avoid big pivots

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>

src/math/lp/lp_primal_core_solver.h

@@ -280,8 +280,8 @@ public:
         // a short row produces short infeasibility explanation and benefits at least one pivot operation
         int choice = -1;
         int nchoices = 0;
-        unsigned num_of_non_free_basics = 1000000;
+        unsigned prev_damage = UINT_MAX;
-        unsigned len = 100000000;
+        unsigned len = UINT_MAX;
         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].size(); k++) {
@@ -296,14 +296,18 @@ public:
                 if (!monoid_can_increase(rc))
                     continue;
             }
-            unsigned damage = get_number_of_basic_vars_that_might_become_inf(j);
+            unsigned damage = numeric_traits<T>::is_big(rc.coeff())? prev_damage:
-            if (damage < num_of_non_free_basics) {
+                get_number_of_basic_vars_that_might_become_inf(j);
-                num_of_non_free_basics = damage;
+            if (damage < prev_damage) {
+                prev_damage = damage;
                 len = this->m_A.m_columns[j].size();
                 choice = k;
                 nchoices = 1;
-            } else if (damage == num_of_non_free_basics &&
+            } else if (damage == prev_damage
-                       this->m_A.m_columns[j].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].size();
             }

src/math/lp/numeric_pair.h

@@ -1,22 +1,22 @@
 /*++
-Copyright (c) 2017 Microsoft Corporation
+  Copyright (c) 2017 Microsoft Corporation
 
-Module Name:
+  Module Name:
 
   <name>
 
-Abstract:
+  Abstract:
 
   <abstract>
 
-Author:
+  Author:
 
   Lev Nachmanson (levnach)
 
-Revision History:
+  Revision History:
 
 
---*/
+  --*/
 #pragma once
 #define lp_for_z3
 #include <string>
@@ -27,14 +27,14 @@ Revision History:
 #include "util/sstream.h"
 #include "util/z3_exception.h"
 #else
- // include "util/numerics/mpq.h"
+// include "util/numerics/mpq.h"
- // include "util/numerics/numeric_traits.h"
+// include "util/numerics/numeric_traits.h"
 #endif
 namespace lp {
 #ifdef lp_for_z3 // rename rationals
-    typedef rational mpq;
+typedef rational mpq;
 #else
-    typedef lp::mpq mpq;
+typedef lp::mpq mpq;
 #endif
 
 
@@ -70,7 +70,7 @@ public:
 
 
 template <>  class numeric_traits<double> {
-    public:
+public:
     static bool precise() { return false; }
     static double g_zero;
     static double const &zero() { return g_zero;  }
@@ -82,11 +82,12 @@ template <>  class numeric_traits<double> {
     static double from_string(std::string const & str) { return atof(str.c_str()); }
     static bool is_pos(const double & d) {return d > 0.0;}
     static bool is_neg(const double & d) {return d < 0.0;}
-    };
+    static bool is_big(const double & d) { return false; }
+};
 
-    template<>
+template<>
-    class numeric_traits<rational> {
+class numeric_traits<rational> {
-    public:
+public:
     static bool precise() { return true; }
     static rational const & zero() { return rational::zero(); }
     static rational const & one() { return rational::one(); }
@@ -97,14 +98,14 @@ template <>  class numeric_traits<double> {
     static bool is_pos(const rational & d) {return d.is_pos();}
     static bool is_neg(const rational & d) {return d.is_neg();}
     static bool is_int(const rational & d) {return d.is_int();}
+    static bool is_big(const rational & d) {return d.is_big();}
     static mpq ceil_ratio(const mpq & a, const mpq & b) {
         return ceil(a / b);
     }
     static mpq floor_ratio(const mpq & a, const mpq & b) {
         return floor(a / b);
     }
-
+};
-    };
 #endif
 
 template <typename X, typename Y>
@@ -295,7 +296,7 @@ numeric_pair<T> operator/(const numeric_pair<T> & r, const X & a) {
 template <typename T> double get_double(const lp::numeric_pair<T> & ) { /* lp_unreachable(); */ return 0;}
 template <typename T>
 class numeric_traits<lp::numeric_pair<T>> {
-  public:
+public:
     static bool precise() { return numeric_traits<T>::precise();}
     static lp::numeric_pair<T> zero() { return lp::numeric_pair<T>(numeric_traits<T>::zero(), numeric_traits<T>::zero()); }
     static bool is_zero(const lp::numeric_pair<T> & v) { return numeric_traits<T>::is_zero(v.x) && numeric_traits<T>::is_zero(v.y); }