/*++
  Copyright (c) 2016 Microsoft Corporation

  Module Name:

  theory_lra.cpp

  Abstract:

  <abstract>

  Author:

  Lev Nachmanson (levnach) 2016-25-3
  Nikolaj Bjorner (nbjorner)

  Revision History:


  --*/
#include "util/stopwatch.h"
#include "util/lp/lp_solver.h"
#include "util/lp/lp_primal_simplex.h"
#include "util/lp/lp_dual_simplex.h"
#include "util/lp/indexed_value.h"
#include "util/lp/lar_solver.h"
#include "util/nat_set.h"
#include "util/optional.h"
#include "util/lp/lp_params.hpp"
#include "util/inf_rational.h"
#include "smt/smt_theory.h"
#include "smt/smt_context.h"
#include "smt/theory_lra.h"
#include "smt/proto_model/numeral_factory.h"
#include "smt/smt_model_generator.h"
#include "smt/arith_eq_adapter.h"
#include "util/nat_set.h"
#include "util/lp/nra_solver.h"
#include "tactic/generic_model_converter.h"
#include "math/polynomial/algebraic_numbers.h"
#include "math/polynomial/polynomial.h"
#include "ast/ast_pp.h"
#include "util/cancel_eh.h"
#include "util/scoped_timer.h"

namespace lp_api {
enum bound_kind { lower_t, upper_t };

std::ostream& operator<<(std::ostream& out, bound_kind const& k) {
    switch (k) {
    case lower_t: return out << "<=";
    case upper_t: return out << ">=";
    }
    return out;
}

class bound { 
    smt::bool_var     m_bv;
    smt::theory_var  m_var;
    bool             m_is_int;
    rational         m_value;
    bound_kind       m_bound_kind;

public:
    bound(smt::bool_var bv, smt::theory_var v, bool is_int, rational const & val, bound_kind k):
        m_bv(bv),
        m_var(v),
        m_is_int(is_int),
        m_value(val),
        m_bound_kind(k) {
    }
    virtual ~bound() {}
    smt::theory_var get_var() const { return m_var; }
    smt::bool_var get_bv() const { return m_bv; }
    bound_kind get_bound_kind() const { return m_bound_kind; }
    bool is_int() const { return m_is_int; }
    rational const& get_value() const { return m_value; }
    inf_rational get_value(bool is_true) const { 
        if (is_true) return inf_rational(m_value);                         // v >= value or v <= value
        if (m_is_int) {
            SASSERT(m_value.is_int());
            if (m_bound_kind == lower_t) return inf_rational(m_value - rational::one()); // v <= value - 1
            return inf_rational(m_value + rational::one());                              // v >= value + 1
        }
        else {
            if (m_bound_kind == lower_t) return inf_rational(m_value, false);  // v <= value - epsilon
            return inf_rational(m_value, true);                                // v >= value + epsilon
        }
    } 
    virtual std::ostream& display(std::ostream& out) const {
        return out << m_value << "  " << get_bound_kind() << " v" << get_var();
    }
};

std::ostream& operator<<(std::ostream& out, bound const& b) {
    return b.display(out);
}

struct stats {
    unsigned m_assert_lower;
    unsigned m_assert_upper;
    unsigned m_add_rows;
    unsigned m_bounds_propagations;
    unsigned m_num_iterations;
    unsigned m_num_iterations_with_no_progress;
    unsigned m_need_to_solve_inf;
    unsigned m_fixed_eqs;
    unsigned m_conflicts;
    unsigned m_bound_propagations1;
    unsigned m_bound_propagations2;
    unsigned m_assert_diseq;
    unsigned m_gomory_cuts;
    stats() { reset(); }
    void reset() {
        memset(this, 0, sizeof(*this));
    }
};

typedef optional<inf_rational> opt_inf_rational;


}

namespace smt {

typedef ptr_vector<lp_api::bound> lp_bounds;
    
class theory_lra::imp {        

    struct scope {
        unsigned m_bounds_lim;
        unsigned m_asserted_qhead;            
        unsigned m_asserted_atoms_lim;
        unsigned m_underspecified_lim;
        unsigned m_var_trail_lim;
        expr*    m_not_handled;
    };

    struct delayed_atom {
        unsigned m_bv;
        bool     m_is_true;
        delayed_atom(unsigned b, bool t): m_bv(b), m_is_true(t) {}
    };

    class resource_limit : public lp::lp_resource_limit {
        imp& m_imp;
    public:
        resource_limit(imp& i): m_imp(i) { }
        virtual bool get_cancel_flag() { return m_imp.m.canceled(); }
    };


    theory_lra&          th;
    ast_manager&         m;
    theory_arith_params& m_arith_params;
    arith_util           a;
    arith_eq_adapter     m_arith_eq_adapter;
    vector<rational>     m_columns;
      

    // temporary values kept during internalization
    struct internalize_state {
        expr_ref_vector     m_terms;                     
        vector<rational>    m_coeffs;
        svector<theory_var> m_vars;
        rational            m_coeff;
        ptr_vector<expr>    m_terms_to_internalize;
        internalize_state(ast_manager& m): m_terms(m) {}
        void reset() {
            m_terms.reset();
            m_coeffs.reset();
            m_coeff.reset();
            m_vars.reset();
            m_terms_to_internalize.reset();
        }
    };
    ptr_vector<internalize_state> m_internalize_states;
    unsigned                      m_internalize_head;

    class scoped_internalize_state {
        imp& m_imp;
        internalize_state& m_st;

        internalize_state& push_internalize(imp& i) {
            if (i.m_internalize_head == i.m_internalize_states.size()) {
                i.m_internalize_states.push_back(alloc(internalize_state, i.m));
            }
            internalize_state& st = *i.m_internalize_states[i.m_internalize_head++];
            st.reset();
            return st;
        }
    public:
        scoped_internalize_state(imp& i): m_imp(i), m_st(push_internalize(i)) {}
        ~scoped_internalize_state() { --m_imp.m_internalize_head; }
        expr_ref_vector&     terms() { return m_st.m_terms; }                     
        vector<rational>&    coeffs() { return m_st.m_coeffs; }
        svector<theory_var>& vars() { return m_st.m_vars; }
        rational&            coeff() { return m_st.m_coeff; }
        ptr_vector<expr>&    terms_to_internalize() { return m_st.m_terms_to_internalize; }            
        void push(expr* e, rational c) { m_st.m_terms.push_back(e); m_st.m_coeffs.push_back(c); }
        void set_back(unsigned i) { 
            if (terms().size() == i + 1) return;
            terms()[i] = terms().back(); 
            coeffs()[i] = coeffs().back();
            terms().pop_back();
            coeffs().pop_back();
        }
    };
       
    typedef vector<std::pair<rational, lp::var_index>> var_coeffs;

    svector<lp::var_index> m_theory_var2var_index;   // translate from theory variables to lar vars
    svector<theory_var>      m_var_index2theory_var;   // reverse map from lp_solver variables to theory variables  
    svector<theory_var>      m_term_index2theory_var;   // reverse map from lp_solver variables to theory variables  
    var_coeffs               m_left_side;              // constraint left side
    mutable std::unordered_map<lp::var_index, rational> m_variable_values; // current model

    enum constraint_source {
        inequality_source,
        equality_source,
        definition_source,
        null_source
    };
    svector<constraint_source>                    m_constraint_sources;
    svector<literal>                              m_inequalities;    // asserted rows corresponding to inequality literals.
    svector<enode_pair>                           m_equalities;      // asserted rows corresponding to equalities.
    svector<theory_var>                           m_definitions;     // asserted rows corresponding to definitions

    svector<delayed_atom>  m_asserted_atoms;        
    expr*                  m_not_handled;
    ptr_vector<app>        m_underspecified;
    unsigned_vector        m_var_trail;
    vector<ptr_vector<lp_api::bound> > m_use_list;        // bounds where variables are used.

    // attributes for incremental version:
    u_map<lp_api::bound*>      m_bool_var2bound;
    vector<lp_bounds>      m_bounds;
    unsigned_vector        m_unassigned_bounds;
    unsigned_vector        m_bounds_trail;
    unsigned               m_asserted_qhead;

    svector<unsigned>       m_to_check;    // rows that should be checked for theory propagation

    svector<std::pair<theory_var, theory_var> >       m_assume_eq_candidates; 
    unsigned                                          m_assume_eq_head;

    unsigned               m_num_conflicts;

    // non-linear arithmetic
    scoped_ptr<nra::solver> m_nra;
    bool                    m_use_nra_model;
    scoped_ptr<scoped_anum> m_a1, m_a2;

    // integer arithmetic
    scoped_ptr<lp::int_solver> m_lia;


    struct var_value_eq {
        imp & m_th;
        var_value_eq(imp & th):m_th(th) {}
        bool operator()(theory_var v1, theory_var v2) const { 
            if (m_th.is_int(v1) != m_th.is_int(v2)) {
                return false;
            }
            return m_th.is_eq(v1, v2);
        }
    };
    struct var_value_hash {
        imp & m_th;
        var_value_hash(imp & th):m_th(th) {}
        unsigned operator()(theory_var v) const { 
            if (m_th.m_use_nra_model) {
                return m_th.is_int(v);
            }
            else {
                return (unsigned)std::hash<lp::mpq>()(m_th.get_value(v)); 
            }
        }
    };
    int_hashtable<var_value_hash, var_value_eq>   m_model_eqs;


    svector<scope>         m_scopes;
    lp_api::stats          m_stats;
    arith_factory*         m_factory;       
    scoped_ptr<lp::lar_solver> m_solver;
    resource_limit         m_resource_limit;
    lp_bounds              m_new_bounds;


    context& ctx() const { return th.get_context(); }
    theory_id get_id() const { return th.get_id(); }
    bool is_int(theory_var v) const {  return is_int(get_enode(v));  }
    bool is_int(enode* n) const { return a.is_int(n->get_owner()); }
    enode* get_enode(theory_var v) const { return th.get_enode(v); }
    enode* get_enode(expr* e) const { return ctx().get_enode(e); }
    expr*  get_owner(theory_var v) const { return get_enode(v)->get_owner(); }        

    void init_solver() {
        if (m_solver) return;

        reset_variable_values();
        m_theory_var2var_index.reset();
        m_solver = alloc(lp::lar_solver); 
        lp_params lp(ctx().get_params());
        m_solver->settings().set_resource_limit(m_resource_limit);
        m_solver->settings().simplex_strategy() = static_cast<lp::simplex_strategy_enum>(lp.simplex_strategy());
        m_solver->settings().bound_propagation() = BP_NONE != propagation_mode();
        m_solver->settings().m_enable_hnf = lp.enable_hnf();
        m_solver->set_track_pivoted_rows(lp.bprop_on_pivoted_rows());

        // todo : do not use m_arith_branch_cut_ratio for deciding on cheap cuts
        unsigned branch_cut_ratio = ctx().get_fparams().m_arith_branch_cut_ratio;
        m_solver->set_cut_strategy(branch_cut_ratio);

        m_solver->settings().m_int_run_gcd_test = ctx().get_fparams().m_arith_gcd_test;
        m_solver->settings().set_random_seed(ctx().get_fparams().m_random_seed);
        m_lia = alloc(lp::int_solver, m_solver.get());
    }

    void ensure_nra() {
        if (!m_nra) {
            m_nra = alloc(nra::solver, *m_solver.get(), m.limit(), ctx().get_params());
            for (auto const& _s : m_scopes) {
                (void)_s;
                m_nra->push();
            }
        }
    }


    void found_not_handled(expr* n) {
        m_not_handled = n;
        if (is_app(n) && is_underspecified(to_app(n))) {
            TRACE("arith", tout << "Unhandled: " << mk_pp(n, m) << "\n";);
            m_underspecified.push_back(to_app(n));
        }
    }

    bool is_numeral(expr* term, rational& r) {
        rational mul(1);
        do {
            if (a.is_numeral(term, r)) {
                r *= mul;
                return true;
            }
            if (a.is_uminus(term, term)) {
                mul.neg();
                continue;
            }
            if (a.is_to_real(term, term)) {
                continue;
            }                
            return false;
        }
        while (false);
        return false;
    }

    void linearize_term(expr* term, scoped_internalize_state& st) {
        st.push(term, rational::one());
        linearize(st);
    } 
        
    void linearize_ineq(expr* lhs, expr* rhs, scoped_internalize_state& st) {
        st.push(lhs, rational::one());
        st.push(rhs, rational::minus_one());
        linearize(st);
    }
        
    void linearize(scoped_internalize_state& st) { 
        expr_ref_vector & terms = st.terms();
        svector<theory_var>& vars = st.vars();
        vector<rational>& coeffs = st.coeffs();
        rational& coeff = st.coeff();
        rational r;
        expr* n1, *n2;
        unsigned index = 0;
        while (index < terms.size()) {
            SASSERT(index >= vars.size());
            expr* n = terms[index].get();
            st.terms_to_internalize().push_back(n);
            if (a.is_add(n)) {
                for (expr* arg : *to_app(n)) {
                    st.push(arg, coeffs[index]);
                }
                st.set_back(index);
            }
            else if (a.is_sub(n)) {
                unsigned sz = to_app(n)->get_num_args();
                terms[index] = to_app(n)->get_arg(0);                    
                for (unsigned i = 1; i < sz; ++i) {
                    st.push(to_app(n)->get_arg(i), -coeffs[index]);
                }
            }
            else if (a.is_mul(n, n1, n2) && is_numeral(n1, r)) {
                coeffs[index] *= r;
                terms[index] = n2;
                st.terms_to_internalize().push_back(n1);
            }
            else if (a.is_mul(n, n1, n2) && is_numeral(n2, r)) {
                coeffs[index] *= r;
                terms[index] = n1;
                st.terms_to_internalize().push_back(n2);
            }
            else if (a.is_mul(n)) {
                theory_var v;
                internalize_mul(to_app(n), v, r);
                coeffs[index] *= r;
                coeffs[vars.size()] = coeffs[index];
                vars.push_back(v);
                ++index;
            }
            else if (a.is_numeral(n, r)) {
                coeff += coeffs[index]*r;
                ++index;
            }
            else if (a.is_uminus(n, n1)) {
                coeffs[index].neg();
                terms[index] = n1;
            }
            else if (is_app(n) && a.get_family_id() == to_app(n)->get_family_id()) {
                bool is_first = !ctx().e_internalized(n);
                app* t = to_app(n);
                internalize_args(t);
                mk_enode(t);
				
