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test that pivoting is correct in dioph_eq.cpp

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Lev Nachmanson 2024-10-30 15:09:55 -07:00 • committed by Lev Nachmanson
parent 0db0efce9f
commit 36293ac773
10 changed files with 399 additions and 223 deletions
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567
src/math/lp/dioph_eq.cpp
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@ -4,7 +4,6 @@
#include "math/lp/lp_utils.h"
#include <list>
#include <queue>
namespace lp {
// This class represents a term with an added constant number c, in form sum {x_i*a_i} + c.
class dioph_eq::imp {
@ -20,17 +19,26 @@ namespace lp {
ret.j() = j();
return ret;
}
term_o(const lar_term& t):lar_term(t), m_c(0) {
SASSERT(m_c.is_zero());
}
const mpq& c() const { return m_c; }
mpq& c() { return m_c; }
term_o():m_c(0) {}
void substitute_var_with_term(const term_o& t, unsigned term_column) {
SASSERT(!t.contains(term_column));
mpq a = get_coeff(term_column); // need to copy it becase the pointer value can be changed during the next loop
void substitute_var_with_term(const term_o& t, unsigned col_to_subs) {
mpq a = get_coeff(col_to_subs); // need to copy it becase the pointer value can be changed during the next loop
const mpq& coeff = t.get_coeff(col_to_subs);
SASSERT(coeff.is_one() || coeff.is_minus_one());
if (coeff.is_one()) {
a = -a;
}
for (auto p : t) {
if (p.j() == col_to_subs)
continue;
this->add_monomial(a * p.coeff(), p.j());
}
this->c() += a * t.c();
this->m_coeffs.erase(term_column);
this->m_coeffs.erase(col_to_subs);
}
friend term_o operator*(const mpq& k, const term_o& term) {
@ -40,6 +48,23 @@ namespace lp {
r.c() = k*term.c();
return r;
}
friend term_o operator+(const term_o& a, const term_o& b) {
term_o r = a.clone();
for(const auto& p : b) {
r.add_monomial(p.coeff(), p.j());
}
r.c() += b.c();
return r;
}
friend term_o operator-(const term_o& a, const term_o& b) {
term_o r = a.clone();
for (const auto& p : b)
r.sub_monomial(p.coeff(), p.j());
r.c() -= b.c();
return r;
}
#if Z3DEBUG
friend bool operator== (const term_o & a, const term_o& b) {
term_o t = a.clone();
@ -64,17 +89,10 @@ namespace lp {
}
return out;
}
std::ostream& print_F(std::ostream & out) {
out << "F:\n";
for (unsigned i : m_f) {
print_eprime_entry(i, out);
}
return out;
}
std::ostream& print_lar_term_L(const lar_term & t, std::ostream & out) const {
return print_linear_combination_customized(t.coeffs_as_vector(),
[](int j)->std::string {return "y"+std::to_string(j);}, out );
[](int j)->std::string {return "x"+std::to_string(j);}, out );
}
std::ostream& print_term_o(term_o const& term, std::ostream& out) const {
@ -140,9 +158,8 @@ namespace lp {
};
struct eprime_entry {
unsigned m_row_index; // the index of the row in the constraint matrix that m_e corresponds to
// we keep the dependency of the equation in m_l
// a more expensive alternative is to keep the history term of m_e : originally m_l is i, the index of row m_e was constructed from
u_dependency *m_l;
// originally m_l is the column defining the term m_e was constructed from
lar_term m_l;
mpq m_c; // the constant of the term
entry_status m_entry_status;
};
@ -153,7 +170,7 @@ namespace lp {
lar_solver& lra;
explanation m_infeas_explanation;
indexed_vector<mpq> m_indexed_work_vector;
// the set of equations that are in S
bool m_report_branch = false;
// set F
@ -161,14 +178,16 @@ namespace lp {
// set S
std::list<unsigned> m_s; // S = {λ(t): t in m_s}
mpq m_c; // the constant of the equation
u_dependency * m_dep = nullptr; // the dependency of the equation
std_vector<unsigned> m_k2s; // k is substituted by using equation in m_eprime[m_k2s[k].first] and m_k2s[k].second
// gives the order of substitution
lar_term m_tmp_l;; // the dependency of the equation
// map to open the term e.m_l
// suppose e.m_l = sum {coeff*k}, then subst(e.m_e) = fix_var(sum {coeff*lar.get_term(k)})
std_vector<unsigned> m_k2s;
unsigned m_conflict_index = -1; // m_eprime[m_conflict_index] gives the conflict
public:
imp(int_solver& lia, lar_solver& lra): lia(lia), lra(lra) {}
term_o get_term_from_e_matrix(unsigned i) {
term_o get_term_from_e_matrix(unsigned i) const {
term_o t;
for (const auto & p: m_e_matrix.m_rows[i]) {
t.add_monomial(p.coeff(), p.var());
@ -176,35 +195,39 @@ namespace lp {
t.c() = m_eprime[i].m_c;
return t;
}
private:
// the row comes from lar_solver
void fill_eprime_entry(const lar_term& t, unsigned term_index) {
