From 49a903c8751b491fae68dfbb9a52645694b0e1f8 Mon Sep 17 00:00:00 2001
From: Nikolaj Bjorner <nbjorner@microsoft.com>
Date: Thu, 13 May 2021 17:23:55 -0700
Subject: [PATCH] na

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
---
 src/math/interval/mod_interval.h     |  1 +
 src/math/interval/mod_interval_def.h | 11 +++++++++++
 src/math/polysat/fixplex_def.h       |  9 ++++-----
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/src/math/interval/mod_interval.h b/src/math/interval/mod_interval.h
index a23a7bdb1..fc0f05695 100644
--- a/src/math/interval/mod_interval.h
+++ b/src/math/interval/mod_interval.h
@@ -61,6 +61,7 @@ public:
         if (is_free()) return out << "free";
         return out << "[" << pp(lo) << ", " << pp(hi) << "["; 
     }
+    Numeral closest_value(Numeral const& n) const;
 };
 
 template<typename Numeral>
diff --git a/src/math/interval/mod_interval_def.h b/src/math/interval/mod_interval_def.h
index 8062015f2..253dd7390 100644
--- a/src/math/interval/mod_interval_def.h
+++ b/src/math/interval/mod_interval_def.h
@@ -109,3 +109,14 @@ mod_interval<Numeral> mod_interval<Numeral>::operator&(mod_interval const& other
         return mod_interval::empty();
     return mod_interval(l, h);
 }
+
+template<typename Numeral>
+Numeral mod_interval<Numeral>::closest_value(Numeral const& n) const {
+    if (contains(n))
+        return n;
+    if (is_empty())
+        return n;
+    if (lo - n < n - hi)
+        return lo;
+    return hi - 1;
+}
diff --git a/src/math/polysat/fixplex_def.h b/src/math/polysat/fixplex_def.h
index e79e091c1..5bfa79687 100644
--- a/src/math/polysat/fixplex_def.h
+++ b/src/math/polysat/fixplex_def.h
@@ -157,8 +157,7 @@ namespace polysat {
         m_var_eqs.reset();
         var_t var = row2base(r);
         m_vars[var].m_is_base = false;
-        m_vars[var].lo = 0;
-        m_vars[var].hi = 0;
+        m_vars[var].set_free();
         m_rows[r.id()].m_base = null_var;
         M.del(r);
         SASSERT(M.col_begin(var) == M.col_end(var));
@@ -248,8 +247,9 @@ namespace polysat {
     lbool fixplex<Ext>::make_var_feasible(var_t x) {
         if (in_bounds(x))
             return l_true;
-        auto val = value(x);
-        numeral new_value = (lo(x) - val < val - hi(x)) ? lo(x) : hi(x) - 1;
+        if (m_vars[x].is_empty())
+            return l_false;
+        numeral new_value = m_vars[x].closest_value(value(x));
         numeral b;
         var_t y = select_pivot_core(x, new_value, b);
 
@@ -418,7 +418,6 @@ namespace polysat {
             return value - hi(v) - 1;    
     }
 
-
     /**
      * The the bounds of variable v.
      * If the current value of v, value(v), is in bounds, no further updates are made.