diff --git a/src/util/lp/bound_analyzer_on_row.h b/src/util/lp/bound_analyzer_on_row.h
index 3d047cd86..549c8e5ce 100644
--- a/src/util/lp/bound_analyzer_on_row.h
+++ b/src/util/lp/bound_analyzer_on_row.h
@@ -59,8 +59,6 @@ public :
     unsigned j;
     void analyze() {
         for (const auto & c : m_row) {
-            if (c.dead())
-                continue;
             if ((m_column_of_l == -2) && (m_column_of_u == -2))
                 break;
             analyze_bound_on_var_on_coeff(c.var(), c.coeff());
@@ -170,7 +168,6 @@ public :
         mpq total;
         lp_assert(is_zero(total));
         for (const auto& p : m_row) {
-            if (p.dead()) continue;
             bool str;
             total -= monoid_min(p.coeff(), p.var(), str);
             if (str)
@@ -179,7 +176,6 @@ public :
 
         
         for (const auto &p : m_row) {
-            if (p.dead()) continue;
             bool str;
             bool a_is_pos = is_pos(p.coeff());
             mpq bound = total / p.coeff() + monoid_min_no_mult(a_is_pos, p.var(), str);
@@ -197,7 +193,6 @@ public :
         mpq total;
         lp_assert(is_zero(total));
         for (const auto &p : m_row) {
-            if (p.dead()) continue;
             bool str;
             total -= monoid_max(p.coeff(), p.var(), str);
             if (str)
@@ -205,7 +200,6 @@ public :
         }
 
         for (const auto& p : m_row) {
-            if (p.dead()) continue;
             bool str;
             bool a_is_pos = is_pos(p.coeff());
             mpq bound = total / p.coeff() + monoid_max_no_mult(a_is_pos, p.var(), str);
@@ -228,7 +222,6 @@ public :
         mpq bound = -m_rs.x;
         bool strict = false;
         for (const auto& p : m_row) {
-            if (p.dead()) continue;
             j = p.var();
             if (j == static_cast<unsigned>(m_column_of_u)) {
                 u_coeff = p.coeff();
@@ -258,7 +251,6 @@ public :
         mpq bound = -m_rs.x;
         bool strict = false;
         for (const auto &p : m_row) {
-            if (p.dead()) continue;
             j = p.var();
             if (j == static_cast<unsigned>(m_column_of_l)) {
                 l_coeff = p.coeff();
diff --git a/src/util/lp/int_solver.cpp b/src/util/lp/int_solver.cpp
index 78206dc53..a77c202a0 100644
--- a/src/util/lp/int_solver.cpp
+++ b/src/util/lp/int_solver.cpp
@@ -100,7 +100,6 @@ bool int_solver::is_gomory_cut_target(const row_strip<mpq>& row) {
     // All non base variables must be at their bounds and assigned to rationals (that is, infinitesimals are not allowed).
     unsigned j;
     for (const auto & p : row) {
-        if (p.dead()) continue;
         j = p.var();
         if (is_base(j)) continue;
         if (!at_bound(j))
@@ -312,7 +311,6 @@ lia_move int_solver::mk_gomory_cut( unsigned inf_col, const row_strip<mpq> & row
     TRACE("gomory_cut",
           tout << "applying cut at:\n"; m_lar_solver->print_row(row, tout); tout << std::endl;
           for (auto & p : row) {
-              if (p.dead()) continue;
               m_lar_solver->m_mpq_lar_core_solver.m_r_solver.print_column_info(p.var(), tout);
           }
           tout << "inf_col = " << inf_col << std::endl;
@@ -327,7 +325,6 @@ lia_move int_solver::mk_gomory_cut( unsigned inf_col, const row_strip<mpq> & row
     mpq f_0  = int_solver::fractional_part(get_value(inf_col));
     mpq one_min_f_0 = 1 - f_0;
     for (const auto & p : row) {
-        if (p.dead()) continue;
         x_j = p.var();
         if (x_j == inf_col)
             continue;
@@ -356,7 +353,6 @@ lia_move int_solver::mk_gomory_cut( unsigned inf_col, const row_strip<mpq> & row
 int int_solver::find_free_var_in_gomory_row(const row_strip<mpq>& row) {
     unsigned j;
     for (const auto & p : row) {
-        if (p.dead()) continue;
         j = p.var();
         if (!is_base(j) && is_free(j))
             return static_cast<int>(j);
@@ -793,7 +789,6 @@ lia_move int_solver::patch_nbasic_columns() {
 mpq get_denominators_lcm(const row_strip<mpq> & row) {
     mpq r(1);
     for  (auto & c : row) {
-        if (c.dead()) continue;
         r = lcm(r, denominator(c.coeff()));
     }
     return r;
@@ -807,7 +802,6 @@ bool int_solver::gcd_test_for_row(static_matrix<mpq, numeric_pair<mpq>> & A, uns
     bool    least_coeff_is_bounded = false;
     unsigned j;
     for (auto &c : A.m_rows[i]) {
-        if (c.dead()) continue;
         j = c.var();
         const mpq& a = c.coeff();
         if (m_lar_solver->column_is_fixed(j)) {
@@ -873,7 +867,6 @@ void int_solver::add_to_explanation_from_fixed_or_boxed_column(unsigned j) {
 }
 void int_solver::fill_explanation_from_fixed_columns(const row_strip<mpq> & row) {
     for (const auto & c : row) {
-        if (c.dead()) continue;
         if (!m_lar_solver->column_is_fixed(c.var()))
             continue;
         add_to_explanation_from_fixed_or_boxed_column(c.var());
@@ -899,7 +892,6 @@ bool int_solver::ext_gcd_test(const row_strip<mpq> & row,
     mpq a;
     unsigned j;
     for (const auto & c : row) {
-        if (c.dead()) continue;
         j = c.var();
         const mpq & a = c.coeff();
         if (m_lar_solver->column_is_fixed(j))
@@ -1031,7 +1023,6 @@ bool int_solver::get_freedom_interval_for_column(unsigned j, bool & inf_l, impq
     lp_assert(settings().use_tableau());
     const auto & A = m_lar_solver->A_r();
     for (const auto &c : A.column(j)) {
-        if (c.dead()) continue;
         row_index = c.var();
         const mpq & a = c.coeff();
         
@@ -1162,14 +1153,12 @@ bool int_solver::at_upper(unsigned j) const {
 void int_solver::display_row_info(std::ostream & out, unsigned row_index) const  {
     auto & rslv = m_lar_solver->m_mpq_lar_core_solver.m_r_solver;
     for (const auto &c: rslv.m_A.m_rows[row_index]) {
-        if (c.dead()) continue;
         if (numeric_traits<mpq>::is_pos(c.coeff()))
             out << "+";
         out << c.coeff() << rslv.column_name(c.var()) << " ";
     }
 
     for (const auto& c: rslv.m_A.m_rows[row_index]) {
-        if (c.dead()) continue;
         rslv.print_column_bound_info(c.var(), out);
     }
     rslv.print_column_bound_info(rslv.m_basis[row_index], out);
diff --git a/src/util/lp/lar_core_solver.h b/src/util/lp/lar_core_solver.h
index 4223f5964..904550339 100644
--- a/src/util/lp/lar_core_solver.h
+++ b/src/util/lp/lar_core_solver.h
@@ -583,7 +583,7 @@ public:
         if (!m_r_solver.m_settings.use_tableau())
             return true;
         for (unsigned j : m_r_solver.m_basis) {
-            lp_assert(m_r_solver.m_A.m_columns[j].live_size() == 1);
+            lp_assert(m_r_solver.m_A.m_columns[j].size() == 1);
         }
         for (unsigned j =0; j < m_r_solver.m_basis_heading.size(); j++) {
             if (m_r_solver.m_basis_heading[j] >= 0) continue;
@@ -632,8 +632,7 @@ public:
     void create_double_matrix(static_matrix<double, double> & A) {
         for (unsigned i = 0; i < m_r_A.row_count(); i++) {
             auto & row = m_r_A.m_rows[i];
-            for (row_cell<mpq> & c : row.m_cells) {
-                if (c.dead()) continue;
+            for (row_cell<mpq> & c : row) {
                 A.add_new_element(i, c.var(), c.get_val().get_double());
             }
         }
diff --git a/src/util/lp/lar_core_solver_def.h b/src/util/lp/lar_core_solver_def.h
index c626362fc..b945b0e51 100644
--- a/src/util/lp/lar_core_solver_def.h
+++ b/src/util/lp/lar_core_solver_def.h
@@ -226,8 +226,7 @@ void lar_core_solver::fill_not_improvable_zero_sum_from_inf_row() {
     unsigned bj = m_r_basis[m_r_solver.m_inf_row_index_for_tableau];
     m_infeasible_sum_sign =  m_r_solver.inf_sign_of_column(bj);
     m_infeasible_linear_combination.clear();
-    for (auto & rc : m_r_solver.m_A.m_rows[m_r_solver.m_inf_row_index_for_tableau].m_cells) {
-        if (rc.dead()) continue;
+    for (auto & rc : m_r_solver.m_A.m_rows[m_r_solver.m_inf_row_index_for_tableau]) {
         m_infeasible_linear_combination.push_back(std::make_pair( rc.get_val(), rc.var()));
     }
 }
diff --git a/src/util/lp/lar_solver.cpp b/src/util/lp/lar_solver.cpp
index 0d8e7f70a..78bd45e94 100644
--- a/src/util/lp/lar_solver.cpp
+++ b/src/util/lp/lar_solver.cpp
@@ -162,7 +162,7 @@ void lar_solver::analyze_new_bounds_on_row_tableau(
     unsigned row_index,
     bound_propagator & bp ) {
 
