src/solver/combined_solver.cpp

/*++
Copyright (c) 2012 Microsoft Corporation

Module Name:

    combined_solver.cpp

Abstract:

    Implements the solver API by combining two solvers.

    This is a replacement for the strategic_solver class.

Author:

    Leonardo (leonardo) 2012-12-11

Notes:

--*/
#include "util/scoped_timer.h"
#include "util/common_msgs.h"
#include "ast/ast_pp.h"
#include "solver/solver.h"
#include "solver/combined_solver_params.hpp"
#include <atomic>
#define PS_VB_LVL 15

/**
   \brief Implementation of the solver API that combines two given solvers.

   The combined solver has two modes:
       - non-incremental
       - incremental
   In non-incremental mode, the first solver is used.
   In incremental mode, the second one is used.

   A timeout for the second solver can be specified.
   If the timeout is reached, then the first solver is executed.

   The object switches to incremental when:
       - push is used
       - assertions are performed after a check_sat
       - parameter ignore_solver1==false
*/
class combined_solver : public solver {
public:
    // Behavior when the incremental solver returns unknown.
    enum inc_unknown_behavior {
        IUB_RETURN_UNDEF,      // just return unknown
        IUB_USE_TACTIC_IF_QF,  // invoke tactic if problem is quantifier free
        IUB_USE_TACTIC         // invoke tactic
    };

private:
    bool                 m_inc_mode;
    bool                 m_check_sat_executed;
    bool                 m_use_solver1_results;
    ref<solver>          m_solver1;
    ref<solver>          m_solver2;
    // We delay sending assertions to solver 2
    // This is relevant for big benchmarks that are meant to be solved
    // by a non-incremental solver.                                                 );

    bool                 m_ignore_solver1;
    inc_unknown_behavior m_inc_unknown_behavior;
    unsigned             m_inc_timeout;

    void switch_inc_mode() {
        m_inc_mode = true;
    }

    struct aux_timeout_eh : public event_handler {
        solver *        m_solver;
        std::atomic<bool> m_canceled;
        aux_timeout_eh(solver * s):m_solver(s), m_canceled(false) {}
        ~aux_timeout_eh() override {
            if (m_canceled) {
                m_solver->get_manager().limit().dec_cancel();
            }
        }
        void operator()(event_handler_caller_t caller_id) override {
            m_canceled = true;
            m_solver->get_manager().limit().inc_cancel();
        }
    };

    void updt_local_params(params_ref const & _p) {
        combined_solver_params p(_p);
        m_inc_timeout    = p.solver2_timeout();
        m_ignore_solver1 = p.ignore_solver1();
        m_inc_unknown_behavior = static_cast<inc_unknown_behavior>(p.solver2_unknown());
    }

    ast_manager& get_manager() const override { return m_solver1->get_manager(); }

    bool has_quantifiers() const {
        unsigned sz = get_num_assertions();
        for (unsigned i = 0; i < sz; i++) {
            if (::has_quantifiers(get_assertion(i)))
                return true;
        }
        return false;
    }

    bool use_solver1_when_undef() const {
        switch (m_inc_unknown_behavior) {
        case IUB_RETURN_UNDEF: return false;
        case IUB_USE_TACTIC_IF_QF: return !has_quantifiers();
        case IUB_USE_TACTIC: return true;
        default:
            UNREACHABLE();
            return false;
        }
    }

public:
    combined_solver(solver * s1, solver * s2, params_ref const & p) {
        m_solver1 = s1;
        m_solver2 = s2;
        updt_local_params(p);
        m_inc_mode            = false;
        m_check_sat_executed  = false;
        m_use_solver1_results = true;
    }

    solver* translate(ast_manager& m, params_ref const& p) override {
        TRACE("solver", tout << "translate\n";);
        solver* s1 = m_solver1->translate(m, p);
        solver* s2 = m_solver2->translate(m, p);
        combined_solver* r = alloc(combined_solver, s1, s2, p);
        r->m_inc_mode = m_inc_mode;
        r->m_check_sat_executed = m_check_sat_executed;
        r->m_use_solver1_results = m_use_solver1_results;
        return r;
    }

