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restore the lemma scheme

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2023-09-07 11:33:14 -07:00
parent 288e66de59
commit 47b64e689c
5 changed files with 39 additions and 91 deletions
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2
src/math/lp/int_solver.cpp
View file

@ -31,7 +31,7 @@ namespace lp {
lra.remove_fixed_vars_from_base();
lp_assert(lia.is_feasible());
for (unsigned j : lra.r_basis())
if (!lra.get_value(j).is_int() && lra.column_is_int(j)&& !lia.is_fixed(j))
if (!lra.get_value(j).is_int() && lra.column_is_int(j) && !lia.is_fixed(j))
patch_basic_column(j);
if (!lia.has_inf_int()) {
lia.settings().stats().m_patches_success++;

113
src/math/lp/monomial_bounds.cpp
View file

@ -258,23 +258,11 @@ namespace nla {
}
}
void monomial_bounds::unit_propagate() {
for (auto const& m : c().m_emons)
void monomial_bounds::unit_propagate() {
for (auto const& m : c().m_emons)
unit_propagate(m);
}
void monomial_bounds::check_for_conflict() {
if (c().lra.crossed_bounds_deps() != nullptr) {
new_lemma lemma(c(), "fixed-values");
lp::explanation ex;
c().lra.fill_explanation_from_crossed_bounds_column(ex);
lemma &= ex;
c().lra.crossed_bounds_deps() = nullptr;
c().lra.crossed_bounds_column() = null_lpvar;
c().lra.set_status(lp::lp_status::OPTIMAL);
}
}
void monomial_bounds::unit_propagate(monic const& m) {
m_propagated.reserve(m.var() + 1, false);
if (m_propagated[m.var()])
@ -284,80 +272,37 @@ namespace nla {
return;
c().trail().push(set_bitvector_trail(m_propagated, m.var()));
lpvar zero_fixed = null_lpvar, non_fixed = null_lpvar;
// find a zero fixed variable and a non-fixed variable
for (lpvar v : m) {
if (c().var_is_fixed(v)) {
if (c().val(v).is_zero()) {
zero_fixed = v;
rational k = fixed_var_product(m);
new_lemma lemma(c(), "fixed-values");
if (k == 0) {
for (auto v : m) {
if (c().var_is_fixed(v) && c().val(v).is_zero()) {
lemma.explain_fixed(v);
break;
}
}
else {
non_fixed = v;
}
lemma += ineq(m.var(), lp::lconstraint_kind::EQ, 0);
}
if (zero_fixed != null_lpvar) {
// the m.var() has to have a zero value
u_dependency* d = this->dep.mk_join(c().lra.get_column_lower_bound_witness(zero_fixed),
c().lra.get_column_upper_bound_witness(zero_fixed));
c().lra.update_column_type_and_bound(m.var(), lp::lconstraint_kind::EQ, mpq(0), d);
} else if (non_fixed != null_lpvar) {
u_dependency* d = nullptr;
rational k(1);
for (auto v : m)
if (v != non_fixed) {
d = this->dep.mk_join(d, c().lra.get_column_upper_bound_witness(v));
d = this->dep.mk_join(d, c().lra.get_column_lower_bound_witness(v));
k *= c().val(v);
}
SASSERT(k.is_pos() || k.is_neg());
// we have m = k* non_fixed: m.var() getting the bounds witnesses of non_fixed
if (k.is_pos()) {
d = c().lra.get_column_upper_bound_witness(non_fixed);
if (d) {
const auto& b = c().lra.get_column_value(non_fixed);
bool strict = b.y.is_neg();
c().lra.update_column_type_and_bound(m.var(), strict ? lp::lconstraint_kind::LT : lp::lconstraint_kind::LE, k * b.x, d);
}
d = c().lra.get_column_lower_bound_witness(non_fixed);
if (d) {
const auto& b = c().lra.get_column_value(non_fixed);
bool strict = b.y.is_pos();
c().lra.update_column_type_and_bound(m.var(), strict ? lp::lconstraint_kind::GT : lp::lconstraint_kind::GE, k * b.x, d);
}
else {
for (auto v : m)
if (c().var_is_fixed(v))
lemma.explain_fixed(v);
lpvar w = non_fixed_var(m);
if (w != null_lpvar) {
lp::lar_term term;
term.add_var(m.var());
term.add_monomial(-k, w);
lemma += ineq(term, lp::lconstraint_kind::EQ, 0);
} else {
d = c().lra.get_column_upper_bound_witness(non_fixed);
if (d) {
const auto& b = c().lra.get_column_value(non_fixed);
bool strict = b.y.is_neg();
c().lra.update_column_type_and_bound(m.var(), strict ? lp::lconstraint_kind::GT : lp::lconstraint_kind::GE, k * b.x, d);
}
d = c().lra.get_column_lower_bound_witness(non_fixed);
if (d) {
const auto& b = c().lra.get_column_value(non_fixed);
bool strict = b.y.is_pos();
c().lra.update_column_type_and_bound(m.var(), strict ? lp::lconstraint_kind::LT : lp::lconstraint_kind::LE, k * b.x, d);
}
lemma += ineq(m.var(), lp::lconstraint_kind::EQ, k);
}
} else {
SASSERT(non_fixed == null_lpvar && zero_fixed == null_lpvar);
rational k(1);
u_dependency* d = nullptr;
for (auto v : m) {
SASSERT(c().var_is_fixed(v));
d = this->dep.mk_join(d, c().lra.get_column_upper_bound_witness(v));
d = this->dep.mk_join(d, c().lra.get_column_lower_bound_witness(v));
k *= c().val(v);
}
SASSERT(k.is_pos() || k.is_neg());
// we have m = k: m.var() getting the bounds witnesses of all fixed variables
c().lra.update_column_type_and_bound(m.var(), lp::lconstraint_kind::EQ, k, d);
}
check_for_conflict();
SASSERT (c().lra.get_status() != lp::lp_status::INFEASIBLE);
}
bool monomial_bounds::is_linear(monic const& m) {
unsigned non_fixed = 0;
for (lpvar v : m) {
@ -379,6 +324,12 @@ namespace nla {
return r;
}
lpvar monomial_bounds::non_fixed_var(monic const& m) {
for (lpvar v : m)
if (!c().var_is_fixed(v))
return v;
return null_lpvar;
}
}