                theory_var v = mk_var(n);
                coeffs[vars.size()] = coeffs[index];
                vars.push_back(v);
                ++index;
                if (!is_first) {
                    // skip recursive internalization
                }
                else if (a.is_to_int(n, n1)) {
                    if (!ctx().relevancy())
                        mk_to_int_axiom(t);
                }
                else if (a.is_to_real(n, n1)) {
                    theory_var v1 = mk_var(n1);
                    internalize_eq(v, v1);                    
                }
                else if (a.is_idiv(n, n1, n2)) {
                    if (!a.is_numeral(n2, r) || r.is_zero()) found_not_handled(n);
                    app * mod = a.mk_mod(n1, n2);
                    ctx().internalize(mod, false);
                    if (ctx().relevancy()) ctx().add_relevancy_dependency(n, mod);
                }
                else if (a.is_mod(n, n1, n2)) {
                    bool is_num = a.is_numeral(n2, r) && !r.is_zero();
                    if (!is_num) {
                        found_not_handled(n);
                    }
                    else {
                        app_ref div(a.mk_idiv(n1, n2), m);
                        mk_enode(div);
                        theory_var w = mk_var(div);
                        theory_var u = mk_var(n1);
                        // add axioms: 
                        // u = v + r*w
                        // abs(r) > v >= 0
                        assert_idiv_mod_axioms(u, v, w, r);
                    }
                    if (!ctx().relevancy() && !is_num) mk_idiv_mod_axioms(n1, n2);                    
                }
                else if (a.is_rem(n, n1, n2)) {
                    if (!a.is_numeral(n2, r) || r.is_zero()) found_not_handled(n);
                    if (!ctx().relevancy()) mk_rem_axiom(n1, n2);                    
                }
                else if (a.is_div(n, n1, n2)) {
                    if (!a.is_numeral(n2, r) || r.is_zero()) found_not_handled(n);
                    if (!ctx().relevancy()) mk_div_axiom(n1, n2);                    
                }
                else if (a.is_power(n)) {
                    found_not_handled(n);
                }
                else {
                    found_not_handled(n);
                }
            }
            else {
                if (is_app(n)) {
                    internalize_args(to_app(n));
                }
                theory_var v = mk_var(n);
                coeffs[vars.size()] = coeffs[index];
                vars.push_back(v);
                ++index;
            }
        }
        for (unsigned i = st.terms_to_internalize().size(); i-- > 0; ) {
            expr* n = st.terms_to_internalize()[i];
            if (is_app(n)) {
                mk_enode(to_app(n));
            }
        }
        st.terms_to_internalize().reset();
    }

    void internalize_args(app* t) {
        for (unsigned i = 0; reflect(t) && i < t->get_num_args(); ++i) {
            if (!ctx().e_internalized(t->get_arg(i))) {
                ctx().internalize(t->get_arg(i), false);
            }
        }
    }

    void internalize_mul(app* t, theory_var& v, rational& r) {
        SASSERT(a.is_mul(t));
        bool _has_var = has_var(t);
        if (!_has_var) {
            internalize_args(t);
            mk_enode(t);
        }
        r = rational::one();
        rational r1;
        v = mk_var(t);
        svector<lp::var_index> vars;
        ptr_vector<expr> todo;
        todo.push_back(t);
        while (!todo.empty()) {
            expr* n = todo.back();
            todo.pop_back();
            if (a.is_mul(n)) {
                for (expr* arg : *to_app(n)) {
                    todo.push_back(arg);
                }
            }
            else if (a.is_numeral(n, r1)) {
                r *= r1;
            }
            else {
                if (!ctx().e_internalized(n)) {
                    ctx().internalize(n, false);
                }
                vars.push_back(get_var_index(mk_var(n)));
            }
        }
        TRACE("arith", tout << mk_pp(t, m) << " " << _has_var << "\n";);
        if (!_has_var) {
            ensure_nra();
            m_nra->add_monomial(get_var_index(v), vars.size(), vars.c_ptr());
        }
    }

    enode * mk_enode(app * n) {
        if (ctx().e_internalized(n)) {
            return get_enode(n);
        }
        else {
            return ctx().mk_enode(n, !reflect(n), false, enable_cgc_for(n));       
        }
    }

    bool enable_cgc_for(app * n) const {
        // Congruence closure is not enabled for (+ ...) and (* ...) applications.
        return !(n->get_family_id() == get_id() && (n->get_decl_kind() == OP_ADD || n->get_decl_kind() == OP_MUL));
    }


    void mk_clause(literal l1, literal l2, unsigned num_params, parameter * params) {
        TRACE("arith", literal lits[2]; lits[0] = l1; lits[1] = l2; ctx().display_literals_verbose(tout, 2, lits); tout << "\n";);
        ctx().mk_th_axiom(get_id(), l1, l2, num_params, params);
    }

    void mk_clause(literal l1, literal l2, literal l3, unsigned num_params, parameter * params) {
        TRACE("arith", literal lits[3]; lits[0] = l1; lits[1] = l2; lits[2] = l3; ctx().display_literals_verbose(tout, 3, lits); tout << "\n";);
        ctx().mk_th_axiom(get_id(), l1, l2, l3, num_params, params);
    }

    bool is_underspecified(app* n) const {
        if (n->get_family_id() == get_id()) {
            switch (n->get_decl_kind()) {
            case OP_DIV:
            case OP_IDIV:
            case OP_REM:
            case OP_MOD:
                return true;
            default:
                break;
            }
        }
        return false;
    }

    bool reflect(app* n) const {
        return m_arith_params.m_arith_reflect || is_underspecified(n);          
    }

    bool has_var(expr* n) {
        if (!ctx().e_internalized(n)) {
            return false;
        }
        enode* e = get_enode(n);
        return th.is_attached_to_var(e);
    }

    theory_var mk_var(expr* n, bool internalize = true) {
        if (!ctx().e_internalized(n)) {
            ctx().internalize(n, false);                
        }
        enode* e = get_enode(n);
        theory_var v;
        if (!th.is_attached_to_var(e)) {
            v = th.mk_var(e);
            SASSERT(m_bounds.size() <= static_cast<unsigned>(v) || m_bounds[v].empty());
            if (m_bounds.size() <= static_cast<unsigned>(v)) {
                m_bounds.push_back(lp_bounds());
                m_unassigned_bounds.push_back(0);
            }
            ctx().attach_th_var(e, &th, v);
        }
        else {
            v = e->get_th_var(get_id());                
        }
        SASSERT(null_theory_var != v);
        return v;
    }
        
    lp::var_index get_var_index(theory_var v) {
        lp::var_index result = UINT_MAX;
        if (m_theory_var2var_index.size() > static_cast<unsigned>(v)) {
            result = m_theory_var2var_index[v];
        }
        if (result == UINT_MAX) {
            result = m_solver->add_var(v, is_int(v));
            m_theory_var2var_index.setx(v, result, UINT_MAX);
            m_var_index2theory_var.setx(result, v, UINT_MAX);
            m_var_trail.push_back(v);
        }
        return result;
    }
        
    void init_left_side(scoped_internalize_state& st) {
        SASSERT(all_zeros(m_columns));
        svector<theory_var> const& vars = st.vars();
        vector<rational> const& coeffs = st.coeffs();
        for (unsigned i = 0; i < vars.size(); ++i) {
            theory_var var = vars[i];
            rational const& coeff = coeffs[i];
            if (m_columns.size() <= static_cast<unsigned>(var)) {
                m_columns.setx(var, coeff, rational::zero());
            }
            else {
                m_columns[var] += coeff;
            }                
        }
        m_left_side.clear();
        // reset the coefficients after they have been used.
        for (unsigned i = 0; i < vars.size(); ++i) {
            theory_var var = vars[i];
            rational const& r = m_columns[var];
            if (!r.is_zero()) {
                m_left_side.push_back(std::make_pair(r, get_var_index(var)));
                m_columns[var].reset();                    
            }
        }
        SASSERT(all_zeros(m_columns));
    }
        
    bool all_zeros(vector<rational> const& v) const {
        for (rational const& r : v) {
            if (!r.is_zero()) {
                return false;
            }
        }
        return true;
    }
        
    void add_eq_constraint(lp::constraint_index index, enode* n1, enode* n2) {
        m_constraint_sources.setx(index, equality_source, null_source);
        m_equalities.setx(index, enode_pair(n1, n2), enode_pair(0, 0));
        ++m_stats.m_add_rows;
    }
        
    void add_ineq_constraint(lp::constraint_index index, literal lit) {
        m_constraint_sources.setx(index, inequality_source, null_source);
        m_inequalities.setx(index, lit, null_literal);
        ++m_stats.m_add_rows;
        TRACE("arith", m_solver->print_constraint(index, tout); tout << "\n";);
    }

    void add_def_constraint(lp::constraint_index index) {
        m_constraint_sources.setx(index, definition_source, null_source);
        m_definitions.setx(index, null_theory_var, null_theory_var);
        ++m_stats.m_add_rows;
    }
        
    void add_def_constraint(lp::constraint_index index, theory_var v) {
        m_constraint_sources.setx(index, definition_source, null_source);
        m_definitions.setx(index, v, null_theory_var);
        ++m_stats.m_add_rows;
    }
        
    void internalize_eq(theory_var v1, theory_var v2) {     
        enode* n1 = get_enode(v1);
        enode* n2 = get_enode(v2);
        app_ref term(m.mk_fresh_const("eq", a.mk_real()), m);
        scoped_internalize_state st(*this);
        st.vars().push_back(v1);
        st.vars().push_back(v2);        
        st.coeffs().push_back(rational::one());
        st.coeffs().push_back(rational::minus_one());
        theory_var z = internalize_linearized_def(term, st);      
        lp::var_index vi = get_var_index(z);
        add_def_constraint(m_solver->add_var_bound(vi, lp::LE, rational::zero()));
        add_def_constraint(m_solver->add_var_bound(vi, lp::GE, rational::zero()));
        TRACE("arith", 
              {
                  expr*  o1 = n1->get_owner();
                  expr*  o2 = n2->get_owner();                  
                  tout << "v" << v1 << " = " << "v" << v2 << ": "
                       << mk_pp(o1, m) << " = " << mk_pp(o2, m) << "\n";
              });
    }

    void del_bounds(unsigned old_size) {
        for (unsigned i = m_bounds_trail.size(); i > old_size; ) {
            --i;
            unsigned v = m_bounds_trail[i];
            lp_api::bound* b = m_bounds[v].back();
            // del_use_lists(b);
            dealloc(b);
            m_bounds[v].pop_back();                        
        }
        m_bounds_trail.shrink(old_size);
    }

    void updt_unassigned_bounds(theory_var v, int inc) {
        TRACE("arith", tout << "v" << v << " " << m_unassigned_bounds[v] << " += " << inc << "\n";);
        ctx().push_trail(vector_value_trail<smt::context, unsigned, false>(m_unassigned_bounds, v));
        m_unassigned_bounds[v] += inc;            
    }
       
    bool is_unit_var(scoped_internalize_state& st) {
        return st.coeff().is_zero() && st.vars().size() == 1 && st.coeffs()[0].is_one();
    }

    theory_var internalize_def(app* term, scoped_internalize_state& st) {
        if (ctx().e_internalized(term)) {
            IF_VERBOSE(0, verbose_stream() << "repeated term\n";);
            return mk_var(term, false);
        }
        linearize_term(term, st);
        if (is_unit_var(st)) {
            return st.vars()[0];
        }
        else {
            theory_var v = mk_var(term);
            SASSERT(null_theory_var != v);
            st.coeffs().resize(st.vars().size() + 1);
            st.coeffs()[st.vars().size()] = rational::minus_one();
            st.vars().push_back(v);
            return v;
        }
    }

    // term - v = 0
    theory_var internalize_def(app* term) {
        scoped_internalize_state st(*this);
        linearize_term(term, st);
        return internalize_linearized_def(term, st);
    }

    theory_var internalize_linearized_def(app* term, scoped_internalize_state& st) {
        if (is_unit_var(st)) {
            return st.vars()[0];
        }
        else {
            init_left_side(st);
            theory_var v = mk_var(term);
            lp::var_index vi = m_theory_var2var_index.get(v, UINT_MAX);
            TRACE("arith", tout << mk_pp(term, m) << " " << v << " " << vi << "\n";);
            if (vi == UINT_MAX) {
                vi = m_solver->add_term(m_left_side, st.coeff());
                m_theory_var2var_index.setx(v, vi, UINT_MAX);
                if (m_solver->is_term(vi)) {
                    m_term_index2theory_var.setx(m_solver->adjust_term_index(vi), v, UINT_MAX);
                }
                else {
                    m_var_index2theory_var.setx(vi, v, UINT_MAX);
                }
                m_var_trail.push_back(v);
                TRACE("arith_verbose", tout << "v" << v << " := " << mk_pp(term, m) << " slack: " << vi << " scopes: " << m_scopes.size() << "\n";
                      m_solver->print_term(m_solver->get_term(vi), tout); tout << "\n";);
            }
            rational val;
            if (a.is_numeral(term, val)) {
                m_fixed_var_table.insert(value_sort_pair(val, is_int(v)), v);
            }
            return v;
        }
    }
        

public:
    imp(theory_lra& th, ast_manager& m, theory_arith_params& ap): 
        th(th), m(m), 
        m_arith_params(ap), 
        a(m), 
        m_arith_eq_adapter(th, ap, a),            
        m_internalize_head(0),
        m_not_handled(0),
        m_asserted_qhead(0), 
        m_assume_eq_head(0),
        m_num_conflicts(0),
        m_use_nra_model(false),
        m_model_eqs(DEFAULT_HASHTABLE_INITIAL_CAPACITY, var_value_hash(*this), var_value_eq(*this)),
        m_solver(nullptr),
        m_resource_limit(*this) {
    }
        