    void set_phase(expr* e) override { m_solver1->set_phase(e); m_solver2->set_phase(e); }
    solver::phase* get_phase() override { auto* p = m_solver1->get_phase(); if (!p) p = m_solver2->get_phase(); return p; }
    void set_phase(solver::phase* p) override { m_solver1->set_phase(p); m_solver2->set_phase(p); }
    void move_to_front(expr* e) override { m_solver1->move_to_front(e); m_solver2->move_to_front(e); }

    void updt_params(params_ref const & p) override {
        solver::updt_params(p);
        m_solver1->updt_params(p);
        m_solver2->updt_params(p);
        updt_local_params(p);
    }

    void collect_param_descrs(param_descrs & r) override {
        m_solver1->collect_param_descrs(r);
        m_solver2->collect_param_descrs(r);
        combined_solver_params::collect_param_descrs(r);
    }

    void set_produce_models(bool f) override {
        m_solver1->set_produce_models(f);
        m_solver2->set_produce_models(f);
    }

    void assert_expr_core(expr * t) override {
        if (m_check_sat_executed)
            switch_inc_mode();
        m_solver1->assert_expr(t);
        m_solver2->assert_expr(t);
    }

    void assert_expr_core2(expr * t, expr * a) override {
        if (m_check_sat_executed)
            switch_inc_mode();
        m_solver1->assert_expr(t, a);
        m_solver2->assert_expr(t, a);
    }

    void push() override {
        switch_inc_mode();
        m_solver1->push();
        m_solver2->push();
        TRACE("pop", tout << "push\n";);
    }

    void pop(unsigned n) override {
        TRACE("pop", tout << n << "\n";);
        switch_inc_mode();
        m_solver1->pop(n);
        m_solver2->pop(n);
    }

    unsigned get_scope_level() const override {
        return m_solver1->get_scope_level();
    }

    lbool get_consequences(expr_ref_vector const& asms, expr_ref_vector const& vars, expr_ref_vector& consequences) override {
        switch_inc_mode();
        m_use_solver1_results = false;
        try {
            return m_solver2->get_consequences(asms, vars, consequences);
        }
        catch (z3_exception& ex) {
            if (!get_manager().inc()) {
                throw;
            }
            else {
                set_reason_unknown(ex.msg());
            }
        }
        return l_undef;
    }

    lbool check_sat_core(unsigned num_assumptions, expr * const * assumptions) override {
        m_check_sat_executed  = true;
        m_use_solver1_results = false;

        if (get_num_assumptions() != 0 ||
            num_assumptions > 0 ||  // assumptions were provided
            m_ignore_solver1)  {
            // must use incremental solver
            switch_inc_mode();
            return m_solver2->check_sat_core(num_assumptions, assumptions);
        }

        if (m_inc_mode) {
            if (m_inc_timeout == UINT_MAX) {
                IF_VERBOSE(PS_VB_LVL, verbose_stream() << "(combined-solver \"using solver 2 (without a timeout)\")\n";);
                lbool r = m_solver2->check_sat_core(num_assumptions, assumptions);
                if (r != l_undef || !use_solver1_when_undef() || !get_manager().inc()) {
                    return r;
                }
            }
            else {
                IF_VERBOSE(PS_VB_LVL, verbose_stream() << "(combined-solver \"using solver 2 (with timeout)\")\n";);
                aux_timeout_eh eh(m_solver2.get());
                lbool r = l_undef;
                try {
                    scoped_timer timer(m_inc_timeout, &eh);
                    r = m_solver2->check_sat_core(num_assumptions, assumptions);
                }
                catch (z3_exception&) {
                    if (!eh.m_canceled) {
                        throw;
                    }
                }
                if ((r != l_undef || !use_solver1_when_undef()) && !eh.m_canceled) {
                    return r;
                }
            }
            IF_VERBOSE(PS_VB_LVL, verbose_stream() << "(combined-solver \"solver 2 failed, trying solver1\")\n";);
        }

