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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
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@ -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() { }
}