diff --git a/src/sat/sat_npn3_finder.cpp b/src/sat/sat_npn3_finder.cpp
index bdea6ba6a..58fa9ba15 100644
--- a/src/sat/sat_npn3_finder.cpp
+++ b/src/sat/sat_npn3_finder.cpp
@@ -69,6 +69,7 @@ namespace sat {
         find_xorand(clauses);
         find_onehot(clauses);
         find_gamble(clauses);
+        find_dot(clauses);
     }
 
     bool npn3_finder::implies(literal a, literal b) const {
@@ -173,6 +174,12 @@ namespace sat {
         return false;
     }
 
+    void npn3_finder::filter(clause_vector& clauses) const
+    {
+        //std::function<bool(clause*)> not_used = [](clause* cp) { return !cp->was_used(); };
+        //clauses.filter_update(not_used);
+    }
+
     void npn3_finder::find_npn3(clause_vector& clauses, on_function_t const& on_function, std::function<bool(binary_hash_table_t const&, ternary_hash_table_t const&, literal, literal, literal, clause&)> const& checker)
     {
         if (!on_function) return;
@@ -193,8 +200,7 @@ namespace sat {
             if (checker(binaries, ternaries, y, z, x, c)) continue;
         }
 
-        std::function<bool(clause*)> not_used = [](clause* cp) { return !cp->was_used(); };
-        clauses.filter_update(not_used);
+        filter(clauses);
     }
 
     void npn3_finder::find_mux(clause_vector& clauses) {
@@ -347,8 +353,7 @@ namespace sat {
             if (try_andxor(z, y, w, x, c)) continue;
         }
 
-        std::function<bool(clause*)> not_used = [](clause* cp) { return !cp->was_used(); };
-        clauses.filter_update(not_used);
+        filter(clauses);
     }
 
     void npn3_finder::find_xorand(clause_vector& clauses) {
@@ -393,8 +398,7 @@ namespace sat {
             if (try_xorand(z, y, w, x, c)) continue;
         }
 
-        std::function<bool(clause*)> not_used = [](clause* cp) { return !cp->was_used(); };
-        clauses.filter_update(not_used);
+        filter(clauses);
     }
 
     void npn3_finder::find_gamble(clause_vector& clauses) {
@@ -432,8 +436,7 @@ namespace sat {
             if (try_gamble(z, w, x, y, c)) continue;
         }
 
-        std::function<bool(clause*)> not_used = [](clause* cp) { return !cp->was_used(); };
-        clauses.filter_update(not_used);
+        filter(clauses);
     }
 
     void npn3_finder::find_onehot(clause_vector& clauses) {
@@ -475,8 +478,65 @@ namespace sat {
             if (try_onehot(z, w, x, y, c)) continue;
         }
 
