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We don't need to handle negative membership constraints explicitly

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CEisenhofer 2026-03-04 19:07:36 +01:00
parent 4e7d83f996
commit b2838b472d
7 changed files with 121 additions and 117 deletions
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76
src/smt/theory_nseq.cpp
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@ -193,10 +193,15 @@ namespace smt {
m_prop_queue.push_back({prop_item::pos_mem_prop, idx});
}
else {
unsigned idx = m_state.neg_mems().size();
// ¬(str ∈ R) ≡ str ∈ complement(R): store as a positive membership
// so the Nielsen graph sees it uniformly; the original negative literal
// is kept in mem_source for conflict reporting.
expr_ref re_compl(m_seq.re.mk_complement(re), get_manager());
euf::snode* sn_re_compl = get_snode(re_compl.get());
unsigned idx = m_state.str_mems().size();
literal lit(v, true);
m_state.add_neg_mem(sn_str, sn_re, lit);
m_prop_queue.push_back({prop_item::neg_mem_prop, idx});
m_state.add_str_mem(sn_str, sn_re_compl, lit);
m_prop_queue.push_back({prop_item::pos_mem_prop, idx});
}
TRACE(seq, tout << "nseq assign_eh: " << (is_true ? "" : "¬")
@ -256,9 +261,6 @@ namespace smt {
case prop_item::pos_mem_prop:
propagate_pos_mem(item.m_idx);
break;
case prop_item::neg_mem_prop:
propagate_neg_mem(item.m_idx);
break;
}
}
}
@ -313,31 +315,6 @@ namespace smt {
ensure_length_var(s_expr);
}
void theory_nseq::propagate_neg_mem(unsigned idx) {
auto const& entry = m_state.get_neg_mem(idx);
if (!entry.m_str || !entry.m_regex)
return;
// ¬(s in Σ*) is always false → conflict
if (m_regex.is_full_regex(entry.m_regex)) {
enode_pair_vector eqs;
literal_vector lits;
lits.push_back(entry.m_lit);
set_conflict(eqs, lits);
return;
}
// ¬(ε in R) where R is nullable → conflict
if (entry.m_str->is_empty() && entry.m_regex->is_nullable()) {
enode_pair_vector eqs;
literal_vector lits;
lits.push_back(entry.m_lit);
set_conflict(eqs, lits);
return;
}
}
void theory_nseq::ensure_length_var(expr* e) {
if (!e || !m_seq.is_seq(e))
return;
@ -397,49 +374,67 @@ namespace smt {
final_check_status theory_nseq::final_check_eh(unsigned /*final_check_round*/) {
// Always assert non-negativity for all string theory vars,
// even when there are no string equations/memberships.
if (assert_nonneg_for_all_vars())
if (assert_nonneg_for_all_vars()) {
IF_VERBOSE(1, verbose_stream() << "nseq final_check: nonneg assertions added, FC_CONTINUE\n";);
return FC_CONTINUE;
}
// If there are unhandled boolean string predicates (prefixof, contains, etc.)
// we cannot declare sat — return unknown.
if (has_unhandled_preds())
if (has_unhandled_preds()) {
IF_VERBOSE(1, verbose_stream() << "nseq final_check: unhandled preds, FC_GIVEUP\n";);
return FC_GIVEUP;
}
if (m_state.empty() && m_ho_terms.empty())
if (m_state.empty() && m_ho_terms.empty()) {
IF_VERBOSE(1, verbose_stream() << "nseq final_check: empty state+ho, FC_DONE (no solve)\n";);
return FC_DONE;
}
// unfold higher-order terms when sequence structure is known
if (unfold_ho_terms())
if (unfold_ho_terms()) {
IF_VERBOSE(1, verbose_stream() << "nseq final_check: unfolded ho_terms, FC_CONTINUE\n";);
return FC_CONTINUE;
}
if (m_state.empty())
if (m_state.empty()) {
IF_VERBOSE(1, verbose_stream() << "nseq final_check: empty state (after ho), FC_DONE (no solve)\n";);
return FC_DONE;
}
IF_VERBOSE(1, verbose_stream() << "nseq final_check: populating graph with "
<< m_state.str_eqs().size() << " eqs, " << m_state.str_mems().size() << " mems\n";);
populate_nielsen_graph();
// assert length constraints derived from string equalities
if (assert_length_constraints())
if (assert_length_constraints()) {
IF_VERBOSE(1, verbose_stream() << "nseq final_check: length constraints asserted, FC_CONTINUE\n";);
return FC_CONTINUE;
}
++m_num_final_checks;
m_nielsen.set_max_search_depth(get_fparams().m_nseq_max_depth);
IF_VERBOSE(1, verbose_stream() << "nseq final_check: calling solve()\n";);
auto result = m_nielsen.solve();
if (result == seq::nielsen_graph::search_result::sat) {
IF_VERBOSE(1, verbose_stream() << "nseq final_check: solve SAT, sat_node="
<< (m_nielsen.sat_node() ? "set" : "null") << "\n";);
// Nielsen found a consistent assignment for positive constraints.
// If there are negative memberships or disequalities we haven't verified,
// we cannot soundly declare sat.
if (!m_state.neg_mems().empty() || !m_state.diseqs().empty())
// If there are disequalities we haven't verified, we cannot soundly declare sat.
if (!m_state.diseqs().empty())
return FC_GIVEUP;
return FC_DONE;
}
if (result == seq::nielsen_graph::search_result::unsat) {
IF_VERBOSE(1, verbose_stream() << "nseq final_check: solve UNSAT\n";);
explain_nielsen_conflict();
return FC_CONTINUE;
}
IF_VERBOSE(1, verbose_stream() << "nseq final_check: solve UNKNOWN, FC_GIVEUP\n";);
return FC_GIVEUP;
}
@ -556,7 +551,6 @@ namespace smt {
out << " str_eqs: " << m_state.str_eqs().size() << "\n";
out << " str_mems: " << m_state.str_mems().size() << "\n";
out << " diseqs: " << m_state.diseqs().size() << "\n";
out << " neg_mems: " << m_state.neg_mems().size() << "\n";
out << " prop_queue: " << m_prop_qhead << "/" << m_prop_queue.size() << "\n";
out << " ho_terms: " << m_ho_terms.size() << "\n";
}