    ~imp() {
        del_bounds(0);
        std::for_each(m_internalize_states.begin(), m_internalize_states.end(), delete_proc<internalize_state>());
    }

    void init(context* ctx) {
        init_solver();
    }
        
    void internalize_is_int(app * n) {
        SASSERT(a.is_is_int(n));
        (void) mk_enode(n);
        if (!ctx().relevancy())
            mk_is_int_axiom(n);        
    }

    bool internalize_atom(app * atom, bool gate_ctx) {
        SASSERT(!ctx().b_internalized(atom));
        bool_var bv = ctx().mk_bool_var(atom);
        ctx().set_var_theory(bv, get_id());
        expr* n1, *n2;
        rational r;
        lp_api::bound_kind k;
        theory_var v = null_theory_var;
        if (a.is_le(atom, n1, n2) && is_numeral(n2, r) && is_app(n1)) {
            v = internalize_def(to_app(n1));
            k = lp_api::upper_t;
        }
        else if (a.is_ge(atom, n1, n2) && is_numeral(n2, r) && is_app(n1)) {
            v = internalize_def(to_app(n1));
            k = lp_api::lower_t;
        }    
        else if (a.is_is_int(atom)) {
            internalize_is_int(atom);
            return true;
        }
        else {
            TRACE("arith", tout << "Could not internalize " << mk_pp(atom, m) << "\n";);
            found_not_handled(atom);
            return true;
        }
        lp_api::bound* b = alloc(lp_api::bound, bv, v, is_int(v), r, k);
        m_bounds[v].push_back(b);
        updt_unassigned_bounds(v, +1);
        m_bounds_trail.push_back(v);
        m_bool_var2bound.insert(bv, b);
        TRACE("arith_verbose", tout << "Internalized " << mk_pp(atom, m) << "\n";);
        mk_bound_axioms(*b);
        //add_use_lists(b);
        return true;
    }
        
    bool internalize_term(app * term) {
        if (ctx().e_internalized(term) && th.is_attached_to_var(ctx().get_enode(term))) {
            // skip
        }
        else {
            internalize_def(term);
        }
        return true;
    }
        
    void internalize_eq_eh(app * atom, bool_var) {
        expr* lhs = 0, *rhs = 0;
        VERIFY(m.is_eq(atom, lhs, rhs));
        enode * n1 = get_enode(lhs);
        enode * n2 = get_enode(rhs);
        if (n1->get_th_var(get_id()) != null_theory_var &&
            n2->get_th_var(get_id()) != null_theory_var &&
            n1 != n2) {
            TRACE("arith_verbose", tout << mk_pp(atom, m) << "\n";);
            m_arith_eq_adapter.mk_axioms(n1, n2);
        }
    }

    void assign_eh(bool_var v, bool is_true) {
        TRACE("arith", tout << mk_pp(ctx().bool_var2expr(v), m) << " " << (is_true?"true":"false") << "\n";);
        m_asserted_atoms.push_back(delayed_atom(v, is_true));
    }

    void new_eq_eh(theory_var v1, theory_var v2) {
        // or internalize_eq(v1, v2);
        m_arith_eq_adapter.new_eq_eh(v1, v2);            
    }

    bool use_diseqs() const {
        return true;
    }

    void new_diseq_eh(theory_var v1, theory_var v2) {
        TRACE("arith", tout << "v" << v1 << " != " << "v" << v2 << "\n";);
        ++m_stats.m_assert_diseq;
        m_arith_eq_adapter.new_diseq_eh(v1, v2);
    }

    void push_scope_eh() {
        m_scopes.push_back(scope());
        scope& s = m_scopes.back();
        s.m_bounds_lim = m_bounds_trail.size();
        s.m_asserted_qhead = m_asserted_qhead;
        s.m_asserted_atoms_lim = m_asserted_atoms.size();
        s.m_not_handled = m_not_handled;
        s.m_underspecified_lim = m_underspecified.size();
        s.m_var_trail_lim = m_var_trail.size();
        m_solver->push();
        if (m_nra) m_nra->push();
    }

    void pop_scope_eh(unsigned num_scopes) {
        if (num_scopes == 0) {
            return;
        }
        unsigned old_size = m_scopes.size() - num_scopes;
        del_bounds(m_scopes[old_size].m_bounds_lim);
        for (unsigned i = m_scopes[old_size].m_var_trail_lim; i < m_var_trail.size(); ++i) {
            lp::var_index vi = m_theory_var2var_index[m_var_trail[i]];
            if (m_solver->is_term(vi)) {
                unsigned ti = m_solver->adjust_term_index(vi);
                m_term_index2theory_var[ti] = UINT_MAX;
            }
            else if (vi < m_var_index2theory_var.size()) {
                m_var_index2theory_var[vi] = UINT_MAX;
            }
            m_theory_var2var_index[m_var_trail[i]] = UINT_MAX;
        }
        m_asserted_atoms.shrink(m_scopes[old_size].m_asserted_atoms_lim);
        m_asserted_qhead = m_scopes[old_size].m_asserted_qhead;
        m_underspecified.shrink(m_scopes[old_size].m_underspecified_lim);
        m_var_trail.shrink(m_scopes[old_size].m_var_trail_lim);
        m_not_handled = m_scopes[old_size].m_not_handled;
        m_scopes.resize(old_size);            
        m_solver->pop(num_scopes);
        // VERIFY(l_false != make_feasible());
        m_new_bounds.reset();
        m_to_check.reset();
        if (m_nra) m_nra->pop(num_scopes);
        TRACE("arith", tout << "num scopes: " << num_scopes << " new scope level: " << m_scopes.size() << "\n";);
    }

    void restart_eh() {
        m_arith_eq_adapter.restart_eh();
    }

    void relevant_eh(app* n) {
        TRACE("arith", tout << mk_pp(n, m) << "\n";);
        expr* n1, *n2;
        if (a.is_mod(n, n1, n2)) 
            mk_idiv_mod_axioms(n1, n2);
        else if (a.is_rem(n, n1, n2))
            mk_rem_axiom(n1, n2);
        else if (a.is_div(n, n1, n2)) 
            mk_div_axiom(n1, n2);
        else if (a.is_to_int(n)) 
            mk_to_int_axiom(n);
        else if (a.is_is_int(n))
            mk_is_int_axiom(n);            
    }

    //  n < 0 || rem(a, n) =  mod(a, n)
    // !n < 0 || rem(a, n) = -mod(a, n)
    void mk_rem_axiom(expr* dividend, expr* divisor) {
        expr_ref zero(a.mk_int(0), m);
        expr_ref rem(a.mk_rem(dividend, divisor), m);
        expr_ref mod(a.mk_mod(dividend, divisor), m);
        expr_ref mmod(a.mk_uminus(mod), m);
        literal dgez = mk_literal(a.mk_ge(divisor, zero));
        mk_axiom(~dgez, th.mk_eq(rem, mod,  false));
        mk_axiom( dgez, th.mk_eq(rem, mmod, false));                    
    }

    // q = 0 or q * (p div q) = p
    void mk_div_axiom(expr* p, expr* q) {
        if (a.is_zero(q)) return;
        literal eqz = th.mk_eq(q, a.mk_real(0), false);
        literal eq  = th.mk_eq(a.mk_mul(q, a.mk_div(p, q)), p, false);
        mk_axiom(eqz, eq);
    }

    // to_int (to_real x) = x
    // to_real(to_int(x)) <= x < to_real(to_int(x)) + 1
    void mk_to_int_axiom(app* n) {
        expr* x = 0, *y = 0;
        VERIFY (a.is_to_int(n, x));            
        if (a.is_to_real(x, y)) {
            mk_axiom(th.mk_eq(y, n, false));
        }
        else {
            expr_ref to_r(a.mk_to_real(n), m);
            expr_ref lo(a.mk_le(a.mk_sub(to_r, x), a.mk_real(0)), m);
            expr_ref hi(a.mk_ge(a.mk_sub(x, to_r), a.mk_real(1)), m);
            mk_axiom(mk_literal(lo));
            mk_axiom(~mk_literal(hi));
        }
    }

    // is_int(x) <=> to_real(to_int(x)) = x
    void mk_is_int_axiom(app* n) {
        expr* x = 0;
        VERIFY(a.is_is_int(n, x));
        literal eq = th.mk_eq(a.mk_to_real(a.mk_to_int(x)), x, false);
        literal is_int = ctx().get_literal(n);
        mk_axiom(~is_int, eq);
        mk_axiom(is_int, ~eq);
    }

    // create axiom for 
    //    u = v + r*w,
    ///   abs(r) > r >= 0
    void assert_idiv_mod_axioms(theory_var u, theory_var v, theory_var w, rational const& r) {
        app_ref term(m);
        term = a.mk_sub(get_enode(u)->get_owner(), 
                        a.mk_add(get_enode(v)->get_owner(),
                                 a.mk_mul(a.mk_numeral(r, true), 
                                          get_enode(w)->get_owner())));
        theory_var z = internalize_def(term);
        lp::var_index vi = get_var_index(z);
        add_def_constraint(m_solver->add_var_bound(vi, lp::GE, rational::zero()));
        add_def_constraint(m_solver->add_var_bound(vi, lp::LE, rational::zero()));
        add_def_constraint(m_solver->add_var_bound(get_var_index(v), lp::GE, rational::zero()));
        add_def_constraint(m_solver->add_var_bound(get_var_index(v), lp::LT, abs(r)));
    }

    void mk_idiv_mod_axioms(expr * p, expr * q) {
        if (a.is_zero(q)) {
            return;
        }
        // if q is zero, then idiv and mod are uninterpreted functions.
        expr_ref div(a.mk_idiv(p, q), m);
        expr_ref mod(a.mk_mod(p, q), m);
        expr_ref zero(a.mk_int(0), m);
        literal q_ge_0     = mk_literal(a.mk_ge(q, zero));
        literal q_le_0     = mk_literal(a.mk_le(q, zero));
        //            literal eqz        = th.mk_eq(q, zero, false);
        literal eq         = th.mk_eq(a.mk_add(a.mk_mul(q, div), mod), p, false);
        literal mod_ge_0   = mk_literal(a.mk_ge(mod, zero));
        // q >= 0 or p = (p mod q) + q * (p div q)
        // q <= 0 or p = (p mod q) + q * (p div q)
        // q >= 0 or (p mod q) >= 0
        // q <= 0 or (p mod q) >= 0
        // q <= 0 or (p mod q) <  q
        // q >= 0 or (p mod q) < -q
        // enable_trace("mk_bool_var");
        mk_axiom(q_ge_0, eq);
        mk_axiom(q_le_0, eq);
        mk_axiom(q_ge_0, mod_ge_0);
        mk_axiom(q_le_0, mod_ge_0);
        mk_axiom(q_le_0, ~mk_literal(a.mk_ge(a.mk_sub(mod, q), zero)));
        mk_axiom(q_ge_0, ~mk_literal(a.mk_ge(a.mk_add(mod, q), zero)));
        rational k;
        if (m_arith_params.m_arith_enum_const_mod && a.is_numeral(q, k) && 
            k.is_pos() && k < rational(8)) {
            unsigned _k = k.get_unsigned();
            literal_buffer lits;
            for (unsigned j = 0; j < _k; ++j) {
                literal mod_j = th.mk_eq(mod, a.mk_int(j), false);
                lits.push_back(mod_j);
                ctx().mark_as_relevant(mod_j);
            }
            ctx().mk_th_axiom(get_id(), lits.size(), lits.begin());                
        }            
    }

    void mk_axiom(literal l) {
        ctx().mk_th_axiom(get_id(), false_literal, l);
        if (ctx().relevancy()) {
            ctx().mark_as_relevant(l);
        }
    }

    void mk_axiom(literal l1, literal l2) {
        if (l1 == false_literal) {
            mk_axiom(l2);
            return;
        }
        ctx().mk_th_axiom(get_id(), l1, l2);
        if (ctx().relevancy()) {
            ctx().mark_as_relevant(l1);
            ctx().add_rel_watch(~l1, ctx().bool_var2expr(l2.var()));
        }
    }

    void mk_axiom(literal l1, literal l2, literal l3) {
        ctx().mk_th_axiom(get_id(), l1, l2, l3);
        if (ctx().relevancy()) {
            ctx().mark_as_relevant(l1);
            ctx().add_rel_watch(~l1, ctx().bool_var2expr(l2.var()));
            ctx().add_rel_watch(~l2, ctx().bool_var2expr(l3.var()));
        }
    }

    literal mk_literal(expr* e) {
        expr_ref pinned(e, m);
        TRACE("mk_bool_var", tout << pinned << " " << pinned->get_id() << "\n";);
        if (!ctx().e_internalized(e)) {
            ctx().internalize(e, false);
        }
        return ctx().get_literal(e);
    }


    void init_search_eh() {
        m_arith_eq_adapter.init_search_eh();
        m_num_conflicts = 0;
    }

    bool can_get_value(theory_var v) const {
        return 
            (v != null_theory_var) &&
            (v < static_cast<theory_var>(m_theory_var2var_index.size())) && 
            (UINT_MAX != m_theory_var2var_index[v]) &&
            (!m_variable_values.empty() || m_solver->is_term(m_theory_var2var_index[v]));
    }

    bool can_get_bound(theory_var v) const {
        return 
            (v != null_theory_var) &&
            (v < static_cast<theory_var>(m_theory_var2var_index.size())) && 
            (UINT_MAX != m_theory_var2var_index[v]);
    }

        
    bool can_get_ivalue(theory_var v) const {
        if (v == null_theory_var || (v >= static_cast<theory_var>(m_theory_var2var_index.size())))
            return false;
        return m_solver->var_is_registered(m_theory_var2var_index[v]);
    }

    mutable vector<std::pair<lp::var_index, rational>> m_todo_terms;
 
    lp::impq get_ivalue(theory_var v) const {
        SASSERT(can_get_ivalue(v));
        lp::var_index vi = m_theory_var2var_index[v];
        if (!m_solver->is_term(vi))
            return m_solver->get_column_value(vi);
        m_todo_terms.push_back(std::make_pair(vi, rational::one()));
        lp::impq result(0);
        while (!m_todo_terms.empty()) {
            vi = m_todo_terms.back().first;
            rational coeff = m_todo_terms.back().second;
            m_todo_terms.pop_back();
            if (m_solver->is_term(vi)) {
                const lp::lar_term& term = m_solver->get_term(vi);
                result += term.m_v * coeff;
                for (const auto & i:  term) {
                    m_todo_terms.push_back(std::make_pair(i.var(), coeff * i.coeff()));
                }                    
            }
            else {
                result += m_solver->get_column_value(vi) * coeff;
            }
        }
        return result;
    }
        
    rational get_value(theory_var v) const {
        
        if (v == null_theory_var || 
            v >= static_cast<theory_var>(m_theory_var2var_index.size())) {
            TRACE("arith", tout << "Variable v" << v << " not internalized\n";);
            return rational::zero();
        }
            
        lp::var_index vi = m_theory_var2var_index[v];
        if (m_variable_values.count(vi) > 0)
            return m_variable_values[vi];
        
