diff --git a/src/math/lp/CMakeLists.txt b/src/math/lp/CMakeLists.txt
index 38aaa4706..3bd1104c1 100644
--- a/src/math/lp/CMakeLists.txt
+++ b/src/math/lp/CMakeLists.txt
@@ -14,6 +14,7 @@ z3_add_component(lp
     indexed_vector.cpp
     int_branch.cpp
     int_cube.cpp
+    int_gcd_test.cpp
     int_solver.cpp
     lar_solver.cpp
     lar_core_solver.cpp
diff --git a/src/math/lp/gomory.cpp b/src/math/lp/gomory.cpp
index d8d8b48c1..7cc8e8f32 100644
--- a/src/math/lp/gomory.cpp
+++ b/src/math/lp/gomory.cpp
@@ -378,9 +378,12 @@ bool gomory::is_gomory_cut_target(const row_strip<mpq>& row) {
 int gomory::find_basic_var() {
     int result = -1;
     unsigned n = 0;
-    bool boxed = false;
     unsigned min_row_size = UINT_MAX;
+#if 0
+    bool boxed = false;
     mpq min_range;
+#endif
+
 
     // Prefer smaller row size
     // Prefer boxed to non-boxed
diff --git a/src/math/lp/int_gcd_test.cpp b/src/math/lp/int_gcd_test.cpp
new file mode 100644
index 000000000..b5a9e8c05
--- /dev/null
+++ b/src/math/lp/int_gcd_test.cpp
@@ -0,0 +1,192 @@
+/*++
+Copyright (c) 2020 Microsoft Corporation
+
+Module Name:
+
+    int_gcd_test.cpp
+
+Abstract:
+
+    Gcd_Test heuristic
+
+Author:
+    Nikolaj Bjorner (nbjorner)
+    Lev Nachmanson (levnach)
+
+Revision History:
+--*/
+
+#include "math/lp/int_solver.h"
+#include "math/lp/lar_solver.h"
+#include "math/lp/int_gcd_test.h"
+
+namespace lp {
+
+    int_gcd_test::int_gcd_test(int_solver& lia): lia(lia), lra(lia.lra) {}
+
+    lia_move int_gcd_test::operator()() {              
+        lia.settings().stats().m_gcd_calls++;
+        TRACE("int_solver", tout << "gcd-test " << lia.settings().stats().m_gcd_calls << "\n";);
+        if (gcd_test()) {
+            return lia_move::undef;
+        }
+        else {
+            lia.settings().stats().m_gcd_conflicts++;
+            TRACE("gcd_test", tout << "gcd conflict\n";);
+            return lia_move::conflict;
+        }
+    }
+
+    bool int_gcd_test::gcd_test() {
+        auto & A = lra.A_r(); // getting the matrix
+        for (unsigned i = 0; i < A.row_count(); i++)
+            if (!gcd_test_for_row(A, i)) 
+                return false;        
+        return true;
+    }
+    
+    static mpq get_denominators_lcm(const row_strip<mpq> & row) {
+        mpq r(1);
+        for  (auto & c : row) {
+            r = lcm(r, denominator(c.coeff()));
+        }
+        return r;
+    }
+    
+    bool int_gcd_test::gcd_test_for_row(static_matrix<mpq, numeric_pair<mpq>> & A, unsigned i) {
+        auto const& row = A.m_rows[i];
+        auto & lcs = lra.m_mpq_lar_core_solver;
+        unsigned basic_var = lcs.m_r_basis[i];
+        
+        if (!lia.column_is_int(basic_var) || lia.get_value(basic_var).is_int())
+            return true;
+        mpq lcm_den = get_denominators_lcm(row);
+        mpq consts(0);
+        mpq gcds(0);
+        mpq least_coeff(0);
+        bool    least_coeff_is_bounded = false;
+        unsigned j;
+        for (auto &c : A.m_rows[i]) {
+            j = c.var();
+            const mpq& a = c.coeff();
+            if (lra.column_is_fixed(j)) {
+                mpq aux = lcm_den * a;
+                consts += aux * lra.column_lower_bound(j).x;
+            }
+            else if (lra.column_is_real(j)) {
+                return true;
+            }
+            else if (gcds.is_zero()) {
+                gcds = abs(lcm_den * a);
+                least_coeff = gcds;
+                least_coeff_is_bounded = lra.column_is_bounded(j);
+            }
+            else {
+                mpq aux = abs(lcm_den * a);
+                gcds = gcd(gcds, aux);
+                if (aux < least_coeff) {
+                    least_coeff = aux;
+                    least_coeff_is_bounded = lra.column_is_bounded(j);
+                }
+                else if (least_coeff_is_bounded && aux == least_coeff) {
+                    least_coeff_is_bounded = lra.column_is_bounded(j);
+                }
+            }
+            SASSERT(gcds.is_int());
+            SASSERT(least_coeff.is_int());
+            TRACE("gcd_test_bug", tout << "coeff: " << a << ", gcds: " << gcds 
+                  << " least_coeff: " << least_coeff << " consts: " << consts << "\n";);
+            
+        }
+        
+        if (gcds.is_zero()) {
+            // All variables are fixed.
+            // This theory guarantees that the assignment satisfies each row, and
+            // fixed integer variables are assigned to integer values.
+            return true;
+        }
+        
+        if (!(consts / gcds).is_int()) {
