z3/lib/propagate_values_tactic.cpp

/*++
Copyright (c) 2011 Microsoft Corporation

Module Name:

    propagate_values_tactic.cpp

Abstract:

    Propagate values using equalities of the form (= t v) where v is a value,
    and atoms t and (not t)

Author:

    Leonardo de Moura (leonardo) 2011-12-28.

Revision History:

--*/
#include"tactical.h"
#include"propagate_values_tactic.h"
#include"th_rewriter.h"
#include"ast_smt2_pp.h"
#include"expr_substitution.h"
#include"goal_shared_occs.h"

class propagate_values_tactic : public tactic {
    struct     imp {
        ast_manager &                 m_manager;
        th_rewriter                   m_r;
        scoped_ptr<expr_substitution> m_subst;
        goal *                        m_goal;
        goal_shared_occs              m_occs;
        unsigned                      m_idx;
        unsigned                      m_max_rounds;
        bool                          m_modified;
        
        imp(ast_manager & m, params_ref const & p):
            m_manager(m),
            m_r(m, p),
            m_goal(0),
            m_occs(m, true /* track atoms */) {
            updt_params_core(p);
        }

        void updt_params_core(params_ref const & p) {
            m_max_rounds = p.get_uint(":max-rounds", 4);
        }
        
        void updt_params(params_ref const & p) {
            m_r.updt_params(p);
            updt_params_core(p);
        }

        ast_manager & m() const { return m_manager; }
        
        void set_cancel(bool f) {
            m_r.set_cancel(f);
        }
        
        bool is_shared(expr * t) {
            return m_occs.is_shared(t);
        }
        
        bool is_shared_neg(expr * t, expr * & atom) {
            if (!m().is_not(t))
                return false;
            atom = to_app(t)->get_arg(0);
            return is_shared(atom);
        }

        bool is_shared_eq(expr * t, expr * & lhs, expr * & value) {
            if (!m().is_eq(t))
                return false;
            expr * arg1 = to_app(t)->get_arg(0);
            expr * arg2 = to_app(t)->get_arg(1);
            if (m().is_value(arg1) && is_shared(arg2)) {
                lhs   = arg2;
                value = arg1;
                return true;
            }
            if (m().is_value(arg2) && is_shared(arg1)) {
                lhs   = arg1;
                value = arg2;
                return true;
            }
            return false;
        }
        
        void push_result(expr * new_curr, proof * new_pr) {
            if (m_goal->proofs_enabled()) {
                proof * pr = m_goal->pr(m_idx);
                new_pr     = m().mk_modus_ponens(pr, new_pr);
            }
            
            expr_dependency_ref new_d(m());
            if (m_goal->unsat_core_enabled()) {
                new_d = m_goal->dep(m_idx);
                expr_dependency * used_d = m_r.get_used_dependencies();
                if (used_d != 0) {
                    new_d = m().mk_join(new_d, used_d);
                    m_r.reset_used_dependencies();
                }
            }
            
            m_goal->update(m_idx, new_curr, new_pr, new_d);
        
            if (is_shared(new_curr)) {
                m_subst->insert(new_curr, m().mk_true(), m().mk_iff_true(new_pr), new_d);
            }
            expr * atom;
            if (is_shared_neg(new_curr, atom)) {
                m_subst->insert(atom, m().mk_false(), m().mk_iff_false(new_pr), new_d);
            }
            expr * lhs, * value;
            if (is_shared_eq(new_curr, lhs, value)) {
                TRACE("shallow_context_simplifier_bug", tout << "found eq:\n" << mk_ismt2_pp(new_curr, m()) << "\n";);
                m_subst->insert(lhs, value, new_pr, new_d);
            }
        }
        
        void process_current() {
            expr * curr = m_goal->form(m_idx);
            expr_ref   new_curr(m());
            proof_ref  new_pr(m());
            
            if (!m_subst->empty()) {
                m_r(curr, new_curr, new_pr);
            }
            else {
                new_curr = curr;
                if (m().proofs_enabled())
                    new_pr   = m().mk_reflexivity(curr);
            }