        if (!m_solver->is_term(vi)) {
            TRACE("arith", tout << "not a term v" << v << "\n";);
            return rational::zero();
        }
        
        m_todo_terms.push_back(std::make_pair(vi, rational::one()));
        rational result(0);
        while (!m_todo_terms.empty()) {
            lp::var_index wi = m_todo_terms.back().first;
            rational coeff = m_todo_terms.back().second;
            m_todo_terms.pop_back();
            if (m_solver->is_term(wi)) {
                const lp::lar_term& term = m_solver->get_term(wi);
                result += term.m_v * coeff;
                for (const auto & i : term.m_coeffs) {
                    if (m_variable_values.count(i.first) > 0) {
                        result += m_variable_values[i.first] * coeff * i.second;
                    }
                    else {
                        m_todo_terms.push_back(std::make_pair(i.first, coeff * i.second));
                    }
                }                    
            }
            else {
                result += m_variable_values[wi] * coeff;
            }
        }
        m_variable_values[vi] = result;
        return result;
    }

    void init_variable_values() {
        if (!m.canceled() && m_solver.get() && th.get_num_vars() > 0) {
            reset_variable_values();
            m_solver->get_model(m_variable_values);
            TRACE("arith", display(tout););
        }
    }

    void reset_variable_values() {
        m_variable_values.clear();
    }

    bool assume_eqs() {        
        svector<lp::var_index> vars;
        theory_var sz = static_cast<theory_var>(th.get_num_vars());
        for (theory_var v = 0; v < sz; ++v) {
            if (th.is_relevant_and_shared(get_enode(v))) { 
                vars.push_back(m_theory_var2var_index[v]);
            }
        }
        if (vars.empty()) {
            return false;
        }
        init_variable_values();
        TRACE("arith", 
              for (theory_var v = 0; v < sz; ++v) {
                  if (th.is_relevant_and_shared(get_enode(v))) { 
                      tout << "v" << v << " ";
                  }
              }
              tout << "\n"; );
        if (!m_use_nra_model) {
            m_solver->random_update(vars.size(), vars.c_ptr());
        }
        m_model_eqs.reset();
        TRACE("arith", display(tout););
            
        unsigned old_sz = m_assume_eq_candidates.size();
        bool result = false;
        int start = ctx().get_random_value();
        for (theory_var i = 0; i < sz; ++i) {
            theory_var v = (i + start) % sz;
            enode* n1 = get_enode(v);
            if (!th.is_relevant_and_shared(n1)) {                    
                continue;
            }
            if (!can_get_value(v)) {
                continue;
            }
            theory_var other = m_model_eqs.insert_if_not_there(v);
            TRACE("arith", tout << "insert: v" << v << " := " << get_value(v) << " found: v" << other << "\n";);
            if (other == v) {
                continue;
            }
            enode* n2 = get_enode(other);
            if (n1->get_root() != n2->get_root()) {
                TRACE("arith", tout << mk_pp(n1->get_owner(), m) << " = " << mk_pp(n2->get_owner(), m) << "\n";
                      tout << mk_pp(n1->get_owner(), m) << " = " << mk_pp(n2->get_owner(), m) << "\n";
                      tout << "v" << v << " = " << "v" << other << "\n";);
                m_assume_eq_candidates.push_back(std::make_pair(v, other));
                result = true;
            }
        }
            
        if (result) {
            ctx().push_trail(restore_size_trail<context, std::pair<theory_var, theory_var>, false>(m_assume_eq_candidates, old_sz));
        }

        return delayed_assume_eqs();
    }

    bool delayed_assume_eqs() {
        if (m_assume_eq_head == m_assume_eq_candidates.size())
            return false;
            
        ctx().push_trail(value_trail<context, unsigned>(m_assume_eq_head));
        while (m_assume_eq_head < m_assume_eq_candidates.size()) {
            std::pair<theory_var, theory_var> const & p = m_assume_eq_candidates[m_assume_eq_head];
            theory_var v1 = p.first;
            theory_var v2 = p.second;
            enode* n1 = get_enode(v1);
            enode* n2 = get_enode(v2);
            m_assume_eq_head++;
            CTRACE("arith", 
                   is_eq(v1, v2) && n1->get_root() != n2->get_root(),
                   tout << "assuming eq: v" << v1 << " = v" << v2 << "\n";);
            if (is_eq(v1, v2) &&  n1->get_root() != n2->get_root() && th.assume_eq(n1, n2)) {
                return true;
            }
        }
        return false;
    }

    bool is_eq(theory_var v1, theory_var v2) {
        if (m_use_nra_model) {
            return m_nra->am().eq(nl_value(v1, *m_a1), nl_value(v2, *m_a2));
        }
        else {
            return get_value(v1) == get_value(v2); 
        }
    }

    bool has_delayed_constraints() const {
        return !m_asserted_atoms.empty();
    }

    final_check_status final_check_eh() {
        m_use_nra_model = false;
        lbool is_sat = l_true;
        if (m_solver->get_status() != lp::lp_status::OPTIMAL) {
            is_sat = make_feasible();
        }
        final_check_status st = FC_DONE;
        switch (is_sat) {
        case l_true:
                
            if (delayed_assume_eqs()) {
                return FC_CONTINUE;
            }
            if (assume_eqs()) {
                return FC_CONTINUE;
            }

            switch (check_lia()) {
            case l_true:
                break;
            case l_false:
                return FC_CONTINUE;
            case l_undef:
                TRACE("arith", tout << "check-lia giveup\n";);
                st = FC_CONTINUE;
                break;
            }
                
            switch (check_nra()) {
            case l_true:
                break;
            case l_false:
                return FC_CONTINUE;
            case l_undef:
                TRACE("arith", tout << "check-nra giveup\n";);
                st = FC_GIVEUP;
                break;
            }
            if (m_not_handled != 0) {            
                TRACE("arith", tout << "unhandled operator " << mk_pp(m_not_handled, m) << "\n";);        
                st = FC_GIVEUP;
            }
                
            return st;
        case l_false:
            set_conflict();
            return FC_CONTINUE;
        case l_undef:
            TRACE("arith", tout << "check feasiable is undef\n";);
            return m.canceled() ? FC_CONTINUE : FC_GIVEUP;
        default:
            UNREACHABLE();
            break;
        }
        TRACE("arith", tout << "default giveup\n";);
        return FC_GIVEUP;
    }

    // create a bound atom representing term >= k is lower_bound is true, and term <= k if it is false
    app_ref mk_bound(lp::lar_term const& term, rational const& k, bool lower_bound) {
        bool is_int = k.is_int();
        rational offset = -k;
        u_map<rational> coeffs;
        term2coeffs(term, coeffs, rational::one(), offset);
        offset.neg();
        if (is_int) {
            // 3x + 6y >= 5 -> x + 3y >= 5/3, then x + 3y >= 2
            // 3x + 6y <= 5 -> x + 3y <= 1
            
            rational g = gcd_reduce(coeffs);
            if (!g.is_one()) {
                if (lower_bound) {
                    offset = div(offset + g - rational::one(), g);
                }
                else {
                    offset = div(offset, g);
                }
            }
        }
        if (!coeffs.empty() && coeffs.begin()->m_value.is_neg()) {
            offset.neg();
            lower_bound = !lower_bound;
            for (auto& kv : coeffs) kv.m_value.neg();
        }

        app_ref atom(m);
        app_ref t = coeffs2app(coeffs, rational::zero(), is_int);
        if (lower_bound) {
            atom = a.mk_ge(t, a.mk_numeral(offset, is_int));
        }
        else {
            atom = a.mk_le(t, a.mk_numeral(offset, is_int));
        }

        TRACE("arith", tout << t << ": " << atom << "\n";
              m_solver->print_term(term, tout << "bound atom: "); tout << (lower_bound?" >= ":" <= ") << k << "\n";);
        ctx().internalize(atom, true);
        ctx().mark_as_relevant(atom.get());
        return atom;
    }

    lbool check_lia() {
        if (m.canceled()) {
            TRACE("arith", tout << "canceled\n";);
            return l_undef;
        }
        lp::lar_term term;
        lp::mpq k;
        lp::explanation ex; // TBD, this should be streamlined accross different explanations
        bool upper;
        switch(m_lia->check(term, k, ex, upper)) {
        case lp::lia_move::sat:
            return l_true;
        case lp::lia_move::branch: {
            TRACE("arith", tout << "branch\n";);
            app_ref b = mk_bound(term, k, !upper);
            // branch on term >= k + 1
            // branch on term <= k
            // TBD: ctx().force_phase(ctx().get_literal(b));
            // at this point we have a new unassigned atom that the 
            // SAT core assigns a value to
            return l_false;
        }
        case lp::lia_move::cut: {
            TRACE("arith", tout << "cut\n";);
            ++m_stats.m_gomory_cuts;
            // m_explanation implies term <= k
            app_ref b = mk_bound(term, k, !upper);
            m_eqs.reset();
            m_core.reset();
            m_params.reset();
            for (auto const& ev : ex.m_explanation) {
                if (!ev.first.is_zero()) { 
                    set_evidence(ev.second);
                }
            }
            literal lit(ctx().get_bool_var(b), false);
            TRACE("arith", 
                  ctx().display_lemma_as_smt_problem(tout << "new cut:\n", m_core.size(), m_core.c_ptr(), m_eqs.size(), m_eqs.c_ptr(), lit);
                  display(tout););
            assign(lit);
            return l_false;
        }
        case lp::lia_move::conflict:
            // ex contains unsat core
            m_explanation = ex.m_explanation;
            set_conflict1();
            return l_false;
        case lp::lia_move::undef:
            TRACE("arith", tout << "lia undef\n";);
            return l_undef;
        case lp::lia_move::continue_with_check:
            return l_undef;
        default:
            UNREACHABLE();
        }
        UNREACHABLE();
        return l_undef;
    }

    lbool check_nra() {
        m_use_nra_model = false;
        if (m.canceled()) {
            TRACE("arith", tout << "canceled\n";);
            return l_undef;
        }
        if (!m_nra) return l_true;
        if (!m_nra->need_check()) return l_true;
        m_a1 = 0; m_a2 = 0;
        lbool r = m_nra->check(m_explanation);
        m_a1 = alloc(scoped_anum, m_nra->am());
        m_a2 = alloc(scoped_anum, m_nra->am());
        switch (r) {
        case l_false:
            set_conflict1();
            break;
        case l_true:
            m_use_nra_model = true;
            if (assume_eqs()) {
                return l_false;
            }
            break;
        case l_undef:
            TRACE("arith", tout << "nra-undef\n";);
        default:
            break;
        }
        return r;
    }

    /**
       \brief We must redefine this method, because theory of arithmetic contains
       underspecified operators such as division by 0.
       (/ a b) is essentially an uninterpreted function when b = 0.
       Thus, 'a' must be considered a shared var if it is the child of an underspecified operator.

       if merge(a / b, x + y) and a / b is root, then x + y become shared and all z + u in equivalence class of x + y.
                      

       TBD: when the set of underspecified subterms is small, compute the shared variables below it.
       Recompute the set if there are merges that invalidate it.
       Use the set to determine if a variable is shared.
    */
    bool is_shared(theory_var v) const {
        if (m_underspecified.empty()) {
            return false;
        }
        enode * n      = get_enode(v);
        enode * r      = n->get_root();
        unsigned usz   = m_underspecified.size();
        TRACE("shared", tout << ctx().get_scope_level() << " " <<  v << " " << r->get_num_parents() << "\n";);
        if (r->get_num_parents() > 2*usz) {
            for (unsigned i = 0; i < usz; ++i) {
                app* u = m_underspecified[i];
                unsigned sz = u->get_num_args();
                for (unsigned j = 0; j < sz; ++j) {
                    if (ctx().get_enode(u->get_arg(j))->get_root() == r) {
                        return true;
                    }
                }
            }
        }
        else {
            for (enode * parent : r->get_const_parents()) {
                if (is_underspecified(parent->get_owner())) {
                    return true;
                }
            }
        }
        return false;
    }

    bool can_propagate() {
#if 0
        if (ctx().at_base_level() && has_delayed_constraints()) {
            // we could add the delayed constraints here directly to the tableau instead of using bounds variables.
        }
#endif
        return m_asserted_atoms.size() > m_asserted_qhead;
    }

    void propagate() {
        flush_bound_axioms();
        if (!can_propagate()) {
            return;
        }
        while (m_asserted_qhead < m_asserted_atoms.size() && !ctx().inconsistent()) {
            bool_var bv  = m_asserted_atoms[m_asserted_qhead].m_bv;
            bool is_true = m_asserted_atoms[m_asserted_qhead].m_is_true;
                
#if 1
            m_to_check.push_back(bv);
#else
            propagate_bound(bv, is_true, b);
#endif
            lp_api::bound& b = *m_bool_var2bound.find(bv);
            assert_bound(bv, is_true, b);
                

            ++m_asserted_qhead;
        }
        if (ctx().inconsistent()) {
            m_to_check.reset();
            return;
        }
        /*for (; qhead < m_asserted_atoms.size() && !ctx().inconsistent(); ++qhead) {
          bool_var bv  = m_asserted_atoms[qhead].m_bv;
          bool is_true = m_asserted_atoms[qhead].m_is_true;
          lp_api::bound& b = *m_bool_var2bound.find(bv);
          propagate_bound_compound(bv, is_true, b);
          }*/

        lbool lbl = make_feasible();
            
        switch(lbl) {
        case l_false:
            TRACE("arith", tout << "propagation conflict\n";);
            set_conflict();
            break;
        case l_true:
            propagate_basic_bounds();
            propagate_bounds_with_lp_solver();
            break;
        case l_undef:
            break;
        }
            
