z3/src/ackermannization/lackr_model_constructor.cpp

/*++
 Copyright (c) 2015 Microsoft Corporation

 Module Name:

  model_constructor.cpp

 Abstract:


 Author:

 Mikolas Janota

 Revision History:
--*/
#include "ackermannization/lackr_model_constructor.h"
#include "model/model_evaluator.h"
#include "ast/ast_smt2_pp.h"
#include "ackermannization/ackr_info.h"
#include "ast/for_each_expr.h"
#include "ast/rewriter/bv_rewriter.h"
#include "ast/rewriter/bool_rewriter.h"
#include <iostream>

struct lackr_model_constructor::imp {
public:
    imp(ast_manager & m,
        ackr_info_ref info,
        model_ref & abstr_model,
        conflict_list & conflicts)
        : m(m)
        , m_info(info)
        , m_abstr_model(abstr_model)
        , m_conflicts(conflicts)
        , m_pinned(m)
        , m_b_rw(m)
        , m_bv_rw(m)
        , m_evaluator(nullptr)
        , m_empty_model(m)
        , m_ackr_helper(m)
    {}
    
    ~imp() { }
    
    //
    // Returns true iff model was successfully constructed.
    // Conflicts are saved as a side effect.
    //
    bool check() {
        bool retv = true;
        for (unsigned i = 0; i < m_abstr_model->get_num_constants(); i++) {
            func_decl * const c = m_abstr_model->get_constant(i);
            app * const  _term = m_info->find_term(c);
            expr * const term  = _term ? _term : m.mk_const(c);
            if (!check_term(term)) retv = false;
        }
        return retv;
    }
    
    
    void make_model(model_ref& destination) {
        for (unsigned i = 0; i < m_abstr_model->get_num_uninterpreted_sorts(); i++) {
            sort * const s = m_abstr_model->get_uninterpreted_sort(i);
            ptr_vector<expr> u = m_abstr_model->get_universe(s);
            destination->register_usort(s, u.size(), u.data());
        }
        
        for (unsigned i = 0; i < m_abstr_model->get_num_functions(); i++) {
            func_decl * const fd = m_abstr_model->get_function(i);
            func_interp * const fi = m_abstr_model->get_func_interp(fd);
            destination->register_decl(fd, fi);
        }
        
        for (auto & kv : m_app2val) {
            app * a = kv.m_key;
            if (a->get_num_args() == 0) 
                destination->register_decl(a->get_decl(), kv.m_value);
        }
        
        obj_map<func_decl, func_interp*> interpretations;
        for (auto & kv : m_values2val) {
            add_entry(kv.m_key, kv.m_value.value, interpretations);
        }
        
        for (auto & kv : interpretations) {
            func_decl* const fd = kv.m_key;
            func_interp* const fi = kv.get_value();
            fi->set_else(m.get_some_value(fd->get_range()));
            destination->register_decl(fd, fi);
        }
    }
    
    void add_entry(app* term, expr* value,
                   obj_map<func_decl, func_interp*>& interpretations) {
        func_interp* fi = nullptr;
        func_decl * const declaration = term->get_decl();
        const unsigned sz = declaration->get_arity();
        SASSERT(sz == term->get_num_args());
        if (!interpretations.find(declaration, fi)) {
            fi = alloc(func_interp, m, sz);
            interpretations.insert(declaration, fi);
        }
        fi->insert_new_entry(term->get_args(), value);
    }
private:
    ast_manager&                    m;    
    ackr_info_ref                   m_info;
    model_ref&                      m_abstr_model;
    conflict_list&                  m_conflicts;
    ast_ref_vector                  m_pinned;
    bool_rewriter                   m_b_rw;
    bv_rewriter                     m_bv_rw;
    scoped_ptr<model_evaluator>     m_evaluator;
    model                           m_empty_model;
private:
    struct val_info { expr * value; app * source_term; };
    typedef obj_map<app, expr *> app2val_t;
    typedef obj_map<app, val_info> values2val_t;
    values2val_t     m_values2val;
    app2val_t        m_app2val;
    ptr_vector<expr> m_stack;
    ackr_helper      m_ackr_helper;
    expr_mark        m_visited;
    
    static inline val_info mk_val_info(expr* value, app* source_term) {
        val_info rv;
        rv.value = value;
        rv.source_term = source_term;
        return rv;
    }
    