-    if (A_r().m_rows[row_index].live_size() > settings().max_row_length_for_bound_propagation)
+    if (A_r().m_rows[row_index].size() > settings().max_row_length_for_bound_propagation)
         return;
     lp_assert(use_tableau());
     bound_analyzer_on_row<row_strip<mpq>>::analyze_row(A_r().m_rows[row_index],
@@ -215,7 +215,6 @@ void lar_solver::explain_implied_bound(implied_bound & ib, bound_propagator & bp
         bound_j = m_var_register.external_to_local(bound_j);
     }
     for (auto const& r : A_r().m_rows[i]) {
-        if (r.dead()) continue;
         unsigned j = r.var();
         if (j == bound_j) continue;
         mpq const& a = r.get_val();
@@ -429,7 +428,6 @@ void lar_solver::set_costs_to_zero(const lar_term& term) {
             jset.insert(j);
         else {
             for (const auto & rc : A_r().m_rows[i])
-                if (rc.alive())
                     jset.insert(rc.var());
         }
     }
@@ -640,8 +638,7 @@ void lar_solver::detect_rows_of_bound_change_column_for_nbasic_column(unsigned j
     
 void lar_solver::detect_rows_of_bound_change_column_for_nbasic_column_tableau(unsigned j) {
     for (auto & rc : m_mpq_lar_core_solver.m_r_A.m_columns[j])
-        if (rc.alive())
-            m_rows_with_changed_bounds.insert(rc.var());
+        m_rows_with_changed_bounds.insert(rc.var());
 }
 
 bool lar_solver::use_tableau() const { return m_settings.use_tableau(); }
@@ -670,7 +667,6 @@ void lar_solver::adjust_x_of_column(unsigned j) {
 bool lar_solver::row_is_correct(unsigned i) const {
     numeric_pair<mpq> r = zero_of_type<numeric_pair<mpq>>();
     for (const auto & c : A_r().m_rows[i]) {
-        if (c.dead()) continue;
         r += c.coeff() * m_mpq_lar_core_solver.m_r_x[c.var()];
     }
     return is_zero(r);
@@ -695,7 +691,6 @@ bool lar_solver::costs_are_used() const {
 void lar_solver::change_basic_columns_dependend_on_a_given_nb_column(unsigned j, const numeric_pair<mpq> & delta) {
     if (use_tableau()) {
         for (const auto & c : A_r().m_columns[j]) {
-            if (c.dead()) continue;
             unsigned bj = m_mpq_lar_core_solver.m_r_basis[c.var()];
             if (tableau_with_costs()) {
                 m_basic_columns_with_changed_cost.insert(bj);
@@ -871,7 +866,7 @@ void lar_solver::fill_last_row_of_A_r(static_matrix<mpq, numeric_pair<mpq>> & A,
     lp_assert(A.row_count() > 0);
     lp_assert(A.column_count() > 0);
     unsigned last_row = A.row_count() - 1;
-    lp_assert(A.m_rows[last_row].live_size() == 0);
+    lp_assert(A.m_rows[last_row].size() == 0);
     for (auto & t : ls->m_coeffs) {
         lp_assert(!is_zero(t.second));
         var_index j = t.first;
@@ -1332,9 +1327,8 @@ void lar_solver::make_sure_that_the_bottom_right_elem_not_zero_in_tableau(unsign
     lp_assert(A_r().row_count() == i + 1 && A_r().column_count() == j + 1);
     auto & last_column = A_r().m_columns[j];
     int non_zero_column_cell_index = -1;
-    for (unsigned k = last_column.cells_size(); k-- > 0;){
+    for (unsigned k = last_column.size(); k-- > 0;){
         auto & cc = last_column[k];
-        if (cc.dead()) continue;
         if (cc.var() == i)
             return;
         non_zero_column_cell_index = k;
@@ -1357,20 +1351,15 @@ void lar_solver::remove_last_row_and_column_from_tableau(unsigned j) {
     auto & last_row = A_r().m_rows[i];
     mpq &cost_j = m_mpq_lar_core_solver.m_r_solver.m_costs[j];
     bool cost_is_nz = !is_zero(cost_j);
-    for (unsigned k = last_row.cells_size(); k-- > 0;) {
+    for (unsigned k = last_row.size(); k-- > 0;) {
         auto &rc = last_row[k];
-        if (rc.dead()) {
-            last_row.pop();
-            continue;
-        }
         if (cost_is_nz) {
             m_mpq_lar_core_solver.m_r_solver.m_d[rc.var()] += cost_j*rc.get_val();
         }
-            
-        A_r().remove_element(rc);
+        A_r().remove_element(last_row, rc);
     }
-    lp_assert(last_row.live_size() == 0);
-    lp_assert(A_r().m_columns[j].live_size() == 0);
+    lp_assert(last_row.size() == 0);
+    lp_assert(A_r().m_columns[j].size() == 0);
     A_r().m_rows.pop_back();
     A_r().m_columns.pop_back();
 	CASSERT("check_static_matrix", A_r().is_correct());
@@ -1379,7 +1368,7 @@ void lar_solver::remove_last_row_and_column_from_tableau(unsigned j) {
 
 void lar_solver::remove_last_column_from_A() {
     // the last column has to be empty
-    lp_assert(A_r().m_columns.back().live_size() == 0);
+    lp_assert(A_r().m_columns.back().size() == 0);
     A_r().m_columns.pop_back();
 }
 
diff --git a/src/util/lp/lp_core_solver_base.h b/src/util/lp/lp_core_solver_base.h
index 00ba437d1..41b6fe31d 100644
--- a/src/util/lp/lp_core_solver_base.h
+++ b/src/util/lp/lp_core_solver_base.h
@@ -212,12 +212,10 @@ public:
         unsigned m = m_A.row_count();
         for (unsigned i = 0; i < m; i++) {
             unsigned bj = m_basis[i];
-            lp_assert(m_A.m_columns[bj].live_size() > 0);
-            if (m_A.m_columns[bj].live_size() > 1)
+            lp_assert(m_A.m_columns[bj].size() > 0);
+            if (m_A.m_columns[bj].size() > 1)
                 return true;
             for (const auto & c : m_A.m_columns[bj]) {
-                if (c.dead())
-                    continue;
                 if (m_A.get_val(c) != one_of_type<mpq>())
                     return true;
                 else
@@ -246,7 +244,6 @@ public:
             } else {
                 auto d = m_costs[j];
                 for (const auto & cc : this->m_A.m_columns[j]) {
-                    if (cc.dead()) continue;
                     d -= this->m_costs[this->m_basis[cc.var()]] * this->m_A.get_val(cc);
                 }
                 if (m_d[j] != d) {
diff --git a/src/util/lp/lp_core_solver_base_def.h b/src/util/lp/lp_core_solver_base_def.h
index 6a9af8a26..c3a0a0a00 100644
--- a/src/util/lp/lp_core_solver_base_def.h
+++ b/src/util/lp/lp_core_solver_base_def.h
@@ -104,7 +104,6 @@ pivot_to_reduced_costs_tableau(unsigned i, unsigned j) {
     if (is_zero(a))
         return;
     for (const row_cell<T> & r: m_A.m_rows[i]){
-        if (r.dead()) continue;
         if (r.var() != j)
             m_d[r.var()] -= a * r.get_val();
     }
@@ -309,8 +308,7 @@ calculate_pivot_row_when_pivot_row_of_B1_is_ready(unsigned pivot_row) {
         if (numeric_traits<T>::is_zero(pi_1)) {
             continue;
         }
-        for (auto & c : m_A.m_rows[i].m_cells) {
-            if (c.dead()) continue;
+        for (auto & c : m_A.m_rows[i]) {
             unsigned j = c.var();
             if (m_basis_heading[j] < 0) {
                 m_pivot_row.add_value_at_index_with_drop_tolerance(j, c.get_val() * pi_1);
@@ -591,10 +589,9 @@ divide_row_by_pivot(unsigned pivot_row, unsigned pivot_col) {
     lp_assert(numeric_traits<T>::precise());
     int pivot_index = -1;
     auto & row = m_A.m_rows[pivot_row];
-    unsigned size = row.cells_size();
+    unsigned size = row.size();
     for (unsigned j = 0; j < size; j++) {
         auto & c = row[j];
-        if (c.dead()) continue;
         if (c.var() == pivot_col) {
             pivot_index = static_cast<int>(j);
             break;
@@ -610,7 +607,6 @@ divide_row_by_pivot(unsigned pivot_row, unsigned pivot_col) {
     this->m_b[pivot_row] /= coeff;
     for (unsigned j = 0; j < size; j++) {
         auto & c = row[j];
-		if (c.dead()) continue;
         if (c.var() != pivot_col) {
             c.coeff() /= coeff;
         }
@@ -621,13 +617,11 @@ divide_row_by_pivot(unsigned pivot_row, unsigned pivot_col) {
 }
 template <typename T, typename X> bool lp_core_solver_base<T, X>::
 pivot_column_tableau(unsigned j, unsigned piv_row_index) {
-    m_A.compress_row_if_needed(piv_row_index);
-    if (!divide_row_by_pivot(piv_row_index, j))
+	if (!divide_row_by_pivot(piv_row_index, j))
         return false;
     auto &column = m_A.m_columns[j];
     int pivot_col_cell_index = -1;
-    for (unsigned k = 0; k < column.cells_size(); k++) {
-        if (column[k].dead()) continue;
+    for (unsigned k = 0; k < column.size(); k++) {
         if (column[k].var() == piv_row_index) {
             pivot_col_cell_index = k;
             break;
@@ -636,16 +630,18 @@ pivot_column_tableau(unsigned j, unsigned piv_row_index) {
     if (pivot_col_cell_index < 0)
         return false;
         
