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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2021-05-13 17:18:09 -07:00
parent cf8b3a0788
commit d833483ca0
2 changed files with 33 additions and 23 deletions
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7
src/math/polysat/fixplex.h
View file

@ -59,6 +59,7 @@ namespace polysat {
unsigned m_num_pivots;
unsigned m_num_infeasible;
unsigned m_num_checks;
unsigned m_num_approx;
stats() { reset(); }
void reset() {
memset(this, 0, sizeof(*this));
@ -152,9 +153,7 @@ namespace polysat {
std::ostream& display(std::ostream& out) const;
std::ostream& display_row(std::ostream& out, row const& r, bool values = true);
void collect_statistics(::statistics & st) const;
row get_infeasible_row();
void del_row(var_t base_var);
private:
@ -189,11 +188,11 @@ namespace polysat {
bool is_fixed(var_t v) const { return lo(v) + 1 == hi(v); }
bool is_valid_variable(var_t v) const { return v < m_vars.size(); }
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; }
row base2row(var_t x) const { return row(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; }
bool row_is_integral(row const& r) const { return m_rows[r.id()].m_integral; }
void set_base_value(var_t x);
numeral solve_for(numeral const& row_value, numeral const& coeff);
bool is_feasible() const;

49
src/math/polysat/fixplex_def.h
View file

@ -118,7 +118,8 @@ namespace polysat {
m_vars[base_var].m_is_base = true;
set_base_value(base_var);
add_patch(base_var);
bool elim = pivot_base_vars();
if (!pivot_base_vars())
++m_stats.m_num_approx;
SASSERT(well_formed_row(r));
SASSERT(well_formed());
return r;
@ -134,10 +135,18 @@ namespace polysat {
return ok;
}
/**
* Eliminate base variable v from all rows except where v is basic.
* Return false if elimination required to multiply a non-basic row with an even number.
* This happens when the parity in the non-basic row is smaller than the parity of v in
* the basic row. It is expected to be a corner case and we don't try to solve this
* inside of fixplex. Instead to deal with the corner case we assume the layer around
* fixplex uses a solution from fixplex as a starting point for a complete search (in polysat).
*/
template<typename Ext>
bool fixplex<Ext>::elim_base(var_t v) {
SASSERT(is_base(v));
row r = row(base2row(v));
row r = base2row(v);
numeral b = row2base_coeff(r);
unsigned tz_b = m.trailing_zeros(b);
for (auto col : M.col_entries(v)) {
@ -151,7 +160,6 @@ namespace polysat {
return true;
}
template<typename Ext>
void fixplex<Ext>::del_row(row const& r) {
m_var_eqs.reset();
@ -170,7 +178,7 @@ namespace polysat {
TRACE("polysat", tout << var << "\n";);
row r;
if (is_base(var)) {
r = row(m_vars[var].m_base2row);
r = base2row(var);
}
else {
unsigned tz = UINT_MAX;
@ -197,7 +205,7 @@ namespace polysat {
// need to move var such that old_base comes in bound.
pivot(old_base, var, coeff, new_value);
SASSERT(is_base(var));
SASSERT(m_vars[var].m_base2row == r.id());
SASSERT(base2row(var).id() == r.id());
SASSERT(vi.contains(value(old_base)));
}
del_row(r);
@ -287,7 +295,7 @@ namespace polysat {
SASSERT(is_base(x));
var_t max = get_num_vars();
var_t result = max;
row r(base2row(x));
row r = base2row(x);
int n = 0;
unsigned best_col_sz = UINT_MAX;
