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Merge pull request #1845 from levnach/gomory

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refactor some parameters into fields in Gomory cuts
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Lev Nachmanson 2018-09-23 20:45:53 -07:00 committed by GitHub
parent 9a09689dfa 066b5334ad
commit 867368c0cd
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1 changed files with 62 additions and 57 deletions
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119
src/util/lp/gomory.cpp
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@ -27,11 +27,15 @@ class gomory::imp {
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
unsigned m_inf_col; // a basis column which has to be an integer but has a not integral value
unsigned m_inf_col; // a basis column which has to be an integer but has a non integral value
const row_strip<mpq>& m_row;
const int_solver& m_int_solver;
const int_solver& m_int_solver;
mpq m_lcm_den;
mpq m_f;
mpq m_one_minus_f;
mpq m_fj;
mpq m_one_minus_fj;
const impq & get_value(unsigned j) const { return m_int_solver.get_value(j); }
bool is_real(unsigned j) const { return m_int_solver.is_real(j); }
bool at_lower(unsigned j) const { return m_int_solver.at_lower(j); }
@ -42,66 +46,60 @@ class gomory::imp {
constraint_index column_upper_bound_constraint(unsigned j) const { return m_int_solver.column_upper_bound_constraint(j); }
bool column_is_fixed(unsigned j) const { return m_int_solver.m_lar_solver->column_is_fixed(j); }
void int_case_in_gomory_cut(const mpq & a, unsigned j,
mpq & lcm_den, const mpq& f0, const mpq& one_minus_f0) {
lp_assert(is_int(j) && !a.is_int());
mpq fj = fractional_part(a);
void int_case_in_gomory_cut(unsigned j) {
lp_assert(is_int(j) && m_fj.is_pos());
TRACE("gomory_cut_detail",
tout << a << " j=" << j << " k = " << m_k;
tout << ", fj: " << fj << ", ";
tout << "a - fj = " << a - fj << ", ";
tout << " k = " << m_k;
tout << ", fj: " << m_fj << ", ";
tout << (at_lower(j)?"at_lower":"at_upper")<< std::endl;
);
lp_assert(fj.is_pos() && (a - fj).is_int());
mpq new_a;
if (at_lower(j)) {
new_a = fj <= one_minus_f0 ? fj / one_minus_f0 : ((1 - fj) / f0);
new_a = m_fj <= m_one_minus_f ? m_fj / m_one_minus_f : ((1 - m_fj) / m_f);
lp_assert(new_a.is_pos());
m_k.addmul(new_a, lower_bound(j).x);
m_ex.push_justification(column_lower_bound_constraint(j), new_a);
m_ex.push_justification(column_lower_bound_constraint(j));
}
else {
lp_assert(at_upper(j));
// the upper terms are inverted: therefore we have the minus
new_a = - (fj <= f0 ? fj / f0 : ((1 - fj) / one_minus_f0));
new_a = - (m_fj <= m_f ? m_fj / m_f : ((1 - m_fj) / m_one_minus_f));
lp_assert(new_a.is_neg());
m_k.addmul(new_a, upper_bound(j).x);
m_ex.push_justification(column_upper_bound_constraint(j), new_a);
m_ex.push_justification(column_upper_bound_constraint(j));
}
m_t.add_monomial(new_a, j);
lcm_den = lcm(lcm_den, denominator(new_a));
TRACE("gomory_cut_detail", tout << "v" << j << " new_a = " << new_a << ", k = " << m_k << ", lcm_den = " << lcm_den << "\n";);
m_lcm_den = lcm(m_lcm_den, denominator(new_a));
TRACE("gomory_cut_detail", tout << "v" << j << " new_a = " << new_a << ", k = " << m_k << ", m_lcm_den = " << m_lcm_den << "\n";);
}
void real_case_in_gomory_cut(const mpq & a, unsigned x_j, const mpq& f0, const mpq& one_minus_f0) {
void real_case_in_gomory_cut(const mpq & a, unsigned j) {
TRACE("gomory_cut_detail_real", tout << "real\n";);
mpq new_a;
if (at_lower(x_j)) {
if (at_lower(j)) {
if (a.is_pos()) {
new_a = a / one_minus_f0;
new_a = a / m_one_minus_f;
}
else {
new_a = a / f0;
new_a.neg();
new_a = - a / m_f;
}
m_k.addmul(new_a, lower_bound(x_j).x); // is it a faster operation than
// k += lower_bound(x_j).x * new_a;
m_ex.push_justification(column_lower_bound_constraint(x_j), new_a);
m_k.addmul(new_a, lower_bound(j).x); // is it a faster operation than
// k += lower_bound(j).x * new_a;
m_ex.push_justification(column_lower_bound_constraint(j));
}
else {
lp_assert(at_upper(x_j));
lp_assert(at_upper(j));
if (a.is_pos()) {
new_a = a / f0;
new_a.neg(); // the upper terms are inverted.
