diff --git a/src/ast/sls/sls_bv_engine.h b/src/ast/sls/sls_bv_engine.h
index f9d26ee702..d63a66131f 100644
--- a/src/ast/sls/sls_bv_engine.h
+++ b/src/ast/sls/sls_bv_engine.h
@@ -21,7 +21,6 @@ Module Name:
 #include "util/stopwatch.h"
 #include "util/lbool.h"
 #include "ast/converters/model_converter.h"
-
 #include "ast/sls/sls_stats.h"
 #include "ast/sls/sls_bv_tracker.h"
 #include "ast/sls/sls_bv_evaluator.h"
@@ -79,8 +78,6 @@ class sls_engine {
     void mk_inv(unsigned bv_sz, const mpz & old_value, mpz & inverted);
     void mk_flip(sort * s, const mpz & old_value, unsigned bit, mpz & flipped);            
 
-
-
     lbool search();  
 
     lbool search_loop();
diff --git a/src/ast/sls/sls_bv_eval.cpp b/src/ast/sls/sls_bv_eval.cpp
index a9e16797ba..997b3c4b3c 100644
--- a/src/ast/sls/sls_bv_eval.cpp
+++ b/src/ast/sls/sls_bv_eval.cpp
@@ -88,7 +88,6 @@ namespace sls {
         return r;
     }
 
-
     void bv_eval::init_eval_bv(app* e) {
         if (bv.is_bv(e)) 
             eval(e).commit_eval();               
@@ -99,7 +98,7 @@ namespace sls {
         if (m.is_eq(e, x, y))
             return bv.is_bv(x);
         if (m.is_ite(e))
-            return bv.is_bv(e->get_arg(0));
+            return bv.is_bv(e->get_arg(1));
         if (e->get_family_id() == bv.get_fid()) {
             switch (e->get_decl_kind()) {
             case OP_BNEG_OVFL:
@@ -680,6 +679,8 @@ namespace sls {
         expr* arg = e->get_arg(i);
         if (m.is_value(arg))
             return false;
+        if (m.is_bool(e) && false && m_rand(10) == 0 && m_lookahead.try_repair_down(e))
+            return true;
         if (e->get_family_id() == bv.get_family_id() && try_repair_bv(e, i)) {
             commit_eval(e, to_app(arg));
             IF_VERBOSE(11, verbose_stream() << "repair " << mk_bounded_pp(e, m) << " : " << mk_bounded_pp(arg, m) << " := " << wval(arg) << "\n";);
@@ -692,9 +693,9 @@ namespace sls {
             ctx.new_value_eh(arg);
             return true;
         }
-        if (m.is_eq(e) && bv.is_bv(arg)) {
-            return try_repair_eq_lookahead(e);
-        }
+        if (m.is_bool(e) && m_lookahead.try_repair_down(e))
+            return true;
+        
         return false;
     }
 
@@ -882,37 +883,9 @@ namespace sls {
         return false;
     }
 
-    bool bv_eval::try_repair_eq_lookahead(app* e) {
-        return m_lookahead.try_repair_down(e);
-
-    }
-
     bool bv_eval::try_repair_eq(bool is_true, bvval& a, bvval const& b) {
         if (is_true) {
-#if 0
-            if (bv.is_bv_add(t)) {
-                bvval tmp(b);
-                unsigned start = m_rand();
-                unsigned sz = to_app(t)->get_num_args();
-                for (unsigned i = 0; i < sz; ++i) {
-                    unsigned j = (start + i) % sz;
-                    for (unsigned k = 0; k < sz; ++k) {
-                        if (k == j)
-                            continue;
-                        auto& c = wval(to_app(t)->get_arg(k));
-                        set_sub(tmp, tmp, c.bits());
-                    }
-                    
-                    auto& c = wval(to_app(t)->get_arg(j));
-                    verbose_stream() << "TRY " << c << " := " << tmp << "\n";
-                    
-
-                }
-            }
-#endif
-            if (m_rand(20) != 0 && a.try_set(b.bits()))
-                return true;
-            return a.set_random(m_rand);
+            return (m_rand(20) != 0 && a.try_set(b.bits())) || a.set_random(m_rand);
         }
         else {
             bool try_above = m_rand(2) == 0;
diff --git a/src/ast/sls/sls_bv_eval.h b/src/ast/sls/sls_bv_eval.h
index 9964b5a338..6dc2d35e4c 100644
--- a/src/ast/sls/sls_bv_eval.h
+++ b/src/ast/sls/sls_bv_eval.h
@@ -121,7 +121,6 @@ namespace sls {
         bool try_repair_comp(bvect const& e, bvval& a, bvval& b, unsigned i);
         bool try_repair_eq(bool is_true, bvval& a, bvval const& b);
         bool try_repair_eq(app* e, unsigned i);
-        bool try_repair_eq_lookahead(app* e);
         bool try_repair_int2bv(bvect const& e, expr* arg);
         void add_p2_1(bvval const& a, bool use_current, bvect& t) const;
 