+            TRACE("gcd_test", tout << "row failed the GCD test:\n"; lia.display_row_info(tout, i););
+            fill_explanation_from_fixed_columns(A.m_rows[i]);
+            return false;
+        }
+        
+        if (least_coeff.is_one() && !least_coeff_is_bounded) {
+            SASSERT(gcds.is_one());
+            return true;
+        }
+        
+        if (least_coeff_is_bounded) {
+            return ext_gcd_test(A.m_rows[i], least_coeff, lcm_den, consts);
+        }
+        return true;
+    }
+    
+    bool int_gcd_test::ext_gcd_test(const row_strip<mpq> & row,
+                                  mpq const & least_coeff, 
+                                  mpq const & lcm_den,
+                                  mpq const & consts) {
+        TRACE("ext_gcd_test", tout << "row = "; lra.print_row(row, tout););
+        mpq gcds(0);
+        mpq l(consts);
+        mpq u(consts);
+        
+        mpq a;
+        unsigned j;
+        for (const auto & c : row) {
+            j = c.var();
+            TRACE("ext_gcd_test", tout << "col = "; lra.m_mpq_lar_core_solver.m_r_solver.print_column_bound_info(j, tout););
+            const mpq & a = c.coeff();
+            if (lra.column_is_fixed(j))
+                continue;
+            SASSERT(!lra.column_is_real(j));
+            mpq ncoeff = lcm_den * a;
+            SASSERT(ncoeff.is_int());
+            mpq abs_ncoeff = abs(ncoeff);
+            if (abs_ncoeff == least_coeff) {
+                SASSERT(lra.column_is_bounded(j));
+                if (ncoeff.is_pos()) {
+                    // l += ncoeff * lra.column_lower_bound(j).x;
+                    l.addmul(ncoeff, lra.column_lower_bound(j).x);
+                    // u += ncoeff * lra.column_upper_bound(j).x;
+                    u.addmul(ncoeff, lra.column_upper_bound(j).x);
+                }
+                else {
+                    // l += ncoeff * upper_bound(j).get_rational();
+                    l.addmul(ncoeff, lra.column_upper_bound(j).x);
+                    // u += ncoeff * lower_bound(j).get_rational();
+                    u.addmul(ncoeff, lra.column_lower_bound(j).x);
+                }
+                lia.add_to_explanation_from_fixed_or_boxed_column(j);
+            }
+            else if (gcds.is_zero()) {
+                gcds = abs_ncoeff; 
+            }
+            else {
+                gcds = gcd(gcds, abs_ncoeff);
+            }
+            SASSERT(gcds.is_int());
+        }
+        
+        if (gcds.is_zero()) {
+            return true;
+        }
+        
+        mpq l1 = ceil(l/gcds);
+        mpq u1 = floor(u/gcds);
+        
+        if (u1 < l1) {
+            fill_explanation_from_fixed_columns(row);
+            return false;
+        }        
+        return true;
+    }
+
+    void int_gcd_test::fill_explanation_from_fixed_columns(const row_strip<mpq> & row) {
+        for (const auto & c : row) {
+            if (lra.column_is_fixed(c.var()))
+                lia.add_to_explanation_from_fixed_or_boxed_column(c.var());
+        }
+    }
+}
diff --git a/src/math/lp/int_gcd_test.h b/src/math/lp/int_gcd_test.h
new file mode 100644
index 000000000..00c97ad6f
--- /dev/null
+++ b/src/math/lp/int_gcd_test.h
@@ -0,0 +1,42 @@
+/*++
+Copyright (c) 2020 Microsoft Corporation
+
+Module Name:
+
+    int_gcd_test.h
+
+Abstract:
+
+    Gcd_Test heuristic
+
+Author:
+    Nikolaj Bjorner (nbjorner)
+    Lev Nachmanson (levnach)
+
+Revision History:
+--*/
+#pragma once
+
+#include "math/lp/lia_move.h"
+
+namespace lp {
+    class int_solver;
+    class lar_solver;
+    class int_gcd_test {
+        class int_solver& lia;
+        class lar_solver& lra;
+
+        bool gcd_test();
+        bool gcd_test_for_row(static_matrix<mpq, numeric_pair<mpq>> & A, unsigned i);
+        bool ext_gcd_test(const row_strip<mpq> & row,
+                                        mpq const & least_coeff, 
+                                        mpq const & lcm_den,
+                                        mpq const & consts);
+        void fill_explanation_from_fixed_columns(const row_strip<mpq> & row);
+
+    public:
+        int_gcd_test(int_solver& lia);
+        ~int_gcd_test() {}
+        lia_move operator()();
+    };
+}
diff --git a/src/math/lp/int_solver.cpp b/src/math/lp/int_solver.cpp
index b61a4feb4..7aa6911ef 100644
--- a/src/math/lp/int_solver.cpp
+++ b/src/math/lp/int_solver.cpp
@@ -9,10 +9,60 @@
 #include <utility>
 #include "math/lp/monic.h"
 #include "math/lp/gomory.h"
-#include "math/lp/int_cube.h"
 #include "math/lp/int_branch.h"
+#include "math/lp/int_gcd_test.h"
+#include "math/lp/int_cube.h"
 namespace lp {
 