int best_so_far = INT_MAX;
@ -361,7 +369,7 @@ namespace polysat {
SASSERT(is_base(x));
unsigned max = get_num_vars();
var_t result = max;
row r(base2row(x));
row r = base2row(x);
for (auto const& c : M.col_entries(r)) {
var_t y = c.var();
if (x == y || y >= result)
@ -382,7 +390,7 @@ namespace polysat {
*/
template<typename Ext>
bool fixplex<Ext>::can_improve(var_t x, numeral const& new_x_value, var_t y, numeral const& b) {
row r(base2row(x));
row r = base2row(x);
numeral row_value = row2value(r) + row2base_coeff(r) * new_x_value;
numeral new_y_value = solve_for(row_value - b * value(y), b);
if (in_bounds(y, new_y_value))
@ -475,7 +483,7 @@ namespace polysat {
SASSERT(is_base(x));
auto r = base2row(x);
mod_interval<numeral> range(0, 1);
for (auto const& e : M.row_entries(row(r))) {
for (auto const& e : M.row_entries(r)) {
var_t v = e.var();
numeral const& c = e.coeff();
range += m_vars[v] * c;
@ -499,7 +507,7 @@ namespace polysat {
bool fixplex<Ext>::is_parity_infeasible_row(var_t x) {
SASSERT(is_base(x));
auto r = base2row(x);
if (row2integral(row(r)))
if (row_is_integral(row(r)))
return false;
numeral fixed = 0;
unsigned parity = UINT_MAX;
@ -640,7 +648,7 @@ namespace polysat {
typename fixplex<Ext>::row
fixplex<Ext>::get_infeasible_row() {
SASSERT(is_base(m_infeasible_var));
return row(base2row(m_infeasible_var));
return base2row(m_infeasible_var);
}
/**
@ -767,13 +775,13 @@ namespace polysat {
template<typename Ext>
void fixplex<Ext>::set_base_value(var_t x) {
SASSERT(is_base(x));
row r(base2row(x));
row r = base2row(x);
m_vars[x].m_value = solve_for(row2value(r), row2base_coeff(r));
bool was_integral = row2integral(r);
bool was_integral = row_is_integral(r);
m_rows[r.id()].m_integral = is_solved(r);
if (was_integral && !row2integral(r))
if (was_integral && !row_is_integral(r))
++m_num_non_integral;
else if (!was_integral && row2integral(r))
else if (!was_integral && row_is_integral(r))
--m_num_non_integral;
}
@ -819,7 +827,7 @@ namespace polysat {
bool fixplex<Ext>::is_offset_row(row const& r, numeral& cx, var_t& x, numeral& cy, var_t & y) const {
x = null_var;
y = null_var;
if (!row2integral(r))
if (!row_is_integral(r))
return false;
for (auto const& e : M.row_entries(r)) {
var_t v = e.var();
@ -941,7 +949,9 @@ namespace polysat {
bool was_fixed = lo(x) + 1 == hi(x);
m_vars[x] &= range;
IF_VERBOSE(0, verbose_stream() << "new-bound v" << x << " " << m_vars[x] << "\n");
if (!was_fixed && lo(x) + 1 == hi(x))
if (m_vars[x].is_empty())
m_infeasible_var = x;
else if (!was_fixed && lo(x) + 1 == hi(x))
fixed_var_eh(r, x);
}
@ -982,7 +992,7 @@ namespace polysat {
var_t s = row2base(r);
if (s == null_var)
continue;
SASSERT(i == base2row(s));
SASSERT(i == base2row(s).id());
VERIFY(well_formed_row(r));
}
for (unsigned i = 0; i < m_vars.size(); ++i) {
@ -994,7 +1004,7 @@ namespace polysat {
template<typename Ext>
bool fixplex<Ext>::well_formed_row(row const& r) const {
var_t s = row2base(r);
VERIFY(base2row(s) == r.id());
VERIFY(base2row(s).id() == r.id());
VERIFY(m_vars[s].m_is_base);
numeral sum = 0;
numeral base_coeff = row2base_coeff(r);
@ -1018,6 +1028,7 @@ namespace polysat {
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);
st.update("fixplex num approximated row additions", m_stats.m_num_approx);
}