-    if (pivot_col_cell_index != 0)
-        m_A.swap_with_head_cell(j, pivot_col_cell_index);
+    if (pivot_col_cell_index != 0) {
+        lp_assert(column.size() > 1);
+        // swap the pivot column cell with the head cell
+        auto c = column[0];
+        column[0]  = column[pivot_col_cell_index];
+        column[pivot_col_cell_index] = c;
 
-    CASSERT("check_static_matrix", m_A.is_correct());
-    while (column.live_size() > 1) {
+        m_A.m_rows[piv_row_index][column[0].m_offset].m_offset = 0;
+        m_A.m_rows[c.var()][c.m_offset].m_offset = pivot_col_cell_index;
+    }
+    while (column.size() > 1) {
         auto & c = column.back();
-        if (c.dead()) {
-            column.pop_last_dead_cell();
-            continue;
-        }
         lp_assert(c.var() != piv_row_index);
         if(! m_A.pivot_row_to_row_given_cell(piv_row_index, c, j)) {
             return false;
@@ -653,9 +649,6 @@ pivot_column_tableau(unsigned j, unsigned piv_row_index) {
         if (m_pivoted_rows!= nullptr)
             m_pivoted_rows->insert(c.var());
     }
-    m_A.compress_column_if_needed(j);
-    lp_assert(column.live_size() == 1);
-    CASSERT("check_static_matrix", m_A.is_correct());
 
     if (m_settings.simplex_strategy() == simplex_strategy_enum::tableau_costs)
         pivot_to_reduced_costs_tableau(piv_row_index, j);
@@ -769,8 +762,7 @@ fill_reduced_costs_from_m_y_by_rows() {
     while (i--) {
         const T & y = m_y[i];
         if (is_zero(y)) continue;
-        for (row_cell<T> & c : m_A.m_rows[i].m_cells) {
-            if (c.dead()) continue;
+        for (row_cell<T> & c : m_A.m_rows[i]) {
             j = c.var();
             if (m_basis_heading[j] < 0) {
                 m_d[j] -= y * c.get_val();
@@ -969,8 +961,7 @@ template <typename T, typename X>  void lp_core_solver_base<T, X>::pivot_fixed_v
         if (get_column_type(basic_j) != column_type::fixed) continue;
         T a;
         unsigned j;
-        for (auto &c : m_A.m_rows[i].m_cells) {
-            if (c.dead()) continue;
+        for (auto &c : m_A.m_rows[i]) {
             j = c.var();
             if (j == basic_j)
                 continue;
@@ -985,8 +976,7 @@ template <typename T, typename X>  void lp_core_solver_base<T, X>::pivot_fixed_v
 template <typename T, typename X> bool lp_core_solver_base<T, X>::remove_from_basis(unsigned basic_j) {
     indexed_vector<T> w(m_basis.size()); // the buffer
     unsigned i = m_basis_heading[basic_j];
-    for (auto &c : m_A.m_rows[i].m_cells) {
-        if (c.dead()) continue;
+    for (auto &c : m_A.m_rows[i]) {
         if (c.var() == basic_j)
             continue;
         if (pivot_column_general(c.var(), basic_j, w))
diff --git a/src/util/lp/lp_primal_core_solver.h b/src/util/lp/lp_primal_core_solver.h
index faf9074f6..db92edb05 100644
--- a/src/util/lp/lp_primal_core_solver.h
+++ b/src/util/lp/lp_primal_core_solver.h
@@ -240,7 +240,6 @@ public:
     unsigned get_number_of_basic_vars_that_might_become_inf(unsigned j) const { // consider looking at the signs here: todo
         unsigned r = 0;
         for (const auto & cc : this->m_A.m_columns[j]) {
-            if (cc.dead()) continue;
             unsigned k = this->m_basis[cc.var()];
             if (this->m_column_types[k] != column_type::free_column)
                 r++;
@@ -254,7 +253,6 @@ public:
         unsigned bj = this->m_basis[i];
         bool bj_needs_to_grow = needs_to_grow(bj);
         for (const row_cell<T>& rc : this->m_A.m_rows[i]) {
-            if (rc.dead()) continue;
             if (rc.var() == bj)
                 continue;
             if (bj_needs_to_grow) {
@@ -286,9 +284,8 @@ public:
         unsigned len = 100000000;
         unsigned bj = this->m_basis[i];
         bool bj_needs_to_grow = needs_to_grow(bj);
-        for (unsigned k = 0; k < this->m_A.m_rows[i].m_cells.size(); k++) {
-            const row_cell<T>& rc = this->m_A.m_rows[i].m_cells[k];
-            if (rc.dead()) continue;
+        for (unsigned k = 0; k < this->m_A.m_rows[i].size(); k++) {
+            const row_cell<T>& rc = this->m_A.m_rows[i][k];
             unsigned j = rc.var();
             if (j == bj)
                 continue;
@@ -302,13 +299,13 @@ public:
             unsigned damage = get_number_of_basic_vars_that_might_become_inf(j);
             if (damage < num_of_non_free_basics) {
                 num_of_non_free_basics = damage;
-                len = this->m_A.m_columns[j].live_size();
+                len = this->m_A.m_columns[j].size();
                 choice = k;
                 nchoices = 1;
             } else if (damage == num_of_non_free_basics &&
-                       this->m_A.m_columns[j].live_size() <= len && (this->m_settings.random_next() % (++nchoices))) {
+                       this->m_A.m_columns[j].size() <= len && (this->m_settings.random_next() % (++nchoices))) {
                 choice = k;
-                len = this->m_A.m_columns[j].live_size();
+                len = this->m_A.m_columns[j].size();
             }
         }
         
@@ -317,7 +314,7 @@ public:
             m_inf_row_index_for_tableau = i;
             return -1;
         }
-        const row_cell<T>& rc = this->m_A.m_rows[i].m_cells[choice];
+        const row_cell<T>& rc = this->m_A.m_rows[i][choice];
         a_ent = rc.coeff();
         return rc.var();
     }
@@ -830,11 +827,11 @@ public:
         this->m_rows_nz.resize(this->m_A.row_count());
         for (unsigned i = 0; i < this->m_A.column_count(); i++) {
             if (this->m_columns_nz[i] == 0)
-                this->m_columns_nz[i] = this->m_A.m_columns[i].live_size();
+                this->m_columns_nz[i] = this->m_A.m_columns[i].size();
         }
         for (unsigned i = 0; i < this->m_A.row_count(); i++) {
          if (this->m_rows_nz[i] == 0)
-            this->m_rows_nz[i] = this->m_A.m_rows[i].live_size();
+            this->m_rows_nz[i] = this->m_A.m_rows[i].size();
         }
     }
     
@@ -864,7 +861,7 @@ public:
     unsigned solve_with_tableau();
 
     bool basis_column_is_set_correctly(unsigned j) const {
-        return this->m_A.m_columns[j].live_size() == 1;
+        return this->m_A.m_columns[j].size() == 1;
             