    // Performs congruence check on a given term.
    bool check_term(expr * term) {
        m_stack.push_back(term);
        const bool rv = _check_stack();
        m_stack.reset();
        return rv;
    }
    
    // Performs congruence check on terms on the stack.
    // Stops upon the first failure.
    // Returns true if and only if all congruence checks succeeded.
    bool _check_stack() {
        if (!m_evaluator) {
            m_evaluator = alloc(model_evaluator, m_empty_model);
        }
        expr *  curr;
        while (!m_stack.empty()) {
            curr = m_stack.back();
            if (m_visited.is_marked(curr)) {
                m_stack.pop_back();
                continue;
            }
            
            switch (curr->get_kind()) {
            case AST_VAR:
                UNREACHABLE();
                return false;
            case AST_APP: {
                app * a = to_app(curr);
                if (for_each_expr_args(m_stack, m_visited, a->get_num_args(), a->get_args())) {
                    m_visited.mark(a, true);
                    m_stack.pop_back();
                    if (!mk_value(a)) return false;
                }
                break;
            }
            case AST_QUANTIFIER:
                UNREACHABLE();
                return false;
            default:
                UNREACHABLE();
                return false;
            }
        }
        return true;
    }
    
    inline bool is_val(expr * e) { return m.is_value(e); }
    
    inline bool eval_cached(app * a, expr *& val) {
        if (is_val(a)) { 
            val = a; 
            return true; 
        }
        return m_app2val.find(a, val);
    }
    
    bool evaluate(app * a, expr_ref& result) {
        SASSERT(!is_val(a));
        const unsigned num = a->get_num_args();
        if (num == 0) { // handle constants
            make_value_constant(a, result);
            return true;
        }
        // evaluate arguments
        expr_ref_vector values(m);
        values.reserve(num);
        expr * const * args = a->get_args();
        for (unsigned i = 0; i < num; ++i) {
            expr * val = nullptr;
            const bool b = eval_cached(to_app(args[i]), val); // TODO: OK conversion to_app?
            CTRACE("model_constructor", m_conflicts.empty() && !b, tout << "fail arg val(\n" << mk_ismt2_pp(args[i], m, 2) << '\n'; );
            if (!b) {
                // bailing out because args eval failed previously
                return false;
            }
            TRACE("model_constructor", tout <<
                  "arg val " << i << "(\n" << mk_ismt2_pp(args[i], m, 2)
                  << " : " << mk_ismt2_pp(val, m, 2) << '\n'; );
            SASSERT(b);
            values[i] = val;
        }
        // handle functions
        if (m_ackr_helper.is_uninterp_fn(a)) { // handle uninterpreted
            app_ref key(m.mk_app(a->get_decl(), values.data()), m);
            if (!make_value_uninterpreted_function(a, key.get(), result)) {
                return false;
            }
        }
        else if (m_ackr_helper.is_select(a)) {
            // fail on select terms
            return false;
        }
        else { // handle interpreted
            make_value_interpreted_function(a, values, result);
        }
        return true;
    }
    
    //
    // Check and record the value for a given term, given that all arguments are already checked.
    //
    bool mk_value(app * a) {
        if (is_val(a))
            return true; // skip numerals
        TRACE("model_constructor", tout << "mk_value(\n" << mk_ismt2_pp(a, m, 2) << ")\n";);
        SASSERT(!m_app2val.contains(a));
        expr_ref result(m);
        if (!evaluate(a, result))
            return false;
        TRACE("model_constructor",
              tout << "map term(\n" << mk_ismt2_pp(a, m, 2) << "\n->"
              << mk_ismt2_pp(result.get(), m, 2)<< ")\n"; );
        CTRACE("model_constructor",
               !is_val(result.get()),
               tout << "eval didn't create a constant \n" << mk_ismt2_pp(a, m, 2) << " " << mk_ismt2_pp(result, m, 2) << "\n";
               );
        m_app2val.insert(a, result.get()); // memoize
        m_pinned.push_back(a);
        m_pinned.push_back(result);
        return true;
    }
    
