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remove case for non-emptiness to combine with standard membership

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as part of revising engine for addressing #5693
This commit is contained in:
Nikolaj Bjorner 2021-12-13 18:17:40 -08:00
parent b2af7ea68f
commit f40becf099
5 changed files with 8 additions and 78 deletions
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1
src/ast/rewriter/seq_skolem.cpp
View file

@ -38,7 +38,6 @@ skolem::skolem(ast_manager& m, th_rewriter& rw):
m_max_unfolding = "seq.max_unfolding";
m_length_limit = "seq.length_limit";
m_is_empty = "re.is_empty";
m_is_non_empty = "re.is_non_empty";
}
expr_ref skolem::mk(symbol const& s, expr* e1, expr* e2, expr* e3, expr* e4, sort* range, bool rw) {

7
src/ast/rewriter/seq_skolem.h
View file

@ -36,7 +36,7 @@ namespace seq {
symbol m_indexof_left, m_indexof_right; // inverse of indexof: (indexof_left s t) + s + (indexof_right s t) = t, for s in t.
symbol m_aut_step; // regex unfolding state
symbol m_accept; // regex
symbol m_is_empty, m_is_non_empty; // regex emptiness check
symbol m_is_empty; // regex emptiness check
symbol m_pre, m_post; // inverse of at: (pre s i) + (at s i) + (post s i) = s if 0 <= i < (len s)
symbol m_postp;
symbol m_eq; // equality atom
@ -73,7 +73,6 @@ namespace seq {
}
expr_ref mk_accept(expr_ref_vector const& args) { return expr_ref(seq.mk_skolem(m_accept, args.size(), args.data(), m.mk_bool_sort()), m); }
expr_ref mk_accept(expr* s, expr* i, expr* r) { return mk(m_accept, s, i, r, nullptr, m.mk_bool_sort()); }
expr_ref mk_is_non_empty(expr* r, expr* u, expr* n) { return mk(m_is_non_empty, r, u, n, m.mk_bool_sort(), false); }
expr_ref mk_is_empty(expr* r, expr* u, expr* n) { return mk(m_is_empty, r, u, n, m.mk_bool_sort(), false); }
expr_ref mk_indexof_left(expr* t, expr* s, expr* offset = nullptr) { return mk(m_indexof_left, t, s, offset); }
@ -153,13 +152,9 @@ namespace seq {
bool is_length_limit(expr* e) const { return is_skolem(m_length_limit, e); }
bool is_length_limit(expr* p, unsigned& lim, expr*& s) const;
bool is_is_empty(expr* e) const { return is_skolem(m_is_empty, e); }
bool is_is_non_empty(expr* e) const { return is_skolem(m_is_non_empty, e); }
bool is_is_empty(expr* e, expr*& r, expr*& u, expr*& n) const {
return is_skolem(m_is_empty, e) && (r = to_app(e)->get_arg(0), u = to_app(e)->get_arg(1), n = to_app(e)->get_arg(2), true);
}
bool is_is_non_empty(expr* e, expr*& r, expr*& u, expr*& n) const {
return is_skolem(m_is_non_empty, e) && (r = to_app(e)->get_arg(0), u = to_app(e)->get_arg(1), n = to_app(e)->get_arg(2), true);
}
void decompose(expr* e, expr_ref& head, expr_ref& tail);