     }
     
@@ -884,7 +881,6 @@ public:
         lp_assert(this->m_basis_heading[j] >= 0);
         unsigned i = static_cast<unsigned>(this->m_basis_heading[j]);
         for (const row_cell<T> & rc : this->m_A.m_rows[i]) {
-            if (rc.dead()) continue;
             unsigned k = rc.var();
             if (k == j)
                 continue;
diff --git a/src/util/lp/lp_primal_core_solver_def.h b/src/util/lp/lp_primal_core_solver_def.h
index eb4a9ce1d..1e9edbd31 100644
--- a/src/util/lp/lp_primal_core_solver_def.h
+++ b/src/util/lp/lp_primal_core_solver_def.h
@@ -975,7 +975,7 @@ template <typename T, typename X>    void lp_primal_core_solver<T, X>::delete_fa
 template <typename T, typename X> void lp_primal_core_solver<T, X>::init_column_norms() {
     lp_assert(numeric_traits<T>::precise() == false);
     for (unsigned j = 0; j < this->m_n(); j++) {
-        this->m_column_norms[j] = T(static_cast<int>(this->m_A.m_columns[j].live_size() + 1)) 
+        this->m_column_norms[j] = T(static_cast<int>(this->m_A.m_columns[j].size() + 1)) 
             
             + T(static_cast<int>(this->m_settings.random_next() % 10000)) / T(100000);
     }
diff --git a/src/util/lp/lp_primal_core_solver_tableau_def.h b/src/util/lp/lp_primal_core_solver_tableau_def.h
index be28bf36f..8f9cf7ff1 100644
--- a/src/util/lp/lp_primal_core_solver_tableau_def.h
+++ b/src/util/lp/lp_primal_core_solver_tableau_def.h
@@ -266,10 +266,9 @@ template <typename T, typename X> int lp_primal_core_solver<T, X>::find_leaving_
     unsigned row_min_nz = this->m_n() + 1;
     m_leaving_candidates.clear();
     auto & col = this->m_A.m_columns[entering];
-    unsigned col_size = col.cells_size();
+    unsigned col_size = col.size();
     for (;k < col_size && unlimited; k++) {
         const column_cell & c = col[k];
-        if (c.dead()) continue;
         unsigned i = c.var();
         const T & ed = this->m_A.get_val(c);
         lp_assert(!numeric_traits<T>::is_zero(ed));
@@ -277,7 +276,7 @@ template <typename T, typename X> int lp_primal_core_solver<T, X>::find_leaving_
         limit_theta_on_basis_column(j, - ed * m_sign_of_entering_delta, t, unlimited);
         if (!unlimited) {
             m_leaving_candidates.push_back(j);
-            row_min_nz = this->m_A.m_rows[i].live_size();
+            row_min_nz = this->m_A.m_rows[i].size();
         }
     }
     if (unlimited) {
@@ -289,7 +288,6 @@ template <typename T, typename X> int lp_primal_core_solver<T, X>::find_leaving_
     X ratio;
     for (;k < col_size; k++) {
         const column_cell & c = col[k];
-        if (c.dead()) continue;
         unsigned i = c.var();
         const T & ed = this->m_A.get_val(c);
          lp_assert(!numeric_traits<T>::is_zero(ed));
@@ -297,7 +295,7 @@ template <typename T, typename X> int lp_primal_core_solver<T, X>::find_leaving_
         unlimited = true;
         limit_theta_on_basis_column(j, -ed * m_sign_of_entering_delta, ratio, unlimited);
         if (unlimited) continue;
-        unsigned i_nz = this->m_A.m_rows[i].live_size();
+        unsigned i_nz = this->m_A.m_rows[i].size();
         if (ratio < t) {
             t = ratio;
             m_leaving_candidates.clear();
@@ -306,7 +304,7 @@ template <typename T, typename X> int lp_primal_core_solver<T, X>::find_leaving_
         } else if (ratio == t && i_nz < row_min_nz) {
             m_leaving_candidates.clear();
             m_leaving_candidates.push_back(j);
-            row_min_nz = this->m_A.m_rows[i].live_size();
+            row_min_nz = this->m_A.m_rows[i].size();
         } else if (ratio == t && i_nz == row_min_nz) {
             m_leaving_candidates.push_back(j);
         }
@@ -361,7 +359,6 @@ update_x_tableau(unsigned entering, const X& delta) {
     this->add_delta_to_x_and_call_tracker(entering, delta);
     if (!this->m_using_infeas_costs) {
         for (const auto & c : this->m_A.m_columns[entering]) {
-            if (c.dead()) continue;
             unsigned i = c.var();
             this->update_x_with_delta_and_track_feasibility(this->m_basis[i], -  delta * this->m_A.get_val(c));
         }
diff --git a/src/util/lp/random_updater_def.h b/src/util/lp/random_updater_def.h
index 06cc01163..c972cc175 100644
--- a/src/util/lp/random_updater_def.h
+++ b/src/util/lp/random_updater_def.h
@@ -83,8 +83,7 @@ void random_updater::add_column_to_sets(unsigned j) {
         add_value(m_lar_solver.get_core_solver().m_r_x[j]);
     } else {
         unsigned row = m_lar_solver.get_core_solver().m_r_heading[j];
-        for (auto & row_c : m_lar_solver.get_core_solver().m_r_A.m_rows[row].m_cells) {
-            if (row_c.dead()) continue;
+        for (auto & row_c : m_lar_solver.get_core_solver().m_r_A.m_rows[row]) {
             unsigned cj = row_c.var();
             if (m_lar_solver.get_core_solver().m_r_heading[cj] < 0) {
                 m_var_set.insert(cj);
diff --git a/src/util/lp/static_matrix.cpp b/src/util/lp/static_matrix.cpp
index d0448b6c9..9d12087bb 100644
--- a/src/util/lp/static_matrix.cpp
+++ b/src/util/lp/static_matrix.cpp
@@ -30,9 +30,6 @@ Revision History:
 #include "util/lp/lar_solver.h"
 namespace lp {
 template void static_matrix<double, double>::add_columns_at_the_end(unsigned int);
-template void static_matrix<double, double>::add_new_element(unsigned i, unsigned j, const double & v);
-template void static_matrix<mpq, mpq>::add_new_element(unsigned i, unsigned j, const mpq & v);
-template void static_matrix<mpq, impq>::add_new_element(unsigned i, unsigned j, const mpq & v);
 template void static_matrix<double, double>::clear();
 #ifdef Z3DEBUG
 template bool static_matrix<double, double>::is_correct() const;
@@ -50,6 +47,7 @@ template double static_matrix<double, double>::get_min_abs_in_row(unsigned int)
 template void static_matrix<double, double>::init_empty_matrix(unsigned int, unsigned int);
 template void static_matrix<double, double>::init_row_columns(unsigned int, unsigned int);
 template static_matrix<double, double>::ref & static_matrix<double, double>::ref::operator=(double const&);
+template void static_matrix<double, double>::set(unsigned int, unsigned int, double const&);
 template static_matrix<double, double>::static_matrix(unsigned int, unsigned int);
 template void static_matrix<mpq, mpq>::add_column_to_vector(mpq const&, unsigned int, mpq*) const;
 template void static_matrix<mpq, mpq>::add_columns_at_the_end(unsigned int);
@@ -65,6 +63,7 @@ template mpq static_matrix<mpq, mpq>::get_min_abs_in_column(unsigned int) const;
 template mpq static_matrix<mpq, mpq>::get_min_abs_in_row(unsigned int) const;
 template void static_matrix<mpq, mpq>::init_row_columns(unsigned int, unsigned int);
 template static_matrix<mpq, mpq>::ref& static_matrix<mpq, mpq>::ref::operator=(mpq const&);
+template void static_matrix<mpq, mpq>::set(unsigned int, unsigned int, mpq const&);
 
 template static_matrix<mpq, mpq>::static_matrix(unsigned int, unsigned int);
 #ifdef Z3DEBUG
@@ -73,11 +72,13 @@ template bool static_matrix<mpq, numeric_pair<mpq> >::is_correct() const;
 template void static_matrix<mpq, numeric_pair<mpq> >::copy_column_to_indexed_vector(unsigned int, indexed_vector<mpq>&) const;
 template mpq static_matrix<mpq, numeric_pair<mpq> >::get_elem(unsigned int, unsigned int) const;
 template void static_matrix<mpq, numeric_pair<mpq> >::init_empty_matrix(unsigned int, unsigned int);
+template void static_matrix<mpq, numeric_pair<mpq> >::set(unsigned int, unsigned int, mpq const&);
+
 
 template bool lp::static_matrix<double, double>::pivot_row_to_row_given_cell(unsigned int, column_cell &, unsigned int);
 template bool lp::static_matrix<lp::mpq, lp::mpq>::pivot_row_to_row_given_cell(unsigned int, column_cell& , unsigned int);
 template bool lp::static_matrix<lp::mpq, lp::numeric_pair<lp::mpq> >::pivot_row_to_row_given_cell(unsigned int, column_cell&, unsigned int);
-template void lp::static_matrix<lp::mpq, lp::numeric_pair<lp::mpq> >::remove_element(lp::row_cell<lp::mpq>&);
+template void lp::static_matrix<lp::mpq, lp::numeric_pair<lp::mpq> >::remove_element(vector<lp::row_cell<lp::mpq>, true, unsigned int>&, lp::row_cell<lp::mpq>&);
 