-        std::function<bool(clause*)> not_used = [](clause* cp) { return !cp->was_used(); };
-        clauses.filter_update(not_used);
+        filter(clauses);
+    }
+
+    void npn3_finder::find_dot(clause_vector& clauses) {
+        if (!m_on_dot) return;
+
+        binary_hash_table_t binaries;
+        ternary_hash_table_t ternaries;
+        quaternary_hash_table_t quaternaries;
+        process_more_clauses(clauses, binaries, ternaries, quaternaries);
+
+        const auto try_dot = [&](literal w, literal x, literal y, literal z, clause &c) {
+          clause *c1, *c2, *c3, *c4;
+          if (!has_ternary(ternaries, ~x, z, ~w, c1)) return false;
+          if (!has_ternary(ternaries, x, ~y, ~w, c2)) return false;
+          if (!has_ternary(ternaries, x, ~z, ~w, c3)) return false;
+          if (!has_ternary(ternaries, ~x, ~z, w, c4)) return false;
+
+          c.mark_used();
+          if (c1) c1->mark_used();
+          if (c2) c2->mark_used();
+          if (c3) c3->mark_used();
+          if (c4) c4->mark_used();
+          m_on_dot(w, ~x, y, z);
+          return true;
+        };
+
+        for (clause* cp : clauses) {
+            clause& c = *cp;
+            if (c.size() != 4 || c.was_used()) continue;
+            literal w = c[0], x = c[1], y = c[2], z = c[3];
+
+            if (try_dot(w, x, y, z, c)) continue;
+            if (try_dot(w, x, z, y, c)) continue;
+            if (try_dot(w, y, x, z, c)) continue;
+            if (try_dot(w, y, z, x, c)) continue;
+            if (try_dot(w, z, x, y, c)) continue;
+            if (try_dot(w, z, y, x, c)) continue;
+            if (try_dot(x, w, y, z, c)) continue;
+            if (try_dot(x, w, z, y, c)) continue;
+            if (try_dot(x, y, w, z, c)) continue;
+            if (try_dot(x, y, z, w, c)) continue;
+            if (try_dot(x, z, w, y, c)) continue;
+            if (try_dot(x, z, y, w, c)) continue;
+            if (try_dot(y, w, x, z, c)) continue;
+            if (try_dot(y, w, z, x, c)) continue;
+            if (try_dot(y, x, w, z, c)) continue;
+            if (try_dot(y, x, z, w, c)) continue;
+            if (try_dot(y, z, w, x, c)) continue;
+            if (try_dot(y, z, x, w, c)) continue;
+            if (try_dot(z, w, x, y, c)) continue;
+            if (try_dot(z, w, y, x, c)) continue;
+            if (try_dot(z, x, w, y, c)) continue;
+            if (try_dot(z, x, y, w, c)) continue;
+            if (try_dot(z, y, w, x, c)) continue;
+            if (try_dot(z, y, x, w, c)) continue;
+        }
+
+        filter(clauses);
     }
 
     void npn3_finder::validate_clause(literal_vector const& clause, vector<literal_vector> const& clauses) {
diff --git a/src/sat/sat_npn3_finder.h b/src/sat/sat_npn3_finder.h
index 9f4293fe4..1d87a1627 100644
--- a/src/sat/sat_npn3_finder.h
+++ b/src/sat/sat_npn3_finder.h
@@ -43,6 +43,7 @@ namespace sat {
         on_function_t m_on_xorand;
         on_function_t m_on_gamble;
         on_function_t m_on_onehot;
+        on_function_t m_on_dot;
 
         typedef svector<std::pair<literal, clause*>> use_list_t;
         scoped_ptr_vector<use_list_t> m_use_lists;
@@ -96,6 +97,7 @@ namespace sat {
         bool has_quaternary(quaternary_hash_table_t const& quaternaries, ternary_hash_table_t const& ternaries, literal w, literal x, literal y, literal z, clause*& c) const;
 
         bool implies(literal a, literal b) const;
+        void filter(clause_vector& clauses) const;
         void find_npn3(clause_vector& clauses, on_function_t const& on_function, std::function<bool(binary_hash_table_t const&, ternary_hash_table_t const&, literal, literal, literal, clause&)> const& checker);
         void find_mux(clause_vector& clauses);
         void validate_if(literal x, literal c, literal t, literal e, clause const& c0, clause const* c1, clause const* c2, clause const* c3);
@@ -105,6 +107,7 @@ namespace sat {
         void find_xorand(clause_vector& clauses);
         void find_gamble(clause_vector& clauses);
         void find_onehot(clause_vector& clauses);
+        void find_dot(clause_vector& clauses);
         void validate_clause(literal x, literal y, literal z, vector<literal_vector> const& clauses);
         void validate_clause(literal_vector const& clause, vector<literal_vector> const& clauses);
 
@@ -119,6 +122,7 @@ namespace sat {
         void set_on_xorand(std::function<void(literal head, literal a, literal b, literal c)> const& f) { m_on_xorand = f; }
         void set_on_gamble(std::function<void(literal head, literal a, literal b, literal c)> const& f) { m_on_gamble = f; }
         void set_on_onehot(std::function<void(literal head, literal a, literal b, literal c)> const& f) { m_on_onehot = f; }
+        void set_on_dot(std::function<void(literal head, literal a, literal b, literal c)> const& f) { m_on_dot = f; }
         void operator()(clause_vector& clauses);
     };
 }