mirrors/z3
3
0
Fork 0
mirror of https://github.com/Z3Prover/z3 synced 2025-04-22 16:45:31 +00:00
Code Activity

overflow example works

Browse source 
- introduce weak/strong eval to temper unit propagation to use only weak evaluation.
- harness the amount of interval propagation provided on overflow constraints
- weak evaluation on overflow constraints is now trivialized
- viable insertion also does conflict detection
This commit is contained in:
Nikolaj Bjorner 2024-01-04 15:55:24 -08:00
parent 5fc208cefc
commit cb672c7992
14 changed files with 122 additions and 76 deletions
Download patch file Download diff file Expand all files Collapse all files

16
src/sat/smt/polysat/constraints.cpp
View file

@ -103,13 +103,13 @@ namespace polysat {
return true;
}
lbool signed_constraint::eval(assignment& a) const {
lbool r = m_constraint->eval(a);
lbool signed_constraint::weak_eval(assignment& a) const {
lbool r = m_constraint->weak_eval(a);
return m_sign ? ~r : r;
}
lbool signed_constraint::eval_unfold(assignment& a) const {
lbool r = m_constraint->eval_unfold(a);
lbool signed_constraint::strong_eval(assignment& a) const {
lbool r = m_constraint->strong_eval(a);
return m_sign ? ~r : r;
}
@ -118,12 +118,4 @@ namespace polysat {
return out << *m_constraint;
}
bool signed_constraint::is_currently_true(core& c) const {
return eval(c.get_assignment()) == l_true;
}
bool signed_constraint::is_currently_false(core& c) const {
return eval(c.get_assignment()) == l_false;
}
}

10
src/sat/smt/polysat/constraints.h
View file

@ -44,8 +44,8 @@ namespace polysat {
virtual std::ostream& display(std::ostream& out, lbool status) const = 0;
virtual std::ostream& display(std::ostream& out) const = 0;
virtual lbool eval() const = 0;
virtual lbool eval(assignment const& a) const = 0;
virtual lbool eval_unfold(assignment const& a) const { return eval(a); }
virtual lbool weak_eval(assignment const& a) const = 0;
virtual lbool strong_eval(assignment const& a) const = 0;
virtual void activate(core& c, bool sign, dependency const& d) = 0;
virtual void propagate(core& c, lbool value, dependency const& d) = 0;
virtual bool is_linear() const { return false; }
@ -76,11 +76,9 @@ namespace polysat {
void propagate(core& c, lbool value, dependency const& d) { m_constraint->propagate(c, value, d); }
bool is_always_true() const { return eval() == l_true; }
bool is_always_false() const { return eval() == l_false; }
bool is_currently_true(core& c) const;
bool is_currently_false(core& c) const;
bool is_linear() const { return m_constraint->is_linear(); }
lbool eval(assignment& a) const;
lbool eval_unfold(assignment& a) const;
lbool weak_eval(assignment& a) const;
lbool strong_eval(assignment& a) const;
lbool eval() const { return m_sign ? ~m_constraint->eval() : m_constraint->eval();}
ckind_t op() const { return m_op; }
bool is_ule() const { return m_op == ule_t; }