m_f.push_back(term_index);
eprime_entry& e = m_eprime[term_index];
e.m_row_index = term_index;
const auto lcm = get_denominators_lcm(t);
mpq & c = e.m_c;
SASSERT(c.is_zero());
// the term has form sum(a_i*x_i) - t.j() = 0,
// i is the index of the term in the lra.m_terms
void fill_eprime_entry(const lar_term& t) {
TRACE("dioph_eq", print_lar_term_L(t, tout) << std::endl;);
unsigned i = static_cast<unsigned>(m_eprime.size());
eprime_entry te = {i, lar_term(t.j()), mpq(0), entry_status::NO_S_NO_F};
m_f.push_back(te.m_row_index);
m_eprime.push_back(te);
eprime_entry& e = m_eprime.back();
m_e_matrix.add_row();
SASSERT(m_e_matrix.row_count() == m_eprime.size()); // this invariant is going to be broken
for (const auto & p: t) {
if (lia.is_fixed(p.var())) {
c += p.coeff()*lia.lower_bound(p.var()).x;
e.m_l = lra.mk_join(e.m_l, lra.get_bound_constraint_witnesses_for_column(p.var()));
}
SASSERT(p.coeff().is_int());
if (is_fixed(p.var()))
e.m_c += p.coeff()*lia.lower_bound(p.var()).x;
else {
m_e_matrix.add_new_element(term_index, p.var(), lcm * p.coeff());
while (p.var() >= m_e_matrix.column_count())
m_e_matrix.add_column();
m_e_matrix.add_new_element(e.m_row_index, p.var(), p.coeff());
}
}
unsigned j = t.j();
if (lia.is_fixed(j)) {
c -= lia.lower_bound(j).x;
e.m_l = lra.mk_join(e.m_l, lra.get_bound_constraint_witnesses_for_column(j));
}
if (is_fixed(j))
e.m_c -= lia.lower_bound(j).x;
else {
m_e_matrix.add_new_element(term_index, j, - lcm);
while (j >= m_e_matrix.column_count())
m_e_matrix.add_column();
m_e_matrix.add_new_element(e.m_row_index, j, - mpq(1));
}
c *= lcm;
e.m_entry_status = entry_status::F;
e.m_entry_status = entry_status::F;
TRACE("dioph_eq", print_eprime_entry(e, tout););
SASSERT(entry_invariant(e));
}
bool all_vars_are_int_and_small(const lar_term& term) const {
@ -219,29 +242,21 @@ namespace lp {
void init() {
m_e_matrix = static_matrix<mpq, mpq>(lra.row_count(), lra.column_count());
m_e_matrix = static_matrix<mpq, mpq>();
m_report_branch = false;
m_k2s.clear();
m_k2s.resize(lra.column_count(), -1);
m_conflict_index = -1;
m_infeas_explanation.clear();
lia.get_term().clear();
m_eprime.clear();
m_eprime.resize(lra.terms().size());
for (unsigned i = 0; i < lra.terms().size(); i++) {
const lar_term* t = lra.terms()[i];
TRACE("dioph_eq", tout << "term "<< i <<":"; lra.print_term(*t, tout) << "\n";
for(const auto & p: *t) {
lra.print_column_info(p.var(), tout);
}
);
if (t->j() == UINT_MAX || !all_vars_are_int_and_small(*t)) {
for (unsigned j = 0; j < lra.column_count(); j++) {
if (!lra.column_is_int(j)|| !lra.column_has_term(j)) continue;
const lar_term& t = lra.get_term(j);
if (!all_vars_are_int_and_small(t)) {
TRACE("dioph_eq", tout << "not all vars are int and small\n";);
m_eprime[i].m_entry_status = entry_status::NO_S_NO_F;
continue;
}
fill_eprime_entry(*t, i);
TRACE("dioph_eq", print_eprime_entry(static_cast<unsigned>(i), tout););
fill_eprime_entry(t);
}
}
@ -250,7 +265,7 @@ namespace lp {
u_dependency * get_dep_from_row(const row_strip<mpq>& row) {
u_dependency* dep = nullptr;
for (const auto & p: row) {
if (!lia.is_fixed(p.var())) continue;
if (!is_fixed(p.var())) continue;
u_dependency * bound_dep = lra.get_bound_constraint_witnesses_for_column(p.var());
dep = lra.mk_join(dep, bound_dep);
}
@ -306,28 +321,29 @@ namespace lp {
// it is needed by the next steps
// the conflict can be used to report "cuts from proofs"
bool normalize_e_by_gcd(unsigned row_index) {
eprime_entry& ep = m_eprime[row_index];
TRACE("dioph_eq", print_eprime_entry(ep, tout) << std::endl;);
eprime_entry& e = m_eprime[row_index];
TRACE("dioph_eq", print_eprime_entry(e, tout) << std::endl;);
mpq g = gcd_of_coeffs(m_e_matrix.m_rows[row_index]);
if (g.is_zero() || g.is_one()) {
SASSERT(g.is_one() || ep.m_c.is_zero());
SASSERT(g.is_one() || e.m_c.is_zero());
return true;
}
TRACE("dioph_eq", tout << "g:" << g << std::endl;);
mpq c_g = m_eprime[row_index].m_c / g;
mpq c_g = e.m_c / g;
if (c_g.is_int()) {
for (auto& p: m_e_matrix.m_rows[row_index]) {
p.coeff() /= g;
}
m_eprime[row_index].m_c = c_g;
// ep.m_l *= (1/g);
TRACE("dioph_eq", tout << "ep_m_e:"; print_eprime_entry(ep, tout) << std::endl;);
e.m_l *= (1/g);
TRACE("dioph_eq", tout << "ep_m_e:"; print_eprime_entry(e, tout) << std::endl;);
SASSERT(entry_invariant(e));
return true;
}
// c_g is not integral
if (lra.settings().stats().m_dio_conflicts % lra.settings().dio_cut_from_proof_period() == 0 &&
!has_fresh_var(ep.m_row_index))