    }

    void propagate_bounds_with_lp_solver() {
        if (BP_NONE == propagation_mode()) {
            return;
        }
        int num_of_p = m_solver->settings().st().m_num_of_implied_bounds;
        (void)num_of_p;
        local_bound_propagator bp(*this);
        m_solver->propagate_bounds_for_touched_rows(bp);
        if (m.canceled()) {
            return;
        }
        int new_num_of_p = m_solver->settings().st().m_num_of_implied_bounds;
        (void)new_num_of_p;
        CTRACE("arith", new_num_of_p > num_of_p, tout << "found " << new_num_of_p << " implied bounds\n";);
        if (m_solver->get_status() == lp::lp_status::INFEASIBLE) {
            set_conflict();
        }
        else {
            for (unsigned i = 0; !m.canceled() && !ctx().inconsistent() && i < bp.m_ibounds.size(); ++i) {
                propagate_lp_solver_bound(bp.m_ibounds[i]);
            }
        }
    }

    bool bound_is_interesting(unsigned vi, lp::lconstraint_kind kind, const rational & bval) const {
        theory_var v;
        if (m_solver->is_term(vi)) {
            v = m_term_index2theory_var.get(m_solver->adjust_term_index(vi), null_theory_var);
        }
        else {
            v = m_var_index2theory_var.get(vi, null_theory_var);
        }

        if (v == null_theory_var) return false;

        if (m_unassigned_bounds[v] == 0 || m_bounds.size() <= static_cast<unsigned>(v)) {
            return false;
        }
        lp_bounds const& bounds = m_bounds[v];
        for (unsigned i = 0; i < bounds.size(); ++i) {
            lp_api::bound* b = bounds[i];
            if (ctx().get_assignment(b->get_bv()) != l_undef) {
                continue;
            }
            literal lit = is_bound_implied(kind, bval, *b);
            if (lit == null_literal) {
                continue;
            }
            return true;
        }
        return false;
    }

    struct local_bound_propagator: public lp::bound_propagator {
        imp & m_imp;
        local_bound_propagator(imp& i) : bound_propagator(*i.m_solver), m_imp(i) {}

        bool bound_is_interesting(unsigned j, lp::lconstraint_kind kind, const rational & v) override {
            return m_imp.bound_is_interesting(j, kind, v);
        }

        void consume(rational const& v, lp::constraint_index j) override {
            m_imp.set_evidence(j);
            m_imp.m_explanation.push_back(std::make_pair(v, j));
        }
    };

        
    void propagate_lp_solver_bound(lp::implied_bound& be) {

        theory_var v;
        lp::var_index vi = be.m_j;
        if (m_solver->is_term(vi)) {
            v = m_term_index2theory_var.get(m_solver->adjust_term_index(vi), null_theory_var);
        }
        else {
            v = m_var_index2theory_var.get(vi, null_theory_var);
        }

        if (v == null_theory_var) return;
        TRACE("arith", tout << "v" << v << " " << be.kind() << " " << be.m_bound << "\n";
              // if (m_unassigned_bounds[v] == 0) m_solver->print_bound_evidence(be, tout);
              );

            
        if (m_unassigned_bounds[v] == 0 || m_bounds.size() <= static_cast<unsigned>(v)) {
            TRACE("arith", tout << "return\n";);
            return;
        }
        lp_bounds const& bounds = m_bounds[v];
        bool first = true;
        for (unsigned i = 0; i < bounds.size(); ++i) {
            lp_api::bound* b = bounds[i];
            if (ctx().get_assignment(b->get_bv()) != l_undef) {
                continue;
            }
            literal lit = is_bound_implied(be.kind(), be.m_bound, *b);
            if (lit == null_literal) {
                continue;
            }
            TRACE("arith", tout << lit << " bound: " << *b << " first: " << first << "\n";);

            m_solver->settings().st().m_num_of_implied_bounds ++;
            if (first) {
                first = false;
                m_core.reset();
                m_eqs.reset();
                m_params.reset();
                m_explanation.clear();
                local_bound_propagator bp(*this);
                m_solver->explain_implied_bound(be, bp);
            }
            CTRACE("arith", m_unassigned_bounds[v] == 0, tout << "missed bound\n";);
            updt_unassigned_bounds(v, -1);
            TRACE("arith",
                  ctx().display_literals_verbose(tout, m_core);
                  tout << "\n --> ";
                  ctx().display_literal_verbose(tout, lit);
                  tout << "\n";
                  display_evidence(tout, m_explanation);
                  m_solver->print_implied_bound(be, tout);
                  );
            DEBUG_CODE(
                for (auto& lit : m_core) {
                    SASSERT(ctx().get_assignment(lit) == l_true);
                });
            ++m_stats.m_bound_propagations1;
            assign(lit);
        }
    }

    literal_vector m_core2;

    void assign(literal lit) {
        //        SASSERT(validate_assign(lit));
        dump_assign(lit);
        if (m_core.size() < small_lemma_size() && m_eqs.empty()) {
            m_core2.reset();
            for (auto const& c : m_core) {
                m_core2.push_back(~c);
            }
            m_core2.push_back(lit);
            justification * js = 0;
            if (proofs_enabled()) {
                js = alloc(theory_lemma_justification, get_id(), ctx(), m_core2.size(), m_core2.c_ptr(),
                           m_params.size(), m_params.c_ptr());
            }
            ctx().mk_clause(m_core2.size(), m_core2.c_ptr(), js, CLS_AUX_LEMMA, 0);
        }
        else {
            ctx().assign(
                lit, ctx().mk_justification(
                    ext_theory_propagation_justification(
                        get_id(), ctx().get_region(), m_core.size(), m_core.c_ptr(), 
                        m_eqs.size(), m_eqs.c_ptr(), lit, m_params.size(), m_params.c_ptr())));            
        }
    }

    literal is_bound_implied(lp::lconstraint_kind k, rational const& value, lp_api::bound const& b) const {
        if ((k == lp::LE || k == lp::LT) && b.get_bound_kind() == lp_api::upper_t && value <= b.get_value()) {
            TRACE("arith", tout << "v <= value <= b.get_value() => v <= b.get_value() \n";);
            return literal(b.get_bv(), false);
        }
        if ((k == lp::GE || k == lp::GT) && b.get_bound_kind() == lp_api::lower_t && b.get_value() <= value) {
            TRACE("arith", tout << "b.get_value() <= value <= v => b.get_value() <= v \n";);
            return literal(b.get_bv(), false);
        }
        if (k == lp::LE && b.get_bound_kind() == lp_api::lower_t && value < b.get_value()) {
            TRACE("arith", tout << "v <= value < b.get_value() => v < b.get_value()\n";);
            return literal(b.get_bv(), true);
        }
        if (k == lp::LT && b.get_bound_kind() == lp_api::lower_t && value <= b.get_value()) {
            TRACE("arith", tout << "v < value <= b.get_value() => v < b.get_value()\n";);
            return literal(b.get_bv(), true);
        }
        if (k == lp::GE && b.get_bound_kind() == lp_api::upper_t && b.get_value() < value) {
            TRACE("arith", tout << "b.get_value() < value <= v => b.get_value() < v\n";);
            return literal(b.get_bv(), true);
        }
        if (k == lp::GT && b.get_bound_kind() == lp_api::upper_t && b.get_value() <= value) {
            TRACE("arith", tout << "b.get_value() <= value < v => b.get_value() < v\n";);
            return literal(b.get_bv(), true);
        }

        return null_literal;
    }

    void mk_bound_axioms(lp_api::bound& b) {
        if (!ctx().is_searching()) {
            //
            // NB. We make an assumption that user push calls propagation 
            // before internal scopes are pushed. This flushes all newly 
            // asserted atoms into the right context.
            //
            m_new_bounds.push_back(&b);
            return;
        }
        theory_var v = b.get_var();
        lp_api::bound_kind kind1 = b.get_bound_kind();
        rational const& k1 = b.get_value();
        lp_bounds & bounds = m_bounds[v];

        lp_api::bound* end = 0;
        lp_api::bound* lo_inf = end, *lo_sup = end;
        lp_api::bound* hi_inf = end, *hi_sup = end;
            
        for (lp_api::bound* other : bounds) {
            if (other == &b) continue;
            if (b.get_bv() == other->get_bv()) continue;
            lp_api::bound_kind kind2 = other->get_bound_kind();
            rational const& k2 = other->get_value();
            if (k1 == k2 && kind1 == kind2) {
                // the bounds are equivalent.
                continue;
            }

            SASSERT(k1 != k2 || kind1 != kind2);
            if (kind2 == lp_api::lower_t) {
                if (k2 < k1) {
                    if (lo_inf == end || k2 > lo_inf->get_value()) {
                        lo_inf = other;
                    }
                }
                else if (lo_sup == end || k2 < lo_sup->get_value()) {
                    lo_sup = other;
                }
            }
            else if (k2 < k1) {
                if (hi_inf == end || k2 > hi_inf->get_value()) {
                    hi_inf = other;
                }
            }
            else if (hi_sup == end || k2 < hi_sup->get_value()) {
                hi_sup = other;
            }
        }        
        if (lo_inf != end) mk_bound_axiom(b, *lo_inf);
        if (lo_sup != end) mk_bound_axiom(b, *lo_sup);
        if (hi_inf != end) mk_bound_axiom(b, *hi_inf);
        if (hi_sup != end) mk_bound_axiom(b, *hi_sup);
    }


    void mk_bound_axiom(lp_api::bound& b1, lp_api::bound& b2) {
        theory_var v = b1.get_var();
        literal   l1(b1.get_bv());
        literal   l2(b2.get_bv());
        rational const& k1 = b1.get_value();
        rational const& k2 = b2.get_value();
        lp_api::bound_kind kind1 = b1.get_bound_kind();
        lp_api::bound_kind kind2 = b2.get_bound_kind();
        bool v_is_int = is_int(v);
        SASSERT(v == b2.get_var());
        if (k1 == k2 && kind1 == kind2) return;
        SASSERT(k1 != k2 || kind1 != kind2);
        parameter coeffs[3] = { parameter(symbol("farkas")), 
                                parameter(rational(1)), parameter(rational(1)) };
            
        if (kind1 == lp_api::lower_t) {
            if (kind2 == lp_api::lower_t) {
                if (k2 <= k1) {
                    mk_clause(~l1, l2, 3, coeffs);
                }
                else {
                    mk_clause(l1, ~l2, 3, coeffs);
                }
            }
            else if (k1 <= k2) {
                // k1 <= k2, k1 <= x or x <= k2
                mk_clause(l1, l2, 3, coeffs);
            }
            else {
                // k1 > hi_inf, k1 <= x => ~(x <= hi_inf)
                mk_clause(~l1, ~l2, 3, coeffs);
                if (v_is_int && k1 == k2 + rational(1)) {
                    // k1 <= x or x <= k1-1
                    mk_clause(l1, l2, 3, coeffs);
                }
            }
        }
        else if (kind2 == lp_api::lower_t) {
            if (k1 >= k2) {
                // k1 >= lo_inf, k1 >= x or lo_inf <= x
                mk_clause(l1, l2, 3, coeffs);
            }
            else {
                // k1 < k2, k2 <= x => ~(x <= k1)
                mk_clause(~l1, ~l2, 3, coeffs); 
                if (v_is_int && k1 == k2 - rational(1)) {
                    // x <= k1 or k1+l <= x
                    mk_clause(l1, l2, 3, coeffs);
                }
                    
            }
        }
        else {
            // kind1 == A_UPPER, kind2 == A_UPPER
            if (k1 >= k2) {
                // k1 >= k2, x <= k2 => x <= k1
                mk_clause(l1, ~l2, 3, coeffs);
            }
            else {
                // k1 <= hi_sup , x <= k1 =>  x <= hi_sup
                mk_clause(~l1, l2, 3, coeffs);
            }
        }        
    }

    typedef lp_bounds::iterator iterator;

    void flush_bound_axioms() {
        CTRACE("arith", !m_new_bounds.empty(), tout << "flush bound axioms\n";);

        while (!m_new_bounds.empty()) {
            lp_bounds atoms;            
            atoms.push_back(m_new_bounds.back());
            m_new_bounds.pop_back();
            theory_var v = atoms.back()->get_var();
            for (unsigned i = 0; i < m_new_bounds.size(); ++i) {
                if (m_new_bounds[i]->get_var() == v) {
                    atoms.push_back(m_new_bounds[i]);
                    m_new_bounds[i] = m_new_bounds.back();
                    m_new_bounds.pop_back();
                    --i;
                }
            }            
            CTRACE("arith_verbose", !atoms.empty(),  
                   for (unsigned i = 0; i < atoms.size(); ++i) {
                       atoms[i]->display(tout); tout << "\n";
                   });
            lp_bounds occs(m_bounds[v]);
                
            std::sort(atoms.begin(), atoms.end(), compare_bounds());
            std::sort(occs.begin(), occs.end(), compare_bounds());
                
            iterator begin1 = occs.begin();
            iterator begin2 = occs.begin();
            iterator end = occs.end();
            begin1 = first(lp_api::lower_t, begin1, end);
            begin2 = first(lp_api::upper_t, begin2, end);
                
            iterator lo_inf = begin1, lo_sup = begin1;
            iterator hi_inf = begin2, hi_sup = begin2;
            iterator lo_inf1 = begin1, lo_sup1 = begin1;
            iterator hi_inf1 = begin2, hi_sup1 = begin2;
            bool flo_inf, fhi_inf, flo_sup, fhi_sup;
            ptr_addr_hashtable<lp_api::bound> visited;
            for (unsigned i = 0; i < atoms.size(); ++i) {
                lp_api::bound* a1 = atoms[i];
                lo_inf1 = next_inf(a1, lp_api::lower_t, lo_inf, end, flo_inf);
                hi_inf1 = next_inf(a1, lp_api::upper_t, hi_inf, end, fhi_inf);
                lo_sup1 = next_sup(a1, lp_api::lower_t, lo_sup, end, flo_sup);
                hi_sup1 = next_sup(a1, lp_api::upper_t, hi_sup, end, fhi_sup);
                if (lo_inf1 != end) lo_inf = lo_inf1; 
                if (lo_sup1 != end) lo_sup = lo_sup1; 
                if (hi_inf1 != end) hi_inf = hi_inf1; 
                if (hi_sup1 != end) hi_sup = hi_sup1; 
                if (!flo_inf) lo_inf = end;
                if (!fhi_inf) hi_inf = end;
                if (!flo_sup) lo_sup = end;
                if (!fhi_sup) hi_sup = end;
                visited.insert(a1);
                if (lo_inf1 != end && lo_inf != end && !visited.contains(*lo_inf)) mk_bound_axiom(*a1, **lo_inf);
                if (lo_sup1 != end && lo_sup != end && !visited.contains(*lo_sup)) mk_bound_axiom(*a1, **lo_sup);
                if (hi_inf1 != end && hi_inf != end && !visited.contains(*hi_inf)) mk_bound_axiom(*a1, **hi_inf);
                if (hi_sup1 != end && hi_sup != end && !visited.contains(*hi_sup)) mk_bound_axiom(*a1, **hi_sup);
            }                            
        }
    }

    struct compare_bounds {
        bool operator()(lp_api::bound* a1, lp_api::bound* a2) const { return a1->get_value() < a2->get_value(); }
    };


    lp_bounds::iterator first(
        lp_api::bound_kind kind, 
        iterator it, 
        iterator end) {
        for (; it != end; ++it) {
            lp_api::bound* a = *it;
            if (a->get_bound_kind() == kind) return it;
        }
        return end;
    }

    lp_bounds::iterator next_inf(
        lp_api::bound* a1, 
        lp_api::bound_kind kind, 
        iterator it, 
        iterator end,
        bool& found_compatible) {
        rational const & k1(a1->get_value());
        iterator result = end;
        found_compatible = false;
        for (; it != end; ++it) {
            lp_api::bound * a2 = *it;            
            if (a1 == a2) continue;
            if (a2->get_bound_kind() != kind) continue;
            rational const & k2(a2->get_value());
            found_compatible = true;
            if (k2 <= k1) {
                result = it;
            }
            else {
                break;
            }
        }
        return result;
    }

    lp_bounds::iterator next_sup(
        lp_api::bound* a1, 
        lp_api::bound_kind kind, 
        iterator it, 
        iterator end,
        bool& found_compatible) {
        rational const & k1(a1->get_value());
        found_compatible = false;
        for (; it != end; ++it) {
            lp_api::bound * a2 = *it;            
            if (a1 == a2) continue;
            if (a2->get_bound_kind() != kind) continue;
            rational const & k2(a2->get_value());
            found_compatible = true;
            if (k1 < k2) {
                return it;
            }
        }
        return end;
    }

    void propagate_basic_bounds() {
        for (auto const& bv : m_to_check) {                
            lp_api::bound& b = *m_bool_var2bound.find(bv);
            propagate_bound(bv, ctx().get_assignment(bv) == l_true, b);
            if (ctx().inconsistent()) break;