48
src/sat/smt/polysat/core.cpp
View file

@ -257,7 +257,7 @@ namespace polysat {
#if 0
// If no saturation propagation was possible, explain the conflict using the variable assignment.
m_unsat_core = explain_eval_unfold(get_constraint(conflict_idx));
m_unsat_core = explain_strong_eval(get_constraint(conflict_idx));
m_unsat_core.push_back(get_dependency(conflict_idx));
s.set_conflict(m_unsat_core, "polysat-bail-out-conflict");
decay_activity();
@ -333,10 +333,10 @@ namespace polysat {
return;
v = w;
}
if (v != null_var && !m_viable.add_unitary(v, idx))
if (v != null_var && !m_viable.add_unitary(v, idx, m_values[v]))
viable_conflict(v);
else if (v == null_var && sc.is_currently_false(*this)) {
auto ex = explain_eval(sc);
else if (v == null_var && weak_eval(sc) == l_false) {
auto ex = explain_weak_eval(sc);
ex.push_back(dep);
s.set_conflict(ex, "infeasible propagation");
}
@ -389,7 +389,7 @@ namespace polysat {
if (!is_assigned(v0) || is_assigned(v1))
continue;
// detect unitary, add to viable, detect conflict?
if (value != l_undef && !m_viable.add_unitary(v1, { idx }))
if (value != l_undef && !m_viable.add_unitary(v1, { idx }, m_values[v]))
viable_conflict(v1);
}
SASSERT(m_watch[v].size() == sz && "size of watch list was not changed");
@ -402,14 +402,14 @@ namespace polysat {
*/
void core::propagate_eval(constraint_id idx) {
auto [sc, d, value] = m_constraint_index[idx.id];
switch (eval(sc)) {
switch (weak_eval(sc)) {
case l_false:
if (value != l_false)
s.propagate(d, true, explain_eval(sc), "eval-propagate");
s.propagate(d, true, explain_weak_eval(sc), "eval-propagate");
break;
case l_true:
if (value != l_true)
s.propagate(d, false, explain_eval(sc), "eval-propagate");
s.propagate(d, false, explain_weak_eval(sc), "eval-propagate");
break;
default:
break;
@ -424,13 +424,13 @@ namespace polysat {
}
void core::propagate(constraint_id id, signed_constraint& sc, lbool value, dependency const& d) {
lbool eval_value = eval(sc);
lbool eval_value = weak_eval(sc);
if (eval_value == l_undef)
sc.propagate(*this, value, d);
else if (value == l_undef)
s.propagate(d, eval_value != l_true, explain_eval(sc), "constraint-propagate");
s.propagate(d, eval_value != l_true, explain_weak_eval(sc), "constraint-propagate");
else if (value != eval_value) {
m_unsat_core = explain_eval(sc);
m_unsat_core = explain_weak_eval(sc);
m_unsat_core.push_back(m_constraint_index[id.id].d);
s.set_conflict(m_unsat_core, "polysat-constraint-core");
decay_activity();
@ -493,7 +493,7 @@ namespace polysat {
s.trail().push(unassign(*this, index.id));
}
dependency_vector core::explain_eval(unsigned_vector const& vars) {
dependency_vector core::explain_weak_eval(unsigned_vector const& vars) {
dependency_vector deps;
for (auto v : vars) {
if (is_assigned(v)) {
@ -504,20 +504,20 @@ namespace polysat {
return deps;
}
dependency_vector core::explain_eval(signed_constraint const& sc) {
return explain_eval(sc.vars());
dependency_vector core::explain_weak_eval(signed_constraint const& sc) {
return explain_weak_eval(sc.vars());
}
dependency_vector core::explain_eval_unfold(signed_constraint const& sc) {
return explain_eval(sc.unfold_vars());
dependency_vector core::explain_strong_eval(signed_constraint const& sc) {
return explain_weak_eval(sc.unfold_vars());
}
lbool core::eval(signed_constraint const& sc) {
return sc.eval(m_assignment);
lbool core::weak_eval(signed_constraint const& sc) {
return sc.weak_eval(m_assignment);
}
lbool core::eval_unfold(signed_constraint const& sc) {
return sc.eval_unfold(m_assignment);
lbool core::strong_eval(signed_constraint const& sc) {
return sc.strong_eval(m_assignment);
}
pdd core::subst(pdd const& p) {
@ -579,12 +579,12 @@ namespace polysat {
return sc;
}
lbool core::eval(constraint_id id) {
return get_constraint(id).eval(m_assignment);
lbool core::weak_eval(constraint_id id) {
return get_constraint(id).weak_eval(m_assignment);
}
lbool core::eval_unfold(constraint_id id) {
return get_constraint(id).eval_unfold(m_assignment);
lbool core::strong_eval(constraint_id id) {
return get_constraint(id).strong_eval(m_assignment);
}
void core::inc_activity(pvar v) {