prepare_lia_branch_report(ep, g, c_g);
!has_fresh_var(e.m_row_index))
prepare_lia_branch_report(e, g, c_g);
return false;
}
@ -335,9 +351,11 @@ namespace lp {
bool normalize_by_gcd() {
for (unsigned l: m_f) {
if (!normalize_e_by_gcd(l)) {
SASSERT(entry_invariant(m_eprime[l]));
m_conflict_index = l;
return false;
}
SASSERT(entry_invariant(m_eprime[l]));
}
return true;
}
@ -352,65 +370,96 @@ namespace lp {
// We look at term e.m_e: it is in form (+-)x_k + sum {a_i*x_i} + c = 0.
// We substitute x_k in t by (+-)coeff*(sum {a_i*x_i} + c), where coeff is the coefficient of x_k in t.
void substitute_k_with_S_entry_for_tigthening(const eprime_entry& e, unsigned k, std::queue<unsigned> & q) {
mpq coeff = m_indexed_work_vector[k]; // need to copy it because the pointer value can be changed during the next loop
void subs_front_in_indexed_vector(std::queue<unsigned> & q) {
unsigned k = pop_front(q);
const eprime_entry& e = entry_for_subs(k);
TRACE("dioph_eq", tout << "k:" << k << ", in "; print_term_o(create_term_from_ind_c(), tout) << std::endl;
tout << "subs with e:"; print_eprime_entry(e, tout) << std::endl;);
mpq coeff = m_indexed_work_vector[k]; // need to copy since it will be zeroed
m_indexed_work_vector.erase(k); // m_indexed_work_vector[k] = 0;
const auto& e_row = m_e_matrix.m_rows[e.m_row_index];
auto it = std::find_if(e_row.begin(), e_row.end(), [k](const auto & c){ return c.var() == k;});
const mpq& k_coeff_in_e = it->coeff();
bool is_one = k_coeff_in_e.is_one();
SASSERT(is_one || k_coeff_in_e.is_minus_one());
m_indexed_work_vector.erase(k);
if (is_one) {
coeff = -coeff;
}
if (is_one) coeff = -coeff;
for (const auto& p: e_row) {
if (p.var() == k) continue;
SASSERT(!this->lia.is_fixed(p.var()));
m_indexed_work_vector.add_value_at_index(p.var(), p.coeff()*coeff);
unsigned j = p.var();
if (j == k) continue;
m_indexed_work_vector.add_value_at_index(j, p.coeff()*coeff);
// do we need to add j to the queue?
if (!is_fresh_var(j) && !m_indexed_work_vector[j].is_zero() && can_substitute(j))
q.push(j);
}
m_c += coeff * e.m_c;
TRACE("dioph_eq", tout << "after subs k:"<< k<< "\n"; print_term_o(create_term_from_ind_c(), tout) << std::endl;);
for (unsigned j: m_indexed_work_vector.m_index) {
if (is_fresh_var(j)) {
continue;
}
if (m_k2s[j] != null_lpvar)
q.push(j);
}
m_tmp_l += coeff * e.m_l;
TRACE("dioph_eq", tout << "after subs k:"<< k<< "\n"; print_term_o(create_term_from_ind_c(), tout) << std::endl;
tout << "m_tmp_l:{"; print_lar_term_L(m_tmp_l, tout); tout << "}, opened:"; print_ml(m_tmp_l, tout) << std::endl;);
}
const eprime_entry& k_th_entry(unsigned k) const {
term_o create_term_from_l(const lar_term& l) {
term_o ret;
for (const auto& p: l) {
const auto & t = lra.get_term(p.j());
ret.add_monomial(-mpq(1), p.j());
for (const auto& q: t) {
ret.add_monomial(p.coeff()*q.coeff(), q.j());
}
}
return ret;
}
bool is_fixed(unsigned j) const {
return (!is_fresh_var(j)) && lra.column_is_fixed(j);
}
template <typename T> term_o fix_vars(const T& t) const {
term_o ret;
for (auto& p: t) {
if (is_fixed(p.var())) {
ret.c() += p.coeff() * this->lra.get_lower_bound(p.var()).x;
} else {
ret.add_monomial(p.coeff(), p.var());
}
}
return ret;
}
const eprime_entry& entry_for_subs(unsigned k) const {
return m_eprime[m_k2s[k]];
}
const unsigned sub_index(unsigned k) const {
return m_k2s[k];
}
// works on m_indexed_work_vector
void substitude_term_on_q_with_S_for_tightening(std::queue<unsigned> &q) {
TRACE("dioph_eq_dep", tout << "dep:"; print_dep(tout, m_dep) << std::endl;);
while (!q.empty()) {
unsigned k = q.front();
q.pop();
const eprime_entry& e = k_th_entry(k);
if (m_indexed_work_vector[k].is_zero()) {
continue;
}
TRACE("dioph_eq", tout << "k:" << k << " in: "; print_eprime_entry(sub_index(k), tout) << std::endl;);
substitute_k_with_S_entry_for_tigthening(e, k, q);
TRACE("dioph_eq", print_queue(q, tout););
m_dep = lra.mk_join(m_dep, e.m_l);
TRACE("dioph_eq", tout << "substituted t:"; print_term_o(create_term_from_ind_c(), tout) << std::endl;
/*tout << "\ndep:"; print_dep(tout, m_dep) << std::endl;*/);
}
template <typename T> T pop_front(std::queue<T>& q) const {
T value = q.front();
q.pop();
return value;
}
void subs_indexed_vector_with_S(std::queue<unsigned> &q) {
while (!q.empty())
subs_front_in_indexed_vector(q);
}
void debug_remove_fresh_vars(term_o& t) {
std::queue<unsigned> q;
for (const auto& p: t) {
if (is_fresh_var(p.j())) {
q.push(p.j());
}
}
while (!q.empty()) {