        }
        m_to_check.reset();
    }
        
    // for glb lo': lo' < lo:
    //   lo <= x -> lo' <= x 
    //   lo <= x -> ~(x <= lo')
    // for lub hi': hi' > hi
    //   x <= hi -> x <= hi'
    //   x <= hi -> ~(x >= hi')

    void propagate_bound(bool_var bv, bool is_true, lp_api::bound& b) {
        if (BP_NONE == propagation_mode()) {
            return;
        }
        lp_api::bound_kind k = b.get_bound_kind();
        theory_var v = b.get_var();
        inf_rational val = b.get_value(is_true);
        lp_bounds const& bounds = m_bounds[v];
        SASSERT(!bounds.empty());
        if (bounds.size() == 1) return;
        if (m_unassigned_bounds[v] == 0) return;

        literal lit1(bv, !is_true);
        literal lit2 = null_literal;
        bool find_glb = (is_true == (k == lp_api::lower_t));
        if (find_glb) {
            rational glb;
            lp_api::bound* lb = 0;
            for (unsigned i = 0; i < bounds.size(); ++i) {
                lp_api::bound* b2 = bounds[i];
                if (b2 == &b) continue;
                rational const& val2 = b2->get_value();
                if ((is_true ? val2 < val : val2 <= val) && (!lb || glb < val2)) {
                    lb = b2;
                    glb = val2;
                }
            }
            if (!lb) return;
            bool sign = lb->get_bound_kind() != lp_api::lower_t;
            lit2 = literal(lb->get_bv(), sign);                    
        }
        else {
            rational lub;
            lp_api::bound* ub = 0;
            for (unsigned i = 0; i < bounds.size(); ++i) {
                lp_api::bound* b2 = bounds[i];
                if (b2 == &b) continue;
                rational const& val2 = b2->get_value();
                if ((is_true ? val < val2 : val <= val2) && (!ub || val2 < lub)) {
                    ub = b2;
                    lub = val2;
                }
            }
            if (!ub) return;
            bool sign = ub->get_bound_kind() != lp_api::upper_t;
            lit2 = literal(ub->get_bv(), sign);
        }
        TRACE("arith", 
              ctx().display_literal_verbose(tout, lit1);
              ctx().display_literal_verbose(tout << " => ", lit2);
              tout << "\n";);
        updt_unassigned_bounds(v, -1);
        ++m_stats.m_bound_propagations2;
        m_params.reset();
        m_core.reset();
        m_eqs.reset();
        m_core.push_back(lit2);
        m_params.push_back(parameter(symbol("farkas")));
        m_params.push_back(parameter(rational(1)));
        m_params.push_back(parameter(rational(1)));
        assign(lit2);
        ++m_stats.m_bounds_propagations;
    }

    svector<lp::var_index> m_todo_vars;

    void add_use_lists(lp_api::bound* b) {
        theory_var v = b->get_var();
        lp::var_index vi = get_var_index(v);
        if (!m_solver->is_term(vi)) {
            return;
        }
        m_todo_vars.push_back(vi);
        while (!m_todo_vars.empty()) {
            vi = m_todo_vars.back();
            m_todo_vars.pop_back();
            lp::lar_term const& term = m_solver->get_term(vi);
            for (auto const& p : term) {
                lp::var_index wi = p.var();
                if (m_solver->is_term(wi)) {
                    m_todo_vars.push_back(wi);
                }
                else {
                    unsigned w = m_var_index2theory_var[wi];
                    m_use_list.reserve(w + 1, ptr_vector<lp_api::bound>());
                    m_use_list[w].push_back(b);
                }
            }
        }
    }

    void del_use_lists(lp_api::bound* b) {
        theory_var v = b->get_var();
        lp::var_index vi = m_theory_var2var_index[v];
        if (!m_solver->is_term(vi)) {
            return;
        }
        m_todo_vars.push_back(vi);
        while (!m_todo_vars.empty()) {
            vi = m_todo_vars.back();
            m_todo_vars.pop_back();
            lp::lar_term const& term = m_solver->get_term(vi);
            for (auto const& coeff : term.m_coeffs) {
                lp::var_index wi = coeff.first;
                if (m_solver->is_term(wi)) {
                    m_todo_vars.push_back(wi);
                }
                else {
                    unsigned w = m_var_index2theory_var[wi];
                    SASSERT(m_use_list[w].back() == b);
                    m_use_list[w].pop_back();
                }
            }
        }
    }

    //
    // propagate bounds to compound terms
    // The idea is that if bounds on all variables in an inequality ax + by + cz >= k
    // have been assigned we may know the truth value of the inequality by using simple
    // bounds propagation.
    // 
    void propagate_bound_compound(bool_var bv, bool is_true, lp_api::bound& b) {
        theory_var v = b.get_var();
        TRACE("arith", tout << mk_pp(get_owner(v), m) << "\n";);
        if (static_cast<unsigned>(v) >= m_use_list.size()) {
            return;
        }
        for (auto const& vb : m_use_list[v]) {
            if (ctx().get_assignment(vb->get_bv()) != l_undef) {
                TRACE("arith_verbose", display_bound(tout << "assigned ", *vb) << "\n";);
                continue;
            }
            inf_rational r;
            // x + y
            // x >= 0, y >= 1 -> x + y >= 1
            // x <= 0, y <= 2 -> x + y <= 2
            literal lit = null_literal;
            if (lp_api::lower_t == vb->get_bound_kind()) {
                if (get_glb(*vb, r) && r >= vb->get_value()) {        // vb is assigned true
                    lit = literal(vb->get_bv(), false);
                }
                else if (get_lub(*vb, r) && r < vb->get_value()) {    // vb is assigned false
                    lit = literal(vb->get_bv(), true);
                }
            }
            else {                     
                if (get_glb(*vb, r) && r > vb->get_value()) {         // VB <= value < val(VB)
                    lit = literal(vb->get_bv(), true);
                }
                else if (get_lub(*vb, r) && r <= vb->get_value()) {   // val(VB) <= value
                    lit = literal(vb->get_bv(), false);
                }
            }                
                
            if (lit != null_literal) {
                TRACE("arith",
                      ctx().display_literals_verbose(tout, m_core);
                      tout << "\n --> ";
                      ctx().display_literal_verbose(tout, lit);
                      tout << "\n";
                      );
                

                assign(lit);
            }
            else {
                TRACE("arith_verbose", display_bound(tout << "skip ", *vb) << "\n";);
            }
        }
    }

    bool get_lub(lp_api::bound const& b, inf_rational& lub) {
        return get_bound(b, lub, true);
    }

    bool get_glb(lp_api::bound const& b, inf_rational& glb) {
        return get_bound(b, glb, false);
    }

    std::ostream& display_bound(std::ostream& out, lp_api::bound const& b) {
        return out << mk_pp(ctx().bool_var2expr(b.get_bv()), m);
    }

    bool get_bound(lp_api::bound const& b, inf_rational& r, bool is_lub) {
        m_core.reset();
        m_eqs.reset();
        m_params.reset();
        r.reset();
        theory_var v = b.get_var();
        lp::var_index vi = m_theory_var2var_index[v];
        SASSERT(m_solver->is_term(vi));
        lp::lar_term const& term = m_solver->get_term(vi);
        for (auto const & coeff : term.m_coeffs) {
            lp::var_index wi = coeff.first;
            lp::constraint_index ci;
            rational value;
            bool is_strict;
            if (m_solver->is_term(wi)) {
                return false;
            }
            if (coeff.second.is_neg() == is_lub) {
                // -3*x ... <= lub based on lower bound for x.
                if (!m_solver->has_lower_bound(wi, ci, value, is_strict)) {
                    return false;
                }
                if (is_strict) {
                    r += inf_rational(rational::zero(), coeff.second.is_pos());
                }
            }
            else {
                if (!m_solver->has_upper_bound(wi, ci, value, is_strict)) {
                    return false;
                }
                if (is_strict) {
                    r += inf_rational(rational::zero(), coeff.second.is_pos());
                }
            }                
            r += value * coeff.second;
            set_evidence(ci);                    
        }
        TRACE("arith_verbose", tout << (is_lub?"lub":"glb") << " is " << r << "\n";);
        return true;
    }

    void assert_bound(bool_var bv, bool is_true, lp_api::bound& b) {
        if (m_solver->get_status() == lp::lp_status::INFEASIBLE) {
            return;
        }
        scoped_internalize_state st(*this);
        st.vars().push_back(b.get_var());
        st.coeffs().push_back(rational::one());
        init_left_side(st);
        lp::lconstraint_kind k = lp::EQ;
        bool is_int = b.is_int();
        switch (b.get_bound_kind()) {
        case lp_api::lower_t:
            k = is_true ? lp::GE : (is_int ? lp::LE : lp::LT);
            break;
        case lp_api::upper_t:
            k = is_true ? lp::LE : (is_int ? lp::GE : lp::GT);
            break;
        }         
        if (k == lp::LT || k == lp::LE) {
            ++m_stats.m_assert_lower;
        }
        else {
            ++m_stats.m_assert_upper;
        }
        auto vi = get_var_index(b.get_var());
        rational bound = b.get_value();
        lp::constraint_index ci;
        if (is_int && !is_true) {
            rational bound = b.get_value(false).get_rational();
            ci = m_solver->add_var_bound(vi, k, bound);
        }
        else {
            ci = m_solver->add_var_bound(vi, k, b.get_value());
        }
        TRACE("arith", tout << "v" << b.get_var() << "\n";);
        add_ineq_constraint(ci, literal(bv, !is_true));

        propagate_eqs(vi, ci, k, b);
    }

    //
    // fixed equalities.
    // A fixed equality is inferred if there are two variables v1, v2 whose
    // upper and lower bounds coincide.
    // Then the equality v1 == v2 is propagated to the core.
    // 

    typedef std::pair<lp::constraint_index, rational> constraint_bound;
    vector<constraint_bound>        m_lower_terms;
    vector<constraint_bound>        m_upper_terms;
    typedef std::pair<rational, bool> value_sort_pair;
    typedef pair_hash<obj_hash<rational>, bool_hash> value_sort_pair_hash;
    typedef map<value_sort_pair, theory_var, value_sort_pair_hash, default_eq<value_sort_pair> > value2var;
    value2var               m_fixed_var_table;

    void propagate_eqs(lp::var_index vi, lp::constraint_index ci, lp::lconstraint_kind k, lp_api::bound& b) {
        if (propagate_eqs()) {
            rational const& value = b.get_value();
            if (k == lp::GE) {
                set_lower_bound(vi, ci, value);
                if (has_upper_bound(vi, ci, value)) {
                    fixed_var_eh(b.get_var(), value);
                }
            }
            else if (k == lp::LE) {
                set_upper_bound(vi, ci, value);
                if (has_lower_bound(vi, ci, value)) {
                    fixed_var_eh(b.get_var(), value);
                }
            }
        }
    }

    bool dump_lemmas() const { return m_arith_params.m_arith_dump_lemmas; }

    bool propagate_eqs() const { return m_arith_params.m_arith_propagate_eqs && m_num_conflicts < m_arith_params.m_arith_propagation_threshold; }

    bound_prop_mode propagation_mode() const { return m_num_conflicts < m_arith_params.m_arith_propagation_threshold ? m_arith_params.m_arith_bound_prop : BP_NONE; }

    unsigned small_lemma_size() const { return m_arith_params.m_arith_small_lemma_size; }

    bool proofs_enabled() const { return m.proofs_enabled(); }

    bool use_tableau() const { return lp_params(ctx().get_params()).simplex_strategy() < 2; }

    void set_upper_bound(lp::var_index vi, lp::constraint_index ci, rational const& v) { set_bound(vi, ci, v, false);  }

    void set_lower_bound(lp::var_index vi, lp::constraint_index ci, rational const& v) { set_bound(vi, ci, v, true);   }

    void set_bound(lp::var_index vi, lp::constraint_index ci, rational const& v, bool is_lower) {
        if (!m_solver->is_term(vi)) {
            // m_solver already tracks bounds on proper variables, but not on terms.
            return;
        }
        lp::var_index ti = m_solver->adjust_term_index(vi);
        auto& vec = is_lower ? m_lower_terms : m_upper_terms;
        if (vec.size() <= ti) {
            vec.resize(ti + 1, constraint_bound(UINT_MAX, rational()));
        }
        constraint_bound& b = vec[ti];
        if (b.first == UINT_MAX || (is_lower? b.second < v : b.second > v)) {
            ctx().push_trail(vector_value_trail<context, constraint_bound>(vec, ti));
            b.first = ci;
            b.second = v;
        }
    }

    bool has_upper_bound(lp::var_index vi, lp::constraint_index& ci, rational const& bound) { return has_bound(vi, ci, bound, false); }

    bool has_lower_bound(lp::var_index vi, lp::constraint_index& ci, rational const& bound) { return has_bound(vi, ci, bound, true); }
       
    bool has_bound(lp::var_index vi, lp::constraint_index& ci, rational const& bound, bool is_lower) {

        if (m_solver->is_term(vi)) {
                
            lp::var_index ti = m_solver->adjust_term_index(vi);
            theory_var v = m_term_index2theory_var.get(ti, null_theory_var);
            rational val;
            TRACE("arith", tout << vi << " " << v << "\n";);
            if (v != null_theory_var && a.is_numeral(get_owner(v), val) && bound == val) {
                ci = UINT_MAX;
                return bound == val;
            }

            auto& vec = is_lower ? m_lower_terms : m_upper_terms;
            if (vec.size() > ti) {
                constraint_bound& b = vec[ti];
                ci = b.first;
                return ci != UINT_MAX && bound == b.second;
            }
            else {
                return false;

