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move all gomory functionality into gomory class

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2020-02-08 13:02:19 -08:00
parent 094f203167
commit d44855f262
4 changed files with 102 additions and 105 deletions
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97
src/math/lp/gomory.cpp
View file

@ -25,7 +25,7 @@
#define SMALL_CUTS 1
namespace lp {
class gomory::imp {
class create_cut {
lar_term & m_t; // the term to return in the cut
mpq & m_k; // the right side of the cut
explanation* m_ex; // the conflict explanation
@ -281,7 +281,7 @@ public:
out << "inf_col = " << m_inf_col << std::endl;
}
lia_move create_cut() {
lia_move cut() {
TRACE("gomory_cut", dump(tout););
// gomory will be t <= k and the current solution has a property t > k
@ -341,7 +341,7 @@ public:
return lia_move::cut;
}
imp(lar_term & t, mpq & k, explanation* ex, unsigned basic_inf_int_j, const row_strip<mpq>& row, const int_solver& int_slv ) :
create_cut(lar_term & t, mpq & k, explanation* ex, unsigned basic_inf_int_j, const row_strip<mpq>& row, const int_solver& int_slv ) :
m_t(t),
m_k(k),
m_ex(ex),
@ -354,14 +354,95 @@ public:
};
lia_move gomory::create_cut() {
return m_imp->create_cut();
lia_move gomory::cut(lar_term & t, mpq & k, explanation* ex, unsigned basic_inf_int_j, const row_strip<mpq>& row) {
create_cut cc(t, k, ex, basic_inf_int_j, row, s);
return cc.cut();
}
gomory::gomory(lar_term & t, mpq & k, explanation* ex, unsigned basic_inf_int_j, const row_strip<mpq>& row, const int_solver& s) {
m_imp = alloc(imp, t, k, ex, basic_inf_int_j, row, s);
bool gomory::is_gomory_cut_target(const row_strip<mpq>& row) {
// All non base variables must be at their bounds and assigned to rationals (that is, infinitesimals are not allowed).
unsigned j;
for (const auto & p : row) {
j = p.var();
if (!s.is_base(j) && (!s.at_bound(j) || !is_zero(s.get_value(j).y))) {
TRACE("gomory_cut", tout << "row is not gomory cut target:\n";
s.display_column(tout, j);
tout << "infinitesimal: " << !is_zero(s.get_value(j).y) << "\n";);
return false;
}
}
return true;
}
gomory::~gomory() { dealloc(m_imp); }
int gomory::find_column() {
int result = -1;
unsigned n = 0;
bool boxed = false;
unsigned min_row_size = UINT_MAX;
mpq min_range;
// Prefer smaller row size
// Prefer boxed to non-boxed
// Prefer smaller ranges
for (unsigned j : s.m_lar_solver->r_basis()) {
if (!s.column_is_int_inf(j))
continue;
const row_strip<mpq>& row = s.m_lar_solver->get_row(s.row_of_basic_column(j));
if (!is_gomory_cut_target(row))
continue;
#if 0
if (is_boxed(j) && (min_row_size == UINT_MAX || 4*row.size() < 5*min_row_size)) {
lar_core_solver & lcs = m_lar_solver->m_mpq_lar_core_solver;
auto new_range = lcs.m_r_upper_bounds()[j].x - lcs.m_r_lower_bounds()[j].x;
if (!boxed) {
result = j;
n = 1;
min_row_size = row.size();
boxed = true;
min_range = new_range;
continue;
}
if (min_range > 2*new_range || ((5*min_range > 4*new_range && (random() % (++n)) == 0))) {
result = j;
n = 1;
min_row_size = row.size();
min_range = std::min(min_range, new_range);
continue;
}
}
#endif
if (min_row_size == UINT_MAX ||
2*row.size() < min_row_size ||
(4*row.size() < 5*min_row_size && s.random() % (++n) == 0)) {
result = j;
n = 1;
min_row_size = std::min(min_row_size, row.size());
}
}
return result;
}
lia_move gomory::cut(lar_term & t, mpq & k, explanation* ex, bool& upper) {
if (s.m_lar_solver->move_non_basic_columns_to_bounds()) {
lp_status st = s.m_lar_solver->find_feasible_solution();
(void)st;
lp_assert(st == lp_status::FEASIBLE || st == lp_status::OPTIMAL);
}
int j = find_column();
if (j == -1) return lia_move::undef;
const row_strip<mpq>& row = s.m_lar_solver->get_row(s.row_of_basic_column(j));
SASSERT(s.m_lar_solver->row_is_correct(s.row_of_basic_column(j)));
SASSERT(is_gomory_cut_target(row));
upper = true;
return cut(t, k, ex, j, row);
}
gomory::~gomory() { }
}

12
src/math/lp/gomory.h
View file

@ -24,11 +24,15 @@ Revision History:
namespace lp {
class int_solver;
class gomory {
class imp;
imp *m_imp;
class int_solver& s;
int find_column();
lia_move cut(lar_term & t, mpq & k, explanation* ex, unsigned basic_inf_int_j, const row_strip<mpq>& row);
bool is_gomory_cut_target(const row_strip<mpq>& row);
public :
gomory(lar_term & t, mpq & k, explanation* ex, unsigned basic_inf_int_j, const row_strip<mpq>& row, const int_solver& s);
lia_move create_cut();
gomory(int_solver& s): s(s) {}
lia_move cut(lar_term & t, mpq & k, explanation* ex, bool& upper);
~gomory();
};
}