unsigned j = pop_front(q);
}
}
lia_move tighten_with_S() {
std::cout << ".";
int change = 0;
for (unsigned j = 0; j < lra.column_count(); j++) {
if (!lra.column_has_term(j) || lra.column_is_free(j) ||
@ -422,10 +471,12 @@ namespace lp {
return lia_move::conflict;
}
}
TRACE("dioph_eq", tout << "change:" << change << "\n";);
if (!change)
return lia_move::undef;
auto st = lra.find_feasible_solution();
if (st != lp::lp_status::FEASIBLE && st != lp::lp_status::OPTIMAL) {
if (st != lp::lp_status::FEASIBLE && st != lp::lp_status::OPTIMAL && st != lp::lp_status::CANCELLED) {
lra.get_infeasibility_explanation(m_infeas_explanation);
return lia_move::conflict;
}
@ -450,41 +501,52 @@ namespace lp {
t.c() = m_c;
return t;
}
void fill_indexed_work_vector_from_term(const lar_term& lar_t) {
m_indexed_work_vector.resize(m_e_matrix.column_count());
m_c = 0;
m_tmp_l = lar_term();
for (const auto& p: lar_t) {
SASSERT(p.coeff().is_int());
if (is_fixed(p.j()))
m_c += p.coeff()*lia.lower_bound(p.j()).x;
else
m_indexed_work_vector.set_value(p.coeff(), p.j());
}
}
// j is the index of the column representing a term
// return true if a new tighter bound was set on j
bool tighten_bounds_for_term_column(unsigned j) {
TRACE("dioph_eq", tout << "j:"; tout << j << std::endl;);
const lar_term& lar_t = lra.get_term(j);
TRACE("dioph_eq", tout << "t: "; print_lar_term_L(lar_t, tout) << std::endl;);
term_o term_to_tighten = lra.get_term(j); // copy the term aside
std::queue<unsigned> q;
for (const auto& p: lar_t) {
if (m_k2s[p.j()] != -1)
for (const auto& p: term_to_tighten) {
if (can_substitute(p.j()))
q.push(p.j());
}
if (q.empty()) {
return false;
}
m_indexed_work_vector.clear();
m_indexed_work_vector.resize(m_e_matrix.column_count());
m_c = 0;
m_dep = nullptr;
for (const auto& p: lar_t) {
if (lia.is_fixed(p.var())) {
m_c += p.coeff()*lia.lower_bound(p.var()).x;
m_dep = lra.mk_join(m_dep, lra.get_bound_constraint_witnesses_for_column(p.var()));
}
else {
m_indexed_work_vector.set_value(p.coeff(), p.j());
}
}
TRACE("dioph_eq", tout << "j:"<< j<< ", t: "; print_lar_term_L(term_to_tighten, tout) << std::endl;);
fill_indexed_work_vector_from_term(term_to_tighten);
TRACE("dioph_eq", tout << "t orig:"; print_lar_term_L(term_to_tighten, tout) << std::endl; tout << "from ind:";
print_term_o(create_term_from_ind_c(), tout) << std::endl;
tout << "m_tmp_l:"; print_lar_term_L(m_tmp_l, tout) << std::endl;
);
subs_indexed_vector_with_S(q);
TRACE("dioph_eq", tout << "t:"; print_term_o(create_term_from_ind_c(), tout) << std::endl;
/*tout << "dep:"; print_dep(tout, dep) << std::endl;*/);
substitude_term_on_q_with_S_for_tightening(q);
TRACE("dioph_eq", tout << "after process_q_with_S\n t:"; print_term_o(create_term_from_ind_c(), tout) << std::endl;
/*tout << "dep:"; print_dep(tout, m_dep) << std::endl;*/);
TRACE("dioph_eq", tout << "after subs\n"; print_term_o(create_term_from_ind_c(), tout) << std::endl;
tout << "term_to_tighten:"; print_lar_term_L(term_to_tighten, tout) << std::endl;
tout << "m_tmp_l:"; print_lar_term_L(m_tmp_l, tout) << std::endl;
tout << "open_ml:"; print_term_o( open_ml(m_tmp_l), tout) << std::endl;
tout << "term_to_tighten + open_ml:"; print_term_o(term_to_tighten + open_ml(m_tmp_l), tout) << std::endl;
print_lar_term_L(remove_fresh_vars(term_to_tighten + open_ml(m_tmp_l)), tout) << std::endl;
);
SASSERT(fix_vars(remove_fresh_vars(term_to_tighten + open_ml(m_tmp_l) - create_term_from_ind_c())).is_empty());
mpq g = gcd_of_coeffs(m_indexed_work_vector);
TRACE("dioph_eq", tout << "after process_q_with_S\nt:"; print_term_o(create_term_from_ind_c(), tout) << std::endl;
tout << "g:" << g << std::endl; /*tout << "dep:"; print_dep(tout, m_tmp_l) << std::endl;*/);
if (g.is_one()) {
TRACE("dioph_eq", tout << "g is one" << std::endl;);
return false;
@ -497,6 +559,18 @@ namespace lp {
// g is not trivial, trying to tighten the bounds
return tighten_bounds_for_term(g, j);
}
void get_expl_from_lar_term(const lar_term & l, explanation& ex) {
for (const auto& p: l) {
if (lra.column_is_fixed(p.j())) {
u_dependency* u = lra.get_bound_constraint_witnesses_for_column(p.j());
for (const auto& ci: lra.flatten(u)) {
ex.push_back(ci);
}
}
}
}
void handle_constant_term(unsigned j) {
if (m_c.is_zero()) {
return;
@ -506,30 +580,21 @@ namespace lp {
u_dependency *b_dep = nullptr;
if (lra.has_upper_bound(j, b_dep, rs, is_strict)) {
if (m_c > rs || (is_strict && m_c == rs)) {
for (const auto& p: lra.flatten(m_dep)) {