            }
        }
        else {
            bool is_strict = false;
            rational b;
            if (is_lower) {
                return m_solver->has_lower_bound(vi, ci, b, is_strict) && b == bound && !is_strict;
            }
            else {
                return m_solver->has_upper_bound(vi, ci, b, is_strict) && b == bound && !is_strict;
            }
        }
    }


    bool is_equal(theory_var x, theory_var y) const { return get_enode(x)->get_root() == get_enode(y)->get_root(); }


    void fixed_var_eh(theory_var v1, rational const& bound) {
        theory_var v2;
        value_sort_pair key(bound, is_int(v1));
        if (m_fixed_var_table.find(key, v2)) {
            if (static_cast<unsigned>(v2) < th.get_num_vars() && !is_equal(v1, v2)) {
                auto vi1 = get_var_index(v1);
                auto vi2 = get_var_index(v2);
                lp::constraint_index ci1, ci2, ci3, ci4;
                TRACE("arith", tout << "fixed: " << mk_pp(get_owner(v1), m) << " " << mk_pp(get_owner(v2), m) << " " << bound << " " << has_lower_bound(vi2, ci3, bound) << "\n";);
                if (has_lower_bound(vi2, ci3, bound) && has_upper_bound(vi2, ci4, bound)) {
                    VERIFY (has_lower_bound(vi1, ci1, bound));
                    VERIFY (has_upper_bound(vi1, ci2, bound));
                    ++m_stats.m_fixed_eqs;
                    m_core.reset();
                    m_eqs.reset();
                    set_evidence(ci1);
                    set_evidence(ci2);
                    set_evidence(ci3);
                    set_evidence(ci4);
                    enode* x = get_enode(v1);
                    enode* y = get_enode(v2);
                    justification* js = 
                        ctx().mk_justification(
                            ext_theory_eq_propagation_justification(
                                get_id(), ctx().get_region(), m_core.size(), m_core.c_ptr(), m_eqs.size(), m_eqs.c_ptr(), x, y, 0, 0));

                    TRACE("arith",
                          for (unsigned i = 0; i <  m_core.size(); ++i) {
                              ctx().display_detailed_literal(tout, m_core[i]);
                              tout << "\n";
                          } 
                          for (unsigned i = 0; i < m_eqs.size(); ++i) {
                              tout << mk_pp(m_eqs[i].first->get_owner(), m) << " = " << mk_pp(m_eqs[i].second->get_owner(), m) << "\n";
                          } 
                          tout << " ==> ";
                          tout << mk_pp(x->get_owner(), m) << " = " << mk_pp(y->get_owner(), m) << "\n";
                          );

                    // parameters are TBD.
                    //                    SASSERT(validate_eq(x, y));
                    ctx().assign_eq(x, y, eq_justification(js));
                }
            }
            else {
                // bounds on v2 were changed.
                m_fixed_var_table.insert(key, v1);
            }
        }
        else {
            m_fixed_var_table.insert(key, v1);
        }
    }

    lbool make_feasible() {
        auto status = m_solver->find_feasible_solution();
        TRACE("arith_verbose", display(tout););
        switch (status) {
        case lp::lp_status::INFEASIBLE:
            return l_false;
        case lp::lp_status::FEASIBLE:
        case lp::lp_status::OPTIMAL:
            //                SASSERT(m_solver->all_constraints_hold());
            return l_true;
        case lp::lp_status::TIME_EXHAUSTED:
                
        default:
            TRACE("arith", tout << "status treated as inconclusive: " << status << "\n";);
            // TENTATIVE_UNBOUNDED, UNBOUNDED, TENTATIVE_DUAL_UNBOUNDED, DUAL_UNBOUNDED, 
            // FLOATING_POINT_ERROR, TIME_EXAUSTED, ITERATIONS_EXHAUSTED, EMPTY, UNSTABLE
            return l_undef;
        }
    }
 
    vector<std::pair<rational, lp::constraint_index>> m_explanation;
    literal_vector      m_core;
    svector<enode_pair> m_eqs;
    vector<parameter>   m_params;

    // lp::constraint_index const null_constraint_index = UINT_MAX; // not sure what a correct fix is

    void set_evidence(lp::constraint_index idx) {
        if (idx == UINT_MAX) {
            return;
        }
        switch (m_constraint_sources[idx]) {
        case inequality_source: {
            literal lit = m_inequalities[idx];
            SASSERT(lit != null_literal);
            m_core.push_back(lit);
            break;
        }
        case equality_source: {
            SASSERT(m_equalities[idx].first  != nullptr);
            SASSERT(m_equalities[idx].second != nullptr);
            m_eqs.push_back(m_equalities[idx]);          
            break;
        }
        case definition_source: {
            // skip definitions (these are treated as hard constraints)
            break;
        }
        default:
            UNREACHABLE();
            break;
        }
    }

    void set_conflict() {
        m_explanation.clear();
        m_solver->get_infeasibility_explanation(m_explanation);
        set_conflict1();
    }

    void set_conflict1() {
        m_eqs.reset();
        m_core.reset();
        m_params.reset();
        // m_solver->shrink_explanation_to_minimum(m_explanation); // todo, enable when perf is fixed
        /*
          static unsigned cn = 0;
          static unsigned num_l = 0;
          num_l+=m_explanation.size();
          std::cout << num_l / (++cn) << "\n";
        */
        ++m_num_conflicts;
        ++m_stats.m_conflicts;
        TRACE("arith", tout << "scope: " << ctx().get_scope_level() << "\n"; display_evidence(tout, m_explanation); );
        TRACE("arith", display(tout););
        for (auto const& ev : m_explanation) {
            if (!ev.first.is_zero()) { 
                set_evidence(ev.second);
            }
        }
        //        SASSERT(validate_conflict());
        dump_conflict();
        ctx().set_conflict(
            ctx().mk_justification(
                ext_theory_conflict_justification(
                    get_id(), ctx().get_region(), 
                    m_core.size(), m_core.c_ptr(), 
                    m_eqs.size(), m_eqs.c_ptr(), m_params.size(), m_params.c_ptr())));
    }

    justification * why_is_diseq(theory_var v1, theory_var v2) {
        return nullptr;
    }

    void reset_eh() {
        m_use_nra_model = false;
        m_arith_eq_adapter.reset_eh();
        m_solver = nullptr;
        m_internalize_head = 0;
        m_not_handled = nullptr;
        del_bounds(0);
        m_unassigned_bounds.reset();
        m_asserted_qhead  = 0;
        m_assume_eq_head = 0;
        m_scopes.reset();
        m_stats.reset();
        m_to_check.reset();
        reset_variable_values();
    }

    void init_model(model_generator & mg) {
        init_variable_values();
        m_factory = alloc(arith_factory, m);
        mg.register_factory(m_factory);
        TRACE("arith", display(tout););
    }

    nlsat::anum const& nl_value(theory_var v, scoped_anum& r) {
        SASSERT(m_nra);
        SASSERT(m_use_nra_model);
        lp::var_index vi = m_theory_var2var_index[v];
        if (m_solver->is_term(vi)) {

            m_todo_terms.push_back(std::make_pair(vi, rational::one()));

            m_nra->am().set(r, 0);
            while (!m_todo_terms.empty()) {
                rational wcoeff = m_todo_terms.back().second;
                //                 lp::var_index wi = m_todo_terms.back().first; // todo : got a warning "wi is not used"
                m_todo_terms.pop_back();
                lp::lar_term const& term = m_solver->get_term(vi);
                scoped_anum r1(m_nra->am());
                rational c1 = term.m_v * wcoeff;
                m_nra->am().set(r1, c1.to_mpq());
                m_nra->am().add(r, r1, r);                
                for (auto const coeff : term.m_coeffs) {
                    lp::var_index wi = coeff.first;
                    c1 = coeff.second * wcoeff;
                    if (m_solver->is_term(wi)) {
                        m_todo_terms.push_back(std::make_pair(wi, c1));
                    }
                    else {
                        m_nra->am().set(r1, c1.to_mpq());
                        m_nra->am().mul(m_nra->value(wi), r1, r1);
                        m_nra->am().add(r1, r, r);
                    }
                }
            }
            return r;
        }
        else {
            return m_nra->value(vi);
        }
    }

    model_value_proc * mk_value(enode * n, model_generator & mg) {
        theory_var v = n->get_th_var(get_id());
        expr* o = n->get_owner();
        if (m_use_nra_model) {
            anum const& an = nl_value(v, *m_a1);
            if (a.is_int(o) && !m_nra->am().is_int(an)) {
                return alloc(expr_wrapper_proc, a.mk_numeral(rational::zero(), a.is_int(o)));
            }
            return alloc(expr_wrapper_proc, a.mk_numeral(nl_value(v, *m_a1), a.is_int(o)));
        }
        else {
            rational r = get_value(v);
            TRACE("arith", tout << "v" << v << " := " << r << "\n";);
            if (a.is_int(o) && !r.is_int()) r = floor(r);
            return alloc(expr_wrapper_proc, m_factory->mk_value(r,  m.get_sort(o)));
        }
    }

    bool get_value(enode* n, expr_ref& r) {
        theory_var v = n->get_th_var(get_id());            
        if (!can_get_bound(v)) return false;
        lp::var_index vi = m_theory_var2var_index[v];
        rational val;
        if (m_solver->has_value(vi, val)) {
            if (is_int(n) && !val.is_int()) return false;
            r = a.mk_numeral(val, is_int(n));
            return true;
        }
        else {
            return false;
        }
    }    

    bool get_lower(enode* n, expr_ref& r) {
        theory_var v = n->get_th_var(get_id());
        if (!can_get_bound(v)) {
            TRACE("arith", tout << "cannot get lower for " << v << "\n";);
            return false;
        }
        lp::var_index vi = m_theory_var2var_index[v];
        lp::constraint_index ci;
        rational val;
        bool is_strict;
        if (m_solver->has_lower_bound(vi, ci, val, is_strict)) {
            r = a.mk_numeral(val, is_int(n));
            return true;
        }
        TRACE("arith", m_solver->print_constraints(tout << "does not have lower bound " << vi << "\n"););
        return false;
    }

    bool get_upper(enode* n, expr_ref& r) {
        theory_var v = n->get_th_var(get_id());
        if (!can_get_bound(v))
            return false;
        lp::var_index vi = m_theory_var2var_index[v];
        lp::constraint_index ci;
        rational val;
        bool is_strict;
        if (m_solver->has_upper_bound(vi, ci, val, is_strict)) {
            r = a.mk_numeral(val, is_int(n));
            return true;
        }
        TRACE("arith", m_solver->print_constraints(tout << "does not have upper bound " << vi << "\n"););
        return false;
    }

    bool validate_eq_in_model(theory_var v1, theory_var v2, bool is_true) const {
        SASSERT(v1 != null_theory_var);
        SASSERT(v2 != null_theory_var);
        return (get_value(v1) == get_value(v2)) == is_true;
    }

    // Auxiliary verification utilities.

    struct scoped_arith_mode {
        smt_params& p;
        scoped_arith_mode(smt_params& p) : p(p) {
            p.m_arith_mode = AS_OLD_ARITH;
        }
        ~scoped_arith_mode() {
            p.m_arith_mode = AS_NEW_ARITH;
        }
    };

    void dump_conflict() {
        if (dump_lemmas()) {
            unsigned id = ctx().display_lemma_as_smt_problem(m_core.size(), m_core.c_ptr(), m_eqs.size(), m_eqs.c_ptr(), false_literal);
            (void)id;
        }
    }

    bool validate_conflict() {
        if (m_arith_params.m_arith_mode != AS_NEW_ARITH) return true;
        scoped_arith_mode _sa(ctx().get_fparams());
        context nctx(m, ctx().get_fparams(), ctx().get_params());
        add_background(nctx);
        cancel_eh<reslimit> eh(m.limit());
        scoped_timer timer(1000, &eh);
        bool result = l_true != nctx.check();
        CTRACE("arith", !result, ctx().display_lemma_as_smt_problem(tout, m_core.size(), m_core.c_ptr(), m_eqs.size(), m_eqs.c_ptr(), false_literal););
        return result;
    }

    void dump_assign(literal lit) {
        if (dump_lemmas()) {                
            unsigned id = ctx().display_lemma_as_smt_problem(m_core.size(), m_core.c_ptr(), m_eqs.size(), m_eqs.c_ptr(), lit);
            (void)id;
        }
    }

    bool validate_assign(literal lit) {
        if (m_arith_params.m_arith_mode != AS_NEW_ARITH) return true;
        scoped_arith_mode _sa(ctx().get_fparams());
        context nctx(m, ctx().get_fparams(), ctx().get_params());
        m_core.push_back(~lit);
        add_background(nctx);
        m_core.pop_back();
        cancel_eh<reslimit> eh(m.limit());
        scoped_timer timer(1000, &eh);
        bool result = l_true != nctx.check();
        CTRACE("arith", !result, ctx().display_lemma_as_smt_problem(tout, m_core.size(), m_core.c_ptr(), m_eqs.size(), m_eqs.c_ptr(), lit);
               display(tout););   
        return result;
    }

    bool validate_eq(enode* x, enode* y) {
        if (m_arith_params.m_arith_mode == AS_NEW_ARITH) return true;
        context nctx(m, ctx().get_fparams(), ctx().get_params());
        add_background(nctx);
        nctx.assert_expr(m.mk_not(m.mk_eq(x->get_owner(), y->get_owner())));
        cancel_eh<reslimit> eh(m.limit());
        scoped_timer timer(1000, &eh);
        return l_true != nctx.check();
    }

