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apply the slack idea in a loop

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2025-05-05 16:21:37 -07:00
parent d413468dce
commit fdcde925d6
2 changed files with 70 additions and 39 deletions
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89
src/math/lp/lar_solver.cpp
View file

@ -8,7 +8,46 @@
namespace lp {
struct column_update {
bool m_is_upper;
unsigned m_j;
impq m_bound;
column m_column;
};
struct imp {
lar_solver &lra;
vector<column_update> m_column_updates;
void set_r_upper_bound(unsigned j, const impq& b) {
lra.m_mpq_lar_core_solver.m_r_upper_bounds[j] = b;
}
void set_r_lower_bound(unsigned j, const impq& b) {
lra.m_mpq_lar_core_solver.m_r_lower_bounds[j] = b;
}
imp(lar_solver& s) : lra(s) {}
void set_column(unsigned j, const column& c) {
lra.m_columns[j] = c;
}
struct column_update_trail : public trail {
imp& m_imp;
column_update_trail(imp & i) : m_imp(i) {}
void undo() override {
auto& [is_upper, j, bound, column] = m_imp.m_column_updates.back();
if (is_upper)
m_imp.set_r_upper_bound(j, bound);
else
m_imp.set_r_lower_bound(j, bound);
m_imp.set_column(j, column);
m_imp.m_column_updates.pop_back();
}
};
};
imp* m_imp;
lp_settings& lar_solver::settings() { return m_settings; }
lp_settings const& lar_solver::settings() const { return m_settings; }
@ -25,7 +64,8 @@ namespace lp {
lar_solver::lar_solver() :
m_mpq_lar_core_solver(m_settings, *this),
m_var_register(),
m_constraints(m_dependencies, *this) {}
m_constraints(m_dependencies, *this), m_imp(alloc(imp, *this)) {
}
// start or ends tracking the rows that were changed by solve()
void lar_solver::track_touched_rows(bool v) {
@ -574,38 +614,25 @@ namespace lp {
A_r().pop(k);
}
struct lar_solver::column_update_trail : public trail {
lar_solver& s;
column_update_trail(lar_solver& s) : s(s) {}
void undo() override {
auto& [is_upper, j, bound, column] = s.m_column_updates.back();
if (is_upper)
s.m_mpq_lar_core_solver.m_r_upper_bounds[j] = bound;
else
s.m_mpq_lar_core_solver.m_r_lower_bounds[j] = bound;
s.m_columns[j] = column;
s.m_column_updates.pop_back();
}
};
void lar_solver::set_upper_bound_witness(lpvar j, u_dependency* dep, impq const& high) {
bool has_upper = m_columns[j].upper_bound_witness() != nullptr;
m_column_updates.push_back({true, j, get_upper_bound(j), m_columns[j]});
m_trail.push(column_update_trail(*this));
m_imp->m_column_updates.push_back({true, j, get_upper_bound(j), m_columns[j]});
m_trail.push(imp::column_update_trail(*this->m_imp));
m_columns[j].set_upper_bound_witness(dep);
if (has_upper)
m_columns[j].set_previous_upper(m_column_updates.size() - 1);
m_columns[j].set_previous_upper(m_imp->m_column_updates.size() - 1);
m_mpq_lar_core_solver.m_r_upper_bounds[j] = high;
insert_to_columns_with_changed_bounds(j);
}
void lar_solver::set_lower_bound_witness(lpvar j, u_dependency* dep, impq const& low) {
bool has_lower = m_columns[j].lower_bound_witness() != nullptr;
m_column_updates.push_back({false, j, get_lower_bound(j), m_columns[j]});
m_trail.push(column_update_trail(*this));
m_imp->m_column_updates.push_back({false, j, get_lower_bound(j), m_columns[j]});
m_trail.push(imp::column_update_trail(*this->m_imp));
m_columns[j].set_lower_bound_witness(dep);
if (has_lower)
m_columns[j].set_previous_lower(m_column_updates.size() - 1);
m_columns[j].set_previous_lower(m_imp->m_column_updates.size() - 1);
m_mpq_lar_core_solver.m_r_lower_bounds[j] = low;
insert_to_columns_with_changed_bounds(j);
}
@ -1196,25 +1223,33 @@ namespace lp {
#if 1
if(is_upper) {
if (ul.previous_upper() != UINT_MAX) {
auto const& [_is_upper, _j, _bound, _column] = m_column_updates[ul.previous_upper()];
unsigned current_update_index = ul.previous_upper();
while (current_update_index != UINT_MAX) {
auto const& [_is_upper, _j, _bound, _column] = m_imp->m_column_updates[current_update_index];
auto new_slack = slack + coeff * (_bound - get_upper_bound(j));
if (sign == get_sign(new_slack)) {
// verbose_stream() << "can weaken j" << j << " " << coeff << " " << get_upper_bound(j) << " " << _bound << "\n";
//verbose_stream() << "can weaken upper j" << j << " " << coeff << " " << get_upper_bound(j) << " " << _bound << "\n";
slack = new_slack;
bound_constr_i = _column.upper_bound_witness();
}
current_update_index = _column.previous_upper(); // Move to the next previous bound in the list
} else
break; // Stop if weakening is not possible with this previous bound
}
}
else {
if (ul.previous_lower() != UINT_MAX) {
auto const& [_is_upper, _j, _bound, _column] = m_column_updates[ul.previous_lower()];
unsigned prev_l = ul.previous_lower();
while (prev_l != UINT_MAX) {
auto const& [_is_upper, _j, _bound, _column] = m_imp->m_column_updates[prev_l];
auto new_slack = slack + coeff * (_bound - get_lower_bound(j));
if (sign == get_sign(new_slack)) {
// verbose_stream() << "can weaken j" << j << " " << coeff << " " << get_lower_bound(j) << " " << _bound << "\n";
//verbose_stream() << "can weaken lower j" << j << " " << coeff << " " << get_lower_bound(j) << " " << _bound << "\n";
slack = new_slack;
bound_constr_i = _column.lower_bound_witness();
prev_l = _column.previous_lower();
}
else
break;
}
}
#endif

14
src/math/lp/lar_solver.h
View file

@ -47,7 +47,7 @@ namespace lp {
class int_branch;
class int_solver;
struct imp;
class lar_solver : public column_namer {
struct term_hasher {
@ -73,13 +73,7 @@ class lar_solver : public column_namer {
}
};
struct column_update {
bool m_is_upper;
unsigned m_j;
impq m_bound;
column m_column;
};
struct column_update_trail;
//////////////////// fields //////////////////////////
trail_stack m_trail;
@ -94,7 +88,6 @@ class lar_solver : public column_namer {
bool m_need_register_terms = false;
var_register m_var_register;
svector<column> m_columns;
vector<column_update> m_column_updates;
constraint_set m_constraints;
// the set of column indices j such that bounds have changed for j
@ -123,6 +116,7 @@ class lar_solver : public column_namer {
map<mpq, unsigned, obj_hash<mpq>, default_eq<mpq>> m_fixed_var_table_real;
// the set of fixed variables which are also base variables
indexed_uint_set m_fixed_base_var_set;
imp* m_imp;
// end of fields
////////////////// nested structs /////////////////////////
@ -742,5 +736,7 @@ public:
std::function<void (const indexed_uint_set& columns_with_changed_bound)> m_find_monics_with_changed_bounds_func = nullptr;
friend int_solver;
friend int_branch;
friend imp;
};
} // namespace lp