 }
 
diff --git a/src/util/lp/static_matrix.h b/src/util/lp/static_matrix.h
index cb6af1379..bb6cdefc8 100644
--- a/src/util/lp/static_matrix.h
+++ b/src/util/lp/static_matrix.h
@@ -1,22 +1,22 @@
 /*++
-  Copyright (c) 2017 Microsoft Corporation
+Copyright (c) 2017 Microsoft Corporation
 
-  Module Name:
+Module Name:
 
-  <name>
+    <name>
 
-  Abstract:
+Abstract:
 
-  <abstract>
+    <abstract>
 
-  Author:
+Author:
 
-  Lev Nachmanson (levnach)
+    Lev Nachmanson (levnach)
 
-  Revision History:
+Revision History:
 
 
-  --*/
+--*/
 
 #pragma once
 #include "util/vector.h"
@@ -29,347 +29,31 @@
 #include <stack>
 namespace lp {
 
-class column_cell {
-    unsigned  m_i; // points to the row
-    unsigned  m_offset;  // the offset of the element in the matrix row, or the next dead cell in the column_strip
-public:
-    column_cell(unsigned  i, unsigned  offset) : m_i(i), m_offset(offset) { }
-    column_cell(unsigned  i) : m_i(i) { }
-
-    // index of of the cell row
-    unsigned  var() const {
-        lp_assert(alive());
-        return m_i;
-    }
-    unsigned  &var() {
-        return m_i;
-    }
-    unsigned  offset() const {
-        lp_assert(alive());
-        return m_offset;
-    }
-    unsigned  & offset() {
-        lp_assert(alive());
-        return m_offset;
-    }
-
-    unsigned next_dead_index() const {
-        lp_assert(dead());
-        return m_offset;
-    }
-    unsigned & next_dead_index() {
-        return m_offset;
-    }
-    
-    bool alive() const { return !dead(); }
-    bool dead() const { return m_i == static_cast<unsigned>(-1); }
-    void set_dead() { m_i = -1;}
-};
-
 template <typename T>
-class row_cell {
-    unsigned  m_j; // points to the column
-    unsigned  m_offset; // offset in column, or the next dead cell in the row_strip
-    T              m_value;
-public:
+struct row_cell {
+    unsigned m_j; // points to the column
+    unsigned m_offset; // offset in column
+    T        m_value;
     row_cell(unsigned j, unsigned offset, T const & val) : m_j(j), m_offset(offset), m_value(val) {
     }
-    row_cell(unsigned j, T const & val) : m_j(j), m_value(val) {
+    row_cell(unsigned j, unsigned offset) : m_j(j), m_offset(offset) {
     }
-
-    const T & get_val() const {
-        lp_assert(alive());
-        return m_value;
-    }
-    T & get_val() { 
-        lp_assert(alive());
-        return m_value;
-    }
-    void set_val(const T& v) {
-        lp_assert(alive());
-        m_value = v;
-    }
-    // index of the cell column
-    unsigned var() const {
-        lp_assert(alive());
-        return m_j;
-    }
-    unsigned  &var() {         
-        return m_j;
-    }
-    const T & coeff() const {
-        lp_assert(alive());
-        return m_value;
-    }
-    T & coeff() {
-        lp_assert(alive());
-        return m_value;
-    }
-    // offset in the column vector
-    unsigned  offset() const {
-        lp_assert(alive());
-        return m_offset;
-    }
-    unsigned  & offset() {
-        return m_offset;
-    }
-    unsigned next_dead_index() const {
-        lp_assert(dead());
-        return m_offset;
-    }
-    unsigned & next_dead_index() {
-        lp_assert(dead());
-        return m_offset;
-    }
-    bool alive() const { return !dead(); }
-    bool dead() const { return m_j == static_cast<unsigned>(-1); }
-    void set_dead() { m_j = static_cast<unsigned>(-1); }
+    const T & get_val() const { return m_value;}
+    T & get_val() { return m_value;}
+    const T & coeff() const { return m_value;}
+    T & coeff() { return m_value;}
+    unsigned var() const { return m_j;}
+    unsigned & var() { return m_j;}
+    unsigned offset() const { return m_offset;}
+    unsigned & offset() { return m_offset;}
+            
 };
 
+struct empty_struct {};
+typedef row_cell<empty_struct> column_cell;
+
 template <typename T>
-class row_strip {
-    unsigned m_live_size;
-    int      m_first_dead;
-public:    
-    row_strip() : m_live_size(0), m_first_dead(-1) {}
-    row_cell<T>* begin() { return m_cells.begin();}
-    const row_cell<T>* begin() const { return m_cells.begin();}
-    row_cell<T>* end() { return m_cells.end();}
-    const row_cell<T>* end() const { return m_cells.end();}
-    unsigned live_size() const { return m_live_size; } 
-    vector<row_cell<T>> m_cells;
-    unsigned cells_size() const { return m_cells.size(); }
-    const row_cell<T> & operator[](unsigned i) const { return m_cells[i]; }
-    row_cell<T> & operator[](unsigned i) { return m_cells[i];}
-
-    void skip_dead_cell(unsigned k) {
-        lp_assert(m_cells[k].dead())
-        auto * c = &m_cells[m_first_dead];
-        for (; c->next_dead_index() != k; c = &m_cells[c->next_dead_index()]);
-        lp_assert(c->next_dead_index() == k);
-        c->next_dead_index() = m_cells[k].next_dead_index();
-    }
-
-    void pop_last_dead_cell() {
-        lp_assert(m_cells.back().dead());
-        unsigned last = m_cells.size() - 1;
-        if (m_first_dead == static_cast<int>(last)) 
-            m_first_dead = m_cells.back().next_dead_index();
-        else {
-            skip_dead_cell(last);
-        }
-        m_cells.pop_back();
-    }
-
-    void pop(){
-        bool dead = m_cells.back().dead();
-        if (dead) {
-            pop_last_dead_cell();
-        } else {
-            m_live_size --;
-            m_cells.pop_back();
-        }
-    }
-    
-    bool empty() const { return m_live_size == 0; }
-
-    void delete_at(unsigned j) {
-        lp_assert(m_cells[j].alive());
-        m_live_size--;
-        if (j == m_cells.size() - 1)
-            m_cells.pop_back();
-        else {
-            auto & c = m_cells[j];
-            c.set_dead();
-            c.next_dead_index() = m_first_dead;
-            m_first_dead = j;
-        }
-        CASSERT("check_static_matrix", is_correct());
-    }
-
-    bool is_correct() const {
-        std::set<unsigned> d0;
-        std::set<unsigned> d1;
-        unsigned alive = 0;
-        for (unsigned i = 0; i < m_cells.size(); i++) {
-            if (m_cells[i].dead())
-                d0.insert(i);
-            else
-                alive ++;
-        }
-
-        if ( alive != m_live_size)
-            return false;
-        
-        for (unsigned i = m_first_dead; i != static_cast<unsigned>(-1) ; i = m_cells[i].next_dead_index())
-            d1.insert(i);
-        return d0 == d1;
-    }
-
-    row_cell<T> & add_cell(unsigned j, const T& val, unsigned & index) {
-#ifdef Z3DEBUG
-        for (const auto & c : m_cells) {
-            if (c.dead()) continue;
-            if (c.var() == j)
-                std::cout << "oops" << std::endl;
-        }
-#endif
-        if (m_first_dead != -1) {
-            auto & ret = m_cells[index = m_first_dead];
-            m_first_dead = ret.next_dead_index();
-            m_live_size++;
-            ret.var() = j;
-            ret.coeff() = val;
-            return ret;
-        }
-        lp_assert(m_live_size == m_cells.size());
-        index = m_live_size++;
-        m_cells.push_back(row_cell<T>(j, val));
-        return m_cells.back();
-    }
-
-    void shrink_to_live() {
-        m_cells.shrink(live_size());
-        m_first_dead = -1;
-    }
-};
-
-class column_strip {
-    vector<column_cell> m_cells;
-    unsigned            m_live_size;
-    int                 m_first_dead;
-public:
-    column_strip() : m_live_size(0), m_first_dead(-1) { }
-    column_cell* begin() { return m_cells.begin();}
-    const column_cell* begin() const { return m_cells.begin();}
-    column_cell* end() { return m_cells.end();}
-    const column_cell* end() const { return m_cells.end();}
-    unsigned live_size() const {
-        return m_live_size;
-    }
-
-    unsigned cells_size() const {
-        return m_cells.size();
-    }
-    
-    column_cell& back() { return m_cells.back(); }
-    void delete_at(unsigned j) {
-        lp_assert(m_cells[j].alive());
-        m_live_size--;
-        if (j == m_cells.size() - 1)
-            m_cells.pop_back();
-        else {
-            auto & c = m_cells[j];
-            c.set_dead();
-            c.next_dead_index() = m_first_dead;
-            m_first_dead = j;
-        }
-        CASSERT("check_static_matrix", is_correct());
-    }
-    
-    const column_cell& operator[] (unsigned i) const { return m_cells[i];}
-    column_cell& operator[](unsigned i) { return m_cells[i];}
-    void pop() {
-        bool dead = m_cells.back().dead();
-        if (dead) {
-            pop_last_dead_cell();
-        } else {
-            m_live_size --;
-            m_cells.pop_back();
-        }
-    }
-    void skip_dead_cell(unsigned k) {
-        lp_assert(m_cells[k].dead())
-        auto * c = &m_cells[m_first_dead];
-        for (; c->next_dead_index() != k; c = &m_cells[c->next_dead_index()]);
-        lp_assert(c->next_dead_index() == k);
-        c->next_dead_index() = m_cells[k].next_dead_index();
-    }
-    
-    void pop_last_dead_cell() {
-        lp_assert(m_cells.back().dead());
-        unsigned last = m_cells.size() - 1;
-        if (m_first_dead == static_cast<int>(last)) 
-            m_first_dead = m_cells.back().next_dead_index();
-        else {
-            skip_dead_cell(last);
-        }
-        m_cells.pop_back();
-    }
-    bool is_correct() const {
-        std::set<unsigned> d0;
-        std::set<unsigned> d1;
-        unsigned alive = 0;
-        for (unsigned i = 0; i < m_cells.size(); i++) {
-            if (m_cells[i].dead())
-                d0.insert(i);
-            else
-                alive ++;
-        }
-
-        if (alive != m_live_size)
-            return false;
-        for (unsigned i = m_first_dead; i != static_cast<unsigned>(-1) ; i = m_cells[i].next_dead_index())
-            d1.insert(i);
-        return d0 == d1;
-    }
-
-    void swap_with_head_cell(unsigned i) {
-        lp_assert(i > 0);
-        lp_assert(m_cells[i].alive());
-        column_cell head_copy = m_cells[0];
-        if (head_copy.dead()) {
-            if (m_first_dead == 0) {
-                m_first_dead = i;
-            } else {
-                column_cell * c = &m_cells[m_first_dead];
-                for (; c->next_dead_index() != 0; c = &m_cells[c->next_dead_index()]);
-                lp_assert(c->next_dead_index() == 0);
-                c->next_dead_index() = i;
-            }
-        }
-        m_cells[0] = m_cells[i];
-        m_cells[i] = head_copy;
-        CASSERT("check_static_matrix", is_correct());
-    }
-
-    column_cell & add_cell(unsigned i, unsigned & index) {
-        if (m_first_dead != -1) {
-            auto & ret = m_cells[index = m_first_dead];
-            m_first_dead = ret.next_dead_index();
-            m_live_size++;
-            ret.var() = i;
-            return ret;
-        }
-        lp_assert(m_live_size == m_cells.size());
-        index = m_live_size++;
-        m_cells.push_back(column_cell(i));
-        return m_cells.back();
-    }
-    void shrink_to_live() {
-        m_cells.shrink(live_size());
-        m_first_dead = -1;
-    }
-};
-
-template <typename A, typename B>
-void compress_cells(A& cells, vector<B>& vec_of_cells) {
-    if (2 * cells.live_size() < cells.cells_size())
-        return;
-    unsigned j = 0; // the available target for copy
-    for (unsigned i = 0; i < cells.cells_size(); i++) {
-        auto & c = cells[i];
-        if (c.dead()) continue;
-        if (i == j) {
-            j++;
-            continue;
-        }
-        vec_of_cells[c.var()][c.offset()].offset() = j;
-        cells[j++] = c;
-    }
-    cells.shrink_to_live();
-}
-
+using row_strip = vector<row_cell<T>>; 
 