m_infeas_explanation.push_back(p);
}
for (const auto& p: lra.flatten(b_dep)) {
m_infeas_explanation.push_back(p);
}
get_expl_from_lar_term(m_tmp_l, m_infeas_explanation);
return;
}
}
if (lra.has_lower_bound(j, b_dep, rs, is_strict)) {
if (m_c < rs || (is_strict && m_c == rs)) {
for (const auto& p: lra.flatten(m_dep)) {
m_infeas_explanation.push_back(p);
}
for (const auto& p: lra.flatten(b_dep)) {
m_infeas_explanation.push_back(p);
}
get_expl_from_lar_term(m_tmp_l, m_infeas_explanation);
}
}
}
// returns true if there is a change in the bounds
// m_indexed_work_vector contains the coefficients of the term
// m_c contains the constant term
// m_dep contains the dependencies of the fixed vars
// m_tmp_l is the linear combination of the equations that removs the substituted variablse
bool tighten_bounds_for_term(const mpq& g, unsigned j) {
mpq rs;
bool is_strict;
@ -538,23 +603,20 @@ namespace lp {
SASSERT(!g.is_zero());
if (lra.has_upper_bound(j, b_dep, rs, is_strict)) {
TRACE("dioph_eq", tout << "ub:" << rs << std::endl;);
TRACE("dioph_eq", tout << "current upper bound for x:" << j << ":" << rs << std::endl;);
rs = (rs - m_c) / g;
TRACE("dioph_eq", tout << "(rs - m_c) / g:" << rs << std::endl;);
if (!rs.is_int()) {
tighten_bound_for_term_for_bound_kind(g, j, lra.mk_join(m_dep, b_dep), rs, true);
tighten_bound_for_term_for_bound_kind(g, j, rs, true);
change = true;
}
}
if (lra.has_lower_bound(j, b_dep, rs, is_strict)) {
TRACE("dioph_eq", tout << "tighten lower bound for x" << j << " with rs:" << rs << std::endl;);
TRACE("dioph_eq", tout << "current lower bound for x" << j << ":" << rs << std::endl;);
rs = (rs - m_c) / g;
TRACE("dioph_eq", tout << "tighten lower bound for x" << j << " with rs:" << rs << std::endl;);
TRACE("dioph_eq", tout << "(rs - m_c) / g:" << rs << std::endl;);
if (!rs.is_int()) {
tighten_bound_for_term_for_bound_kind(g, j, lra.mk_join(m_dep, b_dep), rs, false);
tighten_bound_for_term_for_bound_kind(g, j, rs, false);
change = true;
}
}
@ -562,29 +624,60 @@ namespace lp {
}
void tighten_bound_for_term_for_bound_kind( const mpq& g, unsigned j, u_dependency* dep, const mpq & ub, bool upper) {
void tighten_bound_for_term_for_bound_kind( const mpq& g, unsigned j, const mpq & ub, bool upper) {
// ub = (upper_bound(j) - m_c)/g.
// we have x[j] = t = g*t_+ m_c <= upper_bound(j), then
// t_ <= floor((upper_bound(j) - m_c)/g) = floor(ub)
//
// so xj = g*t_+m_c <= g*floor(ub) + m_c is new upper bound
// <= can be replaced with >= for lower bounds, with ceil instead of floor
mpq bound = g * (upper?floor(ub):ceil(ub))+m_c;
TRACE("dioph_eq", tout << "upper:" << upper << std::endl;
tout << "new " << (upper? "upper":"lower" ) << "bound:" << bound << std::endl;);
mpq bound = g * (upper? floor(ub) : ceil(ub)) + m_c;
TRACE("dioph_eq", tout << "is upper:" << upper << std::endl;
tout << "new " << (upper? "upper":"lower" ) << " bound:" << bound << std::endl;
);
dep = lra.mk_join(dep, upper? lra.get_column_upper_bound_witness(j): lra.get_column_lower_bound_witness(j) );
SASSERT(upper && bound <= lra.get_upper_bound(j).x || !upper && bound >= lra.get_lower_bound(j).x);
SASSERT(upper && bound < lra.get_upper_bound(j).x || !upper && bound > lra.get_lower_bound(j).x);
lconstraint_kind kind = upper? lconstraint_kind::LE: lconstraint_kind::GE;
lra.update_column_type_and_bound(j, kind, bound, dep);
u_dependency* dep = collect_explanation_from_indexed_vector(upper);
dep = lra.mk_join(dep, explain_fixed(m_tmp_l));
u_dependency* j_bound_dep = upper? lra.get_column_upper_bound_witness(j): lra.get_column_lower_bound_witness(j);
dep = lra.mk_join(dep, j_bound_dep);
TRACE("dioph_eq", tout << "jterm:"; print_lar_term_L(lra.get_term(j), tout) << "\ndep:"; print_dep(tout, dep) << std::endl;);
lra.update_column_type_and_bound(j, kind, bound, dep);
}
u_dependency* explain_fixed(const lar_term& t) {
u_dependency* dep = nullptr;
for (const auto& p: t) {
if (is_fixed(p.j())) {
u_dependency* bound_dep = lra.get_bound_constraint_witnesses_for_column(p.j());
dep = lra.mk_join(dep, bound_dep);
}
}
return dep;
}
u_dependency* collect_explanation_from_indexed_vector(bool upper) {
TRACE("dioph_eq",
tout << "new " << (upper? "upper":"lower" ) << "bound:" << bound << std::endl;
/* tout << "bound_dep:\n";print_dep(tout, dep) << std::endl;*/);
tout << (upper?"upper":"lower") << std::endl;
tout << "indexed_vec:"; print_term_o(create_term_from_ind_c(), tout);
);
term_o t = remove_fresh_vars(create_term_from_ind_c());
