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allow gomory cut for a row with free non-basic vars

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2018-09-06 16:47:25 -07:00
parent de4a2b3ea7
commit 064cf9e983
5 changed files with 81 additions and 54 deletions
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69
src/smt/theory_lra.cpp
View file

@ -2042,7 +2042,7 @@ public:
m_eqs.reset();
m_core.reset();
m_params.reset();
for (auto const& ev : ex) {
for (auto const& ev : ex.m_explanation) {
if (!ev.first.is_zero()) {
set_evidence(ev.second);
}
@ -2096,39 +2096,40 @@ public:
return r;
}
niil::lemma m_lemma;
lbool check_aftermath_niil(lbool r) {
switch (r) {
case l_false: {
literal_vector core;
for (auto const& ineq : m_lemma) {
bool is_lower = true, pos = true, is_eq = false;
void process_lemma(const niil::lemma& lemma) {
literal_vector core;
for (auto const& ineq : lemma) {
bool is_lower = true, pos = true, is_eq = false;
switch (ineq.m_cmp) {
case lp::LE: is_lower = false; pos = false; break;
case lp::LT: is_lower = true; pos = true; break;
case lp::GE: is_lower = true; pos = false; break;
case lp::GT: is_lower = false; pos = true; break;
case lp::EQ: is_eq = true; pos = true; break;
case lp::NE: is_eq = true; pos = false; break;
default: UNREACHABLE();
}
TRACE("arith", tout << "is_lower: " << is_lower << " pos " << pos << "\n";);
app_ref atom(m);
if (is_eq) {
atom = mk_eq(ineq.m_term);
}
else {
// create term >= 0 (or term <= 0)
atom = mk_bound(ineq.m_term, rational::zero(), is_lower);
}
literal lit(ctx().get_bool_var(atom), pos);
core.push_back(~lit);
switch (ineq.m_cmp) {
case lp::LE: is_lower = false; pos = false; break;
case lp::LT: is_lower = true; pos = true; break;
case lp::GE: is_lower = true; pos = false; break;
case lp::GT: is_lower = false; pos = true; break;
case lp::EQ: is_eq = true; pos = true; break;
case lp::NE: is_eq = true; pos = false; break;
default: UNREACHABLE();
}
set_conflict_or_lemma(core, false);
break;
TRACE("arith", tout << "is_lower: " << is_lower << " pos " << pos << "\n";);
app_ref atom(m);
if (is_eq) {
atom = mk_eq(ineq.m_term);
}
else {
// create term >= 0 (or term <= 0)
atom = mk_bound(ineq.m_term, rational::zero(), is_lower);
}
literal lit(ctx().get_bool_var(atom), pos);
core.push_back(~lit);
}
set_conflict_or_lemma(core, false);
}
lbool check_aftermath_niil(lbool r, const niil::lemma & lemma) {
switch (r) {
case l_false:
process_lemma(lemma);
break;
case l_true:
if (assume_eqs()) {
return l_false;
@ -2149,9 +2150,9 @@ public:
if (!m_nra && !m_niil) return l_true;
if (!m_switcher.need_check()) return l_true;
m_a1 = nullptr; m_a2 = nullptr;
lbool r = m_nra? m_nra->check(m_explanation): m_niil->check(m_explanation, m_lemma);
return m_nra? check_aftermath_nra(r) : check_aftermath_niil(r);
niil::lemma lemma;
lbool r = m_nra? m_nra->check(m_explanation): m_niil->check(m_explanation, lemma);
return m_nra? check_aftermath_nra(r) : check_aftermath_niil(r, lemma);
}
/**

