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add fixed length heuristic

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2016-02-17 21:20:39 -08:00
parent 8718c1c99f
commit 67958efed2
2 changed files with 71 additions and 0 deletions
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55
src/smt/theory_seq.cpp
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@ -233,6 +233,11 @@ final_check_status theory_seq::final_check_eh() {
TRACE("seq", tout << ">>solve_nqs\n";);
return FC_CONTINUE;
}
if (fixed_length()) {
++m_stats.m_fixed_length;
TRACE("seq", tout << ">>fixed_length\n";);
return FC_CONTINUE;
}
if (branch_variable()) {
++m_stats.m_branch_variable;
TRACE("seq", tout << ">>branch_variable\n";);
@ -430,6 +435,7 @@ lbool theory_seq::assume_equality(expr* l, expr* r) {
return l_undef;
}
bool theory_seq::propagate_length_coherence(expr* e) {
expr_ref head(m), tail(m);
rational lo, hi;
@ -509,6 +515,54 @@ bool theory_seq::check_length_coherence() {
return false;
}
bool theory_seq::fixed_length() {
obj_hashtable<expr>::iterator it = m_length.begin(), end = m_length.end();
bool found = false;
for (; it != end; ++it) {
if (fixed_length(*it)) {
found = true;
}
}
return found;
}
bool theory_seq::fixed_length(expr* e) {
rational lo, hi;
if (!(is_var(e) && lower_bound(e, lo) && upper_bound(e, hi) && lo == hi && lo.is_unsigned() && lo.is_pos())) {
return false;
}
if (is_skolem(m_tail, e) || is_skolem(m_seq_first, e) ||
is_skolem(m_indexof_left, e) || is_skolem(m_indexof_right, e) ||
is_skolem(m_contains_left, e) || is_skolem(m_contains_right, e) ||
m_fixed.contains(e)) {
return false;
}
context& ctx = get_context();
m_trail_stack.push(insert_obj_trail<theory_seq, expr>(m_fixed, e));
m_fixed.insert(e);
unsigned _lo = lo.get_unsigned();
expr_ref seq(e, m), head(m), tail(m);
expr_ref_vector elems(m);
for (unsigned j = 0; j < _lo; ++j) {
mk_decompose(seq, head, tail);
elems.push_back(head);
seq = tail;
}
seq = mk_concat(elems.size(), elems.c_ptr());
TRACE("seq", tout << "Fixed: " << mk_pp(e, m) << " " << lo << "\n";);
add_axiom(~mk_eq(m_util.str.mk_length(e), m_autil.mk_numeral(lo, true), false), mk_seq_eq(seq, e));
if (!ctx.at_base_level()) {
m_trail_stack.push(push_replay(alloc(replay_fixed_length, m, e)));
}
return true;
}
/*
lit => s != ""
*/
@ -1778,6 +1832,7 @@ void theory_seq::collect_statistics(::statistics & st) const {
st.update("seq solve =", m_stats.m_solve_eqs);
st.update("seq add axiom", m_stats.m_add_axiom);
st.update("seq extensionality", m_stats.m_extensionality);
st.update("seq fixed length", m_stats.m_fixed_length);
}
void theory_seq::init_model(expr_ref_vector const& es) {