93
src/math/lp/int_solver.cpp
View file

@ -37,52 +37,6 @@ bool int_solver::has_inf_int() const {
return m_lar_solver->has_inf_int();
}
int int_solver::find_gomory_cut_column() {
int result = -1;
unsigned n = 0;
bool boxed = false;
unsigned min_row_size = UINT_MAX;
mpq min_range;
// Prefer smaller row size
// Prefer boxed to non-boxed
// Prefer smaller ranges
for (unsigned j : m_lar_solver->r_basis()) {
if (!column_is_int_inf(j))
continue;
const row_strip<mpq>& row = m_lar_solver->get_row(row_of_basic_column(j));
if (!is_gomory_cut_target(row))
continue;
if (is_boxed(j) && (min_row_size == UINT_MAX || 4*row.size() < 5*min_row_size)) {
lar_core_solver & lcs = m_lar_solver->m_mpq_lar_core_solver;
auto new_range = lcs.m_r_upper_bounds()[j].x - lcs.m_r_lower_bounds()[j].x;
if (!boxed) {
result = j;
n = 1;
min_row_size = row.size();
boxed = true;
min_range = new_range;
continue;
}
if (min_range > 2*new_range || ((5*min_range > 4*new_range && (random() % (++n)) == 0))) {
result = j;
n = 1;
min_row_size = row.size();
min_range = std::min(min_range, new_range);
continue;
}
}
if (min_row_size == UINT_MAX || (4*row.size() < 5*min_row_size && random() % (++n) == 0)) {
result = j;
n = 1;
min_row_size = std::min(min_row_size, row.size());
}
}
return result;
}
int int_solver::find_inf_int_base_column() {
unsigned inf_int_count = 0;
int j = find_inf_int_boxed_base_column_with_smallest_range(inf_int_count);
@ -140,23 +94,7 @@ int int_solver::find_inf_int_boxed_base_column_with_smallest_range(unsigned & in
result = j;
}
}
return result;
}
bool int_solver::is_gomory_cut_target(const row_strip<mpq>& row) {
// All non base variables must be at their bounds and assigned to rationals (that is, infinitesimals are not allowed).
unsigned j;
for (const auto & p : row) {
j = p.var();
if (!is_base(j) && (!at_bound(j) || !is_zero(get_value(j).y))) {
TRACE("gomory_cut", tout << "row is not gomory cut target:\n";
display_column(tout, j);
tout << "infinitesimal: " << !is_zero(get_value(j).y) << "\n";);
return false;
}
}
return true;
return result;
}
@ -180,20 +118,6 @@ constraint_index int_solver::column_lower_bound_constraint(unsigned j) const {
return m_lar_solver->get_column_lower_bound_witness(j);
}
lia_move int_solver::mk_gomory_cut( unsigned inf_col, const row_strip<mpq> & row) {
lp_assert(column_is_int_inf(inf_col));
gomory gc(m_t, m_k, m_ex, inf_col, row, *this);
return gc.create_cut();
}
lia_move int_solver::proceed_with_gomory_cut(unsigned j) {
const row_strip<mpq>& row = m_lar_solver->get_row(row_of_basic_column(j));
SASSERT(m_lar_solver->row_is_correct(row_of_basic_column(j)));
SASSERT(is_gomory_cut_target(row));
m_upper = true;
return mk_gomory_cut(j, row);
}
unsigned int_solver::row_of_basic_column(unsigned j) const {
return m_lar_solver->row_of_basic_column(j);
@ -340,18 +264,9 @@ lia_move int_solver::gomory_cut() {
if (!should_gomory_cut())
return lia_move::undef;
if (m_lar_solver->move_non_basic_columns_to_bounds()) {
lp_status st = m_lar_solver->find_feasible_solution();
(void)st;
lp_assert(st == lp_status::FEASIBLE || st == lp_status::OPTIMAL);
}
int j = find_gomory_cut_column();
if (j != -1) {
return proceed_with_gomory_cut(j);
}
j = find_inf_int_nbasis_column();
return j == -1? lia_move::sat : create_branch_on_column(j);
gomory gc(*this);
return gc.cut(m_t, m_k, m_ex, m_upper);
}
void int_solver::try_add_term_to_A_for_hnf(unsigned i) {

5
src/math/lp/int_solver.h
View file

@ -35,6 +35,7 @@ struct lp_constraint;
class int_solver {
friend class gomory;
public:
// fields
lar_solver *m_lar_solver;
@ -107,15 +108,11 @@ private:
lia_move branch_or_sat();
int find_any_inf_int_column_basis_first();
int find_inf_int_base_column();
int find_gomory_cut_column();
int find_inf_int_boxed_base_column_with_smallest_range(unsigned&);
int get_kth_inf_int(unsigned) const;
lp_settings& settings();
const lp_settings& settings() const;
void branch_infeasible_int_var(unsigned);
lia_move mk_gomory_cut(unsigned inf_col, const row_strip<mpq>& row);
lia_move proceed_with_gomory_cut(unsigned j);
bool is_gomory_cut_target(const row_strip<mpq>&);
bool at_bound(unsigned j) const;
bool has_lower(unsigned j) const;
bool has_upper(unsigned j) const;