24
src/util/lp/int_solver.cpp
View file

@ -104,11 +104,10 @@ bool int_solver::is_gomory_cut_target(const row_strip<mpq>& row) {
j = p.var();
if (!is_base(j) && (!at_bound(j) || !is_zero(get_value(j).y))) {
TRACE("gomory_cut", tout << "row is not gomory cut target:\n";
display_column(tout, j);
tout << "infinitesimal: " << !is_zero(get_value(j).y) << "\n";);
display_column(tout, j););
return false;
}
}
}
return true;
}
@ -122,7 +121,6 @@ constraint_index int_solver::column_lower_bound_constraint(unsigned j) const {
return m_lar_solver->get_column_lower_bound_witness(j);
}
bool int_solver::current_solution_is_inf_on_cut() const {
const auto & x = m_lar_solver->m_mpq_lar_core_solver.m_r_x;
impq v = m_t.apply(x);
@ -150,6 +148,7 @@ lia_move int_solver::proceed_with_gomory_cut(unsigned j) {
return create_branch_on_column(j);
m_upper = true;
return mk_gomory_cut(j, row);
}
@ -377,10 +376,17 @@ lia_move int_solver::make_hnf_cut() {
#endif
lia_move r = m_hnf_cutter.create_cut(m_t, m_k, m_ex, m_upper, x0);
if (r == lia_move::cut) {
m_lemma->clear();
m_lemma->push_back(ineq());
ineq & f_in = first_in();
mpq k;
bool upper;
lia_move r = m_hnf_cutter.create_cut(f_in.m_term, k, *m_ex, upper, x0);
if (r == lia_move::cut) {
f_in.m_term.m_v = -k;
f_in.m_cmp = upper? lconstraint_kind::LE : GE;
TRACE("hnf_cut",
m_lar_solver->print_term(m_t, tout << "cut:");
tout << " <= " << m_k << std::endl;
print_ineq(f_in, tout << "cut:");
for (unsigned i : m_hnf_cutter.constraints_for_explanation()) {
m_lar_solver->print_constraint(i, tout);
}
@ -861,7 +867,7 @@ bool int_solver::at_bound(unsigned j) const {
case column_type::upper_bound:
return mpq_solver.m_upper_bounds[j] == get_value(j);
default:
return false;
return true; // a free var is always at a bound
}
}
@ -999,7 +1005,7 @@ lia_move int_solver::create_branch_on_column(int j) {
TRACE("check_main_int", tout << "branching" << std::endl;);
lp_assert(m_t.is_empty());
lp_assert(j != -1);
m_t->add_coeff_var(mpq(1), m_lar_solver->adjust_column_index_to_term_index(j));
first_in().add_coeff_var(mpq(1), m_lar_solver->adjust_column_index_to_term_index(j));
if (is_free(j)) {
m_upper = true;
m_k = mpq(0);

28
src/util/lp/int_solver.h
View file

@ -33,6 +33,31 @@ class lar_solver;
template <typename T, typename X>
struct lp_constraint;
struct ineq {
lp::lconstraint_kind m_cmp;
lp::lar_term m_term;
ineq(lp::lconstraint_kind cmp, const lp::lar_term& term) : m_cmp(cmp), m_term(term) {}
ineq() {} // empty constructor
void add_coeff_var(const mpq& c, unsigned j) {
m_term.add_coeff_var(c, j);
}
bool holds(const vector<impq> & x) const {
auto v = m_term.apply(x);
switch(m_cmp) {
case lconstraint_kind::LE: return v <= zero_of_type<impq>();
case lconstraint_kind::LT: return v < zero_of_type<impq>();
case lconstraint_kind::GE: return v >= zero_of_type<impq>();
case lconstraint_kind::GT: return v > zero_of_type<impq>();
case lconstraint_kind::EQ: return v == zero_of_type<impq>();
default:
lp_assert(false);
return false;
}
}
bool is_empty() const { return m_term.is_empty(); }
};
typedef vector<ineq> lemma;
class int_solver {
public:
@ -54,7 +79,6 @@ public:
mpq const& get_offset() const { return m_k; }
explanation const& get_explanation() const { return m_ex; }
bool is_upper() const { return m_upper; }
bool is_base(unsigned j) const;
bool is_real(unsigned j) const;
const impq & lower_bound(unsigned j) const;
@ -116,6 +140,7 @@ private:
unsigned row_of_basic_column(unsigned j) const;
public:
std::ostream & print_ineq(const ineq & in, std::ostream & out) const;
void display_column(std::ostream & out, unsigned j) const;
constraint_index column_upper_bound_constraint(unsigned j) const;
constraint_index column_lower_bound_constraint(unsigned j) const;
@ -140,6 +165,7 @@ public:
int find_inf_int_nbasis_column() const;
lia_move run_gcd_test();
lia_move gomory_cut();
void add_free_vars_ineqs_to_lemma();
lia_move hnf_cut();
lia_move make_hnf_cut();
bool init_terms_for_hnf_cut();

4
src/util/lp/niil_solver.cpp
View file

@ -26,7 +26,7 @@ typedef lp::constraint_index lpci;
typedef std::unordered_set<lpci> expl_set;
typedef nra::mon_eq mon_eq;
typedef lp::var_index lpvar;
typedef lp::ineq ineq;
struct hash_svector {
size_t operator()(const unsigned_vector & v) const {
return svector_hash<unsigned_hash>()(v);
@ -513,7 +513,7 @@ struct solver::imp {
return true;
}
std::ostream & print_ineq(ineq & in, std::ostream & out) const {
std::ostream & print_ineq(const ineq & in, std::ostream & out) const {
m_lar_solver.print_term(in.m_term, out);
out << " " << lp::lconstraint_kind_string(in.m_cmp) << " 0";
return out;

10
src/util/lp/niil_solver.h
View file

@ -24,15 +24,9 @@ Revision History:
#include "util/params.h"
#include "nlsat/nlsat_solver.h"
#include "util/lp/lar_solver.h"
#include "util/lp/int_solver.h"
namespace niil {
struct ineq {
lp::lconstraint_kind m_cmp;
lp::lar_term m_term;
ineq(lp::lconstraint_kind cmp, const lp::lar_term& term) : m_cmp(cmp), m_term(term) {}
};
typedef vector<ineq> lemma;
typedef lp::lemma lemma;
// nonlinear integer incremental linear solver
class solver {
struct imp;