+// this will allow to enable and disable tracking of the pivot rows
+struct check_return_helper {
+    lar_solver&      lra;
+    bool             m_track_pivoted_rows;
+    check_return_helper(lar_solver& ls) :
+        lra(ls),
+        m_track_pivoted_rows(lra.get_track_pivoted_rows())
+    {
+        TRACE("pivoted_rows", tout << "pivoted rows = " << lra.m_mpq_lar_core_solver.m_r_solver.m_pivoted_rows->size() << std::endl;);
+        lra.set_track_pivoted_rows(false);
+    }
+    ~check_return_helper() {
+        TRACE("pivoted_rows", tout << "pivoted rows = " << lra.m_mpq_lar_core_solver.m_r_solver.m_pivoted_rows->size() << std::endl;);
+        lra.set_track_pivoted_rows(m_track_pivoted_rows);
+    }
+};
+
+lia_move int_solver::check(lp::explanation * e) {
+    SASSERT(lra.ax_is_correct());
+    if (!has_inf_int()) return lia_move::sat;
+
+    m_t.clear();
+    m_k.reset();
+    m_ex = e;
+    m_ex->clear();
+    m_upper = false;
+    lia_move r = lia_move::undef;
+
+    gomory gc(*this);
+    int_cube cube(*this);
+    int_branch branch(*this);
+    int_gcd_test gcd(*this);
+
+    if (should_run_gcd_test()) r = gcd();
+
+    check_return_helper pc(lra);
+
+    if (settings().m_int_pivot_fixed_vars_from_basis)
+        lra.pivot_fixed_vars_from_basis();
+
+
+    if (r == lia_move::undef) r = patch_nbasic_columns();
+    ++m_number_of_calls;
+    if (r == lia_move::undef && should_find_cube()) r = cube();
+    if (r == lia_move::undef && should_hnf_cut()) r = hnf_cut();
+    if (r == lia_move::undef && should_gomory_cut()) r = gc(m_t, m_k, m_ex, m_upper);
+    if (r == lia_move::undef) r = branch();
+    return r;
+}
 
 std::ostream& int_solver::display_inf_rows(std::ostream& out) const {
     unsigned num = lra.A_r().column_count();
@@ -98,69 +148,19 @@ unsigned int_solver::column_count() const  {
     return lra.column_count(); 
 }
 