diff --git a/src/ast/sls/sls_bv_evaluator.h b/src/ast/sls/sls_bv_evaluator.h
index d0a71f1587..77fbf9121a 100644
--- a/src/ast/sls/sls_bv_evaluator.h
+++ b/src/ast/sls/sls_bv_evaluator.h
@@ -451,25 +451,34 @@ class sls_evaluator {
             case OP_BLSHR: {
                 SASSERT(n_args == 2);
                 m_mpz_manager.set(result, m_tracker.get_value(args[0]));
-                mpz shift; m_mpz_manager.set(shift, m_tracker.get_value(args[1]));
-                while (!m_mpz_manager.is_zero(shift)) {
-                    m_mpz_manager.machine_div(result, m_two, result);
-                    m_mpz_manager.dec(shift);
+                auto const& shift = m_tracker.get_value(args[1]);
+                if (m_mpz_manager.is_small(shift)) {
+                    int s = m_mpz_manager.get_int(shift);
+                    SASSERT(s >= 0);
+                    m_mpz_manager.machine_div2k(result, s);
                 }
-                m_mpz_manager.del(shift);
+                else 
+                    m_mpz_manager.set(result, m_zero);                
                 break;
             }
             case OP_BSHL: {
                 SASSERT(n_args == 2);
-                m_mpz_manager.set(result, m_tracker.get_value(args[0]));                
-                mpz shift; m_mpz_manager.set(shift, m_tracker.get_value(args[1]));
-                while (!m_mpz_manager.is_zero(shift)) {
-                    m_mpz_manager.mul(result, m_two, result);
-                    m_mpz_manager.dec(shift);
+                m_mpz_manager.set(result, m_tracker.get_value(args[0]));  
+                auto const& shift = m_tracker.get_value(args[1]);
+                if (m_mpz_manager.is_small(shift)) {
+                    int s = m_mpz_manager.get_int(shift);
+                    SASSERT(s >= 0);
+                    int sz = m_bv_util.get_bv_size(n);
+                    if (s >= sz) 
+                        m_mpz_manager.set(result, m_zero);                    
+                    else {
+                        m_mpz_manager.mul2k(result, s);
+                        const mpz& p = m_powers(sz);
+                        m_mpz_manager.rem(result, p, result);
+                    }
                 }
-                const mpz & p = m_powers(m_bv_util.get_bv_size(n));
-                m_mpz_manager.rem(result, p, result);
-                m_mpz_manager.del(shift);                    
+                else 
+                    m_mpz_manager.set(result, m_zero);                               
                 break;
             }
             case OP_SIGN_EXT: {
diff --git a/src/ast/sls/sls_bv_lookahead.cpp b/src/ast/sls/sls_bv_lookahead.cpp
index dec7c24a34..6341f1e0ef 100644
--- a/src/ast/sls/sls_bv_lookahead.cpp
+++ b/src/ast/sls/sls_bv_lookahead.cpp
@@ -18,45 +18,43 @@ Module Name:
 #include "ast/sls/sls_bv_lookahead.h"
 #include "ast/sls/sls_bv_eval.h"
 #include "ast/sls/sls_bv_terms.h"
+#include "ast/ast_pp.h"
 
 namespace sls {
 
     bv_lookahead::bv_lookahead(bv_eval& ev) : 
-        bv(ev.bv), 
+        bv(ev.m), 
         m_ev(ev), 
         ctx(ev.ctx), 
         m(ev.m) {}
 
-    bool bv_lookahead::try_repair_down(expr* e) {
-        return false;
-        auto is_true = m_ev.bval0(e);
-        if (!is_true)
+    bool bv_lookahead::try_repair_down(app* e) {
+        if (!m.is_bool(e))
             return false;
+        if (m_ev.bval1(e) == m_ev.bval0(e))
+            return true;
         auto const& uninterp = m_ev.terms.uninterp_occurs(e);
         if (uninterp.empty())
             return false;
-        //        for (auto e : uninterp)
-        //            verbose_stream() << mk_bounded_pp(e, m) << " ";
-        //        verbose_stream() << "\n";
-
-        expr* t = uninterp[m_ev.m_rand() % uninterp.size()];
+        reset_updates();
 