u_dependency* dep = nullptr;
int bound_sign = upper? 1: -1;
for (const auto& p: t) {
int var_bound_sign = p.coeff().is_pos()? bound_sign: -bound_sign;
u_dependency* bound_dep = (var_bound_sign == 1? lra.get_column_upper_bound_witness(p.var()): lra.get_column_lower_bound_witness(p.var()));
dep = lra.mk_join(dep, bound_dep);
}
return dep;
}
public:
lia_move check() {
init();
while(m_f.size()) {
while (m_f.size()) {
if (!normalize_by_gcd()) {
lra.settings().stats().m_dio_conflicts++;
if (m_report_branch) {
@ -603,6 +696,8 @@ public:
lia_move ret = tighten_with_S();
if (ret == lia_move::conflict) {
lra.settings().stats().m_dio_conflicts++;
enable_trace("arith");
enable_trace("dioph_eq");
return lia_move::conflict;
}
return lia_move::undef;
@ -618,31 +713,6 @@ public:
}
}
// void substitute_var_on_f(unsigned k, int k_sign, const term_o& k_subst, u_dependency * dep, unsigned index_to_avoid) {
// TRACE("dioph_eq", print_term_o(k_subst, tout<< "x" << k<< " -> ") << std::endl; tout << "dep:"; print_dep(tout, dep) << std::endl;);
// for (unsigned e_index: m_f) {
// if (e_index == index_to_avoid) continue;
// term_o& e = m_eprime[e_index].m_e;
// if (!e.contains(k)) continue;
// TRACE("dioph_eq", print_eprime_entry(e_index, tout << "before:") << std::endl;
// tout << "k_coeff:" << e.get_coeff(k) << std::endl;);
// /*
// if (!l_term.is_empty()) {
// if (k_sign == 1)
// add_operator(m_eprime[e_index].m_l, -k_coeff, l_term);
// else
// add_operator(m_eprime[e_index].m_l, k_coeff, l_term);
// }
// */
// m_eprime[e_index].m_l = lra.mk_join(dep, m_eprime[e_index].m_l);
// e.substitute_var_with_term(k_subst, k);
// TRACE("dioph_eq", print_eprime_entry(e_index, tout << "after :") << std::endl;);
// }
// }
std::tuple<mpq, unsigned, int> find_minimal_abs_coeff(unsigned row_index) const {
bool first = true;
mpq ahk;
@ -679,8 +749,10 @@ public:
return print_term_o(get_term_from_e_matrix(i), out);
}
// j is the variable to eliminate, it appears in row e.m_e_matrix with
// coefficient +-1
// a coefficient equal to +-1
void eliminate_var_in_f(eprime_entry& e, unsigned j, int j_sign) {
TRACE("dioph_eq", tout << "eliminate var:" << j << " by using:"; print_eprime_entry(e.m_row_index, tout) << std::endl;);
SASSERT(entry_invariant(e));
unsigned piv_row_index = e.m_row_index;
auto &column = m_e_matrix.m_columns[j];
int pivot_col_cell_index = -1;
@ -708,17 +780,72 @@ public:
cell_to_process--;
continue;
}
SASSERT(c.var() != piv_row_index);
SASSERT(c.var() != piv_row_index && entry_invariant(m_eprime[c.var()]));
mpq coeff = m_e_matrix.get_val(c);
TRACE("dioph_eq", tout << "m_e:" << c.var(); print_e_row(c.var(), tout) << std::endl;);
m_eprime[c.var()].m_c -= j_sign * coeff*m_eprime[piv_row_index].m_c;
m_e_matrix.pivot_row_to_row_given_cell_with_sign(piv_row_index, c, j, -j_sign);
m_eprime[c.var()].m_l = lra.mk_join(m_eprime[c.var()].m_l, m_eprime[piv_row_index].m_l);
TRACE("dioph_eq", tout << "after pivoting c_row:"; print_eprime_entry(c.var(), tout););
unsigned i = c.var();
TRACE("dioph_eq", tout << "before pivot entry :"; print_eprime_entry(i, tout) << std::endl;);
m_eprime[i].m_c -= j_sign * coeff*e.m_c;
m_e_matrix.pivot_row_to_row_given_cell_with_sign(piv_row_index, c, j, j_sign);
m_eprime[i].m_l -= j_sign * coeff * e.m_l;
TRACE("dioph_eq", tout << "after pivoting c_row:"; print_eprime_entry(i, tout););
CTRACE("dioph_eq", !entry_invariant(m_eprime[i]),
tout << "invariant delta:";
{
const auto& e = m_eprime[i];
print_term_o(get_term_from_e_matrix(e.m_row_index) - fix_vars(open_ml(e.m_l)), tout) << std::endl;
}
);
SASSERT(entry_invariant(m_eprime[i]));
cell_to_process--;
}
}
bool entry_invariant(const eprime_entry& e) const {
return remove_fresh_vars(get_term_from_e_matrix(e.m_row_index)) == fix_vars(open_ml(e.m_l));
}
term_o remove_fresh_vars(const term_o& tt) const{
term_o t = tt;
std::queue<unsigned> q;
for (const auto& p: t) {
if (is_fresh_var(p.j())) {
q.push(p.j());
}
}
while (!q.empty()) {
unsigned xt = pop_front(q);
const auto & xt_row = m_e_matrix.m_rows[m_k2s[xt]];
term_o xt_term;
for (const auto & p: xt_row) {
if (p.var() == xt) continue;
xt_term.add_monomial(p.coeff(), p.var());
}
mpq xt_coeff = t.get_coeff(xt);
t.erase_var(xt);
t += xt_coeff * xt_term;
for (const auto & p: t) {
if (is_fresh_var(p.j())) {
q.push(p.j());
}
}
}
return t;
}
std::ostream& print_ml(const lar_term & ml, std::ostream & out) {
term_o opened_ml = open_ml(ml);
return print_term_o(opened_ml, out);
}
