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use var_register in dioph_eq
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Signed-off-by: Lev Nachmanson <[email protected]>
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@levnach
levnach committed Feb 11, 2025
1 parent 480c48f commit d68ebee
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Showing 3 changed files with 66 additions and 56 deletions.
116 changes: 62 additions & 54 deletions src/math/lp/dioph_eq.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,7 @@
To track the explanations of equality t = 0 we initially set m_entries[i].m_l = lar_term(j), and update m_l
accordingly with the pivot operations. The explanation is obtained by replacing term m_l = sum(aj*j) by the linear
combination sum (aj*initt(j)) and joining the explanations of all fixed variables in the latter sum.
entry_invariant(i) guarantees the validity of entry i.
entry_invariant(i) guarantees the validity of the i-th entry.
*/
namespace lp {
// This class represents a term with an added constant number c, in form sum {x_i*a_i} + c.
Expand Down Expand Up @@ -187,6 +187,7 @@ namespace lp {
mpq m_c; // the constant of the term, the term is taken from the row of m_e_matrix with the same index as the entry
entry_status m_entry_status;
};
var_register m_var_register;
std_vector<entry> m_entries;
// the terms are stored in m_A and m_c
static_matrix<mpq, mpq> m_e_matrix; // the rows of the matrix are the terms, without the constant part
Expand Down Expand Up @@ -219,12 +220,21 @@ namespace lp {
t.c() = m_entries[i].m_c;
return t;
}

// adds variable j of lar_solver to the local diophantine handler
unsigned add_var(unsigned j) {
return this->m_var_register.add_var(j, true);
}

unsigned local_to_lar_solver(unsigned j) const {
return m_var_register.local_to_external(j);
}

// 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_entry(const lar_term& t) {
TRACE("dioph_eq", print_lar_term_L(t, tout) << std::endl;);
unsigned i = static_cast<unsigned>(m_entries.size());
entry te = {lar_term(t.j()), mpq(0), entry_status::NO_S_NO_F};
entry te = {lar_term(t.j()), mpq(0), entry_status::F};
unsigned entry_index = m_entries.size();
m_f.push_back(entry_index);
m_entries.push_back(te);
Expand All @@ -237,64 +247,52 @@ namespace lp {
if (is_fixed(p.var()))
e.m_c += p.coeff()*lia.lower_bound(p.var()).x;
else {
while (p.var() >= m_e_matrix.column_count())
unsigned lj = add_var(p.var());
while (lj >= m_e_matrix.column_count())
m_e_matrix.add_column();
m_e_matrix.add_new_element(entry_index, p.var(), p.coeff());
m_e_matrix.add_new_element(entry_index, lj, p.coeff());
}
}
unsigned j = t.j();
if (is_fixed(j))
e.m_c -= lia.lower_bound(j).x;
if (is_fixed(t.j()))
e.m_c -= lia.lower_bound(t.j()).x;
else {
while (j >= m_e_matrix.column_count())
unsigned lj = add_var(t.j());
while (lj >= m_e_matrix.column_count())
m_e_matrix.add_column();
m_e_matrix.add_new_element(entry_index, j, - mpq(1));
m_e_matrix.add_new_element(entry_index, lj, - mpq(1));
}
e.m_entry_status = entry_status::F;
TRACE("dioph_eq", print_entry(entry_index, tout););
SASSERT(entry_invariant(i));
SASSERT(entry_invariant(entry_index));
}

bool all_vars_are_int_and_small(const lar_term& term) const {
bool all_vars_are_int(const lar_term& term) const {
for (const auto& p : term) {
if (!lia.column_is_int(p.var()))
return false;
if (p.coeff().is_big())
return false;
}
return true;
}


void init() {
m_e_matrix = static_matrix<mpq, mpq>();
m_report_branch = false;
m_k2s.clear();
m_fresh_definitions.clear();
m_conflict_index = -1;
m_infeas_explanation.clear();
lia.get_term().clear();
m_entries.clear();
m_var_register.clear();

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";);
if (!all_vars_are_int(t)) {
TRACE("dioph_eq", tout << "not all vars are integrall\n";);
continue;
}
fill_entry(t);
}

}

// look only at the fixed columns
u_dependency * get_dep_from_row(const row_strip<mpq>& row) {
u_dependency* dep = nullptr;
for (const auto & p: row) {
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);
}
return dep;
}

template <typename K> mpq gcd_of_coeffs(const K & k) {
Expand Down Expand Up @@ -333,7 +331,7 @@ namespace lp {
*/
lar_term& t = lia.get_term();
for (const auto& p: m_e_matrix.m_rows[ei]) {
t.add_monomial(p.coeff()/g, p.var());
t.add_monomial(p.coeff()/g, local_to_lar_solver(p.var()));
}
lia.offset() = floor(-new_c);
lia.is_upper() = true;
Expand Down Expand Up @@ -427,7 +425,7 @@ namespace lp {
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());
const auto & t = lra.get_term(local_to_lar_solver(p.j()));
ret.add_monomial(-mpq(1), p.j());
for (const auto& q: t) {
ret.add_monomial(p.coeff()*q.coeff(), q.j());
Expand All @@ -437,7 +435,7 @@ namespace lp {
}

bool is_fixed(unsigned j) const {
return (!is_fresh_var(j)) && lra.column_is_fixed(j);
return lra.column_is_fixed(j);
}

template <typename T> term_o fix_vars(const T& t) const {
Expand Down Expand Up @@ -471,9 +469,10 @@ namespace lp {
}

lia_move tighten_with_S() {
for (unsigned j = 0; j < lra.column_count(); j++) {
for (unsigned j = 0; j < lra.column_count(); j++) {
if (!lra.column_has_term(j) || lra.column_is_free(j) ||
lra.column_is_fixed(j) || !lia.column_is_int(j)) continue;
is_fixed(j) || !lia.column_is_int(j)) continue;

if (tighten_bounds_for_term_column(j))
return lia_move::conflict;
}
Expand Down Expand Up @@ -509,18 +508,22 @@ namespace lp {
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());
m_indexed_work_vector.set_value(p.coeff(), lar_solver_to_local(p.j()));
}