        IF_VERBOSE(PS_VB_LVL, verbose_stream() << "(combined-solver \"using solver 1\")\n";);
        m_use_solver1_results = true;
        return m_solver1->check_sat_core(num_assumptions, assumptions);
    }

    void set_progress_callback(progress_callback * callback) override {
        m_solver1->set_progress_callback(callback);
        m_solver2->set_progress_callback(callback);
    }

    unsigned get_num_assertions() const override {
        return m_solver1->get_num_assertions();
    }

    expr * get_assertion(unsigned idx) const override {
        return m_solver1->get_assertion(idx);
    }

    unsigned get_num_assumptions() const override {
        return m_solver1->get_num_assumptions() + m_solver2->get_num_assumptions();
    }

    expr_ref_vector cube(expr_ref_vector& vars, unsigned backtrack_level) override {
        switch_inc_mode();
        return m_solver2->cube(vars, backtrack_level);
    }

    expr * get_assumption(unsigned idx) const override {
        unsigned c1 = m_solver1->get_num_assumptions();
        if (idx < c1) return m_solver1->get_assumption(idx);
        return m_solver2->get_assumption(idx - c1);
    }

    std::ostream& display(std::ostream & out, unsigned n, expr* const* es) const override {
        return m_solver1->display(out, n, es);
    }

    void collect_statistics(statistics & st) const override {
        m_solver2->collect_statistics(st);
        if (m_use_solver1_results)
            m_solver1->collect_statistics(st);
    }

    void get_unsat_core(expr_ref_vector & r) override {
        if (m_use_solver1_results)
            m_solver1->get_unsat_core(r);
        else
            m_solver2->get_unsat_core(r);
    }

    void get_model_core(model_ref & m) override {
        if (m_use_solver1_results)
            m_solver1->get_model(m);
        else
            m_solver2->get_model(m);
    }

    void get_levels(ptr_vector<expr> const& vars, unsigned_vector& depth) override {
        if (m_use_solver1_results)
            m_solver1->get_levels(vars, depth);
        else
            m_solver2->get_levels(vars, depth);
    }

    expr_ref_vector get_trail() override {
        if (m_use_solver1_results)
            return m_solver1->get_trail();
        else
            return m_solver2->get_trail();
    }

    proof * get_proof() override {
        if (m_use_solver1_results)
            return m_solver1->get_proof();
        else
            return m_solver2->get_proof();
    }

    std::string reason_unknown() const override {
        if (m_use_solver1_results)
            return m_solver1->reason_unknown();
        else
            return m_solver2->reason_unknown();
    }

    void set_reason_unknown(char const* msg) override {
        m_solver1->set_reason_unknown(msg);
        m_solver2->set_reason_unknown(msg);
    }

    void get_labels(svector<symbol> & r) override {
        if (m_use_solver1_results)
            return m_solver1->get_labels(r);
        else
            return m_solver2->get_labels(r);
    }

};


solver * mk_combined_solver(solver * s1, solver * s2, params_ref const & p) {
    return alloc(combined_solver, s1, s2, p);
}

class combined_solver_factory : public solver_factory {
    scoped_ptr<solver_factory> m_f1;
    scoped_ptr<solver_factory> m_f2;
public:
    combined_solver_factory(solver_factory * f1, solver_factory * f2):m_f1(f1), m_f2(f2) {}
    ~combined_solver_factory() override {}

    solver * operator()(ast_manager & m, params_ref const & p, bool proofs_enabled, bool models_enabled, bool unsat_core_enabled, symbol const & logic) override {
        return mk_combined_solver((*m_f1)(m, p, proofs_enabled, models_enabled, unsat_core_enabled, logic),
                                  (*m_f2)(m, p, proofs_enabled, models_enabled, unsat_core_enabled, logic),
                                  p);
    }
};

solver_factory * mk_combined_solver_factory(solver_factory * f1, solver_factory * f2) {
    return alloc(combined_solver_factory, f1, f2);
}