-        auto& v = wval(t);
-        if (v.set_random(m_ev.m_rand)) {
-            //verbose_stream() << "set random " << mk_bounded_pp(t, m) << "\n";
-            ctx.new_value_eh(t);
-            return true;
-        }
-        return false;
+        IF_VERBOSE(4,
+            verbose_stream() << mk_bounded_pp(e, m) << "\n";
+            for (auto e : uninterp)
+                verbose_stream() << mk_bounded_pp(e, m) << " ";
+            verbose_stream() << "\n");
 
+        for (auto e : uninterp) 
+            add_updates(e);
 
-        for (auto e : uninterp) {
-            auto& v = wval(e);
-            v.get_variant(m_ev.m_tmp, m_ev.m_rand);
-            auto d = lookahead(e, m_ev.m_tmp);
-            //verbose_stream() << mk_bounded_pp(e, m) << " " << d << "\n";
+#if 0
+        for (unsigned i = 0; i < m_num_updates; ++i) {
+            auto const& [e, score, new_value] = m_updates[i];
+            verbose_stream() << mk_bounded_pp(e, m) << " " << new_value << " score: " << score << "\n";
         }
-        return false;
+#endif
+        
+        return apply_update();
     }
 
     double bv_lookahead::lookahead(expr* e, bvect const& new_value) {
@@ -76,7 +74,7 @@ namespace sls {
         unsigned max_depth = get_depth(e);
         for (unsigned depth = max_depth; depth <= max_depth; ++depth) {
             for (unsigned i = 0; !has_tabu && i < m_update_stack[depth].size(); ++i) {
-                e = m_update_stack[depth][i];
+                auto e = m_update_stack[depth][i];
                 if (bv.is_bv(e)) {
                     auto& v = m_ev.eval(to_app(e));
                     if (insert_update(e)) {
@@ -89,24 +87,133 @@ namespace sls {
                         has_tabu = true;
                 }
                 else if (m.is_bool(e) && m_ev.can_eval1(to_app(e))) {
+                    if (!ctx.is_relevant(e))
+                        continue;
                     bool is_true = ctx.is_true(e);
                     bool is_true_new = m_ev.bval1(to_app(e));
                     bool is_true_old = m_ev.bval1_tmp(to_app(e));
-                    // verbose_stream() << "parent " << mk_bounded_pp(e, m) << " " << is_true << " " << is_true_new << " " << is_true_old << "\n";
-                    if (is_true == is_true_new && is_true_new != is_true_old)
+                    if (is_true_new == is_true_old)
+                        continue;
+                    if (is_true == is_true_new)
                         ++make_count;
-                    if (is_true == is_true_old && is_true_new != is_true_old)
+                    if (is_true == is_true_old)
                         ++break_count;
                 }
+                else {
+                    IF_VERBOSE(1, verbose_stream() << "skipping " << mk_bounded_pp(e, m) << "\n");
+                    has_tabu = true;
+                }
             }
             m_update_stack[depth].reset();
         }
         restore_lookahead();
+        // verbose_stream() << has_tabu << " " << new_value << " " << make_count << " " << break_count << "\n";
+
         if (has_tabu)
             return -10000;
         return make_count - break_count;
     }
 