new_a = - a / m_f;
}
else {
new_a = a / one_minus_f0;
new_a = a / m_one_minus_f;
}
m_k.addmul(new_a, upper_bound(x_j).x); // k += upper_bound(x_j).x * new_a;
m_ex.push_justification(column_upper_bound_constraint(x_j), new_a);
m_k.addmul(new_a, upper_bound(j).x); // k += upper_bound(j).x * new_a;
m_ex.push_justification(column_upper_bound_constraint(j));
}
TRACE("gomory_cut_detail_real", tout << a << "*v" << x_j << " k: " << m_k << "\n";);
m_t.add_monomial(new_a, x_j);
TRACE("gomory_cut_detail_real", tout << a << "*v" << j << " k: " << m_k << "\n";);
m_t.add_monomial(new_a, j);
}
lia_move report_conflict_from_gomory_cut() {
@ -111,7 +109,7 @@ class gomory::imp {
return lia_move::conflict;
}
void adjust_term_and_k_for_some_ints_case_gomory(mpq &lcm_den) {
void adjust_term_and_k_for_some_ints_case_gomory() {
lp_assert(!m_t.is_empty());
// k = 1 + sum of m_t at bounds
auto pol = m_t.coeffs_as_vector();
@ -134,16 +132,16 @@ class gomory::imp {
m_t.add_monomial(mpq(1), v);
}
} else {
lcm_den = lcm(lcm_den, denominator(m_k));
lp_assert(lcm_den.is_pos());
TRACE("gomory_cut_detail", tout << "pol.size() > 1 den: " << lcm_den << std::endl;);
if (!lcm_den.is_one()) {
m_lcm_den = lcm(m_lcm_den, denominator(m_k));
lp_assert(m_lcm_den.is_pos());
TRACE("gomory_cut_detail", tout << "pol.size() > 1 den: " << m_lcm_den << std::endl;);
if (!m_lcm_den.is_one()) {
// normalize coefficients of integer parameters to be integers.
for (auto & pi: pol) {
pi.first *= lcm_den;
pi.first *= m_lcm_den;
SASSERT(!is_int(pi.second) || pi.first.is_int());
}
m_k *= lcm_den;
m_k *= m_lcm_den;
}
// negate everything to return -pol <= -m_k
for (const auto & pi: pol) {
@ -275,14 +273,14 @@ public:
// gomory will be t <= k and the current solution has a property t > k
m_k = 1;
m_t.clear();
mpq lcm_den(1);
mpq m_lcm_den(1);
bool some_int_columns = false;
mpq f0 = fractional_part(get_value(m_inf_col));
TRACE("gomory_cut_detail", tout << "f0: " << f0 << ", ";
tout << "1 - f0: " << 1 - f0 << ", get_value(m_inf_col).x - f0 = " << get_value(m_inf_col).x - f0;);
lp_assert(f0.is_pos() && (get_value(m_inf_col).x - f0).is_int());
mpq m_f = fractional_part(get_value(m_inf_col));
TRACE("gomory_cut_detail", tout << "m_f: " << m_f << ", ";
tout << "1 - m_f: " << 1 - m_f << ", get_value(m_inf_col).x - m_f = " << get_value(m_inf_col).x - m_f;);
lp_assert(m_f.is_pos() && (get_value(m_inf_col).x - m_f).is_int());
mpq one_min_f0 = 1 - f0;
mpq one_min_m_f = 1 - m_f;
for (const auto & p : m_row) {
unsigned j = p.var();
if (j == m_inf_col) {
@ -290,20 +288,26 @@ public:
TRACE("gomory_cut_detail", tout << "seeing basic var";);
continue;
}
// make the format compatible with the format used in: Integrating Simplex with DPLL(T)
mpq a = - p.coeff();
if (is_real(j))
real_case_in_gomory_cut(a, j, f0, one_min_f0);
else if (!a.is_int()) { // fj will be zero and no monomial will be added
// use -p.coeff() to make the format compatible with the format used in: Integrating Simplex with DPLL(T)
if (is_real(j)) {
real_case_in_gomory_cut(- p.coeff(), j);
} else {
if (p.coeff().is_int()) {
// m_fj will be zero and no monomial will be added
continue;
}
some_int_columns = true;
int_case_in_gomory_cut(a, j, lcm_den, f0, one_min_f0);
m_fj = fractional_part(-p.coeff());
m_one_minus_fj = 1 - m_fj;
int_case_in_gomory_cut(j);
}
}
if (m_t.is_empty())
return report_conflict_from_gomory_cut();
if (some_int_columns)
adjust_term_and_k_for_some_ints_case_gomory(lcm_den);
adjust_term_and_k_for_some_ints_case_gomory();
lp_assert(m_int_solver.current_solution_is_inf_on_cut());
TRACE("gomory_cut_detail", dump_cut_and_constraints_as_smt_lemma(tout););
m_int_solver.m_lar_solver->subs_term_columns(m_t);
@ -317,9 +321,10 @@ public:
m_ex(ex),
m_inf_col(basic_inf_int_j),
m_row(row),
m_int_solver(int_slv)
{
}
m_int_solver(int_slv),
m_lcm_den(1),
m_f(fractional_part(get_value(basic_inf_int_j).x)),
m_one_minus_f(1 - m_f) {}
};