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change the definition of Gomory row

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2024-01-14 13:37:30 -10:00
parent d8df203622
commit 91ca55e5ad
1 changed files with 41 additions and 17 deletions

58
src/math/lp/gomory.cpp
View file

@ -261,7 +261,26 @@ public:
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 << "\n";);
lp_assert(m_f.is_pos() && (get_value(m_inf_col).x - m_f).is_int());
auto set_polarity_for_int = [&](const mpq & a, lpvar j) {
if (a.is_pos()) {
if (at_lower(j))
set_polarity(row_polarity::MAX);
else if (at_upper(j))
set_polarity(row_polarity::MIN);
else
set_polarity(row_polarity::MIXED);
}
else {
if (at_lower(j))
set_polarity(row_polarity::MIN);
else if (at_upper(j))
set_polarity(row_polarity::MAX);
else
set_polarity(row_polarity::MIXED);
}
};
m_abs_max = 0;
for (const auto & p : m_row) {
mpq t = abs(ceil(p.coeff()));
@ -288,18 +307,9 @@ public:
m_one_minus_fj = 1 - m_fj;
int_case_in_gomory_cut(j);
}
if (p.coeff().is_pos()) {
if (at_lower(j))
set_polarity(row_polarity::MAX);
else
set_polarity(row_polarity::MIN);
}
else {
if (at_lower(j))
set_polarity(row_polarity::MIN);
else
set_polarity(row_polarity::MAX);
}
if (m_polarity != row_polarity::MIXED)
set_polarity_for_int(p.coeff(), j);
}
if (m_found_big) {
@ -338,12 +348,22 @@ public:
bool gomory::is_gomory_cut_target(lpvar k) {
SASSERT(lia.is_base(k));
// All non base variables must be at their bounds and assigned to rationals (that is, infinitesimals are not allowed).
const row_strip<mpq>& row = lra.get_row(lia.row_of_basic_column(k));
// Consider monomial c*x from the row, where x is non-basic.
// Then, for each such monomial, one of following conditions
// has to hold for the row to be eligible for Gomory cut:
// 1) c is integral and x integral varible with an integral value
// 2) the value of x is at a bound and has no infinitesimals.
unsigned j;
for (const auto & p : row) {
j = p.var();
if ( k != j && (!lia.at_bound(j) || lia.get_value(j).y != 0)) {
if (k == j) continue;
if (p.coeff().is_int() && lia.column_is_int(j) && lia.get_value(j).is_int()) continue;
if ( !lia.at_bound(j) || lia.get_value(j).y != 0) {
TRACE("gomory_cut", tout << "row is not gomory cut target:\n";
lia.display_column(tout, j);
tout << "infinitesimal: " << !(lia.get_value(j).y ==0) << "\n";);
@ -351,6 +371,8 @@ public:
}
}
return true;
// Condition 1) above can be relaxed even more, allowing any value for x, but it will change the calculation for m_f.
}
// return the minimal distance from the variable value to an integer
@ -417,14 +439,16 @@ public:
rp = row_polarity::MAX;
else if (lia.at_upper(j))
rp = row_polarity::MIN;
else SASSERT(false);
else
rp = row_polarity::MIXED;
}
else {
if (lia.at_lower(j))
rp = row_polarity::MIN;
else if (lia.at_upper(j))
rp = row_polarity::MAX;
else SASSERT(false);
else
rp = row_polarity::MIXED;
}
if (ret == row_polarity::UNDEF)