            TRACE("shallow_context_simplifier_bug", tout << mk_ismt2_pp(curr, m()) << "\n---->\n" << mk_ismt2_pp(new_curr, m()) << "\n";);
            push_result(new_curr, new_pr);
            if (new_curr != curr)
                m_modified = true;
        }

        void operator()(goal_ref const & g, 
                        goal_ref_buffer & result, 
                        model_converter_ref & mc, 
                        proof_converter_ref & pc,
                        expr_dependency_ref & core) {
            SASSERT(g->is_well_sorted());
            mc = 0; pc = 0; core = 0;
            tactic_report report("propagate-values", *g);
            m_goal = g.get();

            bool forward   = true;
            expr_ref   new_curr(m());
            proof_ref  new_pr(m());
            unsigned size  = m_goal->size();
            m_idx          = 0;
            m_modified     = false;
            unsigned round = 0;

            if (m_goal->inconsistent())
                goto end;

            m_subst = alloc(expr_substitution, m(), g->unsat_core_enabled(), g->proofs_enabled());
            m_r.set_substitution(m_subst.get());
            m_occs(*m_goal);

            while (true) {
                TRACE("propagate_values", m_goal->display(tout););
                if (forward) {
                    for (; m_idx < size; m_idx++) {
                        process_current();
                        if (m_goal->inconsistent()) 
                            goto end;
                    }
                    if (m_subst->empty() && !m_modified)
                        goto end;
                    m_occs(*m_goal);
                    m_idx        = m_goal->size();
                    forward      = false;
                    m_subst->reset();
                    m_r.set_substitution(m_subst.get()); // reset, but keep substitution
                }
                else {
                    while (m_idx > 0) {
                        m_idx--;
                        process_current();
                        if (m_goal->inconsistent()) 
                            goto end;
                    }
                    if (!m_modified)
                        goto end;
                    m_subst->reset();
                    m_r.set_substitution(m_subst.get()); // reset, but keep substitution
                    m_modified   = false;
                    m_occs(*m_goal);
                    m_idx        = 0;
                    size         = m_goal->size();
                    forward      = true;
                }
                round++;
                if (round >= m_max_rounds)
                    break;
                IF_VERBOSE(100, verbose_stream() << "starting new round, goal size: " << m_goal->num_exprs() << std::endl;);
                TRACE("propgate_values", tout << "round finished\n"; m_goal->display(tout); tout << "\n";);
            }
        end:
            m_goal->elim_redundancies();
            m_goal->inc_depth();
            result.push_back(m_goal);
            SASSERT(m_goal->is_well_sorted());
            TRACE("propagate_values", m_goal->display(tout););
            m_goal = 0;
        }
    };
    
    imp *      m_imp;
    params_ref m_params;
public:
    propagate_values_tactic(ast_manager & m, params_ref const & p):
        m_params(p) {
        m_imp = alloc(imp, m, p);
    }

    virtual tactic * translate(ast_manager & m) {
        return alloc(propagate_values_tactic, m, m_params);
    }
    
    virtual ~propagate_values_tactic() {
        dealloc(m_imp);
    }

    virtual void updt_params(params_ref const & p) {
        m_params = p;
        m_imp->updt_params(p);
    }

    virtual void collect_param_descrs(param_descrs & r) {
        th_rewriter::get_param_descrs(r);
        r.insert(":max-rounds", CPK_UINT, "(default: 2) maximum number of rounds.");
    }
    
    virtual void operator()(goal_ref const & in, 
                            goal_ref_buffer & result, 
                            model_converter_ref & mc, 
                            proof_converter_ref & pc,
                            expr_dependency_ref & core) {
        (*m_imp)(in, result, mc, pc, core);
    }
    
    virtual void cleanup() {
        ast_manager & m = m_imp->m();
        imp * d = m_imp;
        #pragma omp critical (tactic_cancel)
        {
            m_imp = 0;
        }
        dealloc(d);
        d = alloc(imp, m, m_params);
        #pragma omp critical (tactic_cancel)
        {
            m_imp = d;
        }
    }
    
protected:
    virtual void set_cancel(bool f) {
        if (m_imp)
            m_imp->set_cancel(f);
    }
};

tactic * mk_propagate_values_tactic(ast_manager & m, params_ref const & p) {
    return clean(alloc(propagate_values_tactic, m, p));
}