14
src/sat/smt/polysat/core.h
View file

@ -86,7 +86,7 @@ namespace polysat {
void propagate_assignment(pvar v, rational const& value, dependency dep);
void propagate_activation(constraint_id idx, signed_constraint& sc, dependency dep);
void propagate(constraint_id id, signed_constraint& sc, lbool value, dependency const& d);
dependency_vector explain_eval(unsigned_vector const& vars);
dependency_vector explain_weak_eval(unsigned_vector const& vars);
void add_watch(unsigned idx, unsigned var);
@ -169,13 +169,13 @@ namespace polysat {
constraint_id_vector const& assigned_constraints() const { return m_prop_queue; }
dependency get_dependency(constraint_id idx) const;
// dependency_vector get_dependencies(constraint_id_vector const& ids) const;
lbool eval(constraint_id id);
lbool eval_unfold(constraint_id id);
lbool weak_eval(constraint_id id);
lbool strong_eval(constraint_id id);
dependency propagate(signed_constraint const& sc, dependency_vector const& deps) { return s.propagate(sc, deps, nullptr); }
lbool eval(signed_constraint const& sc);
lbool eval_unfold(signed_constraint const& sc);
dependency_vector explain_eval(signed_constraint const& sc);
dependency_vector explain_eval_unfold(signed_constraint const& sc);
lbool weak_eval(signed_constraint const& sc);
lbool strong_eval(signed_constraint const& sc);
dependency_vector explain_weak_eval(signed_constraint const& sc);
dependency_vector explain_strong_eval(signed_constraint const& sc);
svector<pvar> find_conflict_variables(constraint_id idx);
bool inconsistent() const;

39
src/sat/smt/polysat/forbidden_intervals.cpp
View file

@ -102,13 +102,31 @@ namespace polysat {
fi.side_cond.push_back(s.cs().ule(e2, 1));
}
else {
// A := div(2^N - 1, b2.val())
// := hi_val - 1
// max B such that A*B < 2^N
// := ceil(2^N / A) - 1
// := div(2^N + A - 1, A) - 1
// := div(bound + A, A) - 1
// [0, div(bound, b2.val()) + 1[
rational A = div(bound, b2.val());
rational B = div(bound + A, A) - 1;
if (A >= 4 && B >= 4) {
_backtrack.released = false;
return false;
}
rational lo_val(0);
rational hi_val(div(bound, b2.val()) + 1);
rational hi_val = A + 1;
pdd lo = m.mk_val(lo_val);
pdd hi = m.mk_val(hi_val);
SASSERT(b2.val() <= B);
SASSERT(A * B <= bound);
SASSERT((A + 1) * B > bound);
SASSERT(A * (B + 1) > bound);
fi.interval = eval_interval::proper(lo, lo_val, hi, hi_val);
fi.side_cond.push_back(s.cs().ule(e2, b2.val()));
fi.side_cond.push_back(s.cs().ule(e2, B));
}
}
@ -119,8 +137,23 @@ namespace polysat {
}
else {
// [div(bound, b2.val()) + 1, 0[
rational lo_val(div(bound, b2.val()) + 1);
// A := div(2^N - 1, b2.val())
// min B . A*B >= 2^N
// := ceil(2^N / A)
// := div(2^N + A - 1, A)
rational A = div(bound, b2.val()) + 1;
rational B = div(bound + A, A);
if (A >= 4 && B >= 4) {
_backtrack.released = false;
return false;
}
rational lo_val = A;
rational hi_val(0);
SASSERT(A * B > bound);
SASSERT(A * (B - 1) <= bound);
SASSERT((A - 1) * B <= bound);
SASSERT(b2.val() >= B);
pdd lo = m.mk_val(lo_val);
pdd hi = m.mk_val(hi_val);
fi.interval = eval_interval::proper(lo, lo_val, hi, hi_val);

6
src/sat/smt/polysat/op_constraint.cpp
View file

@ -45,7 +45,11 @@ namespace polysat {
return eval(p, q, r);
}
lbool op_constraint::eval(assignment const& a) const {
lbool op_constraint::weak_eval(assignment const& a) const {
return eval();
}
lbool op_constraint::strong_eval(assignment const& a) const {
return eval(a.apply_to(p), a.apply_to(q), a.apply_to(r));
}

