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add accounting for integrality

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2021-05-04 11:57:25 -07:00
parent fd1758ffab
commit 8cd1ddf445
2 changed files with 51 additions and 11 deletions
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11
src/math/polysat/fixplex.h
View file

@ -70,6 +70,7 @@ namespace polysat {
};
struct row_info {
bool m_integral { true };
var_t m_base;
numeral m_value;
numeral m_base_coeff;
@ -80,6 +81,7 @@ namespace polysat {
mutable manager m;
mutable matrix M;
unsigned m_max_iterations { UINT_MAX };
unsigned m_num_non_integral { 0 };
var_heap m_to_patch;
vector<var_info> m_vars;
vector<row_info> m_rows;
@ -150,6 +152,12 @@ namespace polysat {
bool is_free(var_t v) const { return lo(v) == hi(v); }
bool is_non_free(var_t v) const { return !is_free(v); }
bool is_base(var_t x) const { return m_vars[x].m_is_base; }
unsigned base2row(var_t x) const { return m_vars[x].m_base2row; }
numeral const& row2value(row const& r) const { return m_rows[r.id()].m_value; }
numeral const& row2base_coeff(row const& r) const { return m_rows[r.id()].m_base_coeff; }
var_t row2base(row const& r) const { return m_rows[r.id()].m_base; }
bool row2integral(row const& r) const { return m_rows[r.id()].m_integral; }
void set_base_value(var_t x);
bool is_feasible() const;
int get_num_non_free_dep_vars(var_t x_j, int best_so_far);
void add_patch(var_t v);
@ -158,6 +166,9 @@ namespace polysat {
pivot_strategy_t pivot_strategy() { return m_bland ? S_BLAND : S_DEFAULT; }
var_t select_error_var(bool least);
bool is_solved(row const& r) const;
bool is_solved(var_t v) const { SASSERT(is_base(v)); return is_solved(base2row(v)); }
bool well_formed() const;
bool well_formed_row(row const& r) const;

51
src/math/polysat/fixplex_def.h
View file

@ -114,7 +114,7 @@ namespace polysat {
m_rows[r.id()].m_value = value;
m_vars[base_var].m_base2row = r.id();
m_vars[base_var].m_is_base = true;
m_vars[base_var].m_value = 0 - (value / base_coeff);
set_base_value(base_var);
// TBD: record when base_coeff does not divide value
add_patch(base_var);
if (!m_base_vars.empty()) {
@ -148,7 +148,7 @@ namespace polysat {
row_info& ri = m_rows[r.id()];
var_t s = ri.m_base;
ri.m_value += delta * c.get_row_entry().m_coeff;
m_vars[s].m_value = 0 - (ri.m_value / ri.m_base_coeff);
set_base_value(s);
add_patch(s);
}
}
@ -234,7 +234,7 @@ namespace polysat {
SASSERT(is_base(x));
var_t max = get_num_vars();
var_t result = max;
row r = row(m_vars[x].m_base2row);
row r(base2row(x));
int n = 0;
unsigned best_col_sz = UINT_MAX;
int best_so_far = INT_MAX;
@ -378,7 +378,7 @@ namespace polysat {
template<typename Ext>
bool fixplex<Ext>::is_infeasible_row(var_t x) {
SASSERT(is_base(x));
auto r = m_vars[x].m_base2row;
auto r = base2row(x);
numeral lo_sum = 0, hi_sum = 0, diff = 0;
for (auto const& e : M.row_entries(row(r))) {
var_t v = e.m_var;
@ -444,7 +444,7 @@ namespace polysat {
row_x.m_base_coeff = b;
yI.m_base2row = rx;
yI.m_is_base = true;
yI.m_value = 0 - row_x.m_value / b;
set_base_value(y);
xI.m_is_base = false;
xI.m_value = new_value;
row r_x(rx);
@ -458,8 +458,9 @@ namespace polysat {
unsigned rz = r_z.id();
if (rz == rx)
continue;
auto z = row2base(r_z);
auto& row_z = m_rows[rz];
var_info& zI = m_vars[rz];
var_info& zI = m_vars[z];
numeral c = col.get_row_entry().m_coeff;
unsigned tz2 = trailing_zeros(c);
SASSERT(tz1 <= tz2);
@ -469,7 +470,7 @@ namespace polysat {
M.add(r_z, c1, r_x);
row_z.m_value = (b1 * (row_z.m_value - old_value_y)) + c1 * row_x.m_value;
row_z.m_base_coeff *= b1;
zI.m_value = 0 - row_z.m_value / row_z.m_base_coeff;
set_base_value(z);
SASSERT(well_formed_row(r_z));
add_patch(row_z.m_base);
}
@ -488,7 +489,7 @@ namespace polysat {
typename fixplex<Ext>::row
fixplex<Ext>::get_infeasible_row() {
SASSERT(is_base(m_infeasible_var));
return row(m_vars[m_infeasible_var].m_base2row);
return row(base2row(m_infeasible_var));
}
/**
@ -513,7 +514,10 @@ namespace polysat {
void fixplex<Ext>::add_patch(var_t v) {
SASSERT(is_base(v));
CTRACE("polysat", !in_bounds(v), tout << "Add patch: v" << v << "\n";);
if (!in_bounds(v))
if (in_bounds(v)) {
}
else
m_to_patch.insert(v);
}
@ -569,6 +573,30 @@ namespace polysat {
}
}
/**
* Check if row is solved with respect to integrality constraints.
* The value of the row is allowed to be off by the base coefficient
* representing the case where there is a rational, but not integer solution.
*/
template<typename Ext>
bool fixplex<Ext>::is_solved(row const& r) const {
return (value(row2base(r)) * row2base_coeff(r)) + row2value(r) == 0;
}
template<typename Ext>
void fixplex<Ext>::set_base_value(var_t x) {
SASSERT(is_base(x));
auto r = base2row(x);
m_vars[x].m_value = 0 - (m_rows[r].m_value / m_rows[r].m_base_coeff);
bool was_integral = m_rows[r].m_integral;
m_rows[r].m_integral = is_solved(row(r));
if (was_integral && !row2integral(row(r)))
++m_num_non_integral;
else if (!was_integral && row2integral(row(r)))
--m_num_non_integral;
}
template<typename Ext>
std::ostream& fixplex<Ext>::display(std::ostream& out) const {
M.display(out);
@ -601,7 +629,7 @@ namespace polysat {
var_t s = m_rows[i].m_base;
if (s == null_var)
continue;
SASSERT(i == m_vars[s].m_base2row);
SASSERT(i == base2row(s));
VERIFY(well_formed_row(row(i)));
}
for (unsigned i = 0; i < m_vars.size(); ++i) {
@ -614,7 +642,7 @@ namespace polysat {
bool fixplex<Ext>::well_formed_row(row const& r) const {
var_t s = m_rows[r.id()].m_base;
(void)s;
SASSERT(m_vars[s].m_base2row == r.id());
SASSERT(base2row(s) == r.id());
SASSERT(m_vars[s].m_is_base);
numeral sum = 0;
numeral base_coeff = m_rows[r.id()].m_base_coeff;
@ -636,5 +664,6 @@ namespace polysat {
st.update("fixplex num pivots", m_stats.m_num_pivots);
st.update("fixplex num infeasible", m_stats.m_num_infeasible);
st.update("fixplex num checks", m_stats.m_num_checks);
st.update("fixplex num non-integral", m_num_non_integral);
}
}