 // each assignment for this matrix should be issued only once!!!
 template <typename T, typename X>
@@ -383,13 +67,13 @@ class static_matrix
         unsigned m_n;
         dim(unsigned m, unsigned n) :m_m(m), m_n(n) {}
     };
-    // fields
-    std::stack<dim>          m_stack;
+    std::stack<dim> m_stack;
 public:
-    vector<int>              m_vector_of_row_offsets;
-    indexed_vector<T>        m_work_vector;
-    vector<row_strip<T>>     m_rows;
-    vector<column_strip>     m_columns;
+    typedef vector<column_cell> column_strip;
+    vector<int> m_vector_of_row_offsets;
+    indexed_vector<T> m_work_vector;
+    vector<row_strip<T>> m_rows;
+    vector<column_strip> m_columns;
     // starting inner classes
     class ref {
         static_matrix & m_matrix;
@@ -397,9 +81,9 @@ public:
         unsigned m_col;
     public:
         ref(static_matrix & m, unsigned row, unsigned col):m_matrix(m), m_row(row), m_col(col) {}
-        ref & operator=(T const & v) { m_matrix.add_new_element( m_row, m_col, v); return *this; }
+        ref & operator=(T const & v) { m_matrix.set( m_row, m_col, v); return *this; }
 
-        ref operator=(ref & v) { m_matrix.add_new_element(m_row, m_col, v.m_matrix.get(v.m_row, v.m_col)); return *this; }
+        ref operator=(ref & v) { m_matrix.set(m_row, m_col, v.m_matrix.get(v.m_row, v.m_col)); return *this; }
 
         operator T () const { return m_matrix.get_elem(m_row, m_col); }
     };
@@ -415,7 +99,7 @@ public:
 public:
 
     const T & get_val(const column_cell & c) const {
-        return m_rows[c.var()][c.offset()].get_val();
+        return m_rows[c.var()][c.m_offset].get_val();
     }
 
     column_cell & get_column_cell(const row_cell<T> &rc) {
@@ -424,7 +108,7 @@ public:
     
     void init_row_columns(unsigned m, unsigned n);
 
-    // constructor with no parameters
+        // constructor with no parameters
     static_matrix() {}
 
     // constructor
@@ -459,11 +143,11 @@ public:
 
     void remove_last_column(unsigned j);
 
-    void remove_element(row_cell<T> & elem_to_remove);
+    void remove_element(vector<row_cell<T>> & row, row_cell<T> & elem_to_remove);
     
     void multiply_column(unsigned column, T const & alpha) {
         for (auto & t : m_columns[column]) {
-            auto & r = m_rows[t.var()].m_cells[t.offset()];
+            auto & r = m_rows[t.var()][t.offset()];
             r.coeff() *= alpha;
         }
     }
@@ -482,6 +166,8 @@ public:
         return column_cell(column, offset);
     }
 
+    void set(unsigned row, unsigned col, T const & val);
+
     ref operator()(unsigned row, unsigned col) { return ref(*this, row, col); }
 
     std::set<std::pair<unsigned, unsigned>>  get_domain();
@@ -490,8 +176,8 @@ public:
 
     T get_max_abs_in_row(unsigned row) const;
     void add_column_to_vector (const T & a, unsigned j, T * v) const {
-        for (const auto & c : m_columns[j]) {
-            v[c.var()] += a * get_val(c);
+        for (const auto & it : m_columns[j]) {
+            v[it.var()] += a * get_val(it);
         }
     }
 
@@ -504,6 +190,9 @@ public:
     void check_consistency();
 #endif
 
+
+    void cross_out_row(unsigned k);
+
     //
     void fix_row_indices_in_each_column_for_crossed_row(unsigned k);
 
@@ -514,9 +203,9 @@ public:
     T get_elem(unsigned i, unsigned j) const;
 
 
-    unsigned number_of_non_zeroes_in_column(unsigned j) const { return m_columns[j].live_size(); }
+    unsigned number_of_non_zeroes_in_column(unsigned j) const { return m_columns[j].size(); }
 
-    unsigned number_of_non_zeroes_in_row(unsigned i) const { return m_rows[i].live_size(); }
+    unsigned number_of_non_zeroes_in_row(unsigned i) const { return m_rows[i].size(); }
 
     unsigned number_of_non_zeroes() const {
         unsigned ret = 0;
@@ -549,12 +238,12 @@ public:
         m_stack.push(d);
     }
 
-    void pop_row_columns(const row_strip<T> & row) {
+    void pop_row_columns(const vector<row_cell<T>> & row) {
         for (auto & c : row) {
-            if (c.dead()) {
-                continue;
-            }
-            m_columns[c.var()].delete_at(c.offset());
+            unsigned j = c.m_j;
+            auto & col = m_columns[j];
+            lp_assert(col[col.size() - 1].var() == m_rows.size() -1 ); // todo : start here!!!!
+            col.pop_back();
         }
     }
 