70
src/smt/seq_regex.cpp
View file

@ -246,8 +246,7 @@ namespace smt {
}
if (info.interpreted) {
update_state_graph(r);
update_state_graph(r);
if (m_state_graph.is_dead(get_state_id(r))) {
STRACE("seq_regex_brief", tout << "(dead) ";);
th.add_axiom(~lit);
@ -519,15 +518,12 @@ namespace smt {
void seq_regex::propagate_ne(expr* r1, expr* r2) {
TRACE("seq_regex", tout << "propagate NEQ: " << mk_pp(r1, m) << ", " << mk_pp(r2, m) << std::endl;);
STRACE("seq_regex_brief", tout << "PNEQ ";);
// TBD: rewrite to use state_graph
// why is is_non_empty even needed, why not just not(in_empty)
sort* seq_sort = nullptr;
VERIFY(u().is_re(r1, seq_sort));
expr_ref r = symmetric_diff(r1, r2);
expr_ref emp(re().mk_empty(r->get_sort()), m);
expr_ref n(m.mk_fresh_const("re.char", seq_sort), m);
expr_ref is_non_empty = sk().mk_is_non_empty(r, r, n);
th.add_axiom(th.mk_eq(r1, r2, false), th.mk_literal(is_non_empty));
expr_ref s(m.mk_fresh_const("re.member", seq_sort), m);
expr_ref is_member(re().mk_in_re(s, r), m);
th.add_axiom(th.mk_eq(r1, r2, false), th.mk_literal(is_member));
}
bool seq_regex::is_member(expr* r, expr* u) {
@ -537,62 +533,7 @@ namespace smt {
return true;
}
return r == u;
}
/**
* is_non_empty(r, u) => nullable or \/_i (c_i and is_non_empty(r_i, u union r))
*
* for each (c_i, r_i) in cofactors (min-terms)
*
* is_non_empty(r_i, u union r) := false if r_i in u
*
*/
void seq_regex::propagate_is_non_empty(literal lit) {
expr* e = ctx.bool_var2expr(lit.var()), *r = nullptr, *u = nullptr, *n = nullptr;
VERIFY(sk().is_is_non_empty(e, r, u, n));
if (block_if_empty(r, lit))
return;
TRACE("seq_regex", tout << "propagate nonempty: " << mk_pp(e, m) << std::endl;);
STRACE("seq_regex_brief", tout
<< std::endl << "PNE(" << expr_id_str(e) << "," << state_str(r)
<< "," << expr_id_str(u) << "," << expr_id_str(n) << ") ";);
expr_ref is_nullable = is_nullable_wrapper(r);
if (m.is_true(is_nullable))
return;
literal null_lit = th.mk_literal(is_nullable);
expr_ref hd = mk_first(r, n);
expr_ref d(m);
d = mk_derivative_wrapper(hd, r);
literal_vector lits;
lits.push_back(~lit);
if (null_lit != false_literal)
lits.push_back(null_lit);
expr_ref_pair_vector cofactors(m);
get_cofactors(d, cofactors);
for (auto const& p : cofactors) {
if (is_member(p.second, u))
continue;
expr_ref cond(p.first, m);
seq_rw().elim_condition(hd, cond);
rewrite(cond);
if (m.is_false(cond))
continue;
expr_ref next_non_empty = sk().mk_is_non_empty(p.second, re().mk_union(u, p.second), n);
if (!m.is_true(cond))
next_non_empty = m.mk_and(cond, next_non_empty);
lits.push_back(th.mk_literal(next_non_empty));
}
th.add_axiom(lits);
}
}
/*
Given a string s, index i, and a derivative r, return an
@ -915,6 +856,7 @@ namespace smt {
}
m_state_graph.mark_done(r_id);
}
STRACE("seq_regex", m_state_graph.display(tout););
STRACE("seq_regex_brief", tout << std::endl;);
STRACE("seq_regex_brief", m_state_graph.display(tout););

4
src/smt/seq_regex.h
View file

@ -203,9 +203,7 @@ namespace smt {
void propagate_eq(expr* r1, expr* r2);
void propagate_ne(expr* r1, expr* r2);
void propagate_is_non_empty(literal lit);
void propagate_ne(expr* r1, expr* r2);
void propagate_is_empty(literal lit);

4
src/smt/theory_seq.cpp
View file

@ -3014,10 +3014,6 @@ void theory_seq::assign_eh(bool_var v, bool is_true) {
if (is_true)
m_regex.propagate_is_empty(lit);
}
else if (m_sk.is_is_non_empty(e)) {
if (is_true)
m_regex.propagate_is_non_empty(lit);
}
else if (m_sk.is_eq(e, e1, e2)) {
if (is_true) {
propagate_eq(lit, e1, e2, true);