mirror of
https://github.com/Z3Prover/z3
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move constraint handler functionality to self-contained / separate classes.
Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner
parent
0d78a10630
commit
5163492d5b
5 changed files with 134 additions and 117 deletions
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@ -12,16 +12,126 @@ Author:
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--*/
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#include "math/polysat/constraint.h"
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#include "math/polysat/solver.h"
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#include "math/polysat/log.h"
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namespace polysat {
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constraint* constraint::eq(unsigned lvl, pdd const& p, p_dependency_ref& d) {
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return alloc(eq_constraint, lvl, p, dep);
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eq_constraint& constraint::to_eq() {
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return *dynamic_cast<eq_constraint*>(this);
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}
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std::ostream& constraint::display(std::ostream& out) const {
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eq_constraint const& constraint::to_eq() const {
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return *dynamic_cast<eq_constraint const*>(this);
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}
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constraint* constraint::eq(unsigned lvl, pdd const& p, p_dependency_ref& d) {
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return alloc(eq_constraint, lvl, p, d);
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}
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std::ostream& eq_constraint::display(std::ostream& out) const {
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return out << p() << " == 0";
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}
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bool eq_constraint::propagate(solver& s, pvar v) {
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LOG_H3("Propagate " << s.m_vars[v] << " in " << *this);
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SASSERT(!vars().empty());
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auto var = s.m_vars[v].var();
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unsigned idx = 0;
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if (vars()[idx] != v)
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idx = 1;
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SASSERT(v == vars()[idx]);
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// find other watch variable.
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for (unsigned i = vars().size(); i-- > 2; ) {
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if (!s.is_assigned(vars()[i])) {
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std::swap(vars()[idx], vars()[i]);
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return true;
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}
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}
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LOG("Assignments: " << s.m_search);
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auto q = p().subst_val(s.m_search);
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LOG("Substituted: " << p() << " := " << q);
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TRACE("polysat", tout << p() << " := " << q << "\n";);
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if (q.is_zero())
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return false;
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if (q.is_never_zero()) {
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LOG("Conflict (never zero under current assignment)");
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// we could tag constraint to allow early substitution before
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// swapping watch variable in case we can detect conflict earlier.
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s.set_conflict(*this);
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return false;
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}
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// at most one variable remains unassigned.
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auto other_var = vars()[1 - idx];
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// Detect and apply unit propagation.
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if (!q.is_linear())
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return false;
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// a*x + b == 0
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rational a = q.hi().val();
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rational b = q.lo().val();
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rational inv_a;
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if (a.is_odd()) {
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// v1 = -b * inverse(a)
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unsigned sz = q.power_of_2();
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VERIFY(a.mult_inverse(sz, inv_a));
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rational val = mod(inv_a * -b, rational::power_of_two(sz));
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s.m_cjust[other_var].push_back(this);
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s.propagate(other_var, val, *this);
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return false;
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}
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SASSERT(!b.is_odd()); // otherwise p.is_never_zero() would have been true above
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// TBD
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// constrain viable using condition on x
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// 2*x + 2 == 0 mod 4 => x is odd
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//
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// We have:
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// 2^j*a'*x + 2^j*b' == 0 mod m, where a' is odd (but not necessarily b')
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// <=> 2^j*(a'*x + b') == 0 mod m
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// <=> a'*x + b' == 0 mod (m-j)
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// <=> x == -b' * inverse_{m-j}(a') mod (m-j)
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// ( <=> 2^j*x == 2^j * -b' * inverse_{m-j}(a') mod m )
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//
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// x == c mod (m-j)
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// Which x in 2^m satisfy this?
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// => x \in { c + k * 2^(m-j) | k = 0, ..., 2^j - 1 }
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unsigned rank_a = a.trailing_zeros(); // j
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SASSERT(b == 0 || rank_a <= b.trailing_zeros());
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rational aa = a / rational::power_of_two(rank_a); // a'
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rational bb = b / rational::power_of_two(rank_a); // b'
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rational inv_aa;
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unsigned small_sz = q.power_of_2() - rank_a; // m - j
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VERIFY(aa.mult_inverse(small_sz, inv_aa));
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rational cc = mod(inv_aa * -bb, rational::power_of_two(small_sz));
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LOG(m_vars[other_var] << " = " << cc << " + k * 2^" << small_sz);
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// TODO: better way to update the BDD, e.g. construct new one (only if rank_a is small?)
