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roll back the branching experiment

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2020-02-07 17:35:42 -08:00
parent bbfcd00627
commit 5ee7103e3c
1 changed files with 45 additions and 120 deletions
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165
src/math/lp/int_solver.cpp
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@ -37,138 +37,63 @@ bool int_solver::has_inf_int() const {
return m_lar_solver->has_inf_int();
}
int int_solver::find_inf_int_nbasis_column() {
int result = -1;
unsigned n = 0;
for (unsigned j : m_lar_solver->r_nbasis())
if (column_is_int_inf(j) && settings().random_next() % (++n) == 0)
result = j;
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);
if (j != -1)
return j;
if (inf_int_count == 0)
return -1;
unsigned k = random() % inf_int_count;
return get_kth_inf_int(k);
}
int int_solver::find_inf_int_base_column() {
int int_solver::get_kth_inf_int(unsigned k) const {
for (unsigned j : m_lar_solver->r_basis())
if (column_is_int_inf(j) && k-- == 0)
return j;
lp_assert(false);
return -1;
}
int int_solver::find_inf_int_nbasis_column() const {
for (unsigned j : m_lar_solver->r_nbasis())
if (!column_is_int_inf(j))
return j;
return -1;
}
int int_solver::find_inf_int_boxed_base_column_with_smallest_range(unsigned & inf_int_count) {
inf_int_count = 0;
int result = -1;
mpq range;
mpq new_range;
mpq small_range_thresold(1024);
unsigned n = 0;
lar_core_solver & lcs = m_lar_solver->m_mpq_lar_core_solver;
#if 1
mpq range, distance;
vector<unsigned> const& r_basis = m_lar_solver->r_basis();
if (r_basis.empty()) return -1;
struct candidate {
mpq range, distance;
unsigned j;
candidate(mpq const& r, mpq const& d, unsigned j):
range(r), distance(d), j(j) {}
bool operator<(candidate const& other) const {
return
(range < other.range) ||
(range == other.range &&
(distance < other.distance || (distance == other.distance && j < other.j)));
}
};
vector<candidate> candidates;
unsigned start = settings().random_next() % r_basis.size();
for (unsigned i = r_basis.size(); i-- > 0 && candidates.size() <= 20; ) {
unsigned j = (start + i) % r_basis.size();
if (!column_is_int_inf(j))
continue;
distance = abs(get_value(j).x - floor(get_value(j).x));
if (has_upper(j) && has_lower(j)) {
range = lcs.m_r_upper_bounds()[j].x - lcs.m_r_lower_bounds()[j].x;
}
else {
range = abs(get_value(j).x);
}
candidates.push_back(candidate(range, distance, j));
}
if (candidates.empty()) {
return -1;
}
std::sort(candidates.begin(), candidates.end(), [](candidate const& a, candidate const& b) { return a < b; });
unsigned n = 1;
candidate c = candidates[0];
for (unsigned j = 1; j < candidates.size(); ++j) {
candidate const& c1 = candidates[j];
unsigned k = candidates.size() - j;
if (c.range == c1.range && c.distance == c1.distance && (settings().random_next() % (++n) == 0)) {
c = c1;
}
else if (settings().random_next() % (k+1)*(k+1) == 0) {
n = 1;
c = c1;
}
else {
break;
}
}
return c.j;
#else
int box_result = -1, inf_result = -1, small_result = -1;
mpq range, new_range;
mpq small_range_threshold(1024);
unsigned box_n = 0, inf_n = 0, small_n = 0;
for (unsigned j : m_lar_solver->r_basis()) {
if (!column_is_int_inf(j))
if (!column_is_int_inf(j))
continue;
std::function<void(void)> update_small = [&,this]() {
if (settings().random_next() % (++small_n) == 0) {
small_result = j;
}
};
bool is_small = true;
if (abs(get_value(j)) < small_range_threshold) {
update_small();
}
else if (has_upper(j) && lcs.m_r_upper_bounds()[j].x - get_value(j).x < small_range_threshold) {
update_small();
}
else if (has_lower(j) && get_value(j).x - lcs.m_r_lower_bounds()[j].x < small_range_threshold) {
update_small();
}
else {
is_small = false;
}
if (!is_boxed(j)) {
if (settings().random_next() % (++inf_n) == 0) {
inf_result = j;
}
inf_int_count++;
if (!is_boxed(j))
continue;
}
lp_assert(!is_fixed(j));
new_range = lcs.m_r_upper_bounds()[j].x - lcs.m_r_lower_bounds()[j].x;
if (new_range > small_range_threshold) {
if (!is_small && settings().random_next() % (++inf_n) == 0) {
inf_result = j;
}
if (new_range > small_range_thresold)
continue;
if (result == -1 || new_range < range) {
result = j;
range = new_range;
n = 1;
}
else if (box_result == -1 || new_range < range) {
box_result = j;
range = new_range;
box_n = 1;
}
else if (new_range == range) {
box_result = j;
box_n = 1;
}
else if (new_range == range && settings().random_next() % (++box_n) == 0) {
lp_assert(box_n > 1);
box_result = j;
else if (new_range == range && settings().random_next() % (++n) == 0) {
lp_assert(n > 1);
result = j;
}
}
IF_VERBOSE(10, verbose_stream() << box_result << " " << box_n << " " << small_result << " " << small_n << " " << inf_result << " " << inf_n << "\n");
if (box_result != -1 && settings().random_next() % (4*box_n + 2*small_n + inf_n) < 4*box_n) return box_result;
if (small_result != -1 && settings().random_next() % (2*small_n + inf_n) < 2*small_n) return small_result;
return inf_result;
#endif
return result;
}
bool int_solver::is_gomory_cut_target(const row_strip<mpq>& row) {