+    void bv_lookahead::try_set(expr* e, bvect const& new_value) {
+        if (!wval(e).can_set(new_value))
+            return;
+        auto d = lookahead(e, new_value);
+        if (d > 0)
+            add_update(d, e, new_value);
+    }
+
+    void bv_lookahead::add_updates(expr* e) {
+        SASSERT(bv.is_bv(e));
+        auto& v = wval(e);
+        double d = 0;
+        while (m_v_saved.size() < v.bits().size()) {
+            m_v_saved.push_back(0);
+            m_v_updated.push_back(0);
+        }
+        m_v_saved.set_bw(v.bw);
+        m_v_updated.set_bw(v.bw);
+        v.bits().copy_to(v.nw, m_v_saved);
+        m_v_saved.copy_to(v.nw, m_v_updated);
+
+        // flip a single bit
+        for (unsigned i = 0; i < v.bw; ++i) {
+            m_v_updated.set(i, !m_v_updated.get(i));
+            try_set(e, m_v_updated);
+            //verbose_stream() << "flip " << d << " " << m_v_updated << "\n";
+            m_v_updated.set(i, !m_v_updated.get(i));
+        }
+        if (v.bw <= 1)
+            return;
+
+        // invert
+        for (unsigned i = 0; i < v.nw; ++i)
+            m_v_updated[i] = ~m_v_updated[i];
+        v.clear_overflow_bits(m_v_updated);
+        try_set(e, m_v_updated);
+
+        // increment
+        m_v_saved.copy_to(v.nw, m_v_updated);
+        v.add1(m_v_updated);
+        try_set(e, m_v_updated);       
+
+        // decrement
+        m_v_saved.copy_to(v.nw, m_v_updated);
+        v.sub1(m_v_updated);
+        try_set(e, m_v_updated);
+
+        // random
+        v.get_variant(m_v_updated, m_ev.m_rand);
+        try_set(e, m_v_updated);
+    }
+
+    bool bv_lookahead::apply_update() {
+        double sum_score = 0;
+        for (unsigned i = 0; i < m_num_updates; ++i) 
+            sum_score += m_updates[i].score;        
+        double pos = (sum_score * m_ev.m_rand()) / (double)m_ev.m_rand.max_value();
+        for (unsigned i = 0; i < m_num_updates; ++i) {
+            auto const& [e, score, new_value] = m_updates[i];
+            pos -= score;
+            if (pos <= 0) {
+                //verbose_stream() << "apply " << mk_bounded_pp(e, m) << " new value " << new_value << " " << score << "\n";
+                apply_update(e, new_value);
+                return true;
+            }
+        }
+        return false;
+    }
+
+    void bv_lookahead::apply_update(expr* e, bvect const& new_value) {
+        SASSERT(bv.is_bv(e));
+        SASSERT(is_uninterp(e));
+        SASSERT(m_restore.empty());
+        wval(e).eval = new_value;
+        VERIFY(wval(e).commit_eval());
+        insert_update_stack(e);
+        unsigned max_depth = get_depth(e);
+        for (unsigned depth = max_depth; depth <= max_depth; ++depth) {
+            for (unsigned i = 0; i < m_update_stack[depth].size(); ++i) {
+                auto e = m_update_stack[depth][i];
+                if (bv.is_bv(e)) {
+                    m_ev.eval(to_app(e)); // updates wval(e).eval
+                    VERIFY(wval(e).commit_eval());
+                    for (auto p : ctx.parents(e)) {
+                        insert_update_stack(p);
+                        max_depth = std::max(max_depth, get_depth(p));
+                    }                    
+                }
+                else if (m.is_bool(e) && m_ev.can_eval1(to_app(e))) {
+                    VERIFY(m_ev.repair_up(e));
+                }
+                else {
+                    UNREACHABLE();                    
+                }
+            }
+            m_update_stack[depth].reset();
+        }
+        m_in_update_stack.reset();        
+    }
+
     bool bv_lookahead::insert_update(expr* e) {
         m_restore.push_back(e);
         m_on_restore.mark(e);
@@ -118,8 +225,10 @@ namespace sls {
     void bv_lookahead::insert_update_stack(expr* e) {
         unsigned depth = get_depth(e);
         m_update_stack.reserve(depth + 1);
-        if (!m_update_stack[depth].contains(e))
+        if (!m_in_update_stack.is_marked(e)) {
+            m_in_update_stack.mark(e);
             m_update_stack[depth].push_back(e);
+        }    
     }
 
     void bv_lookahead::restore_lookahead() {
@@ -127,6 +236,7 @@ namespace sls {
             wval(e).restore_value();
         m_restore.reset();
         m_on_restore.reset();
+        m_in_update_stack.reset();
     }
 
     sls::bv_valuation& bv_lookahead::wval(expr* e) const {
diff --git a/src/ast/sls/sls_bv_lookahead.h b/src/ast/sls/sls_bv_lookahead.h
index d43359698c..15b810ec05 100644
--- a/src/ast/sls/sls_bv_lookahead.h
+++ b/src/ast/sls/sls_bv_lookahead.h
@@ -18,36 +18,60 @@ Module Name:
 