-// this will allow to enable and disable tracking of the pivot rows
-struct check_return_helper {
-    lar_solver&      lra;
-    bool             m_track_pivoted_rows;
-    check_return_helper(lar_solver& ls) :
-        lra(ls),
-        m_track_pivoted_rows(lra.get_track_pivoted_rows())
-    {
-        TRACE("pivoted_rows", tout << "pivoted rows = " << lra.m_mpq_lar_core_solver.m_r_solver.m_pivoted_rows->size() << std::endl;);
-        lra.set_track_pivoted_rows(false);
-    }
-    ~check_return_helper() {
-        TRACE("pivoted_rows", tout << "pivoted rows = " << lra.m_mpq_lar_core_solver.m_r_solver.m_pivoted_rows->size() << std::endl;);
-        lra.set_track_pivoted_rows(m_track_pivoted_rows);
-    }
-};
 
 bool int_solver::should_find_cube() {
     return m_number_of_calls % settings().m_int_find_cube_period == 0;
 }
 
-lia_move int_solver::find_cube() {
-    int_cube ic(*this);
-    if (should_find_cube()) {
-        return ic();
-    }
-    else {
-        return lia_move::undef;
-    }
-}
-
 bool int_solver::should_run_gcd_test() {
     return settings().m_int_run_gcd_test;    
 }
 
-lia_move int_solver::run_gcd_test() {
-    if (should_run_gcd_test()) {
-        settings().stats().m_gcd_calls++;
-        TRACE("int_solver", tout << "gcd-test " << settings().stats().m_gcd_calls << "\n";);
-        if (!gcd_test()) {
-            settings().stats().m_gcd_conflicts++;
-            TRACE("gcd_test", tout << "gcd conflict\n";);
-            return lia_move::conflict;
-        }
-    }
-    return lia_move::undef;
-}
-
 bool int_solver::should_gomory_cut() {
     return m_number_of_calls % settings().m_int_gomory_cut_period == 0;
 }
 
-lia_move int_solver::gomory_cut() {
-    TRACE("int_solver", tout << "gomory " << m_number_of_calls << "\n";);
-    gomory gc(*this);
-    if (should_gomory_cut()) {
-        return gc(m_t, m_k, m_ex, m_upper);
-    }
-    else {
-        return lia_move::undef;
-    }
-}
-
 void int_solver::try_add_term_to_A_for_hnf(unsigned i) {
     mpq rs;
     const lar_term* t = lra.terms()[i];
@@ -234,56 +234,16 @@ bool int_solver::should_hnf_cut() {
 }
 
 lia_move int_solver::hnf_cut() {
-    lia_move r = lia_move::undef;
-    if (should_hnf_cut()) {
-        r = make_hnf_cut();
-        if (r == lia_move::undef) {
-            m_hnf_cut_period *= 2;
-        }
-        else {
-            m_hnf_cut_period = settings().hnf_cut_period();
-        }
+    lia_move r = make_hnf_cut();
+    if (r == lia_move::undef) {
+        m_hnf_cut_period *= 2;
+    }
+    else {
+        m_hnf_cut_period = settings().hnf_cut_period();
     }
     return r;
 }
 