@@ -580,13 +269,12 @@ public:
                 m_columns.pop_back(); // delete the last column
             m_stack.pop();
         }
-        CASSERT("check_static_matrix", is_correct());
+        lp_assert(is_correct());
     }
 
     void multiply_row(unsigned row, T const & alpha) {
-        for (auto & t : m_rows[row].m_cells) {
-            if (t.alive())
-                t.coeff() *= alpha;
+        for (auto & t : m_rows[row]) {
+            t.m_value *= alpha;
         }
     }
 
@@ -599,8 +287,8 @@ public:
     T dot_product_with_column(const vector<T> & y, unsigned j) const {
         lp_assert(j < column_count());
         T ret = numeric_traits<T>::zero();
-        for (auto & c : m_columns[j]) {
-            ret += y[c.var()] * get_val(c);
+        for (auto & it : m_columns[j]) {
+            ret += y[it.var()] * get_val(it); // get_value_of_column_cell(it);
         }
         return ret;
     }
@@ -614,20 +302,18 @@ public:
         m_rows[i] = m_rows[ii];
         m_rows[ii] = t;
         // now fix the columns
-        for (const auto & rc : m_rows[i]) {
-            if (rc.dead()) continue;
-            column_cell & cc = m_columns[rc.var()][rc.offset()];
+        for (auto & rc : m_rows[i]) {
+            column_cell & cc = m_columns[rc.m_j][rc.m_offset];
             lp_assert(cc.var() == ii);
             cc.var() = i;
         }
-        for (const auto & rc : m_rows[ii]) {
-            if (rc.dead()) continue;
-            column_cell & cc = m_columns[rc.var()][rc.offset()];
+        for (auto & rc : m_rows[ii]) {
+            column_cell & cc = m_columns[rc.m_j][rc.m_offset];
             lp_assert(cc.var() == i);
             cc.var() = ii;
         }
+    
     }
-
     void fill_last_row_with_pivoting_loop_block(unsigned j, const vector<int> & basis_heading) {
         int row_index = basis_heading[j];
         if (row_index < 0)
@@ -637,18 +323,17 @@ public:
             return;
         
         for (const auto & c : m_rows[row_index]) {
-            if (c.dead()) continue;
-            if (c.var() == j) {
+            if (c.m_j == j) {
                 continue;
             }
-            T & wv = m_work_vector.m_data[c.var()];
+            T & wv = m_work_vector.m_data[c.m_j];
             bool was_zero = is_zero(wv);
-            wv -= alpha * c.coeff();
+            wv -= alpha * c.m_value;
             if (was_zero)
-                m_work_vector.m_index.push_back(c.var());
+                m_work_vector.m_index.push_back(c.m_j);
             else {
                 if (is_zero(wv)) {
-                    m_work_vector.erase_from_index(c.var());
+                    m_work_vector.erase_from_index(c.m_j);
                 }
             }
         }
@@ -666,7 +351,7 @@ public:
         lp_assert(row_count() > 0);
         m_work_vector.resize(column_count());
         T a;
-        // we use the form -it + 1 = 0
+         // we use the form -it + 1 = 0
         m_work_vector.set_value(one_of_type<T>(), bj);
         for (auto p : row) {
             m_work_vector.set_value(-p.coeff(), p.var());
@@ -682,10 +367,10 @@ public:
         unsigned last_row = row_count() - 1;
     
         for (unsigned j : m_work_vector.m_index) {
-            add_new_element(last_row, j, m_work_vector.m_data[j]);
+            set (last_row, j, m_work_vector.m_data[j]);
         }
         lp_assert(column_count() > 0);
-        add_new_element(last_row, column_count() - 1, one_of_type<T>());
+        set(last_row, column_count() - 1, one_of_type<T>());
     }
 
     void copy_column_to_vector (unsigned j, vector<T> & v) const {
@@ -702,8 +387,7 @@ public:
         L ret = zero_of_type<L>();
         lp_assert(row < m_rows.size());
         for (auto & it : m_rows[row]) {
-            if (it.dead()) continue;
-            ret += w[it.var()] * it.coeff();
+            ret += w[it.m_j] * it.get_val();
         }
         return ret;
     }
@@ -715,8 +399,8 @@ public:
         column_cell_plus(const column_cell & c, const static_matrix& A) :
             m_c(c), m_A(A) {}
         unsigned var() const { return m_c.var(); }
-        const T & coeff() const { return m_A.m_rows[var()][m_c.offset()].get_val(); }
-        bool dead() const { return m_c.dead(); }
+        const T & coeff() const { return m_A.m_rows[var()][m_c.m_offset].get_val(); }
+        
     };
     
     struct column_container {
@@ -728,7 +412,7 @@ public:
             // fields
             const column_cell *m_c;
             const static_matrix& m_A;
-            const column_cell *m_end;
+
             //typedefs
             
             
@@ -742,19 +426,13 @@ public:
             reference operator*() const {
                 return column_cell_plus(*m_c, m_A);
             }        
-            self_type operator++() {  self_type i = *this;
-                m_c++;
-                return i;
-            }
-
-            self_type operator++(int) {
-                m_c++;
-                return *this;
-            }
+            self_type operator++() {  self_type i = *this; m_c++; return i;  }
+            self_type operator++(int) { m_c++; return *this; }
 
             const_iterator(const column_cell* it, const static_matrix& A) :
                 m_c(it),
-                m_A(A){}
+                m_A(A)
+            {}
             bool operator==(const self_type &other) const {
                 return m_c == other.m_c;
             }
@@ -772,30 +450,8 @@ public:
 
     column_container column(unsigned j) const {
         return column_container(j, *this);
-        
     }
 
-    void swap_with_head_cell(unsigned j, unsigned offset) {
-        column_strip & col = m_columns[j];
-        column_cell & head = col[0];
-        column_cell & cc   = col[offset];
-        if (head.alive()) {
-            m_rows[head.var()][head.offset()].offset() = offset;
-        }
-        lp_assert(cc.alive());
-        m_rows[cc.var()][cc.offset()].offset() = 0;
-        col.swap_with_head_cell(offset);
-    }
-
-    
-    void compress_row_if_needed(unsigned i) {
-        compress_cells(m_rows[i], m_columns);
-    }
-
-    void compress_column_if_needed(unsigned j) {
-        compress_cells(m_columns[j], m_rows);
-    }
-    
     ref_row operator[](unsigned i) const { return ref_row(*this, i);}
     typedef T coefftype;
     typedef X argtype;
diff --git a/src/util/lp/static_matrix_def.h b/src/util/lp/static_matrix_def.h
index 43c91cefa..1dcaa34f8 100644
--- a/src/util/lp/static_matrix_def.h
+++ b/src/util/lp/static_matrix_def.h
@@ -36,10 +36,8 @@ void  static_matrix<T, X>::init_row_columns(unsigned m, unsigned n) {
 
 
 template <typename T, typename X> void static_matrix<T, X>::scan_row_ii_to_offset_vector(const row_strip<T> & rvals) {
-	for (unsigned j = 0; j < rvals.cells_size(); j++) {
-		if (rvals[j].dead()) continue;
-		m_vector_of_row_offsets[rvals[j].var()] = j;
-	}
+    for (unsigned j = 0; j < rvals.size(); j++)
+        m_vector_of_row_offsets[rvals[j].var()] = j;
 }
 
 
@@ -48,39 +46,33 @@ template <typename T, typename X> bool static_matrix<T, X>::pivot_row_to_row_giv
     lp_assert(i < row_count() && ii < column_count() && i != ii);
     T alpha = -get_val(c);
     lp_assert(!is_zero(alpha));
-    compress_row_if_needed(ii);
     auto & rowii = m_rows[ii];
-    remove_element(rowii[c.offset()]);
+    remove_element(rowii, rowii[c.m_offset]);
     scan_row_ii_to_offset_vector(rowii);
-    unsigned prev_size_ii = rowii.cells_size();
+    unsigned prev_size_ii = rowii.size();
     // run over the pivot row and update row ii
-    for (const auto & iv : m_rows[i].m_cells) {
-        if (iv.dead()) continue;
+    for (const auto & iv : m_rows[i]) {
         unsigned j = iv.var();
         if (j == pivot_col) continue;
-        lp_assert(!is_zero(iv.coeff()));
-        T alv = alpha * iv.coeff();
+        T alv = alpha * iv.m_value;
+        lp_assert(!is_zero(iv.m_value));
         int j_offs = m_vector_of_row_offsets[j];
         if (j_offs == -1) { // it is a new element
             add_new_element(ii, j, alv);
         }
         else {
-            rowii[j_offs].coeff() += alv;
+            rowii[j_offs].m_value += alv;
         }
     }
     // clean the work vector
     for (unsigned k = 0; k < prev_size_ii; k++) {
-        auto & c = rowii[k];
-        if (c.dead()) continue;
-        m_vector_of_row_offsets[c.var()] = -1;
+        m_vector_of_row_offsets[rowii[k].var()] = -1;
     }
+
     // remove zeroes
-    for (unsigned k = rowii.cells_size(); k-- > 0;  ) {
-        auto & c = rowii[k];
-        if (c.dead())
-            continue;
-        if (is_zero(c.coeff())) 
-            remove_element(c);
+    for (unsigned k = rowii.size(); k-- > 0;  ) {
+        if (is_zero(rowii[k].m_value)) 
+            remove_element(rowii, rowii[k]);
     }
     return !rowii.empty();
 }
@@ -115,12 +107,12 @@ template <typename T, typename X>    void static_matrix<T, X>::init_empty_matrix
     init_row_columns(m, n);
 }
 
