make difference logic simplex optimizer incremental

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/math/simplex/simplex.h

@@ -142,6 +142,7 @@ namespace simplex {
         void  set_value(var_t var, eps_numeral const& b);        
         void  set_cancel(bool f) { m_cancel = f; }
         void  set_max_iterations(unsigned m) { m_max_iterations = m; }
+        void  reset();
         lbool make_feasible();
         lbool minimize(var_t var);
         eps_numeral const& get_value(var_t v);

src/math/simplex/simplex_def.h

@@ -310,6 +310,16 @@ namespace simplex {
         }
     }
 
+    template<typename Ext>
+    void simplex<Ext>::reset() {
+        M.reset();
+        m_to_patch.reset();
+        m_vars.reset();
+        m_row2base.reset();
+        m_left_basis.reset();
+        m_base_vars.reset();
+    }
+
     template<typename Ext>
     lbool simplex<Ext>::make_feasible() {
         ++m_stats.m_num_checks;

src/math/simplex/sparse_matrix.h

@@ -145,6 +145,7 @@ namespace simplex {
 
         sparse_matrix(manager& m): m(m) {}
         ~sparse_matrix();
+        void reset();
         
         class row {
             unsigned m_id;            

src/math/simplex/sparse_matrix_def.h

@@ -280,6 +280,16 @@ namespace simplex {
         }
     }
 
+    template<typename Ext>
+    void sparse_matrix<Ext>::reset() {
+        m_rows.reset();
+        m_dead_rows.reset();
+        m_columns.reset();
+        m_var_pos.reset();
+        m_var_pos_idx.reset();
+
+    }
+
     template<typename Ext>
     void sparse_matrix<Ext>::ensure_var(var_t v) {
         while (m_columns.size() <= v) {