 #include "ast/bv_decl_plugin.h"
 #include "ast/sls/sls_context.h"
+#include "ast/sls/sls_bv_valuation.h"
 
 namespace sls {
     class bv_eval;
-    class bv_valuation;
-    class bvect;
 
     class bv_lookahead {
         bv_util bv;
         bv_eval& m_ev;
         context& ctx;
         ast_manager& m;
+        bvect m_v_saved, m_v_updated;
 
         ptr_vector<expr> m_restore;
         vector<ptr_vector<expr>> m_update_stack;
-        expr_mark m_on_restore;
+        expr_mark m_on_restore, m_in_update_stack;
+        struct update {
+            expr* e;
+            double score;
+            bvect value;            
+        };
+        vector<update> m_updates;
+        unsigned m_num_updates = 0;
+        void reset_updates() { m_num_updates = 0; }
+        void add_update(double score, expr* e, bvect const& value) { 
+            if (m_num_updates == m_updates.size())
+                m_updates.push_back({ e, score, value });
+            else {
+                auto& u = m_updates[m_num_updates];
+                u.e = e;
+                u.score = score;
+                u.value = value;
+            }
+            m_num_updates++;
+        }
+        
 
         bv_valuation& wval(expr* e) const;
 
         void insert_update_stack(expr* e);
-        bool insert_update(expr* e);
-        
+        bool insert_update(expr* e);        
         void restore_lookahead();
-
         double lookahead(expr* e, bvect const& new_value);
 
+        void try_set(expr* e, bvect const& new_value);
+        void add_updates(expr* e);
+        void apply_update(expr* e, bvect const& new_value);
+        bool apply_update();
+
+
     public:
         bv_lookahead(bv_eval& ev);
         bool on_restore(expr* e) const;
 
-        bool try_repair_down(expr* e);
+        bool try_repair_down(app* e);
 
     };
 }
\ No newline at end of file
diff --git a/src/ast/sls/sls_bv_terms.cpp b/src/ast/sls/sls_bv_terms.cpp
index 9004128b96..a28af99921 100644
--- a/src/ast/sls/sls_bv_terms.cpp
+++ b/src/ast/sls/sls_bv_terms.cpp
@@ -127,6 +127,7 @@ namespace sls {
         ptr_vector<expr> todo;
         todo.append(to_app(e)->get_num_args(), to_app(e)->get_args());
         expr_mark marked;
+        expr* c, * th, * el;
         for (unsigned i = 0; i < todo.size(); ++i) {
             e = todo[i];
             if (marked.is_marked(e))
@@ -136,6 +137,10 @@ namespace sls {
                 for (expr* arg : *to_app(e))
                     todo.push_back(arg);
             }
+            else if (m.is_ite(e, c, th, el)) {
+                todo.push_back(th);
+                todo.push_back(el);
+            }
             else if (bv.is_bv(e))
                 occs.push_back(e);
         }
diff --git a/src/ast/sls/sls_stats.h b/src/ast/sls/sls_stats.h
index 9468e9c8d3..ae1a8cbeae 100644
--- a/src/ast/sls/sls_stats.h
+++ b/src/ast/sls/sls_stats.h
@@ -6,24 +6,21 @@
 namespace bv {
     class sls_stats {
     public:
-        unsigned        m_restarts;
+        unsigned        m_restarts = 0;
+        unsigned        m_full_evals = 0;
+        unsigned        m_incr_evals = 0;
+        unsigned        m_moves = 0; 
+        unsigned        m_flips = 0;
+        unsigned        m_incs = 0;
+        unsigned        m_decs = 0;
+        unsigned        m_invs = 0;
         stopwatch       m_stopwatch;
-        unsigned        m_full_evals;
-        unsigned        m_incr_evals;
-        unsigned        m_moves, m_flips, m_incs, m_decs, m_invs;
         
-        sls_stats() :
-            m_restarts(0),
-            m_full_evals(0),
-            m_incr_evals(0),
-            m_moves(0),
-            m_flips(0),
-            m_incs(0),
-            m_decs(0),
-            m_invs(0) {
+        sls_stats() {
             m_stopwatch.reset();
             m_stopwatch.start();
         }
+
         void reset() {
             m_full_evals = m_flips = m_incr_evals = 0;
             m_stopwatch.reset();
@@ -44,7 +41,6 @@ namespace bv {
             st.update("sls DEC moves", m_decs);
             st.update("sls INV moves", m_invs);
             st.update("sls moves", m_moves);
-
         }
         
     };
diff --git a/src/tactic/sls/sls_tactic.cpp b/src/tactic/sls/sls_tactic.cpp
index f50edcaccd..59a5c6ac94 100644
--- a/src/tactic/sls/sls_tactic.cpp
+++ b/src/tactic/sls/sls_tactic.cpp
@@ -213,9 +213,6 @@ class sls_tactic : public tactic {
     }
 
     void cleanup() override {
-        sls_engine * d = alloc(sls_engine, m, m_params);
-        std::swap(d, m_engine);            
-        dealloc(d);
     }
     
     void collect_statistics(statistics & st) const override {