-lia_move int_solver::check(lp::explanation * e) {
-    SASSERT(lra.ax_is_correct());
-    if (!has_inf_int()) return lia_move::sat;
-
-#define CHECK_RET(fn)                                                   \
-    r = fn;                                                             \
-    if (r != lia_move::undef) { TRACE("int_solver", tout << #fn << "\n";); return r; }
-
-    m_t.clear();
-    m_k.reset();
-    m_ex = e;
-    m_ex->clear();
-    m_upper = false;
-    lia_move r;
-
-    CHECK_RET(run_gcd_test());
-
-    check_return_helper pc(lra);
-
-    if (settings().m_int_pivot_fixed_vars_from_basis)
-        lra.pivot_fixed_vars_from_basis();
-
-    CHECK_RET(patch_nbasic_columns());
-    ++m_number_of_calls;
-    CHECK_RET(find_cube());        
-    CHECK_RET(hnf_cut());    
-    CHECK_RET(gomory_cut());
-    CHECK_RET(branch_or_sat());
-    return r;
-}
-
-lia_move int_solver::branch_or_sat() {
-    int_branch b(*this);
-    return b();
-}
-
-
 void int_solver::set_value_for_nbasic_column_ignore_old_values(unsigned j, const impq & new_val) {
     lp_assert(!is_base(j));
     auto & x = lra.m_mpq_lar_core_solver.m_r_x[j];
@@ -351,166 +311,14 @@ lia_move int_solver::patch_nbasic_columns() {
     return lia_move::undef;
 }
 
-mpq get_denominators_lcm(const row_strip<mpq> & row) {
-    mpq r(1);
-    for  (auto & c : row) {
-        r = lcm(r, denominator(c.coeff()));
-    }
-    return r;
-}
-    
-bool int_solver::gcd_test_for_row(static_matrix<mpq, numeric_pair<mpq>> & A, unsigned i) {
-    auto const& row = A.m_rows[i];
-    auto & lcs = lra.m_mpq_lar_core_solver;
-    unsigned basic_var = lcs.m_r_basis[i];
-
-    if (!column_is_int(basic_var) || get_value(basic_var).is_int())
-        return true;
-    mpq lcm_den = get_denominators_lcm(row);
-    mpq consts(0);
-    mpq gcds(0);
-    mpq least_coeff(0);
-    bool    least_coeff_is_bounded = false;
-    unsigned j;
-    for (auto &c : A.m_rows[i]) {
-        j = c.var();
-        const mpq& a = c.coeff();
-        if (lra.column_is_fixed(j)) {
-            mpq aux = lcm_den * a;
-            consts += aux * lra.column_lower_bound(j).x;
-        }
-        else if (lra.column_is_real(j)) {
-            return true;
-        }
-        else if (gcds.is_zero()) {
-            gcds = abs(lcm_den * a);
-            least_coeff = gcds;
-            least_coeff_is_bounded = lra.column_is_bounded(j);
-        }
-        else {
-            mpq aux = abs(lcm_den * a);
-            gcds = gcd(gcds, aux);
-            if (aux < least_coeff) {
-                least_coeff = aux;
-                least_coeff_is_bounded = lra.column_is_bounded(j);
-            }
-            else if (least_coeff_is_bounded && aux == least_coeff) {
-                least_coeff_is_bounded = lra.column_is_bounded(j);
-            }
-        }
-        SASSERT(gcds.is_int());
-        SASSERT(least_coeff.is_int());
-        TRACE("gcd_test_bug", tout << "coeff: " << a << ", gcds: " << gcds 
-              << " least_coeff: " << least_coeff << " consts: " << consts << "\n";);
-        
-    }
-    
-    if (gcds.is_zero()) {
-        // All variables are fixed.
-        // This theory guarantees that the assignment satisfies each row, and
-        // fixed integer variables are assigned to integer values.
-        return true;
-    }
-        
-    if (!(consts / gcds).is_int()) {
-        TRACE("gcd_test", tout << "row failed the GCD test:\n"; display_row_info(tout, i););
-        fill_explanation_from_fixed_columns(A.m_rows[i]);
-        return false;
-    }
-        
-    if (least_coeff.is_one() && !least_coeff_is_bounded) {
-        SASSERT(gcds.is_one());
-        return true;
-    }
-        
-    if (least_coeff_is_bounded) {
-        return ext_gcd_test(A.m_rows[i], least_coeff, lcm_den, consts);
-    }
-    return true;
-}
-
-
+// TBD: move to gcd-test
 void int_solver::add_to_explanation_from_fixed_or_boxed_column(unsigned j) {
     constraint_index lc, uc;
     lra.get_bound_constraint_witnesses_for_column(j, lc, uc);
     m_ex->push_justification(lc);
     m_ex->push_justification(uc);
 }
-void int_solver::fill_explanation_from_fixed_columns(const row_strip<mpq> & row) {
-    for (const auto & c : row) {
-        if (!lra.column_is_fixed(c.var()))
-            continue;
-        add_to_explanation_from_fixed_or_boxed_column(c.var());
-    }
-}
-    
-bool int_solver::gcd_test() {
-    auto & A = lra.A_r(); // getting the matrix
-    for (unsigned i = 0; i < A.row_count(); i++)
-        if (!gcd_test_for_row(A, i)) 
-            return false;        
-    return true;
-}
 