    // Constants from the abstract model are directly mapped to the concrete one.
    void make_value_constant(app * const a, expr_ref& result) {
        SASSERT(a->get_num_args() == 0);
        func_decl * const fd = a->get_decl();
        expr * val = m_abstr_model->get_const_interp(fd);
        if (val == nullptr) { // TODO: avoid model completion?
            sort * s = fd->get_range();
            val = m_abstr_model->get_some_value(s);
        }
        result = val;
    }
    
    bool make_value_uninterpreted_function(app* a,
                                           app* key,
                                           expr_ref& result) {
        // get ackermann constant
        app * const ac = m_info->get_abstr(a);
        func_decl * const a_fd = a->get_decl();
        SASSERT(ac->get_num_args() == 0);
        SASSERT(a_fd->get_range() == ac->get_decl()->get_range());
        expr_ref value(m);
        value = m_abstr_model->get_const_interp(ac->get_decl());
        // get ackermann constant's interpretation
        if (value.get() == nullptr) { // TODO: avoid model completion?
            sort * s = a_fd->get_range();
            value = m_abstr_model->get_some_value(s);
        }
        // check congruence
        val_info vi;
        if(m_values2val.find(key,vi)) { // already is mapped to a value
            SASSERT(vi.source_term);
            const bool ok =  vi.value == value;
            if (!ok) {
                TRACE("model_constructor",
                      tout << "already mapped by(\n" << mk_ismt2_pp(vi.source_term, m, 2) << "\n->"
                      << mk_ismt2_pp(vi.value, m, 2) << ")\n"; );
                m_conflicts.push_back(std::make_pair(a, vi.source_term));
            }
            result = vi.value;
            return ok;
        } 
        else {                        // new value
            result = value;
            vi.value = value;
            vi.source_term = a;
            m_values2val.insert(key,vi);
            m_pinned.push_back(vi.source_term);
            m_pinned.push_back(vi.value);
            m_pinned.push_back(key);
            return true;
        }
        UNREACHABLE();
        return true;
    }
    
    void make_value_interpreted_function(app* a,
                                         expr_ref_vector& values,
                                         expr_ref& result) {
        const unsigned num = values.size();
        func_decl * const fd = a->get_decl();
        const family_id fid = fd->get_family_id();
        expr_ref term(m);
        term = m.mk_app(a->get_decl(), num, values.data());
        m_evaluator->operator() (term, result);
        TRACE("model_constructor",
              tout << "eval(\n" << mk_ismt2_pp(term.get(), m, 2) << "\n->"
              << mk_ismt2_pp(result.get(), m, 2) << ")\n"; );
        return;
        if (fid == m_b_rw.get_fid()) {
            decl_kind k = fd->get_decl_kind();
            if (k == OP_EQ) {
                // theory dispatch for =
                SASSERT(num == 2);
                family_id s_fid = values[0]->get_sort()->get_family_id();
                if (s_fid == m_bv_rw.get_fid())
                    m_bv_rw.mk_eq_core(values.get(0), values.get(1), result);
            } else {
                m_b_rw.mk_app_core(fd, num, values.data(), result);
            }
        } else {
            if (fid == m_bv_rw.get_fid()) {
                m_bv_rw.mk_app_core(fd, num, values.data(), result);
            }
            else {
                UNREACHABLE();
            }
        }
    }
};

lackr_model_constructor::lackr_model_constructor(ast_manager& m, ackr_info_ref info)
    : m_imp(nullptr)
    , m(m)
    , m_state(UNKNOWN)
    , m_info(info)
    , m_ref_count(0)
{}

lackr_model_constructor::~lackr_model_constructor() {
    dealloc(m_imp);
}

bool lackr_model_constructor::check(model_ref& abstr_model) {
    m_conflicts.reset();
    dealloc(m_imp);
    m_imp = alloc(lackr_model_constructor::imp, m, m_info, abstr_model, m_conflicts);
    const bool rv = m_imp->check();
    m_state = rv ? CHECKED : CONFLICT;
    return rv;
}

void lackr_model_constructor::make_model(model_ref& model) {
    SASSERT(m_state == CHECKED);
    m_imp->make_model(model);
}