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vector<rational> viable;
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for (rational k = rational::zero(); k < rational::power_of_two(rank_a); k += 1) {
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rational val = cc + k * rational::power_of_two(small_sz);
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viable.push_back(val);
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}
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LOG_V("still viable: " << viable);
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unsigned i = 0;
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for (rational r = rational::zero(); r < rational::power_of_two(q.power_of_2()); r += 1) {
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while (i < viable.size() && viable[i] < r)
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++i;
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if (i < viable.size() && viable[i] == r)
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continue;
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if (s.is_viable(other_var, r)) {
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s.add_non_viable(other_var, r);
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}
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}
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LOG("TODO");
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return false;
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}
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}
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@ -26,6 +26,8 @@ namespace polysat {
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class ule_constraint;
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class constraint {
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friend class eq_constraint;
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friend class ule_constraint;
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unsigned m_level;
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ckind_t m_kind;
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p_dependency_ref m_dep;
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@ -39,8 +41,9 @@ namespace polysat {
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bool is_sle() const { return m_kind == ckind_t::sle_t; }
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ckind_t kind() const { return m_kind; }
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virtual std::ostream& display(std::ostream& out) const = 0;
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eq_constraint& to_eq() { return *dynamic_cast<eq_constraint*>(this); }
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eq_constraint const& to_eq() { return *dynamic_cast<eq_constraint const*>(this); }
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virtual bool propagate(solver& s, pvar v) = 0;
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eq_constraint& to_eq();
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eq_constraint const& to_eq() const;
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p_dependency* dep() const { return m_dep; }
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unsigned_vector& vars() { return m_vars; }
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unsigned level() const { return m_level; }
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@ -49,12 +52,14 @@ namespace polysat {
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class eq_constraint : public constraint {
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pdd m_poly;
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public:
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eq_constraint(unsigned lvl, pdd const& p, pdd const& q, p_dependency_ref& dep,):
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eq_constraint(unsigned lvl, pdd const& p, p_dependency_ref& dep):
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constraint(lvl, dep, ckind_t::eq_t), m_poly(p) {
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m_vars.append(p.free_vars());
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}
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pdd const & p() const { return m_poly; }
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std::ostream& display(std::ostream& out) const override;
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bool propagate(solver& s, pvar v) override;
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};
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inline std::ostream& operator<<(std::ostream& out, constraint const& c) { return c.display(out); }
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@ -66,6 +66,7 @@ std::pair<std::ostream&, bool>
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polysat_log(LogLevel msg_level, std::string fn, std::string /* pretty_fn */)
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{
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std::ostream& os = std::cerr;
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#if 0
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int const fd = fileno(stderr);
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size_t width = 20;
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@ -82,6 +83,10 @@ polysat_log(LogLevel msg_level, std::string fn, std::string /* pretty_fn */)
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os << "[" << fn << "] " << std::string(padding, ' ');
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os << std::string(polysat_log_indent_level, ' ');
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return {os, (bool)color};
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#else
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return {os, false};
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#endif
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}
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polysat_log_indent::polysat_log_indent(int amount)
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@ -215,7 +215,7 @@ namespace polysat {
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bool solver::propagate(pvar v, constraint& c) {
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switch (c.kind()) {
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case ckind_t::eq_t:
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return propagate_eq(v, c);
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return c.to_eq().propagate(*this, v);
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case ckind_t::ule_t:
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case ckind_t::sle_t:
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NOT_IMPLEMENTED_YET();
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@ -225,110 +225,6 @@ namespace polysat {
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return false;
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}
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bool solver::propagate_eq(pvar v, constraint& c) {
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LOG_H3("Propagate " << m_vars[v] << " in " << c);
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SASSERT(c.kind() == ckind_t::eq_t);
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SASSERT(!c.vars().empty());
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auto var = m_vars[v].var();
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auto& vars = c.vars();
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unsigned idx = 0;
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if (vars[idx] != v)
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idx = 1;
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SASSERT(v == vars[idx]);
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// find other watch variable.
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for (unsigned i = vars.size(); i-- > 2; ) {
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if (!is_assigned(vars[i])) {
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std::swap(vars[idx], vars[i]);
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return true;
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}
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}
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LOG("Assignments: " << m_search);
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auto p = c.p().subst_val(m_search);
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LOG("Substituted: " << c.p() << " := " << p);
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TRACE("polysat", tout << c.p() << " := " << p << "\n";);
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if (p.is_zero())
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return false;
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if (p.is_never_zero()) {
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LOG("Conflict (never zero under current assignment)");
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// we could tag constraint to allow early substitution before
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// swapping watch variable in case we can detect conflict earlier.