3
src/sat/smt/polysat/op_constraint.h
View file

@ -75,7 +75,8 @@ namespace polysat {
std::ostream& display(std::ostream& out, lbool status) const override;
std::ostream& display(std::ostream& out) const override;
lbool eval() const override;
lbool eval(assignment const& a) const override;
lbool weak_eval(assignment const& a) const override;
lbool strong_eval(assignment const& a) const override;
bool is_always_true() const { return false; }
bool is_always_false() const { return false; }
void activate(core& c, bool sign, dependency const& dep) override;

6
src/sat/smt/polysat/saturation.cpp
View file

@ -25,7 +25,7 @@ namespace polysat {
bool has_conflict = false;
for (auto idx : c.assigned_constraints()) {
auto sc = c.get_constraint(idx);
lbool eval_value = c.eval_unfold(sc);
lbool eval_value = c.strong_eval(sc);
if (eval_value == l_true)
continue;
@ -77,9 +77,9 @@ namespace polysat {
}
else if (std::holds_alternative<signed_constraint>(e)) {
auto sc = *std::get_if<signed_constraint>(&e);
if (c.eval(sc) != l_false)
if (c.strong_eval(sc) != l_false)
return;
auto d = c.propagate(~sc, c.explain_eval(sc));
auto d = c.propagate(~sc, c.explain_strong_eval(sc));
lemma.push_back(d);
}
else

9
src/sat/smt/polysat/ule_constraint.cpp
View file

@ -131,13 +131,10 @@ namespace polysat {
unsigned const rhs_vars = rhs.free_vars().size();
unsigned const diff_vars = (lhs - rhs).free_vars().size();
if (diff_vars < lhs_vars || diff_vars < rhs_vars) {
LOG("reduce number of varables");
// verbose_stream() << "IN: " << ule_pp(to_lbool(is_positive), lhs, rhs) << "\n";
if (lhs_vars <= rhs_vars)
rhs = lhs - rhs - 1;
else
lhs = rhs - lhs;
// verbose_stream() << "OUT: " << ule_pp(to_lbool(is_positive), lhs, rhs) << "\n";
}
}
@ -231,7 +228,7 @@ namespace polysat {
lhs *= x;
SASSERT(lhs.leading_coefficient().is_power_of_two());
}
// verbose_stream() << "simplified " << lhs << " <= " << rhs << "\n";
TRACE("bv", tout << "simplified " << lhs << " <= " << rhs << "\n");
} // simplify_impl
}
@ -346,11 +343,11 @@ namespace polysat {
return eval(lhs(), rhs());
}
lbool ule_constraint::eval(assignment const& a) const {
lbool ule_constraint::weak_eval(assignment const& a) const {
return eval(a.apply_to(lhs()), a.apply_to(rhs()));
}
lbool ule_constraint::eval_unfold(assignment const& a) const {
lbool ule_constraint::strong_eval(assignment const& a) const {
return eval(a.apply_to(unfold_lhs()), a.apply_to(unfold_rhs()));
}

4
src/sat/smt/polysat/ule_constraint.h
View file

@ -38,8 +38,8 @@ namespace polysat {
std::ostream& display(std::ostream& out, lbool status) const override;
std::ostream& display(std::ostream& out) const override;
lbool eval() const override;
lbool eval(assignment const& a) const override;
lbool eval_unfold(assignment const& a) const override;
lbool weak_eval(assignment const& a) const override;
lbool strong_eval(assignment const& a) const override;
bool is_linear() const override { return lhs().is_linear_or_value() && rhs().is_linear_or_value(); }
void activate(core& c, bool sign, dependency const& dep);
void propagate(core& c, lbool value, dependency const& dep) {}

6
src/sat/smt/polysat/umul_ovfl_constraint.cpp
View file

@ -68,7 +68,11 @@ namespace polysat {
return eval(p(), q());
}
lbool umul_ovfl_constraint::eval(assignment const& a) const {
lbool umul_ovfl_constraint::weak_eval(assignment const& a) const {
return eval();
}
lbool umul_ovfl_constraint::strong_eval(assignment const& a) const {
return eval(a.apply_to(p()), a.apply_to(q()));
}