term_o open_ml(const lar_term & ml) const {
term_o r;
for (const auto& p : ml) {
r += p.coeff()*(lra.get_term(p.var()) - lar_term(p.var()));
}
return r;
}
// it clears the row, and puts the term in the work vector
void move_row_to_work_vector(unsigned e_index) {
unsigned h = m_eprime[e_index].m_row_index;
// backup the term at h
@ -731,30 +858,30 @@ public:
m_e_matrix.remove_element(hrow, c);
}
}
// k is the variable to substitute
void fresh_var_step(unsigned e_index, unsigned k, const mpq& ahk) {
move_row_to_work_vector(e_index);
// step 7 from the paper
// k is the variable to substitute
void fresh_var_step(unsigned h, unsigned k, const mpq& ahk) {
move_row_to_work_vector(h); // it clears the row, and puts the term in the work vector
// step 7 from the paper
// xt is the fresh variable
unsigned xt = m_e_matrix.column_count();
unsigned xt = std::max(m_e_matrix.column_count(), lra.column_count()); // use var_register later
unsigned fresh_row = m_e_matrix.row_count();
m_e_matrix.add_row(); // for the fresh variable definition
m_e_matrix.add_column(); // the fresh variable itself
while (xt >= m_e_matrix.column_count())
m_e_matrix.add_column();
// Add a new row for the fresh variable definition
/* Let eh = sum(ai*xi) + c. For each i != k, let ai = qi*ahk + ri, and let c = c_q * ahk + c_r.
eh = ahk*(x_k + sum{qi*xi|i != k} + c_q) + sum {ri*xi|i!= k} + c_r.
Then -xt + x_k + sum {qi*x_i)| i != k} + c_q will be the fresh row
eh = ahk*xt + sum {ri*x_i | i != k} + c_r is the row m_e_matrix[e.m_row_index]
*/
auto & e = m_eprime[e_index];
auto & e = m_eprime[h];
mpq q, r;
q = machine_div_rem(e.m_c, ahk, r);
e.m_c = r;
unsigned h = e.m_row_index;
m_eprime.push_back({fresh_row, nullptr, q, entry_status::S});
m_e_matrix.add_new_element(h, xt, ahk);
m_eprime.push_back({fresh_row, lar_term(), mpq(0), entry_status::NO_S_NO_F});
m_e_matrix.add_new_element(fresh_row, xt, -mpq(1));
m_e_matrix.add_new_element(fresh_row, k, mpq(1));
for (unsigned i: m_indexed_work_vector.m_index) {
@ -767,13 +894,12 @@ public:
m_e_matrix.add_new_element(fresh_row, i, q);
}
// add entry to S
unsigned last_in_s = m_eprime.size() - 1;
m_s.push_back(last_in_s);
m_k2s.resize(k+1, -1);
m_k2s[k] = last_in_s;
TRACE("dioph_eq", tout << "changed entry:"; print_eprime_entry(e_index, tout)<< std::endl;
tout << "added to S:\n"; print_eprime_entry(last_in_s, tout););
m_k2s.resize(std::max(k + 1, xt + 1), -1);
m_k2s[k] = m_k2s[xt] = fresh_row;
TRACE("dioph_eq", tout << "changed entry:"; print_eprime_entry(h, tout)<< std::endl;
tout << "added entry for fresh var:\n"; print_eprime_entry(fresh_row, tout) << std::endl;);
SASSERT(entry_invariant(m_eprime[h]));
SASSERT(entry_invariant(m_eprime[fresh_row]));
eliminate_var_in_f(m_eprime.back(), k, 1);
}
@ -786,13 +912,15 @@ public:
out << "{\n";
print_term_o(get_term_from_e_matrix(e.m_row_index), out << "\tm_e:") << ",\n";
//out << "\tstatus:" << (int)e.m_entry_status;
if (print_dep)
this->print_dep(out<< "\tm_l:", e.m_l) << "\n";
if (print_dep) {
out << "\tm_l:{"; print_lar_term_L(e.m_l, out) << "}, ";
print_ml(e.m_l, out<< " \topened m_l:") << "\n";
}
out << "}\n";
return out;
}
// k is the index of the index of the variable with the coefficient +-1 that is being substituted
// k is the index of the variable that is being substituted
void move_entry_from_f_to_s(unsigned k, unsigned h) {
SASSERT(m_eprime[h].m_entry_status == entry_status::F);
m_eprime[h].m_entry_status = entry_status::S;
@ -810,7 +938,8 @@ public:
unsigned h = -1;
auto it = m_f.begin();
while (it != m_f.end()) {
if (m_e_matrix.m_rows[m_eprime[*it].m_row_index].size() == 0) {
SASSERT(*it ==m_eprime[*it].m_row_index);
if (m_e_matrix.m_rows[*it].size() == 0) {
if (m_eprime[*it].m_c.is_zero()) {
it = m_f.erase(it);
continue;
@ -842,6 +971,7 @@ public:
for (auto ci: m_infeas_explanation) {
ex.push_back(ci.ci());
}
TRACE("dioph_eq", lra.print_expl(tout, ex););
return;
}
SASSERT(ex.empty());
@ -855,7 +985,7 @@ public:
lra.explain_fixed_column(p.var(), ex);
}
*/
for (auto ci: lra.flatten(ep.m_l)) {
for (auto ci: lra.flatten(eq_deps(ep.m_l))) {
ex.push_back(ci);
}
TRACE("dioph_eq", lra.print_expl(tout, ex););
@ -864,6 +994,13 @@ public:
bool is_fresh_var(unsigned j) const {
return j >= lra.column_count();
}
bool can_substitute(unsigned k) {
return k < m_k2s.size() && m_k2s[k] != -1;
}
u_dependency * eq_deps(const lar_term& t) {
NOT_IMPLEMENTED_YET();
return nullptr;
}
};
// Constructor definition
dioph_eq::dioph_eq(int_solver& lia) {

