mirror of
https://github.com/Z3Prover/z3
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96 lines
3.2 KiB
C++
96 lines
3.2 KiB
C++
/*++
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Copyright (c) 2017 Microsoft Corporation
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Module Name:
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<name>
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Abstract:
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<abstract>
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Author:
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Lev Nachmanson (levnach)
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Revision History:
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--*/
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#pragma once
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#include <set>
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#include "util/vector.h"
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#include <unordered_map>
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#include <string>
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#include <algorithm>
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#include "util/lp/lp_settings.h"
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#include "util/lp/linear_combination_iterator.h"
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// see http://research.microsoft.com/projects/z3/smt07.pdf
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// The class searches for a feasible solution with as many different values of variables as it can find
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namespace lp {
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template <typename T> struct numeric_pair; // forward definition
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class lar_core_solver; // forward definition
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class random_updater {
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struct interval {
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bool upper_bound_is_set;
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numeric_pair<mpq> upper_bound;
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bool low_bound_is_set;
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numeric_pair<mpq> low_bound;
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interval() : upper_bound_is_set(false),
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low_bound_is_set(false) {}
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void set_low_bound(const numeric_pair<mpq> & v) {
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if (low_bound_is_set) {
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low_bound = std::max(v, low_bound);
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} else {
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low_bound = v;
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low_bound_is_set = true;
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}
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}
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void set_upper_bound(const numeric_pair<mpq> & v) {
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if (upper_bound_is_set) {
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upper_bound = std::min(v, upper_bound);
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} else {
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upper_bound = v;
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upper_bound_is_set = true;
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}
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}
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bool is_empty() const {return
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upper_bound_is_set && low_bound_is_set && low_bound >= upper_bound;
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}
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bool low_bound_holds(const numeric_pair<mpq> & a) const {
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return low_bound_is_set == false || a >= low_bound;
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}
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bool upper_bound_holds(const numeric_pair<mpq> & a) const {
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return upper_bound_is_set == false || a <= upper_bound;
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}
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bool contains(const numeric_pair<mpq> & a) const {
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return low_bound_holds(a) && upper_bound_holds(a);
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}
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std::string lbs() { return low_bound_is_set ? T_to_string(low_bound):std::string("inf");}
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std::string rbs() { return upper_bound_is_set? T_to_string(upper_bound):std::string("inf");}
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std::string to_str() { return std::string("[")+ lbs() + ", " + rbs() + "]";}
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};
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std::set<var_index> m_var_set;
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lar_core_solver & m_core_solver;
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unsigned range;
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linear_combination_iterator<mpq>* m_column_j; // the actual column
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interval find_shift_interval(unsigned j);
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interval get_interval_of_non_basic_var(unsigned j);
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void add_column_to_sets(unsigned j);
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void random_shift_var(unsigned j);
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std::unordered_map<numeric_pair<mpq>, unsigned> m_values; // it maps a value to the number of time it occurs
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void diminish_interval_to_leave_basic_vars_feasible(numeric_pair<mpq> &nb_x, interval & inter);
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void shift_var(unsigned j, interval & r);
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void diminish_interval_for_basic_var(numeric_pair<mpq> &nb_x, unsigned j, mpq & a, interval & r);
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numeric_pair<mpq> get_random_from_interval(interval & r);
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void add_value(numeric_pair<mpq>& v);
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void remove_value(numeric_pair<mpq> & v);
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public:
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random_updater(lar_core_solver & core_solver, const vector<unsigned> & column_list);
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void update();
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};
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}
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