From e0b95979e633163726297c58c7fb8ac887648171 Mon Sep 17 00:00:00 2001
From: Lev Nachmanson <levnach@hotmail.com>
Date: Mon, 23 Mar 2020 15:11:57 -0700
Subject: [PATCH] detect the status change in lar_solver::add_equality()

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
---
 src/math/lp/lar_solver.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/math/lp/lar_solver.cpp b/src/math/lp/lar_solver.cpp
index 1e8a31342..72e88e97f 100644
--- a/src/math/lp/lar_solver.cpp
+++ b/src/math/lp/lar_solver.cpp
@@ -2368,6 +2368,9 @@ std::pair<constraint_index, constraint_index> lar_solver::add_equality(lpvar j,
     coeffs.push_back(std::make_pair(mpq(1),j));
     coeffs.push_back(std::make_pair(mpq(-1),k));    
     unsigned term_index = add_term(coeffs, UINT_MAX); // UINT_MAX is the external null var
+    if (get_column_value(j) != get_column_value(k))
+        set_status(lp_status::UNKNOWN);
+
     return std::pair<constraint_index, constraint_index>(
         add_var_bound(term_index, lconstraint_kind::LE, mpq(0)),
         add_var_bound(term_index, lconstraint_kind::GE, mpq(0)));