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fix bugs in patching

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2020-05-29 14:55:31 -07:00
parent e7bb8e57cb
commit c355ee025a
3 changed files with 40 additions and 58 deletions
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37
src/math/lp/lar_solver.cpp
View file

@ -565,40 +565,6 @@ bool lar_solver::remove_from_basis(unsigned j) {
return m_mpq_lar_core_solver.m_r_solver.remove_from_basis(j);
}
// val is the new value to be assigned to x[j]
// return true iff can find a new basic column that would be feasible
// after the pivoting
bool lar_solver::remove_from_basis(unsigned basic_j, const mpq& val) {
SASSERT(is_base(basic_j));
impq del(0);
const auto& slv = m_mpq_lar_core_solver.m_r_solver;
bool grow = val < get_column_value(basic_j).x; // grow = true means that the monomial of the pivoted var has to grow
for (auto &c : A_r().m_rows[row_of_basic_column(basic_j)]) {
lpvar j = c.var();
if (j == basic_j) {
SASSERT(c.coeff().is_one());
continue;
}
bool can_pivot = column_is_free(j);
if (!can_pivot &&
((grow && slv.monoid_can_increase(c))|| (!grow && slv.monoid_can_decrease(c)))) {
if (del.is_zero())
del = impq(val) - get_column_value(basic_j);
impq j_val = get_column_value(j) - del / c.coeff();
if (inside_bounds(j, j_val))
can_pivot = true;
}
if (can_pivot) {
pivot_column_tableau(c.var(), row_of_basic_column(basic_j));
return true;
}
}
return false;
}
lar_term lar_solver::get_term_to_maximize(unsigned j_or_term) const {
if (tv::is_term(j_or_term)) {
return get_term(j_or_term);
@ -1292,7 +1258,8 @@ void lar_solver::get_rid_of_inf_eps() {
mpq delta = m_mpq_lar_core_solver.find_delta_for_strict_bounds(mpq(1));
for (unsigned j = 0; j < number_of_vars(); j++) {
auto & r = m_mpq_lar_core_solver.m_r_x[j];
r = impq(r.x + delta * r.y);
if (!r.y.is_zero())
r = impq(r.x + delta * r.y);
}
}

6
src/math/lp/lar_solver.h
View file

@ -260,7 +260,6 @@ class lar_solver : public column_namer {
void update_delta_for_terms(const impq & delta, unsigned j, const vector<unsigned>&);
void fill_vars_to_terms(vector<vector<unsigned>> & vars_to_terms);
bool remove_from_basis(unsigned);
bool remove_from_basis(unsigned, const mpq&);
lar_term get_term_to_maximize(unsigned ext_j) const;
bool sum_first_coords(const lar_term& t, mpq & val) const;
void collect_rounded_rows_to_fix();
@ -362,14 +361,13 @@ public:
const ChangeReport& change_report) {
if (is_base(j)) {
TRACE("nla_solver", get_int_solver()->display_row_info(tout, row_of_basic_column(j)) << "\n";);
if (!remove_from_basis(j, val))
return false;
remove_from_basis(j);
}
impq ival(val);
if (is_blocked(j, ival))
return false;
TRACE("nla_solver", tout << "not blocked\n";);
impq delta = get_column_value(j) - ival;
for (const auto &c : A_r().column(j)) {
unsigned row_index = c.var();