3
src/sat/smt/polysat/umul_ovfl_constraint.h
View file

@ -35,7 +35,8 @@ namespace polysat {
std::ostream& display(std::ostream& out, lbool status) const override;
std::ostream& display(std::ostream& out) const override;
lbool eval() const override;
lbool eval(assignment const& a) const override;
lbool weak_eval(assignment const& a) const override;
lbool strong_eval(assignment const& a) const override;
void activate(core& c, bool sign, dependency const& dep) override;
void propagate(core& c, lbool value, dependency const& dep) override;
bool is_linear() const override { return p().is_linear_or_value() && q().is_linear_or_value(); }

31
src/sat/smt/polysat/viable.cpp
View file

@ -488,13 +488,15 @@ namespace polysat {
auto after = last;
unsigned bw = c.size(last.e->var);
TRACE("bv", display_explain(tout));
result.append(m_fixed_bits.explain());
if (last.e->interval.is_full()) {
if (m_var != last.e->var)
result.push_back(offset_claim(m_var, { last.e->var, 0 }));
for (auto const& sc : last.e->side_cond)
result.push_back(c.propagate(sc, c.explain_eval(sc)));
result.push_back(c.propagate(sc, c.explain_weak_eval(sc)));
result.push_back(c.get_dependency(last.e->constraint_index));
SASSERT(m_explain.size() == 1);
}
@ -510,7 +512,7 @@ namespace polysat {
if (m_var != e.e->var)
result.push_back(offset_claim(m_var, { e.e->var, 0 }));
for (auto const& sc : e.e->side_cond)
result.push_back(c.propagate(sc, c.explain_eval(sc)));
result.push_back(c.propagate(sc, c.explain_weak_eval(sc)));
result.push_back(c.get_dependency(index));
if (e.e == last.e)
break;
@ -575,7 +577,7 @@ namespace polysat {
auto sc = cs.ult(t - vlo, vhi - vlo);
SASSERT(!sc.is_always_false());
if (!sc.is_always_true())
deps.push_back(c.propagate(sc, c.explain_eval(sc)));
deps.push_back(c.propagate(sc, c.explain_weak_eval(sc)));
t.reset(lo.manager());
t = c.value(mod(e.value, rational::power_of_two(aw)), aw);
}
@ -586,19 +588,19 @@ namespace polysat {
auto sc = cs.ult(t - lo, hi - lo);
SASSERT(!sc.is_always_false());
if (!sc.is_always_true())
deps.push_back(c.propagate(sc, c.explain_eval(sc)));
deps.push_back(c.propagate(sc, c.explain_weak_eval(sc)));
}
/*
* Register constraint at index 'idx' as unitary in v.
*/
bool viable::add_unitary(pvar v, constraint_id idx) {
bool viable::add_unitary(pvar v, constraint_id idx, rational& var_value) {
if (c.is_assigned(v))
return true;
auto [sc, d, value] = c.m_constraint_index[idx.id];
SASSERT(value != l_undef);
if (value == l_false)
auto [sc, d, truth_value] = c.m_constraint_index[idx.id];
SASSERT(truth_value != l_undef);
if (truth_value == l_false)
sc = ~sc;
if (!sc.is_linear())
@ -708,6 +710,12 @@ namespace polysat {
m_var = v;
return false;
}
switch (find_viable(v, var_value)) {
case find_t::empty:
return false;
default:
break;
}
return true;
}
@ -961,6 +969,13 @@ namespace polysat {
return out;
}
std::ostream& viable::display_explain(std::ostream& out) const {
display_state(out);
for (auto const& e : m_explain)
display_one(out << e.value << " ", m_var, e.e) << "\n";
return out;
}
/*
* Lower bounds are strictly ascending.
* Intervals don't contain each-other (since lower bounds are ascending, it suffices to check containment in one direction).

3
src/sat/smt/polysat/viable.h
View file

@ -141,6 +141,7 @@ namespace polysat {
offset_slices m_overlaps;
void init_overlaps(pvar v);
std::ostream& display_state(std::ostream& out) const;
std::ostream& display_explain(std::ostream& out) const;
public:
viable(core& c);
@ -160,7 +161,7 @@ namespace polysat {
/*
* Register constraint at index 'idx' as unitary in v.
*/
bool add_unitary(pvar v, constraint_id);
bool add_unitary(pvar v, constraint_id, rational& value);
/*
* Ensure data-structures tracking variable v.