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create bounds for gomory cuts with big numbers

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Lev Nachmanson 2023-12-23 19:27:18 -10:00 committed by Lev Nachmanson
parent af7691224e
commit a3529a0046
1 changed files with 23 additions and 22 deletions
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45
src/math/lp/gomory.cpp
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@ -39,8 +39,9 @@ struct create_cut {
#if SMALL_CUTS #if SMALL_CUTS
mpq m_abs_max, m_big_number; mpq m_abs_max, m_big_number;
#endif #endif
int m_polarity; int m_polarity;
bool m_found_big; bool m_found_big;
u_dependency* m_dep;
const impq & get_value(unsigned j) const { return lia.get_value(j); } const impq & get_value(unsigned j) const { return lia.get_value(j); }
bool is_int(unsigned j) const { return lia.column_is_int(j) || (lia.is_fixed(j) && bool is_int(unsigned j) const { return lia.column_is_int(j) || (lia.is_fixed(j) &&
@ -330,6 +331,10 @@ public:
if (some_int_columns) if (some_int_columns)
simplify_inequality(); simplify_inequality();
m_dep = nullptr;
for (auto c : *m_ex)
m_dep = lia.lra.join_deps(lia.lra.dep_manager().mk_leaf(c.ci()), m_dep);
TRACE("gomory_cut", print_linear_combination_of_column_indices_only(m_t.coeffs_as_vector(), tout << "gomory cut: "); tout << " >= " << m_k << std::endl;); TRACE("gomory_cut", print_linear_combination_of_column_indices_only(m_t.coeffs_as_vector(), tout << "gomory cut: "); tout << " >= " << m_k << std::endl;);
TRACE("gomory_cut_detail", dump_cut_and_constraints_as_smt_lemma(tout); TRACE("gomory_cut_detail", dump_cut_and_constraints_as_smt_lemma(tout);
lia.lra.display(tout)); lia.lra.display(tout));
@ -512,10 +517,10 @@ public:
lia_move gomory::get_gomory_cuts(unsigned num_cuts) { lia_move gomory::get_gomory_cuts(unsigned num_cuts) {
struct cut_result {explanation ex; lar_term t; mpq k; int polarity; lpvar j;}; struct cut_result {u_dependency *dep; lar_term t; mpq k; int polarity; lpvar j;};
vector<cut_result> big_cuts; vector<cut_result> big_cuts;
struct polar_pair {int polarity; lpvar j; u_dependency *dep;}; struct polar_pair {int polarity; u_dependency *dep;};
vector<polar_pair> polar_vars; std::unordered_map<lpvar, polar_pair> polar_vars;
unsigned_vector columns_for_cuts = gomory_select_int_infeasible_vars(num_cuts); unsigned_vector columns_for_cuts = gomory_select_int_infeasible_vars(num_cuts);
// define inline helper functions // define inline helper functions
@ -524,15 +529,12 @@ public:
return all_of(t, [&](auto ci) { return ci.coeff().is_small(); }); return all_of(t, [&](auto ci) { return ci.coeff().is_small(); });
}; };
auto add_cut = [&](cut_result const& cr) { auto add_cut = [&](cut_result const& cr) {
u_dependency* dep = nullptr; u_dependency* dep = cr.dep;
for (auto c : cr.ex)
dep = lra.join_deps(lra.dep_manager().mk_leaf(c.ci()), dep);
lp::lpvar term_index = lra.add_term(cr.t.coeffs_as_vector(), UINT_MAX); lp::lpvar term_index = lra.add_term(cr.t.coeffs_as_vector(), UINT_MAX);
term_index = lra.map_term_index_to_column_index(term_index); term_index = lra.map_term_index_to_column_index(term_index);
lra.update_column_type_and_bound(term_index, lra.update_column_type_and_bound(term_index,
lp::lconstraint_kind::GE, lp::lconstraint_kind::GE,
lia.m_k, dep); lia.m_k, dep);
return dep;
}; };
auto _check_feasible = [&](void) { auto _check_feasible = [&](void) {
lra.find_feasible_solution(); lra.find_feasible_solution();
@ -552,17 +554,16 @@ public:
if (r != lia_move::cut) if (r != lia_move::cut)
continue; continue;
cut_result cr = {*lia.m_ex, lia.m_t, lia.m_k, cc.m_polarity, j}; cut_result cr = {cc.m_dep, lia.m_t, lia.m_k, cc.m_polarity, j};
if (abs(cr.polarity) == 1) // need to delay the update of the bounds for j in a polar case, because simplify_inequality relies on the old bounds
polar_vars[j] = {cr.polarity, cc.m_dep};
if (!is_small_cut(lia.m_t)) { if (!is_small_cut(lia.m_t)) {
big_cuts.push_back(cr); big_cuts.push_back(cr);
continue; continue;
} }
has_small_cut = true; has_small_cut = true;
auto dep = add_cut(cr); add_cut(cr);
if (abs(cr.polarity) == 1) // need to delay the update of the bounds for j in a polar case, because simplify_inequality relies on the old bounds
polar_vars.push_back({cr.polarity, j, dep}); // todo : polarity for big cuts
if (lia.settings().get_cancel_flag()) if (lia.settings().get_cancel_flag())
return lia_move::undef; return lia_move::undef;
} }
@ -581,12 +582,14 @@ public:
return lia_move::conflict; return lia_move::conflict;
} }
// this way we create bounds for the variables in polar cases even where the terms had big numbers
for (auto const& p : polar_vars) { for (auto const& p : polar_vars) {
if (p.polarity == 1) { if (p.second.polarity == 1) {
lra.update_column_type_and_bound(p.j, lp::lconstraint_kind::LE, floor(lra.get_column_value(p.j).x), p.dep); lra.update_column_type_and_bound(p.first, lp::lconstraint_kind::LE, floor(lra.get_column_value(p.first).x), p.second.dep);
} }
else if (p.polarity == -1) { else {
lra.update_column_type_and_bound(p.j, lp::lconstraint_kind::GE, ceil(lra.get_column_value(p.j).x), p.dep); SASSERT(p.second.polarity == -1);
lra.update_column_type_and_bound(p.first, lp::lconstraint_kind::GE, ceil(lra.get_column_value(p.first).x), p.second.dep);
} }
} }
@ -598,8 +601,6 @@ public:
if (has_small_cut || big_cuts.size()) if (has_small_cut || big_cuts.size())
return lia_move::continue_with_check; return lia_move::continue_with_check;
lra.move_non_basic_columns_to_bounds(); lra.move_non_basic_columns_to_bounds();
return lia_move::undef; return lia_move::undef;