    void add_background(context& nctx) {
        for (literal c : m_core) {
            expr_ref tmp(m);
            ctx().literal2expr(c, tmp);
            nctx.assert_expr(tmp);
        }
        for (auto const& eq : m_eqs) {
            nctx.assert_expr(m.mk_eq(eq.first->get_owner(), eq.second->get_owner()));
        }
    }        

    theory_lra::inf_eps value(theory_var v) {
        lp::impq ival = get_ivalue(v);
        return inf_eps(0, inf_rational(ival.x, ival.y));
    }

    theory_lra::inf_eps maximize(theory_var v, expr_ref& blocker, bool& has_shared) {
        lp::impq term_max;
        lp::lp_status st;
        if (!can_get_bound(v)) {
            st = lp::lp_status::UNBOUNDED;
        }
        else {
            lp::var_index vi = m_theory_var2var_index[v];
            st = m_solver->maximize_term(vi, term_max);
        }
        switch (st) {
        case lp::lp_status::OPTIMAL: {
            inf_rational val(term_max.x, term_max.y);
            blocker = mk_gt(v);
            return inf_eps(rational::zero(), val);
        }
        case lp::lp_status::FEASIBLE: {
            inf_rational val(term_max.x, term_max.y);
            blocker = mk_gt(v);
            return inf_eps(rational::zero(), val);
        }
        default:
            SASSERT(st == lp::lp_status::UNBOUNDED);
            TRACE("arith", tout << "Unbounded v" << v << "\n";);
            has_shared = false;
            blocker = m.mk_false();
            return inf_eps(rational::one(), inf_rational());
        }
    }

    expr_ref mk_gt(theory_var v) {
        lp::impq val = get_ivalue(v);
        expr* obj = get_enode(v)->get_owner();
        rational r = val.x;
        expr_ref e(m);
        if (a.is_int(m.get_sort(obj))) {
            if (r.is_int()) {
                r += rational::one();
            }
            else {
                r = ceil(r);
            }
            e = a.mk_numeral(r, m.get_sort(obj));
            e = a.mk_ge(obj, e);
        }
        else {
            e = a.mk_numeral(r, m.get_sort(obj));
            if (val.y.is_neg()) {
                e = a.mk_ge(obj, e);
            }
            else {
                e = a.mk_gt(obj, e);
            }
        }
        TRACE("opt", tout << "v" << v << " " << val << " " << r << " " << e << "\n";);
        return e;
    }

    theory_var add_objective(app* term) {
        return internalize_def(term);
    }

    void term2coeffs(lp::lar_term const& term, u_map<rational>& coeffs, rational const& coeff, rational& offset) {
        for (const auto & ti : term) {
            theory_var w;
            if (m_solver->is_term(ti.var())) {
                //w = m_term_index2theory_var.get(m_solver->adjust_term_index(ti.var()), null_theory_var);
                //if (w == null_theory_var) // if extracing expressions directly from nested term
                lp::lar_term const& term1 = m_solver->get_term(ti.var());
                rational coeff2 = coeff * ti.coeff();
                term2coeffs(term1, coeffs, coeff2, offset);
                continue;
            }
            else {
                w = m_var_index2theory_var[ti.var()];
            }
            rational c0(0);
            coeffs.find(w, c0);
            coeffs.insert(w, c0 + ti.coeff() * coeff);
        }
        offset += coeff * term.m_v;
    }

    app_ref coeffs2app(u_map<rational> const& coeffs, rational const& offset, bool is_int) {
        expr_ref_vector args(m);
         for (auto const& kv : coeffs) {
            theory_var w = kv.m_key;
            expr* o = get_enode(w)->get_owner();
            if (kv.m_value.is_zero()) {
                // continue
            }
            else if (kv.m_value.is_one()) {
                args.push_back(o);
            }
            else {
                args.push_back(a.mk_mul(a.mk_numeral(kv.m_value, is_int), o));                
            }
        }
        if (!offset.is_zero()) {
            args.push_back(a.mk_numeral(offset, is_int));
        }
        switch (args.size()) {
        case 0:
            return app_ref(a.mk_numeral(rational::zero(), is_int), m);
        case 1:
            return app_ref(to_app(args[0].get()), m);
        default:
            return app_ref(a.mk_add(args.size(), args.c_ptr()), m);
        }
    }

    app_ref mk_term(lp::lar_term const& term, bool is_int) {     
        u_map<rational> coeffs;
        rational offset;
        term2coeffs(term, coeffs, rational::one(), offset);
        return coeffs2app(coeffs, offset, is_int);
    }

    rational gcd_reduce(u_map<rational>& coeffs) {
        rational g(0);
         for (auto const& kv : coeffs) {
             g = gcd(g, kv.m_value);
         }
         if (!g.is_one() && !g.is_zero()) {
             for (auto& kv : coeffs) {
                 kv.m_value /= g;
             }             
         }
         return g;
    }

    app_ref mk_obj(theory_var v) {
        lp::var_index vi = m_theory_var2var_index[v];
        bool is_int = a.is_int(get_enode(v)->get_owner());
        if (m_solver->is_term(vi)) {           
            return mk_term(m_solver->get_term(vi), is_int);
        }
        else {
            theory_var w = m_var_index2theory_var[vi];
            return app_ref(get_enode(w)->get_owner(), m);
        }
    }

    expr_ref mk_ge(generic_model_converter& fm, theory_var v, inf_rational const& val) {
        rational r = val.get_rational();
        bool is_strict =  val.get_infinitesimal().is_pos();
        app_ref b(m);
        bool is_int = a.is_int(get_enode(v)->get_owner());
        if (is_strict) {
            b = a.mk_le(mk_obj(v), a.mk_numeral(r, is_int));
        }
        else {
            b = a.mk_ge(mk_obj(v), a.mk_numeral(r, is_int));
        }
        if (!ctx().b_internalized(b)) {
            fm.hide(b->get_decl());
            bool_var bv = ctx().mk_bool_var(b);
            ctx().set_var_theory(bv, get_id());
            // ctx().set_enode_flag(bv, true);
            lp_api::bound_kind bkind = lp_api::bound_kind::lower_t;
            if (is_strict) bkind = lp_api::bound_kind::upper_t;
            lp_api::bound* a = alloc(lp_api::bound, bv, v, is_int, r, bkind);
            mk_bound_axioms(*a);
            updt_unassigned_bounds(v, +1);
            m_bounds[v].push_back(a);
            m_bounds_trail.push_back(v);
            m_bool_var2bound.insert(bv, a);
            TRACE("arith", tout << mk_pp(b, m) << "\n";);
        }
        if (is_strict) {
            b = m.mk_not(b);
        }
        TRACE("arith", tout << b << "\n";);
        return expr_ref(b, m);
            
    }


    void display(std::ostream & out) const {
        if (m_solver) {
            m_solver->print_constraints(out);
            m_solver->print_terms(out);
            // auto pp = lp ::core_solver_pretty_printer<lp::mpq, lp::impq>(m_solver->m_mpq_lar_core_solver.m_r_solver, out);
            // pp.print();
        }
        unsigned nv = th.get_num_vars();
        for (unsigned v = 0; v < nv; ++v) {
            if (!ctx().is_relevant(get_enode(v))) out << "irr: ";
            out << "v" << v;
            if (can_get_value(v)) out << " = " << get_value(v); 
            if (is_int(v)) out << ", int";
            if (ctx().is_shared(get_enode(v))) out << ", shared";
            out << " := "; th.display_var_flat_def(out, v) << "\n";
        }
    }

    void display_evidence(std::ostream& out, vector<std::pair<rational, lp::constraint_index>> const& evidence) {
        for (auto const& ev : evidence) {
            expr_ref e(m);
            SASSERT(!ev.first.is_zero()); 
            if (ev.first.is_zero()) { 
                continue;
            }
            unsigned idx = ev.second;
            switch (m_constraint_sources.get(idx, null_source)) {
            case inequality_source: {
                literal lit = m_inequalities[idx];
                ctx().literal2expr(lit, e);
                out << e << " " << ctx().get_assignment(lit) << "\n";
                break;
            }
            case equality_source: 
                out << mk_pp(m_equalities[idx].first->get_owner(), m) << " = " 
                    << mk_pp(m_equalities[idx].second->get_owner(), m) << "\n"; 
                break;
            case definition_source: {
                theory_var v = m_definitions[idx];
                if (v != null_theory_var) 
                    out << "def: v" << v << " := " << mk_pp(th.get_enode(v)->get_owner(), m) << "\n";
                break;
            }
            case null_source:                    
            default:
                UNREACHABLE();
                break; 
            }
        }
        for (auto const& ev : evidence) {
            m_solver->print_constraint(ev.second, out << ev.first << ": "); 
        }
    }

    void collect_statistics(::statistics & st) const {
        m_arith_eq_adapter.collect_statistics(st);
        st.update("arith-lower", m_stats.m_assert_lower);
        st.update("arith-upper", m_stats.m_assert_upper);
        st.update("arith-rows", m_stats.m_add_rows);
        st.update("arith-propagations", m_stats.m_bounds_propagations);
        st.update("arith-iterations", m_stats.m_num_iterations);
        st.update("arith-factorizations", m_solver->settings().st().m_num_factorizations);
        st.update("arith-pivots", m_stats.m_need_to_solve_inf);
        st.update("arith-plateau-iterations", m_stats.m_num_iterations_with_no_progress);
        st.update("arith-fixed-eqs", m_stats.m_fixed_eqs);
        st.update("arith-conflicts", m_stats.m_conflicts);
        st.update("arith-bound-propagations-lp", m_stats.m_bound_propagations1);
        st.update("arith-bound-propagations-cheap", m_stats.m_bound_propagations2);
        st.update("arith-diseq", m_stats.m_assert_diseq);
        st.update("arith-make-feasible", m_solver->settings().st().m_make_feasible);
        st.update("arith-max-columns", m_solver->settings().st().m_max_cols);
        st.update("arith-max-rows", m_solver->settings().st().m_max_rows);
        st.update("gcd-calls", m_solver->settings().st().m_gcd_calls);
        st.update("gcd-conflict", m_solver->settings().st().m_gcd_conflicts);
        st.update("cube-calls", m_solver->settings().st().m_cube_calls);
        st.update("cube-success", m_solver->settings().st().m_cube_success);
        st.update("arith-patches", m_solver->settings().st().m_patches);
        st.update("arith-patches-success", m_solver->settings().st().m_patches_success);
        st.update("arith-hnf-calls", m_solver->settings().st().m_hnf_cutter_calls);
        st.update("arith-hnf-cuts", m_solver->settings().st().m_hnf_cuts);
    }        
};
    
theory_lra::theory_lra(ast_manager& m, theory_arith_params& ap):
    theory(m.get_family_id("arith")) {
    m_imp = alloc(imp, *this, m, ap);
}    
theory_lra::~theory_lra() {
    dealloc(m_imp);
}   
theory* theory_lra::mk_fresh(context* new_ctx) {
    return alloc(theory_lra, new_ctx->get_manager(), new_ctx->get_fparams());
}
void theory_lra::init(context * ctx) {
    theory::init(ctx);
    m_imp->init(ctx);
}
bool theory_lra::internalize_atom(app * atom, bool gate_ctx) {
    return m_imp->internalize_atom(atom, gate_ctx);
}
bool theory_lra::internalize_term(app * term) {
    return m_imp->internalize_term(term);
}
void theory_lra::internalize_eq_eh(app * atom, bool_var v) {
    m_imp->internalize_eq_eh(atom, v);
}
void theory_lra::assign_eh(bool_var v, bool is_true) {
    m_imp->assign_eh(v, is_true);
}
void theory_lra::new_eq_eh(theory_var v1, theory_var v2) {
    m_imp->new_eq_eh(v1, v2);
}
bool theory_lra::use_diseqs() const {
    return m_imp->use_diseqs();
}
void theory_lra::new_diseq_eh(theory_var v1, theory_var v2) {
    m_imp->new_diseq_eh(v1, v2);
}
void theory_lra::push_scope_eh() {
    theory::push_scope_eh();
    m_imp->push_scope_eh();
}
void theory_lra::pop_scope_eh(unsigned num_scopes) {
    m_imp->pop_scope_eh(num_scopes);
    theory::pop_scope_eh(num_scopes);
}
void theory_lra::restart_eh() {
    m_imp->restart_eh();
}
void theory_lra::relevant_eh(app* e) {
    m_imp->relevant_eh(e);
}
void theory_lra::init_search_eh() {
    m_imp->init_search_eh();
}
final_check_status theory_lra::final_check_eh() {
    return m_imp->final_check_eh();
}
bool theory_lra::is_shared(theory_var v) const {
    return m_imp->is_shared(v);
}
bool theory_lra::can_propagate() {
    return m_imp->can_propagate();
}
void theory_lra::propagate() {
    m_imp->propagate();
}
justification * theory_lra::why_is_diseq(theory_var v1, theory_var v2) {
    return m_imp->why_is_diseq(v1, v2);
}
void theory_lra::reset_eh() {
    m_imp->reset_eh();
}
void theory_lra::init_model(model_generator & m) {
    m_imp->init_model(m);
}
model_value_proc * theory_lra::mk_value(enode * n, model_generator & mg) {
    return m_imp->mk_value(n, mg);
}
bool theory_lra::get_value(enode* n, expr_ref& r) {
    return m_imp->get_value(n, r);
}
bool theory_lra::get_lower(enode* n, expr_ref& r) {
    return m_imp->get_lower(n, r);
}
bool theory_lra::get_upper(enode* n, expr_ref& r) {
    return m_imp->get_upper(n, r);
}

bool theory_lra::validate_eq_in_model(theory_var v1, theory_var v2, bool is_true) const {
    return m_imp->validate_eq_in_model(v1, v2, is_true);
}
void theory_lra::display(std::ostream & out) const {
    m_imp->display(out);
}
void theory_lra::collect_statistics(::statistics & st) const {
    m_imp->collect_statistics(st);
}
theory_lra::inf_eps theory_lra::value(theory_var v) {
    return m_imp->value(v);
}
theory_lra::inf_eps theory_lra::maximize(theory_var v, expr_ref& blocker, bool& has_shared) {
    return m_imp->maximize(v, blocker, has_shared);
}
theory_var theory_lra::add_objective(app* term) {
    return m_imp->add_objective(term);
}
expr_ref theory_lra::mk_ge(generic_model_converter& fm, theory_var v, inf_rational const& val) {
    return m_imp->mk_ge(fm, v, val);
}



}
