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https://github.com/Z3Prover/z3
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266 lines
10 KiB
C++
266 lines
10 KiB
C++
/*++
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Copyright (c) 2011 Microsoft Corporation
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Module Name:
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bound_propagator.h
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Abstract:
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Bound propagators for arithmetic.
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Support class for implementing strategies and search procedures
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Author:
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Leonardo de Moura (leonardo) 2011-06-18.
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Revision History:
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--*/
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#ifndef _BOUND_PROPAGATOR_H_
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#define _BOUND_PROPAGATOR_H_
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#include"mpq.h"
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#include"vector.h"
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#include"params.h"
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#include"statistics.h"
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#include"numeral_buffer.h"
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#include"linear_equation.h"
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class bound_propagator {
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public:
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typedef unsigned var;
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typedef unsigned assumption;
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typedef unsynch_mpq_manager numeral_manager;
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typedef unsigned_vector assumption_vector;
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typedef unsigned constraint_id;
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typedef numeral_buffer<mpz, numeral_manager> mpz_buffer;
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typedef svector<double> double_vector;
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static const assumption null_assumption = UINT_MAX;
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static const var null_var = UINT_MAX;
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static const unsigned null_constraint_idx = UINT_MAX;
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class trail_info {
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unsigned m_x_lower;
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public:
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trail_info(var x, bool is_lower):m_x_lower((x << 1) + static_cast<unsigned>(is_lower)) {}
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trail_info():m_x_lower(UINT_MAX) {}
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var x() const { return m_x_lower >> 1; }
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bool is_lower() const { return (m_x_lower & 1) != 0; }
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};
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protected:
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enum ckind { LINEAR // only linear equalities so far.
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};
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/**
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\brief Constraints don't need justification.
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*/
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class constraint {
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friend class bound_propagator;
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unsigned m_kind:2;
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unsigned m_dead:1;
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unsigned m_timestamp; // Constraint tried to propagate new bounds using bounds with timestamp < m_timestamp.
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unsigned m_act; // activity
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unsigned m_counter; // number of times the constraint propagated
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union {
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linear_equation * m_eq;
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};
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};
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enum bkind { AXIOM, // doesn't need justification
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ASSUMPTION, // aka external case-split, it is used to connect with external search engine.
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DERIVED, // implied
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DECISION // internal case-split
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};
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struct bound {
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mpq m_k;
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double m_approx_k;
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unsigned m_lower:1;
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unsigned m_strict:1;
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unsigned m_mark:1;
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unsigned m_kind:2;
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unsigned m_level:27;
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unsigned m_timestamp;
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union {
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assumption m_assumption;
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unsigned m_constraint_idx;
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};
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bound * m_prev;
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bound(numeral_manager & m, mpq const & k, double approx_k, bool lower, bool strict, unsigned lvl, unsigned ts, bkind bk,
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unsigned c_idx, assumption a, bound * prev);
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bound * at(unsigned timestamp);
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bkind kind() const { return static_cast<bkind>(m_kind); }
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bool is_lower() const { return m_lower != 0; }
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};
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typedef ptr_vector<bound> var2bound;
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typedef svector<var> var_vector;
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typedef svector<constraint> constraint_vector;
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typedef unsigned_vector c_idx_vector;
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typedef c_idx_vector wlist;
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typedef small_object_allocator allocator;
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typedef linear_equation_manager lin_eq_manager;
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numeral_manager & m;
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allocator & m_allocator;
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lin_eq_manager m_eq_manager;
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constraint_vector m_constraints;
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char_vector m_is_int;
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char_vector m_dead;
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var2bound m_lowers;
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var2bound m_uppers;
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vector<wlist> m_watches;
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svector<trail_info> m_trail;
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unsigned m_qhead;
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c_idx_vector m_reinit_stack;
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unsigned_vector m_lower_refinements; // number of times a lower bound was propagated for each variable (loop prevention)
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unsigned_vector m_upper_refinements; // number of times a upper bound was propagated for each variable (loop prevention)
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unsigned m_timestamp;
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var m_conflict;
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mpq m_tmp;
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struct scope {
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unsigned m_trail_limit;
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unsigned m_qhead_old;
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unsigned m_reinit_stack_limit;
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unsigned m_timestamp_old:31;
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unsigned m_in_conflict:1;
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};
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svector<scope> m_scopes;
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unsigned_vector m_to_reset_ts; // temp field: ids of the constraints we must reset the field m_timestamp
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// config
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unsigned m_max_refinements; // maximum number of refinements per round
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double m_small_interval;
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double m_threshold; // improvement threshold
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double m_strict2double;
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// statistics
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unsigned m_conflicts;
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unsigned m_propagations;
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unsigned m_false_alarms;
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void del_constraint(constraint & cnstr);
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void del_constraints_core();