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set_conflict(c);
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return false;
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}
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// at most one variable remains unassigned.
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auto other_var = vars[1 - idx];
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// SASSERT(!is_assigned(other_var));
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// Detect and apply unit propagation.
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if (!p.is_linear())
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return false;
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// a*x + b == 0
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rational a = p.hi().val();
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rational b = p.lo().val();
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rational inv_a;
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if (a.is_odd()) {
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// v1 = -b * inverse(a)
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unsigned sz = p.power_of_2();
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VERIFY(a.mult_inverse(sz, inv_a));
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rational val = mod(inv_a * -b, rational::power_of_two(sz));
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m_cjust[other_var].push_back(&c);
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propagate(other_var, val, c);
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return false;
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}
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SASSERT(!b.is_odd()); // otherwise p.is_never_zero() would have been true above
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// TBD
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// constrain viable using condition on x
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// 2*x + 2 == 0 mod 4 => x is odd
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//
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// We have:
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// 2^j*a'*x + 2^j*b' == 0 mod m, where a' is odd (but not necessarily b')
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// <=> 2^j*(a'*x + b') == 0 mod m
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// <=> a'*x + b' == 0 mod (m-j)
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// <=> x == -b' * inverse_{m-j}(a') mod (m-j)
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// ( <=> 2^j*x == 2^j * -b' * inverse_{m-j}(a') mod m )
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//
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// x == c mod (m-j)
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// Which x in 2^m satisfy this?
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// => x \in { c + k * 2^(m-j) | k = 0, ..., 2^j - 1 }
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unsigned rank_a = a.trailing_zeros(); // j
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SASSERT(b == 0 || rank_a <= b.trailing_zeros());
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rational aa = a / rational::power_of_two(rank_a); // a'
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rational bb = b / rational::power_of_two(rank_a); // b'
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rational inv_aa;
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unsigned small_sz = p.power_of_2() - rank_a; // m - j
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VERIFY(aa.mult_inverse(small_sz, inv_aa));
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rational cc = mod(inv_aa * -bb, rational::power_of_two(small_sz));
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LOG(m_vars[other_var] << " = " << cc << " + k * 2^" << small_sz);
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// TODO: better way to update the BDD, e.g. construct new one (only if rank_a is small?)
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vector<rational> viable;
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for (rational k = rational::zero(); k < rational::power_of_two(rank_a); k += 1) {
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rational val = cc + k * rational::power_of_two(small_sz);
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viable.push_back(val);
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}
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LOG_V("still viable: " << viable);
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unsigned i = 0;
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for (rational r = rational::zero(); r < rational::power_of_two(p.power_of_2()); r += 1) {
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while (i < viable.size() && viable[i] < r)
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++i;
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if (i < viable.size() && viable[i] == r)
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continue;
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if (is_viable(other_var, r)) {
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add_non_viable(other_var, r);
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}
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}
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LOG("TODO");
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return false;
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}
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void solver::propagate(pvar v, rational const& val, constraint& c) {
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if (is_viable(v, val)) {
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m_free_vars.del_var_eh(v);
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@ -645,8 +541,8 @@ namespace polysat {
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constraint* c = m_conflict[0];
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constraint* d = m_cjust[v].back();
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if (c->is_eq() && d->is_eq()) {
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pdd p = c->p();
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pdd q = d->p();
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pdd p = c->to_eq().p();
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pdd q = d->to_eq().p();
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pdd r = p;
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if (!p.resolve(v, q, r))
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return nullptr;
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@ -668,13 +564,13 @@ namespace polysat {
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bool solver::is_always_false(constraint& c) {
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if (c.is_eq())
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return c.p().is_never_zero();
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return c.to_eq().p().is_never_zero();
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return false;
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}
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bool solver::eval_to_false(constraint& c) {
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if (c.is_eq()) {
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pdd r = c.p().subst_val(m_search);
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pdd r = c.to_eq().p().subst_val(m_search);
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return r.is_never_zero();
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}
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return false;
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@ -32,6 +32,8 @@ namespace polysat {
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stats() { reset(); }
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};
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friend class eq_constraint;
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typedef ptr_vector<constraint> constraints;
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trail_stack& m_trail;
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@ -120,7 +122,6 @@ namespace polysat {
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void propagate(pvar v);
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bool propagate(pvar v, constraint& c);
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bool propagate_eq(pvar v, constraint& c);
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void propagate(pvar v, rational const& val, constraint& c);
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void erase_watch(pvar v, constraint& c);
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void erase_watch(constraint& c);
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