @@ namespace sat {
             IF_VERBOSE(1, verbose_stream() << "(sat.local_search :unsat)\n");
             return;
         }
-
+        if (is_unit(best_var)) {
+            goto reflip;
+        }
         flip_walksat(best_var);
         literal lit(best_var, !cur_solution(best_var));
         if (!propagate(lit)) {
-            IF_VERBOSE(0, verbose_stream() << "failed literal " << lit << "\n");
             if (is_true(lit)) { 
                 flip_walksat(best_var);
             }
@@ -774,6 +780,7 @@ namespace sat {
     }
 
     void local_search::flip_walksat(bool_var flipvar) {
+        VERIFY(!is_unit(flipvar));
         m_vars[flipvar].m_value = !cur_solution(flipvar);
 
         bool flip_is_true = cur_solution(flipvar);
diff --git a/src/sat/sat_solver.cpp b/src/sat/sat_solver.cpp
index 792883977..90ac876d2 100644
--- a/src/sat/sat_solver.cpp
+++ b/src/sat/sat_solver.cpp
@@ -529,26 +529,26 @@ namespace sat {
         IF_VERBOSE(1, verbose_stream() << "(sat-defrag)\n");
         clause_allocator& alloc = m_cls_allocator[!m_cls_allocator_idx];
         ptr_vector<clause> new_clauses, new_learned;
-        ptr_addr_map<clause, clause_offset> cls2offset;
         for (clause* c : m_clauses) c->unmark_used();
         for (clause* c : m_learned) c->unmark_used();
 
+#if 0
         svector<bool_var> vars;
         for (unsigned i = 0; i < num_vars(); ++i) vars.push_back(i);
         std::stable_sort(vars.begin(), vars.end(), cmp_activity(*this));
         literal_vector lits;
         for (bool_var v : vars) lits.push_back(to_literal(v)), lits.push_back(~to_literal(v));
-
         // walk clauses, reallocate them in an order that defragments memory and creates locality.
         //for (literal lit : lits) {
         //watch_list& wlist = m_watches[lit.index()];
+#endif
         for (watch_list& wlist : m_watches) {            
             for (watched& w : wlist) {
                 if (w.is_clause()) {
                     clause& c1 = get_clause(w);
                     clause_offset offset;
                     if (c1.was_used()) {
-                        offset = cls2offset[&c1];
+                        offset = c1.get_new_offset();
                     }
                     else {
                         clause* c2 = alloc.copy_clause(c1); 
@@ -560,7 +560,7 @@ namespace sat {
                             new_clauses.push_back(c2);
                         }
                         offset = get_offset(*c2);
-                        cls2offset.insert(&c1, offset);
+                        c1.set_new_offset(offset);
                     }
                     w = watched(w.get_blocked_literal(), offset);
                 }
diff --git a/src/solver/parallel_params.pyg b/src/solver/parallel_params.pyg
index 58c00aa97..2d58cbb81 100644
--- a/src/solver/parallel_params.pyg
+++ b/src/solver/parallel_params.pyg
@@ -5,7 +5,7 @@ def_module_params('parallel',
                   params=(
                           ('enable', BOOL, False, 'enable parallel solver by default on selected tactics (for QF_BV)'),
                           ('threads.max', UINT, 10000, 'caps maximal number of threads below the number of processors'),
-                          ('conquer.batch_size', UINT, 1000, 'number of cubes to batch together for fast conquer'),
+                          ('conquer.batch_size', UINT, 100, 'number of cubes to batch together for fast conquer'),
                           ('conquer.restart.max', UINT, 5, 'maximal number of restarts during conquer phase'),
 	                  ('conquer.delay', UINT, 10, 'delay of cubes until applying conquer'),
 	                  ('conquer.backtrack_frequency', UINT, 10, 'frequency to apply core minimization during conquer'),
diff --git a/src/solver/parallel_tactic.cpp b/src/solver/parallel_tactic.cpp
index 748ee5d64..ac147672e 100644
--- a/src/solver/parallel_tactic.cpp
+++ b/src/solver/parallel_tactic.cpp
@@ -99,6 +99,8 @@ class parallel_tactic : public tactic {
             }
         }
 
+        bool in_shutdown() const { return m_shutdown; }
+
         void add_task(solver_state* task) {
             std::lock_guard<std::mutex> lock(m_mutex);
             m_tasks.push_back(task);
@@ -285,6 +287,7 @@ class parallel_tactic : public tactic {
             p.set_uint("restart.max", pp.simplify_restart_max() * mult);
             p.set_bool("lookahead_simplify", true);
             p.set_bool("retain_blocked_clauses", retain_blocked);
+            if (m_depth > 1) p.set_uint("bce_delay", 0);
             get_solver().updt_params(p);
         }
 
@@ -479,8 +482,8 @@ private:
                 break;
 
             }
-            if (cubes.size() >= conquer_batch_size() || (!cubes.empty() && m_queue.is_idle())) {
-                spawn_cubes(s, std::max(2u, width), cubes);
+            if (cubes.size() >= conquer_batch_size()) {
+                spawn_cubes(s, 10*width, cubes);
                 first = false;
                 cubes.reset();
             }
@@ -575,6 +578,7 @@ private:
         }
         catch (z3_exception& ex) {            
             IF_VERBOSE(1, verbose_stream() << ex.msg() << "\n";);
+            if (m_queue.in_shutdown()) return;
             m_queue.shutdown();
             std::lock_guard<std::mutex> lock(m_mutex);
             if (ex.has_error_code()) {