-template <typename T, typename X> unsigned static_matrix<T, X>::lowest_row_in_column(unsigned col) {
+template <typename T, typename X>    unsigned static_matrix<T, X>::lowest_row_in_column(unsigned col) {
+    lp_assert(col < column_count());
     column_strip & colstrip = m_columns[col];
-    lp_assert(colstrip.live_size() > 0);
+    lp_assert(colstrip.size() > 0);
     unsigned ret = 0;
-    for (const auto & t : colstrip) {
-        if (t.dead()) continue;
+    for (auto & t : colstrip) {
         if (t.var() > ret) {
             ret = t.var();
         }
@@ -147,7 +139,7 @@ template <typename T, typename X> void static_matrix<T, X>::remove_last_column(u
         auto & row = m_rows[it.var()];
         unsigned offset = row.size() - 1;
         for (auto row_it = row.rbegin(); row_it != row.rend(); row_it ++) {
-            if (row_it->var() == j) {
+            if (row_it-.var() == j) {
                 row.erase(row.begin() + offset);
                 break;
             }
@@ -158,6 +150,18 @@ template <typename T, typename X> void static_matrix<T, X>::remove_last_column(u
     m_vector_of_row_offsets.pop_back();
 }
 
+
+
+
+template <typename T, typename X>    void static_matrix<T, X>::set(unsigned row, unsigned col, T const & val) {
+    if (numeric_traits<T>::is_zero(val)) return;
+    lp_assert(row < row_count() && col < column_count());
+    auto & r = m_rows[row];
+    unsigned offs_in_cols = static_cast<unsigned>(m_columns[col].size());
+    m_columns[col].push_back(make_column_cell(row, static_cast<unsigned>(r.size())));
+    r.push_back(make_row_cell(col, offs_in_cols, val));
+}
+
 template <typename T, typename X>
 std::set<std::pair<unsigned, unsigned>>  static_matrix<T, X>::get_domain() {
     std::set<std::pair<unsigned, unsigned>> ret;
@@ -262,9 +266,50 @@ template <typename T, typename X>    void static_matrix<T, X>::check_consistency
 }
 #endif
 
+
+template <typename T, typename X>    void static_matrix<T, X>::cross_out_row(unsigned k) {
+#ifdef Z3DEBUG
+    check_consistency();
+#endif
+    cross_out_row_from_columns(k, m_rows[k]);
+    fix_row_indices_in_each_column_for_crossed_row(k);
+    m_rows.erase(m_rows.begin() + k);
+#ifdef Z3DEBUG
+    regen_domain();
+    check_consistency();
+#endif
+}
+
+
+template <typename T, typename X>    void static_matrix<T, X>::fix_row_indices_in_each_column_for_crossed_row(unsigned k) {
+    for (unsigned j = 0; j < m_columns.size(); j++) {
+        auto & col = m_columns[j];
+        for (int i = 0; i < col.size(); i++) {
+            if (col[i].var() > k) {
+                col[i].var()--;
+            }
+        }
+    }
+}
+
+template <typename T, typename X>    void static_matrix<T, X>::cross_out_row_from_columns(unsigned k, row_strip<T> & row) {
+    for (auto & t : row) {
+        cross_out_row_from_column(t.var(), k);
+    }
+}
+
+template <typename T, typename X>    void static_matrix<T, X>::cross_out_row_from_column(unsigned col, unsigned k) {
+    auto & s = m_columns[col];
+    for (unsigned i = 0; i < s.size(); i++) {
+        if (s[i].var() == k) {
+            s.erase(s.begin() + i);
+            break;
+        }
+    }
+}
+
 template <typename T, typename X>    T static_matrix<T, X>::get_elem(unsigned i, unsigned j) const { // should not be used in efficient code !!!!
     for (auto & t : m_rows[i]) {
-        if (t.dead()) continue;
         if (t.var() == j) {
             return t.get_val();
         }
@@ -297,22 +342,16 @@ template <typename T, typename X> bool static_matrix<T, X>::is_correct() const {
         auto &r = m_rows[i];
         std::unordered_set<unsigned> s;
         for (auto & rc : r) {
-            if (rc.dead()) continue;
             if (s.find(rc.var()) != s.end()) {
                 return false;
             }
             s.insert(rc.var());
             if (rc.var() >= m_columns.size())
                 return false;
-            const auto& col = m_columns[rc.var()];
-            if (col.cells_size() <= rc.offset())
+            if (rc.m_offset >= m_columns[rc.var()].size())
                 return false;
-            const auto &cc = col[rc.offset()];
-            if (cc.dead())
+            if (rc.get_val() != get_val(m_columns[rc.var()][rc.m_offset]))
                 return false;
-            if (& m_rows[cc.var()][cc.offset()] != & rc) {
-                return false;
-            }
             if (is_zero(rc.get_val())) {
                 return false;
             }
@@ -324,56 +363,51 @@ template <typename T, typename X> bool static_matrix<T, X>::is_correct() const {
         auto & c = m_columns[j];
         std::unordered_set<unsigned> s;
         for (auto & cc : c) {
-            if (cc.dead())
-                continue;
             if (s.find(cc.var()) != s.end()) {
                 return false;
             }
             s.insert(cc.var());
             if (cc.var() >= m_rows.size())
                 return false;
-            auto & rc = m_rows[cc.var()][cc.offset()];
-            if (rc.dead())
+            if (cc.m_offset >= m_rows[cc.var()].size())
                 return false;
-            if (&cc != &m_columns[rc.var()][rc.offset()])
+            if (get_val(cc) != m_rows[cc.var()][cc.m_offset].get_val())
                 return false;
         }
     }
 
-    for (auto & row: m_rows) {
-        if (! row.is_correct())
-            return false;
-    }
-    for (auto & col: m_columns) {
-        if (! col.is_correct())
-            return false;
-    }
+   
     
     return true;
 }
 
 template <typename T, typename X>
-void static_matrix<T, X>::remove_element(row_cell<T> & rc) {
-    lp_assert(rc.alive());
-    unsigned j = rc.var();
-    unsigned j_offset = rc.offset();
-    auto & col = m_columns[j];
-    column_cell & c = col[j_offset];
-    unsigned i = c.var();
-    unsigned i_offset = c.offset();
-    col.delete_at(j_offset);
-    m_rows[i].delete_at(i_offset);
-}
+void static_matrix<T, X>::remove_element(vector<row_cell<T>> & row_vals, row_cell<T> & row_el_iv) {
+    unsigned column_offset = row_el_iv.m_offset;
+    auto & column_vals = m_columns[row_el_iv.var()];
+    column_cell& cs = m_columns[row_el_iv.var()][column_offset];
+    unsigned row_offset = cs.m_offset;
+    if (column_offset != column_vals.size() - 1) {
+        auto & cc = column_vals[column_offset] = column_vals.back(); // copy from the tail
+        m_rows[cc.var()][cc.offset()].offset() = column_offset;
+    }
+    
+    if (row_offset != row_vals.size() - 1) {
+        auto & rc = row_vals[row_offset] = row_vals.back(); // copy from the tail
+        m_columns[rc.var()][rc.offset()].offset() = row_offset;
+    }
 
+    column_vals.pop_back();
+    row_vals.pop_back();
+}
 template <typename T, typename X>
-void static_matrix<T, X>::add_new_element(unsigned i, unsigned j, const T& val) {
-    auto & row = m_rows[i];
-    auto & col = m_columns[j];
-    unsigned offset_in_row, offset_in_col;
-    row_cell<T>& rc = row.add_cell(j, val, offset_in_row);
-    column_cell& cc = col.add_cell(i, offset_in_col);
-    rc.offset() = offset_in_col;
-    cc.offset() = offset_in_row;
+void static_matrix<T, X>::add_new_element(unsigned row, unsigned col, const T& val) {
+    auto & row_vals = m_rows[row];
+    auto & col_vals = m_columns[col];
+    unsigned row_el_offs = static_cast<unsigned>(row_vals.size());
+    unsigned col_el_offs = static_cast<unsigned>(col_vals.size());
+    row_vals.push_back(row_cell<T>(col, col_el_offs, val));
+    col_vals.push_back(column_cell(row, row_el_offs));
 }
 
 }