add hook for in-processing simplification for NLA

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/math/lp/nla_core.cpp

@@ -1556,9 +1556,6 @@ lbool core::check() {
 
     if (no_effect())
         m_monomial_bounds.propagate();
-
-    if (no_effect() && improve_bounds())
-        return l_false;
 
     {
         std::function<void(void)> check1 = [&]() { if (no_effect() && run_horner) m_horner.horner_lemmas(); };
@@ -1793,35 +1790,17 @@ void core::set_use_nra_model(bool m) {
 
 void core::collect_statistics(::statistics & st) {
 }
-
-bool core::improve_bounds() {
-    return false;
-
-    uint_set seen;
-    bool bounds_improved = false;
-    auto insert = [&](lpvar v) {
-        if (seen.contains(v))
-            return;
-        seen.insert(v);
-        if (lra.improve_bound(v, false))
-            bounds_improved = true, lp_settings().stats().m_nla_bounds_improvements++;
-        if (lra.improve_bound(v, true))
-            bounds_improved = true, lp_settings().stats().m_nla_bounds_improvements++;
-    };
-    for (auto & m : m_emons) {
-        insert(m.var());
-        for (auto v : m.vars())
-            insert(v);
-    }
-    return bounds_improved;
-}
 
 void core::propagate() {
     clear();
     m_monomial_bounds.unit_propagate();
     m_monics_with_changed_bounds.reset();
 }
 
+    void core::simplify() {
+        // in-processing simplifiation can go here, such as bounds improvements.
+    }
+
 
 
 } // end of nla

src/math/lp/nla_core.h

@@ -104,8 +104,6 @@ class core {
 
     void check_weighted(unsigned sz, std::pair<unsigned, std::function<void(void)>>* checks);
     void add_bounds();
-    // try to improve bounds for variables in monomials.
-    bool improve_bounds();
 
 public:    
     // constructor
@@ -386,6 +384,8 @@ class core {
     bool  no_lemmas_hold() const;
 
     void propagate();
+
+    void simplify();
 
     lbool  test_check();
     lpvar map_to_root(lpvar) const;

src/math/lp/nla_solver.h

@@ -38,6 +38,7 @@ namespace nla {
         bool need_check();
         lbool check();
         void propagate();
+        void simplify() { m_core->simplify(); }
         lbool check_power(lpvar r, lpvar x, lpvar y);
         bool is_monic_var(lpvar) const;
         bool influences_nl_var(lpvar) const;

src/smt/theory_lra.cpp

@@ -1091,6 +1091,8 @@ class theory_lra::imp {
 
     void restart_eh() {
         m_arith_eq_adapter.restart_eh();
+        if (m_nla)
+            m_nla->simplify();
     }
 
     void relevant_eh(app* n) {