-bool int_solver::ext_gcd_test(const row_strip<mpq> & row,
-                              mpq const & least_coeff, 
-                              mpq const & lcm_den,
-                              mpq const & consts) {
-    TRACE("ext_gcd_test", tout << "row = "; lra.print_row(row, tout););
-    mpq gcds(0);
-    mpq l(consts);
-    mpq u(consts);
-
-    mpq a;
-    unsigned j;
-    for (const auto & c : row) {
-        j = c.var();
-        TRACE("ext_gcd_test", tout << "col = "; lra.m_mpq_lar_core_solver.m_r_solver.print_column_bound_info(j, tout););
-        const mpq & a = c.coeff();
-        if (lra.column_is_fixed(j))
-            continue;
-        SASSERT(!lra.column_is_real(j));
-        mpq ncoeff = lcm_den * a;
-        SASSERT(ncoeff.is_int());
-        mpq abs_ncoeff = abs(ncoeff);
-        if (abs_ncoeff == least_coeff) {
-            SASSERT(lra.column_is_bounded(j));
-            if (ncoeff.is_pos()) {
-                // l += ncoeff * lra.column_lower_bound(j).x;
-                l.addmul(ncoeff, lra.column_lower_bound(j).x);
-                // u += ncoeff * lra.column_upper_bound(j).x;
-                u.addmul(ncoeff, lra.column_upper_bound(j).x);
-            }
-            else {
-                // l += ncoeff * upper_bound(j).get_rational();
-                l.addmul(ncoeff, lra.column_upper_bound(j).x);
-                // u += ncoeff * lower_bound(j).get_rational();
-                u.addmul(ncoeff, lra.column_lower_bound(j).x);
-            }
-            add_to_explanation_from_fixed_or_boxed_column(j);
-        }
-        else if (gcds.is_zero()) {
-            gcds = abs_ncoeff; 
-        }
-        else {
-            gcds = gcd(gcds, abs_ncoeff);
-        }
-        SASSERT(gcds.is_int());
-    }
-        
-    if (gcds.is_zero()) {
-        return true;
-    }
-        
-    mpq l1 = ceil(l/gcds);
-    mpq u1 = floor(u/gcds);
-        
-    if (u1 < l1) {
-        fill_explanation_from_fixed_columns(row);
-        return false;
-    }        
-    return true;
-}
 
 int_solver::int_solver(lar_solver& lar_slv) :
     lra(lar_slv),
diff --git a/src/math/lp/int_solver.h b/src/math/lp/int_solver.h
index 42de3cc2e..1cfe4a74b 100644
--- a/src/math/lp/int_solver.h
+++ b/src/math/lp/int_solver.h
@@ -38,6 +38,7 @@ class int_solver {
     friend class gomory;
     friend class int_cube;
     friend class int_branch;
+    friend class int_gcd_test;
 public:
     // fields
     lar_solver&         lra;
@@ -107,7 +108,6 @@ private:
     bool should_gomory_cut();
     bool should_hnf_cut();
 
-    lia_move branch_or_sat();
     lp_settings& settings();
     const lp_settings& settings() const;
     bool at_bound(unsigned j) const;
@@ -128,12 +128,10 @@ private:
     bool has_inf_int() const;
 public:
     bool is_term(unsigned j) const;
-    lia_move find_cube();
     unsigned column_count() const;
     bool all_columns_are_bounded() const;
     void find_feasible_solution();
     lia_move run_gcd_test();
-    lia_move gomory_cut();
     lia_move hnf_cut();
     lia_move make_hnf_cut();
     bool init_terms_for_hnf_cut();