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template<bool LOWER>
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bool relevant_bound(var x, double approx_k) const;
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bool relevant_lower(var x, double approx_k) const;
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bool relevant_upper(var x, double approx_k) const;
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bool get_interval_size(var x, double & r) const;
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void check_feasibility(var x);
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bool assert_lower_core(var x, mpq & k, bool strict, bkind bk, unsigned c_idx, assumption a);
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bool assert_upper_core(var x, mpq & k, bool strict, bkind bk, unsigned c_idx, assumption a);
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bool propagate(unsigned c_idx);
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bool propagate_eq(unsigned c_idx);
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bool propagate_lower(unsigned c_idx, unsigned i);
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bool propagate_upper(unsigned c_idx, unsigned i);
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void undo_trail(unsigned old_sz);
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typedef std::pair<var, bound *> var_bound;
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svector<var_bound> m_todo;
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void explain(var x, bound * b, unsigned ts, assumption_vector & ex) const;
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bool is_a_i_pos(linear_equation const & eq, var x) const;
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template<bool LOWER, typename Numeral>
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bool get_bound(unsigned sz, Numeral const * as, var const * xs, mpq & r, bool & st) const;
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void init_eq(linear_equation * eq);
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public:
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bound_propagator(numeral_manager & m, allocator & a, params_ref const & p);
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~bound_propagator();
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void updt_params(params_ref const & p);
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static void get_param_descrs(param_descrs & r);
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void collect_statistics(statistics & st) const;
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void reset_statistics();
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double strict2double() const { return m_strict2double; }
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bool is_int(var x) const { return m_is_int[x] != 0; }
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unsigned scope_lvl() const { return m_scopes.size(); }
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void mk_var(var x, bool is_int);
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void del_var(var x);
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bool is_dead(var x) const { return m_dead[x] != 0; }
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void mk_eq(unsigned sz, mpq * as, var * xs);
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void mk_eq(unsigned sz, mpz * as, var * xs);
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void del_constraints();
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void assert_lower(var x, mpq const & k, bool strict, assumption a = null_assumption) {
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m.set(m_tmp, k);
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assert_lower_core(x, m_tmp, strict, a == null_assumption ? AXIOM : ASSUMPTION, 0, a);
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}
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void assert_upper(var x, mpq const & k, bool strict, assumption a = null_assumption) {
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m.set(m_tmp, k);
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assert_upper_core(x, m_tmp, strict, a == null_assumption ? AXIOM : ASSUMPTION, 0, a);
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}
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void assert_decided_lower(var x, mpq const & k) {
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m.set(m_tmp, k);
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assert_lower_core(x, m_tmp, false, DECISION, 0, null_assumption);
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}
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void assert_decided_upper(var x, mpq const & k) {
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m.set(m_tmp, k);
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assert_upper_core(x, m_tmp, false, DECISION, 0, null_assumption);
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}
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void propagate();
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void push();
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void pop(unsigned num_scopes);
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void reset();
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bool has_lower(var x) const { return m_lowers[x] != 0; }
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bool has_upper(var x) const { return m_uppers[x] != 0; }
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bool lower(var x, mpq & k, bool & strict, unsigned & ts) const;
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bool upper(var x, mpq & k, bool & strict, unsigned & ts) const;
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bool is_fixed(var x) const { return has_lower(x) && has_upper(x) && m.eq(m_lowers[x]->m_k, m_uppers[x]->m_k) && !inconsistent(); }
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mpq const & lower(var x, bool & strict) const { SASSERT(has_lower(x)); bound * b = m_lowers[x]; strict = b->m_strict; return b->m_k; }
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mpq const & upper(var x, bool & strict) const { SASSERT(has_upper(x)); bound * b = m_uppers[x]; strict = b->m_strict; return b->m_k; }
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mpq const & lower(var x) const { SASSERT(has_lower(x)); return m_lowers[x]->m_k; }
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mpq const & upper(var x) const { SASSERT(has_upper(x)); return m_uppers[x]->m_k; }
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double approx_lower(var x) const {
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SASSERT(has_lower(x));
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return m_lowers[x]->m_strict ? m_lowers[x]->m_approx_k + m_strict2double : m_lowers[x]->m_approx_k;
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}
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double approx_upper(var x) const {
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SASSERT(has_upper(x));
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return m_uppers[x]->m_strict ? m_uppers[x]->m_approx_k - m_strict2double : m_uppers[x]->m_approx_k;
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}
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bool is_zero(var x) const { return has_lower(x) && has_upper(x) && m.is_zero(lower(x)) && m.is_zero(upper(x)); }
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void explain_lower(var x, unsigned ts, assumption_vector & ex) const { explain(x, m_lowers[x], ts, ex); }
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void explain_upper(var x, unsigned ts, assumption_vector & ex) const { explain(x, m_uppers[x], ts, ex); }
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void explain_lower(var x, assumption_vector & ex) const { explain_lower(x, m_timestamp, ex); }
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void explain_upper(var x, assumption_vector & ex) const { explain_upper(x, m_timestamp, ex); }
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var conflict_var() const { return m_conflict; }
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bool inconsistent() const { return m_conflict != null_var; }
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unsigned trail_size() const { return m_trail.size(); }
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unsigned qhead() const { return m_qhead; }
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typedef svector<trail_info>::const_iterator trail_iterator;
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trail_iterator begin_trail() const { return m_trail.begin(); }
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trail_iterator end_trail() const { return m_trail.end(); }
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bool lower(unsigned sz, mpq const * as, var const * xs, mpq & r, bool & st) const;
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bool upper(unsigned sz, mpq const * as, var const * xs, mpq & r, bool & st) const;
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void display(std::ostream & out) const;
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void display_var_bounds(std::ostream & out, var x, bool approx = true, bool precise = true) const;
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void display_bounds(std::ostream & out, bool approx = true, bool precise = true) const;
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void display_precise_bounds(std::ostream & out) const { display_bounds(out, false, true); }
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void display_approx_bounds(std::ostream & out) const { display_bounds(out, true, false); }
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void display_constraints(std::ostream & out) const;
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void display_bounds_of(std::ostream & out, linear_equation const & eq) const;
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unsigned get_num_false_alarms() const { return m_false_alarms; }
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unsigned get_num_propagations() const { return m_propagations; }
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};
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#endif
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