throttle dioph equalities

Signed-off-by: Lev Nachmanson <[email protected]>

Author: levnach

src/math/lp/dioph_eq.cpp

@@ -561,7 +561,7 @@ namespace lp {
                     return lia_move::conflict;
                 }
                 rewrite_eqs();
-                if (m_conflict_index != -1) {
+                if (m_conflict_index != UINT_MAX) {
                     lra.settings().stats().m_dio_conflicts++;
                     return lia_move::conflict;
                 }
@@ -777,18 +777,19 @@ namespace lp {
             unsigned h = -1;
             auto it = m_f.begin(); 
             while (it != m_f.end()) {
-                if (m_e_matrix.m_rows[m_eprime[*it].m_row_index].size() == 0) 
+                if (m_e_matrix.m_rows[m_eprime[*it].m_row_index].size() == 0) {
                     if (m_eprime[*it].m_c.is_zero()) {
                         it = m_f.erase(it);
                         continue;
                     } else {
                         m_conflict_index = *it;
                         return;
                     }
+                }
                 h = *it;
                 break;
             }
-            if (h == -1) return; 
+            if (h == UINT_MAX) return; 
             auto& eprime_entry = m_eprime[h];
             TRACE("dioph_eq", print_eprime_entry(h, tout););
             auto [ahk, k, k_sign] = find_minimal_abs_coeff(eprime_entry.m_row_index);

src/math/lp/int_solver.cpp

@@ -41,13 +41,17 @@ namespace lp {
         mpq                 m_k;               // the right side of the cut
         hnf_cutter          m_hnf_cutter;
         unsigned            m_hnf_cut_period;
+        unsigned            m_dioph_eq_period;
         int_gcd_test        m_gcd;
 
         bool column_is_int_inf(unsigned j) const {
             return lra.column_is_int(j) && (!lia.value_is_int(j));
         }
 
-        imp(int_solver& lia): lia(lia), lra(lia.lra), lrac(lia.lrac), m_hnf_cutter(lia), m_gcd(lia)  {} 
+        imp(int_solver& lia): lia(lia), lra(lia.lra), lrac(lia.lrac), m_hnf_cutter(lia), m_gcd(lia)  {
+            m_hnf_cut_period = settings().hnf_cut_period();
+            m_dioph_eq_period = settings().m_dioph_eq_period;
+        } 
 
         bool has_lower(unsigned j) const {
             switch (lrac.m_column_types()[j]) {
@@ -170,11 +174,14 @@ namespace lp {
 
             if (r == lia_move::conflict) {
                 de.explain(*this->m_ex);
+                m_dioph_eq_period = settings().m_dioph_eq_period;
                 return lia_move::conflict;
             } else if (r == lia_move::branch)  {
+                m_dioph_eq_period = settings().m_dioph_eq_period;
                 return lia_move::branch;
             }
 
+            m_dioph_eq_period *= 2; // the overflow is fine, maybe to try again
             return lia_move::undef;
         }
 
@@ -190,7 +197,7 @@ namespace lp {
         }
 
         bool should_solve_dioph_eq() {
-            return lia.settings().dio_eqs() && m_number_of_calls % settings().m_dioph_eq_period == 0;
+            return lia.settings().dio_eqs() && m_number_of_calls % m_dioph_eq_period == 0;
         }
 
         bool should_hnf_cut() {

src/math/lp/lp_settings.h

@@ -219,7 +219,7 @@ struct lp_settings {
     unsigned         column_number_threshold_for_using_lu_in_lar_solver = 4000;
     unsigned         m_int_gomory_cut_period = 4;
     unsigned         m_int_find_cube_period = 4;
-    unsigned         m_dioph_eq_period = 4;
+    unsigned         m_dioph_eq_period = 1;
 private:
     unsigned         m_hnf_cut_period = 4;
     bool             m_int_run_gcd_test = true;