}
unsigned lar_solver_to_local(unsigned j) const {
return m_var_register.external_to_local(j);
}
// j is the index of the column representing a term
// return true if a conflict was found
bool tighten_bounds_for_term_column(unsigned j) {
term_o term_to_tighten = lra.get_term(j); // copy the term aside
if (!all_vars_are_int(term_to_tighten)) return false;
std::queue<unsigned> q;
for (const auto& p: term_to_tighten) {
if (can_substitute(p.j()) && !lra.column_is_fixed(p.j()))
q.push(p.j());
if (!lra.column_is_fixed(p.j()) && can_substitute(lar_solver_to_local(p.j())))
q.push(lar_solver_to_local(p.j()));
}
if (q.empty()) {
return false;
Expand All @@ -540,7 +543,9 @@ namespace lp {
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());
SASSERT(
fix_vars(term_to_tighten + open_ml(m_tmp_l)) ==
term_to_lar_solver(remove_fresh_vars(create_term_from_ind_c())));
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;*/);
Expand Down Expand Up @@ -743,14 +748,8 @@ namespace lp {
entry& e = m_entries[ei];
TRACE("dioph_eq", tout << "eliminate var:" << j << " by using:"; print_entry(ei, tout) << std::endl;);
auto &column = m_e_matrix.m_columns[j];
int pivot_col_cell_index = -1;
for (unsigned k = 0; k < column.size(); k++) {
if (column[k].var() == ei) {
pivot_col_cell_index = k;
break;
}
}
SASSERT(pivot_col_cell_index != -1);
auto it = std::find_if(column.begin(), column.end(), [ei](const auto &cell) {return cell.var() == ei;});
unsigned pivot_col_cell_index = std::distance(column.begin(), it);
if (pivot_col_cell_index != 0) {
// swap the pivot column cell with the head cell
auto c = column[0];
Expand Down Expand Up @@ -789,9 +788,18 @@ namespace lp {
}
}

term_o term_to_lar_solver(const term_o& eterm) const {
term_o ret;
for (const auto& p : eterm) {
ret.add_monomial(p.coeff(), local_to_lar_solver(p.var()));
}
ret.c() = eterm.c();
return ret;
}

bool entry_invariant(unsigned ei) const {
const auto &e = m_entries[ei];
bool ret = remove_fresh_vars(get_term_from_entry(ei)) == fix_vars(open_ml(e.m_l));
bool ret = term_to_lar_solver(remove_fresh_vars(get_term_from_entry(ei))) == fix_vars(open_ml(e.m_l));
if (ret) return true;
TRACE("dioph_eq",
tout << "get_term_from_entry("<< ei <<"):";
Expand Down Expand Up @@ -861,7 +869,7 @@ namespace lp {
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 = std::max(m_e_matrix.column_count(), lra.column_count()); // use var_register later
unsigned xt = add_var(UINT_MAX);
unsigned fresh_row = m_e_matrix.row_count();
m_e_matrix.add_row(); // for the fresh variable definition
while (xt >= m_e_matrix.column_count())
Expand Down Expand Up @@ -914,18 +922,18 @@ namespace lp {
if (need_print_dep) {
out << "\tm_l:{"; print_lar_term_L(e.m_l, out) << "}, ";
print_ml(e.m_l, out<< " \tfixed expl of m_l:") << "\n";
print_dep(out, explain_fixed_in_meta_term(e.m_l)) << std::endl;
print_dep(out, explain_fixed_in_meta_term(e.m_l)) << ",";
}
switch (e.m_entry_status)
{
case entry_status::F:
out << "\tin F\n";
out << "in F\n";
break;
case entry_status::S:
out << "\tin S\n";
out << "in S\n";
break;
default:
out << "\tNOSF\n";
out << "NOSF\n";
}
out << "}\n";
return out;
Expand Down Expand Up @@ -995,7 +1003,7 @@ namespace lp {
}

bool is_fresh_var(unsigned j) const {
return j >= lra.column_count();
return m_var_register.local_to_external(j) == UINT_MAX;
}
bool can_substitute(unsigned k) {
return k < m_k2s.size() && m_k2s[k] != UINT_MAX;
Expand Down
4 changes: 3 additions & 1 deletion src/math/lp/int_solver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -290,7 +290,9 @@ namespace lp {
for (unsigned j : lra.r_basis()) {
if (!column_is_int_inf(j))
continue;

if (settings().get_cancel_flag()){
return -1;
}
SASSERT(!lia.is_fixed(j));

unsigned usage = lra.usage_in_terms(j);
Expand Down
2 changes: 1 addition & 1 deletion src/math/lp/var_register.h
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Original file line number Diff line number Diff line change
Expand Up @@ -74,7 +74,7 @@ class var_register {
return ret;
}

// returns UINT_MAX if
// returns UINT_MAX if local_var is greater than or equal than the number of local variables
unsigned local_to_external(unsigned local_var) const {
unsigned k = local_var;
if (k >= m_local_to_external.size())
Expand Down

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