4
src/math/lp/explanation.h
View file

@ -26,10 +26,10 @@ class explanation {
typedef vector<std::pair<unsigned, mpq>> pair_vec;
typedef hashtable<unsigned, u_hash, u_eq> ci_set;
// Only one of the fields below is used. The first call adding an entry decides which one it is.
public:
vector<std::pair<constraint_index, mpq>> m_vector;
ci_set m_set;
public:
explanation() = default;
explanation() {}
template <typename T>
explanation(const T& t) {

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

@ -113,6 +113,8 @@ public:
if (was_zero)
m_index.push_back(j);
}
SASSERT(v.is_zero() ==
( std::find(m_index.begin(), m_index.end(), j) == m_index.end()));
}
void erase(unsigned j);

2
src/math/lp/int_solver.cpp
View file

@ -181,7 +181,7 @@ namespace lp {
return lia_move::branch;
}
m_dioph_eq_period *= 2; // the overflow is fine, maybe to try again
// m_dioph_eq_period *= 2;
return lia_move::undef;
}

3
src/math/lp/lar_solver.cpp
View file

@ -1950,7 +1950,8 @@ namespace lp {
// SASSERT(validate_bound(j, kind, right_side, dep));
TRACE(
"lar_solver_feas",
tout << "j" << j << " " << lconstraint_kind_string(kind) << " " << right_side << std::endl;
tout << "j" << j << " " << lconstraint_kind_string(kind) << " " << right_side << std::endl;
print_column_info(j, tout) << "\n";
if (dep) {
tout << "dep:\n";
auto cs = flatten(dep);

1
src/math/lp/lar_solver.h
View file

@ -653,6 +653,7 @@ public:
inline int_solver* get_int_solver() { return m_int_solver; }
inline const int_solver* get_int_solver() const { return m_int_solver; }
inline const lar_term& get_term(lpvar j) const {
SASSERT(column_has_term(j));
return *m_columns[j].term();
}
lp_status find_feasible_solution();

28
src/math/lp/lar_term.h
View file

@ -51,7 +51,7 @@ public:
return;
auto *e = m_coeffs.find_core(j);
if (e == nullptr) {
m_coeffs.insert(j, c);
m_coeffs.insert(j, -c);
} else {
e->get_data().m_value -= c;
if (e->get_data().m_value.is_zero())
@ -90,6 +90,21 @@ public:
}
// constructors
lar_term() = default;
<<<<<<< HEAD
=======
lar_term(lar_term&& other) noexcept = default;
// copy assignment operator
lar_term& operator=(const lar_term& other) = default;
// move assignment operator
lar_term& operator=(lar_term&& other) noexcept = default;
~lar_term() = default;
lar_term(const lar_term& a) {
for (auto const& p : a) {
add_monomial(p.coeff(), p.var());
}
}
>>>>>>> 956229fb6 (test that pivoting is correct in dioph_eq.cpp)
lar_term(const vector<std::pair<mpq, unsigned>>& coeffs) {
for (auto const& p : coeffs) {
add_monomial(p.first, p.second);
@ -205,7 +220,16 @@ public:
}
return r;
}
friend lar_term operator-(const lar_term& a, const lar_term& b) {
lar_term r(a);
for (const auto& p : b) {
r.sub_monomial(p.coeff(), p.j());
}
return r;
}
lar_term& operator+=(const lar_term& a) {
for (const auto& p : a) {
add_monomial(p.coeff(), p.j());

12
src/math/lp/lp_utils.h
View file

@ -90,8 +90,18 @@ std::ostream& print_linear_combination_customized(const vector<std::pair<T, unsi
out << "0";
return out;
}
// Copy term to a std_vector and sort by p.j()
std_vector<std::pair<T, unsigned>> sorted_coeffs;
sorted_coeffs.reserve(coeffs.size());
for (const auto& p : coeffs) {
sorted_coeffs.emplace_back(p.first, p.second);
}
std::sort(sorted_coeffs.begin(), sorted_coeffs.end(),
[](const auto& a, const auto& b) { return a.second < b.second; });
// Print the sorted term
bool first = true;
for (const auto & it : coeffs) {
for (const auto & it : sorted_coeffs) {
T val = it.first;
if (first) {
first = false;

1
src/math/lp/static_matrix.h
View file

@ -46,6 +46,7 @@ typedef vector<column_cell> column_strip;
template <typename T>
using row_strip = vector<row_cell<T>>;
template <typename K> mpq get_denominators_lcm(const K & row) {
SASSERT(row.size() > 0);
mpq r = mpq(1);
for (const auto & c : row)
r = lcm(r, denominator(c.coeff()));

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

@ -90,7 +90,7 @@ inline void static_matrix<T, X>::pivot_row_to_row_given_cell_with_sign(unsigned
column_cell& c, unsigned pivot_col, int pivot_sign) {
unsigned ii = c.var();
SASSERT(ii != piv_row_index);
T alpha = get_val(c) * pivot_sign;
T alpha = - get_val(c) * pivot_sign;
SASSERT(!is_zero(alpha));
auto & rowii = m_rows[ii];
remove_element(rowii, rowii[c.offset()]);