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fix bogus axioms

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2025-10-24 13:35:41 +02:00
parent 5079b10597
commit 4068460a0f
3 changed files with 31 additions and 9 deletions
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6
src/ast/rewriter/finite_set_axioms.cpp
View file

@ -230,14 +230,18 @@ void finite_set_axioms::in_range_axiom(expr* r) {
if (!u.is_range(r, lo, hi))
return;
theory_axiom* ax = alloc(theory_axiom, m, "range-bounds");
arith_util a(m);
expr_ref lo_le_hi(a.mk_le(a.mk_sub(lo, hi), a.mk_int(0)), m);
m_rewriter(lo_le_hi);
ax->clause.push_back(m.mk_not(lo_le_hi));
ax->clause.push_back(u.mk_in(lo, r));
m_add_clause(ax);
ax = alloc(theory_axiom, m, "range-bounds", r);
ax->clause.push_back(m.mk_not(lo_le_hi));
ax->clause.push_back(u.mk_in(hi, r));
m_add_clause(ax);
arith_util a(m);
ax = alloc(theory_axiom, m, "range-bounds", r);
ax->clause.push_back(m.mk_not(u.mk_in(a.mk_add(hi, a.mk_int(1)), r)));
m_add_clause(ax);

29
src/smt/theory_finite_set.cpp
View file

@ -228,12 +228,16 @@ namespace smt {
ctx.attach_th_var(e, this, mk_var(e));
// Assert immediate axioms
// if (!ctx.relevancy())
add_immediate_axioms(term);
if (!ctx.relevancy())
add_immediate_axioms(term);
return true;
}
void theory_finite_set::relevant_eh(app* t) {
add_immediate_axioms(t);
}
void theory_finite_set::apply_sort_cnstr(enode* n, sort* s) {
SASSERT(u.is_finite_set(s));
if (!is_attached_to_var(n))
@ -248,9 +252,6 @@ namespace smt {
/**
* Every dissequality has to be supported by at distinguishing element.
*
* TODO: we can avoid instantiating the extensionality axiom if we know statically that e1, e2
* can never be equal (say, they have different cardinalities or they are finite sets by construction
* with elements that can differentiate the sets)
*/
void theory_finite_set::new_diseq_eh(theory_var v1, theory_var v2) {
TRACE(finite_set, tout << "new_diseq_eh: v" << v1 << " != v" << v2 << "\n");
@ -263,10 +264,23 @@ namespace smt {
std::swap(e1, e2);
if (!is_new_axiom(e1, e2))
return;
if (are_forced_distinct(n1, n2))
return;
m_axioms.extensionality_axiom(e1, e2);
}
}
//
// TODO: add implementation that detects sets that are known to be distinct.
// for example,
// . x in a is assigned to true and y in b is assigned to false and x ~ y
// . or upper-bound(set.size(a)) < lower-bound(set.size(b))
// where upper and lower bounds can be queried using arith_value
//
bool theory_finite_set::are_forced_distinct(enode* a, enode* b) {
return false;
}
/**
* Final check for the finite set theory.
* The Final Check method is called when the solver has assigned truth values to all Boolean variables.
@ -297,12 +311,13 @@ namespace smt {
* These are unit clauses that can be added immediately.
* - (set.in x set.empty) is false
* - (set.subset S T) <=> (= (set.union S T) T) (or (= (set.intersect S T) S))
* - (set.singleton x) -> (set.in x (set.singleton x))
* - (set.range lo hi) -> lo-1,hi+1 not in range, lo, hi in range if lo <= hi *
*
* Other axioms:
* - (set.singleton x) -> (set.in x (set.singleton x))
* - (set.singleton x) -> (set.size (set.singleton x)) = 1
* - (set.empty) -> (set.size (set.empty)) = 0
* - (set.range lo hi) -> lo-1,hi+1 not in range, lo, hi in range
*/
void theory_finite_set::add_immediate_axioms(app* term) {
expr *elem = nullptr, *set = nullptr;

3
src/smt/theory_finite_set.h
View file

@ -160,6 +160,7 @@ namespace smt {
bool can_propagate() override;
void propagate() override;
void assign_eh(bool_var v, bool is_true) override;
void relevant_eh(app *n) override;
theory * mk_fresh(context * new_ctx) override;
char const * get_name() const override { return "finite_set"; }
@ -200,6 +201,8 @@ namespace smt {
std::ostream &display_var(std::ostream &out, theory_var v) const;
bool are_forced_distinct(enode *a, enode *b);
public:
theory_finite_set(context& ctx);
~theory_finite_set() override;