3
src/math/lp/monomial_bounds.h
View file

@ -35,10 +35,11 @@ namespace nla {
void unit_propagate(monic const& m);
bool is_linear(monic const& m);
rational fixed_var_product(monic const& m);
lpvar non_fixed_var(monic const& m);
public:
monomial_bounds(core* core);
void propagate();
void unit_propagate();
void check_for_conflict();
};
}

10
src/math/lp/nla_core.cpp
View file

@ -1818,18 +1818,14 @@ bool core::improve_bounds() {
}
return bounds_improved;
}
// returns false if and only if makes lp_solver inconsistent
bool core::propagate(vector<lemma>& lemmas) {
void core::propagate(vector<lemma>& lemmas) {
// propagate linear monomials, those that have all, or all but one, variables fixed
lemmas.reset();
m_lemma_vec = &lemmas;
m_monomial_bounds.unit_propagate();
if (lra.get_status() == lp::lp_status::INFEASIBLE) {
TRACE("nla_solver", tout << "propagation found infeasibility\n";);
return false;
}
return true;
}

2
src/math/lp/nla_core.h
View file

@ -392,7 +392,7 @@ public:
bool no_lemmas_hold() const;
bool propagate(vector<lemma>& lemmas);
void propagate(vector<lemma>& lemmas);
lbool test_check(vector<lemma>& l);
lpvar map_to_root(lpvar) const;