55
src/math/lp/nla_core.cpp
View file

@ -1215,7 +1215,7 @@ bool core::var_breaks_correct_monic_as_factor(lpvar j, const monic& m) const {
if (!val(var(m)).is_zero())
return true;
if (!val(j).is_zero()) // j was not zero: the new value does not matter - m must have another zero product
if (!val(j).is_zero()) // j was not zero: the new value does not matter - m must have another zero factor
return false;
// do we have another zero in m?
for (lpvar k : m) {
@ -1287,29 +1287,38 @@ bool core::has_real(const monic& m) const {
return true;
return false;
}
// returns true if the patching is blocking
bool core::patch_is_blocked(lpvar u, const monic& m, const lp::impq& ival) const {
SASSERT(m_to_refine.contains(m.var()));
if (m_cautious_patching && !m_lar_solver.inside_bounds(u, ival))
bool core::patch_is_blocked(lpvar u, const monic& patched_m, const lp::impq& ival) const {
if (m_cautious_patching &&
(!m_lar_solver.inside_bounds(u, ival) || (var_is_int(u) && ival.is_int() == false))) {
TRACE("nla_solver", tout << "u = " << u << " blocked, for feas or integr\n";);
return true; // blocking
}
if (var_breaks_correct_monic(u)) {
TRACE("nla_solver", tout << "u = " << u << " blocked as used in a correct monomial\n";);
return true;
}
bool ret = u == m.var() || (m.contains_var(u) && var_breaks_correct_monic_as_factor(u, m));
bool ret = u == patched_m.var() || (patched_m.contains_var(u) && var_breaks_correct_monic_as_factor(u, patched_m));
TRACE("nla_solver", tout << "u = " << u << ", m = "; print_monic(m, tout) <<
TRACE("nla_solver", tout << "u = " << u << ", patched_m = "; print_monic(patched_m, tout) <<
"ret = " << ret << "\n";);
return ret;
}
bool core::try_to_patch(lpvar k, const rational& v, const monic & m) {
auto is_blocked = [this, k, m](lpvar u, const lp::impq& v)
{ return u != k && patch_is_blocked(u, m, v); };
bool core::try_to_patch(lpvar patched_var, const rational& v, const monic & m) {
auto is_blocked = [this, patched_var, m](lpvar u, const lp::impq& iv)
{
if (!m_lar_solver.inside_bounds(u, iv))
return true;
if (u == patched_var)
return false;
return patch_is_blocked(u, m, iv);
};
auto change_report = [this](lpvar u) { update_to_refine_of_var(u); };
return m_lar_solver.try_to_patch(k, v, is_blocked, change_report);
return m_lar_solver.try_to_patch(patched_var, v, is_blocked, change_report);
}
bool in_power(const svector<lpvar>& vs, unsigned l) {
@ -1348,31 +1357,36 @@ void core::patch_monomial(lpvar j) {
return;
}
// Now we try patching the factor variables.
TRACE("nla_solver", tout << " trying squares\n";);
// handle perfect squares
if (m.vars().size() == 2 && m.vars()[0] == m.vars()[1]) {
rational root;
if (v.is_perfect_square(root)) {
lpvar k = m.vars()[0];
if (!var_is_int(k) &&
!var_breaks_correct_monic(k) &&
(try_to_patch(k, root, m) || try_to_patch(k, -root, m))
) {
if (!var_breaks_correct_monic(k) && (try_to_patch(k, root, m) || try_to_patch(k, -root, m))) {
TRACE("nla_solver", tout << "patched square\n";);
return;
}
}
TRACE("nla_solver", tout << " cannot patch\n";);
return;
}
// We have v != abc. Let us suppose we patch b. Then b should
// be equal to v/ac = v/(abc/b) = b(v/abc)
// We have v != abc, but we need to have v = abc.
// If we patch b then b should be equal to v/ac = v/(abc/b) = b(v/abc)
if (!v.is_zero()) {
rational r = val(j) / v;
SASSERT(m.is_sorted());
TRACE("nla_solver", tout << "r = " << r << ", v = " << v << "\n";);
for (unsigned l = 0; l < m.size(); l++) {
lpvar k = m.vars()[l];
if (!in_power(m.vars(), l) &&
!var_is_int(k) &&
!var_breaks_correct_monic(k) &&
try_to_patch(k, r * val(k), m)) { // r * val(k) gives the right value of k
TRACE("nla_solver", tout << "patched j " << j << "\n";);
SASSERT(mul_val(m) == var_val(m));
erase_from_to_refine(j);
break;
@ -1385,13 +1399,15 @@ void core::patch_monomials_on_to_refine() {
auto to_refine = m_to_refine.index();
// the rest of the function might change m_to_refine, so have to copy
unsigned sz = to_refine.size();
TRACE("nla_solver", tout << "sz = " << sz << "\n";);
unsigned start = random();
for (unsigned i = 0; i < sz; i++) {
patch_monomial(to_refine[(start + i) % sz]);
if (m_to_refine.size() == 0)
break;
}
TRACE("nla_solver", tout << "sz = " << sz << ", m_to_refine = " << m_to_refine.size() <<
(sz > m_to_refine.size()? " less" : "same" ) << "\n";);
}
void core::patch_monomials() {
@ -1400,7 +1416,8 @@ void core::patch_monomials() {
if (m_to_refine.size() == 0 || !m_nla_settings.expensive_patching()) {
return;
}
m_cautious_patching = false; //
NOT_IMPLEMENTED_YET();
m_cautious_patching = false;
patch_monomials_on_to_refine();
m_lar_solver.push();
save_tableau();