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fix a bug in the lar_solver::m_status update during push/pop

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Signed-off-by: Lev Nachmanson <levnach@microsoft.com>

progress in gomory cut

Signed-off-by: Lev Nachmanson <levnach@microsoft.com>

the first version of Gomory cut, probably broken

Signed-off-by: Lev Nachmanson <levnach@microsoft.com>

rename a function

Signed-off-by: Lev Nachmanson <levnach@microsoft.com>

gomory cut worked on a toy example

Signed-off-by: Lev Nachmanson <levnach@microsoft.com>

track the set of integer variables that are not set to integer values

Signed-off-by: Lev Nachmanson <levnach@microsoft.com>
This commit is contained in:
Lev Nachmanson 2017-07-10 16:34:23 -07:00 • committed by Lev Nachmanson
parent 0164ea9abb
commit aba7dcab3e
21 changed files with 682 additions and 455 deletions
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43
src/util/lp/int_solver.h
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@ -8,7 +8,6 @@
#include "util/lp/iterator_on_row.h"
#include "util/lp/int_set.h"
#include "util/lp/lar_term.h"
namespace lp {
class lar_solver;
template <typename T, typename X>
@ -23,6 +22,9 @@ enum class lia_move {
struct explanation {
vector<std::pair<mpq, constraint_index>> m_explanation;
void push_justification(constraint_index j, const mpq& v) {
m_explanation.push_back(std::make_pair(v, j));
}
};
class int_solver {
@ -31,10 +33,15 @@ public:
lar_solver *m_lar_solver;
int_set m_old_values_set;
vector<impq> m_old_values_data;
int_set m_inf_int_set;
unsigned m_branch_cut_counter;
linear_combination_iterator<mpq>* m_iter_on_gomory_row;
unsigned m_gomory_cut_inf_column;
bool m_found_free_var_in_gomory_row;
// methods
int_solver(lar_solver* lp);
int_set& inf_int_set();
const int_set& inf_int_set() const;
// main function to check that solution provided by lar_solver is valid for integral values,
// or provide a way of how it can be adjusted.
lia_move check(lar_term& t, mpq& k, explanation& ex);
@ -78,6 +85,7 @@ private:
const impq & lower_bound(unsigned j) const;
const impq & upper_bound(unsigned j) const;
bool is_int(unsigned j) const;
bool is_real(unsigned j) const;
bool is_base(unsigned j) const;
bool is_boxed(unsigned j) const;
bool value_is_int(unsigned j) const;
@ -88,8 +96,7 @@ private:
const impq & get_value(unsigned j) const;
void display_column(std::ostream & out, unsigned j) const;
bool inf_int_set_is_correct() const;
void init_inf_int_set();
void update_column_in_inf_set_set(unsigned j);
void update_column_in_int_inf_set(unsigned j);
bool column_is_int_inf(unsigned j) const;
void trace_inf_rows() const;
int find_inf_int_base_column();
@ -97,7 +104,33 @@ private:
lp_settings& settings();
void move_non_base_vars_to_bounds();
void branch_infeasible_int_var(unsigned);
bool mk_gomory_cut(unsigned row_index, explanation & ex);
lia_move mk_gomory_cut(lar_term& t, mpq& k,explanation & ex);
lia_move report_conflict_from_gomory_cut(mpq & k);
lia_move report_gomory_cut(lar_term& t, mpq& k, mpq& lcm_den, unsigned num_ints);
void init_check_data();
bool constrain_free_vars(linear_combination_iterator<mpq> * r);
lia_move proceed_with_gomory_cut(lar_term& t, mpq& k, explanation& ex);
int find_next_free_var_in_gomory_row();
bool is_gomory_cut_target();
bool at_bound(unsigned j) const;
bool at_lower(unsigned j) const;
bool at_upper(unsigned j) const;
inline static bool is_rational(const impq & n) {
return is_zero(n.y);
}
inline static
mpq fractional_part(const impq & n) {
lp_assert(is_rational);
return n.x - floor(n.x);
}
void real_case_in_gomory_cut(const mpq & a, unsigned x_j, mpq & k, lar_term& t, explanation & ex);
void int_case_in_gomory_cut(const mpq & a, unsigned x_j, mpq & k, lar_term& t, explanation& ex, mpq & lcm_den);
constraint_index column_upper_bound_constraint(unsigned j) const;
constraint_index column_low_bound_constraint(unsigned j) const;
void display_row_info(std::ostream & out, unsigned row_index) const;
void gomory_cut_adjust_t_and_k_for_size_1(const vector<std::pair<mpq, unsigned>> & pol, lar_term & t, mpq &k);
void gomory_cut_adjust_t_and_k_for_size_gt_1(vector<std::pair<mpq, unsigned>> & pol, lar_term & t, mpq &k, unsigned num_ints, mpq &lcm_den);
};
}